Unpaginated      |      Vol_VII-0005                                                                                                                  

THE METEOROLOGY OF THE ARCTIC REGION

       

By

Sverre Petterssen, W. C. Jacobs,

and B. C. Haynes

Unpaginated      |      Vol_VII-0006                                                                                                                  
EA: Meteorology

[Sverre Petterssen, W.C. Jacobs and B.C. Haynes]

       

THE METEOROLOGY OF THE ARCTIC REGION

	Page
Introduction	1
Composition and Structure	4
Inversions and Lapse Rates	19
Acoustic Phenomena	25
Optical Phenomena	37
Air Masses and Fronts	46
Cyclones and Anticyclones	52
Atmospheric Pressure	56
Surface Wind	66
Upper-Air Winds	98
Air Temperature	107
Precipitation, Snowfall, Thunderstorms	164
Humidity	211
Cloudiness and Ceilings	228
Fog and Visibility	264
Sunshine, Illumination	287
Information on Diagram	302
Reference to Literature	304
Legend to Diagrams	308

        Note : The diagrams referred to in this paper are of a dimension too

large to be included in the present binding. These diagrams

may be consulted in the Stefansson Collection where they are

filed. (December, 1954)

001      |      Vol_VII-0007                                                                                                                  

       

INTRODUCTION

        From the broadest point of view the climatic regions of the

world may be divided into five principal types, vis.,

        A. Tropical Rainy Climates , which comprise the tropical rain

forests, the tropical monsoon systems, and the adjoining savannas.

        B. Dry Climates , which comprise the deserts and steppes in

subtropical and adjacent latitudes.

        C. Warm Temperate Climates , which comprise the part of the

midlatitude rainy belt that is not normally covered by snow in

winter.

        D. Snow-Forest Climates , which comprise the mid and high

latitude belt with extensive forests and snow cover during the

winter.

        E. Polar Climates , which comprise the tundra regions and the

fields of perpetual snow and ice.

        Fig. 1 The distribution of these types of climatic regions in the nor–

thern hemisphere is shown in Fig. 1. Each of these regions may be

divided into sub-regions, depending upon the amount rainfall,

002      |      Vol_VII-0008                                                                                                                  
seasonal variations, and other limiting factors that affect the

natural vegetation. In this respect the Polar Climate may be said

to be the simplest of all principal climatic types, inasmuch as it

suffices to divide it into two subtypes, namely the Tundra Climate

and the Frost Climate .

        The Frost Climate occupies the regions of perpetual snow and

ice, while the Tundra Climate is characterized by bare ground during

the warm season. The vegetation typical of the tundra consists

largely of mosses, lichens and grasses with dwarf trees in sheltered

places. Along its equatorward border the tundra merges with the

vegetation of the snow-forest climatic zone of the northern hemi–

sphere, and the border between these two climatic zones has been

found to coincide very nearly with the line along which the mean

July temperature is 50°F (10°C). Using this isotherm as a criterion,

it is convenient to extend the border between the Polar Climate and

the adjoining regions across the oceans, as shown in Fig. 1.

        From a meteorological point of view it is convenient to define

003      |      Vol_VII-0009                                                                                                                  
the Arctic Region as the region around the North Pole occupied by

Polar Climates (Fig. 1.), excluding the isolated islands of such

climates that occur in certain mountainous regions in lower lati–

tudes. It should be noted, however, the weather conditions typical

of the arctic are normally encountered also in the regions occupied

by the snow-forest climate (i.e., regions D in Fig. 1).

        Fig. 2 The normal distribution of the air temperature as a function

of latitude and as a mean for all meridians is shown in Fig. 2.

Using the 10°C July isotherm as the line of demarkation between the

arctic region and the adjacent climatic zones, it will be seen that

the mean position of this isotherm is about 66°N. The area of the

arctic region, as defined above, is therefore about one-twelvth of

the area of the northern hemisphere. Using the correspondence iso–

therm of the warmest month in the southern hemisphere as the border

of the antarctic region, it will be seen from Fig. 2 that this

isotherm is found about 48°S, indicating that the area of the

antarctic region is about three times as large as that of the

[ ?] arctic region.

004      |      Vol_VII-0010                                                                                                                  

       

COMPOSITION AND STRUCTURE

        Composition of Dry Air . - The air consists of mixture of a number

of gases. Most of these are present in a perfectly mixed state,

with the result that their relative amounts are constant all over

the world, at least up to 25-30 km. (80,000 - 100,000 ft.). The

most important of the constituents are given in Table I, which is

summarized from a recent publication of the International Meteoro–

logical Organization [ 21 ] . The amounts are expressed in terms

of mol. fractions, which for all practical purposes may be taken

to indicate the volume percentage occupied by each gas.

TABLE I. - Principal Constituents of Dry Air .

Nitrogen	78.09 per cent
Oxygen	20.95 per cent
Argon	0.93 per cent
Carbon Dioxide	0.03 per cent

        In addition to these principal constituents, there are traces

of Neon, Helium, Krypton, Hydrogen, Xenon, Ozone and Radon, but

005      |      Vol_VII-0011                                                                                                                  
their amounts are so small that they are of no practical importance.

        The amount of carbon dioxide is not quite constant. The vege–

table world continuously consumes carbon dioxide which, again, is

produced by the animal world, through burning of fuels, volcanic

action, and various processes of decay in the soil. Although these

processes are not always balanced, the oceans, by dissolving the

excess of carbon dioxide, so effectively regulate it that no great

variations arise. In view of the absence of local sources, the

amount of carbon dioxide in the arctic is likely to be rather less

than the normal for the atmosphere as a whole.

        Ozone, which is present in minute amounts in the atmosphere,

shows a considerable variation with season, latitude and height;

it also varies with the weather situation.

        Extensive investigations by Dobson [ 11 ] , Tönsberg [ ], and

Langlo Olson [ 46 ] , Craig [ 10 ] and others have revealed the fol–

lowing broad features of the distribution and variation of the

amount of ozone.

        (a) The amount of ozone per unit volume increases with

006      |      Vol_VII-0012                                                                                                                  
elevation, reaches a maximum value somewhere between 20 and 30 km.

(65 - 100,000 ft.) and then decreases.

        Fig. 3 (b) The total amount of ozone (in a vertical air column) has

a pronounced annual variation with a maximum in spring and a minumum

in late autumn (Fig. 3).

        (c) The total amount of ozone in middle latitudes varies

aperiodically with the general weather situation, the amount being

larger when the air current is from a northerly direction than when

it is from a southerly direction.

        From the foregoing discussion it follows that the composition of

the dry atmosphere in the arctic region is essentially the same as

elsewhere, except that the arctic region is particularly rich in

ozone, and probably slightly deficient in carbon dioxide content.

007      |      Vol_VII-0013                                                                                                                  
Water Vapor . - The air also contains a variable amount of water

vapor. In many respects the water vapor is the most important

constituent of the atmosphere. The maximum amount of water vapor

that the air can absorb depends entirely upon the temperature; the

higher the temperature of the air the more water vapor can it hold,

the air being saturated with moisture when the maximum is reached.

        The amount of water present in the air is conveniently

expressed by the pressure that it exerts. This pressure is usually

expressed in millibars, 1 mb. corresponding to 0.75 mm. or 0.029

inches of mercury under standard conditions.

        The maximum amount of water vapor, or the saturation vapor

pressure , various temperatures is given in Table II. Comparing

these figures with the curves in Fig. 2, it will be seen that the

maximum vapor pressure corresponding to the mean temperatures in

the vicinity of the North Pole would be about 0.1 mb. in January,

6.0 mb. in July, and 2.8 mb. as a mean for the year. The amount of

water vapor in the arctic may, therefore, vary by several thousand

percent during the year.

008      |      Vol_VII-0014                                                                                                                  

TABLE II. Saturation Vapor Pressure (E, in millibars) at various

temperatures . E _w refers to a water surface , and E _i to ice surface .

T(°C)	T(°F)	E w	T(°C)	T(°F)	E w	E i
30	86.0	42.4	−5	23	4.21	4.02
28	82.4	37.8	−10	14	2.86	2.60
26	78.8	33.6	−15	5	1.91	1.65
24	75.2	29.8	−20	−4	1.25	1.03
20	68	23.4	−30	−22	0.51	0.38
15	59	17.0	−40	−40	0.19	0.13
10	50	12.3	−50	−68	0.06	0.04
5	41	8.7	−60	−86		0.01
0	32	6.1	−70	−104		0.003

009      |      Vol_VII-0015                                                                                                                  

        Comparing the arctic region with the equatorial belt, it will

be seen from Fig. 2 Table II that the saturation vapor pressure

in the vicinity of the North Pole is about one-sixth in July, and

about one-four hundredth in January, of the saturation vapor pressure

near equator. Since the air normally is not quite saturated,

the contrasts of the actual amounts of water vapor will be somewhat

less. Nevertheless, the moisture content is expressed in ab–

solute amounts, the arctic region stands out as being excessively

dry during the cold season. This absolute dryness, together with

the low temperature, constitutes an environmental factor of great

importance.

        Although the arctic air is dry, on an absolute scale, it is

not so in terms of relative humidity. Let e denote the actual

vapor pressure and E the saturation vapor pressure corresponding

to the air temperature. The relative humidity is then defined as

100 e/E, i.e., the actual vapor pressure expressed as a percentage

of the maximum value at the temperature in question. The distribu–

tion of the relative humidity, as a function of latitude and a

010      |      Vol_VII-0016                                                                                                                  
Fig. 4 mean for all meridians, is shown in Fig. 4. It will be seen that

the relative humidity in the arctic is normally about 10 per cent

higher than in middle latitudes, and about 5 per cent lower than

in the equatorial belt.

        Impurities. - Apart from the above-mentioned gaseous constituents,

the atmosphere contains a variety of impurities, such as dusts, soots

and salts.

        The main source of dust is the dry climatic regions (Fig. 1).

The coarser material is never carried far from its source, but minute

dust particles are readily kept soaring by the turbulent motion and

carried long distances from their place of origin by the general

air currents. Before dusty air from the arid regions arrives in

the arctic, it will normally have been cooled so much that conden–

sation has occurred; the precipitation of water from the clouds

washes out the dust to a very large extent, with the result that

the air in the arctic region is particularly free of dust. This

is especially true in winter when the rate of cooling of the north–

ward moving air masses is largest.

011      |      Vol_VII-0017                                                                                                                  

        The industrial regions and forest fires constitute the main

source of soot*, but since these sources are far removed from the

arctic, the impurities will normally have been removed, either

through precipitation or sedimentation, before the air arrives in

the arctic.

* In addition, soot may be supplied by volcanic eruptions.

        Observations show that the air normally contains considerable

amount of salts. Through the action of the winds, spray is whirled

up from the oceans, and when the spray droplets evaporate the salt

remains in the air. These minute salt particles constitute highly

effective nuclei of condensation, and are, therefore, washed out

of the air through the precipitation processes.

        The arctic air masses are, therefore, characterized by ex–

tremely low values of turbidity, and this influences the visual

range very greatly. In the arctic, the sky, when clear, is

characterized by the brilliance of stars during periods of darkness,

012      |      Vol_VII-0018                                                                                                                  
and by intense blueness during periods of light or dusk. Distant

objects (e.g., mountain ranges) stand out with great clarity in

shape and detail.

        The purity of the arctic air is noticeable even in low and

middle latitudes when these regions are invaded by arctic air masses.

As has been shown by Bergeron [ 3 ] , the opalescent turbidity can

be used as a means of indentifying traveling air masses, and this

technique has been of importance in the development of the methods

of weather analysis and forecasting.

        Troposphere and Stratosphere . - Although the state of the atmosphere

is subject to incessant variations, the mean (or normal) state indi–

cates a division of the atmosphere into fairly well-defined layers.

This stratification of the atmosphere is not immediately apparent

in the distribution along the vertical of atmospheric pressure and

density, but it stands out clearly in the distribution of tempera–

ture.

        Fig. 5 Some typical examples of the distribution along the vertical

of the air temperature are shown in Fig. 5, which is reproduced

013      |      Vol_VII-0019                                                                                                                  
from a recent publication of the Canadian Meteorological Service [ 27 ] .

Disregarding for the moment the conditions near the earth’s surface,

it will be seen that the temperature decreases with elevation at a

fairly regular rate of about 60°C per km. (10°F per 3,000 ft.) up to

about 8 km. (26,000 ft.) in winter and to about 10 km. (33,000 ft.)

in summer. At higher levels the temperature is either constant or

increases slightly with elevation.

        The lower part of the atmosphere, in which the temperature de–

creases with elevation, is called the troposphere , and the upper

part, in which the temperature is constant or increases with eleva–

tion, is called the stratosphere . The transition from the tropo–

sphere to the stratosphere, which usually is quite distinct, is

called the tropopause .

        The examples shown in Fig. 5 represent the conditions on the

fringe of the arctic. In the central part of the arctic region

still lower temperatures would be observed, particularly in the

lower half of the troposphere.

014      |      Vol_VII-0020                                                                                                                  

        Fig. 6 Fig. 7 The mean thermal structure of the atmosphere up to 20 km.

(62,000 ft.) above sea level is shown in Figs. 6 and 7 for winter

and summer respectively. These diagrams represent the mean con–

ditions for 18 meridional sections at intervals of 20 degrees

starting from Greenwich meridian. The observational material used

for the construction is that contained in “The Normal Weather Maps”

[ 47 ] . The northernmost parts of the diagrams are largely based

upon extrapolations and tests for consistency. Although this may

have led to errors in detail, there can be little doubt that the

diagrams represent the essential features of the thermal structure.

        Considering first the conditions in January, it will be seen

that the mean positions of tropopause, which is found at about

8 km. (26, 000 ft.) in the polar region, rises slowly southward to

about 50°N, and then rises at a rapid rate to about 25°N, where it

becomes horizontal at about 17 km. (56,000 ft.).

        It will be seen from Fig. 6 that there are five regions in the

atmosphere (below 20 km.) which are characterized by extreme tempera–

tures. The coldest region is found at about 17 km. (56,000 ft.)

015      |      Vol_VII-0021                                                                                                                  
above sea level in the equatorial belt, where the mean temperature

is about −75°C (−105°F). The next coldest region is found in the

vicinity of the arctic tropopause, where the mean temperature is

about −63°C (−81°F). The third coldest region is found at the sur–

face over the arctic fields of snow and ice, where the mean tempera–

ture varies between −25 and −41°C (−13 and −42°F). This lower cap

of cold air is separated from the upper cold region by a layer of

relatively warmer and fairly uniform air with temperatures in the

vicinity of −26°C (−13°F) at about 2 km. (6500 ft.) above the ice.

        In contrast to these cold regions we find two warm regions,

one at low levels near the equator, and a second in the troposphere

in subpolar latitudes.

        In summer (Fig. 7) the conditions are largely the same as in

winter, except that the cold regions in the arctic are less distinct.

In all seasons, the temperature in the troposphere decreases north–

ward, whereas in the stratosphere the temperature decreases, on the

whole, from the arctic toward the equator.

016      |      Vol_VII-0022                                                                                                                  

        Fig. 8 The annual variation of temperature, as a mean for all meridians,

is shown in Fig. 8. It will be seen the maximum variation occurs

at low levels in the arctic. This variation decreases rapidly with

elevation and reaches a minimum of about 20°C (36°F) at about 3 km.

(10,000 ft.) above which level there is a slight increase up to

about 5-6 km. (16,000-20,000 ft.) and then a rapid decrease up to

10 km. (33,000 ft.) which is the mean summer position of the tropo–

pause. In the stratosphere the annual variation is relatively small.

Considering the conditions level for level, the annual variation of

temperature of the free atmosphere decreases from the pole to the

equator. The same is true of the conditions at the earth’s surface

if one considers the mean for all meridions It should be noted,

however, that the annual variation near the earth’s surface is

larger in Northern Russia, Siberia, and Canada than it is at the

pole (see p. ).

        At heights greater than those shown in Figs. 6-8, ordinary

observations are so sparse that the meridional structure and annual

017      |      Vol_VII-0023                                                                                                                  
variation cannot be evaluated with much confidence. From observa–

tions of meteors and sound waves and from a few direct observations

by rockets and sounding balloons it is possible to piece togather

a picture of the broad features of the uppermost atmosphere, and

these may be summarized as follows. The stratosphere is almost

isothermal up to about 35 km. (21 miles); above this level the

temperature increases rapidly and reaches a maximum of about 75°C

(167°F) at a height of about 60 km. (37 miles) whereafter it de–

creases to about −25°C (−13°F) at about 80 km. (50 miles). This

warm layer is sometimes called the mesosphere.

        Above the mesosphere lies the ionosphere which extends up to

great heights and merges gradually with empty space. The ionosphere

is characterized by free electric charges. Some of the gaseous par–

ticles are broken down into ions and free electrons by absorption of

the ultraviolet radiation from the sun, which also causes a dissocia–

tion of oxygen and nitrogen molecules into their atomic forms and

causes very high temperature at extreme heights. The ionosphere

018      |      Vol_VII-0024                                                                                                                  
is the abode of the aurora borealis; it is divided into several

layers that reflect radio waves in various wave lengths.

019      |      Vol_VII-0025                                                                                                                  

       

INVERSIONS AND LAPSE RATES

        Fig. 9 Although the temperature normally decreases with height in the

troposphere as a whole, the lower part of the arctic region forms

an exception (see Fig. 6). Here the temperature normally increases

from the earth’s surface up to a distance which rarely exceeds 2 km.

(6,000 ft.) and sometimes may be as low as 200 m. (600 ft.) or less.

Some examples are shown in Fig. 9.

        The rate at which the temperature decreases with elevation is

called the lapse rate . A layer through which the temperature in–

creases with elevation is called an inversion , and such layers are

characterized by counterlapse . The base of the inversion is the

level where the counterlapse commences, and the top of the inversion

is the level where the counterlapse changes into a lapse of tempera–

ture.

        It is convenient to compare the observed lapse or counterlapse

with the adiabatic lapse rate, which is the rate at which a unit of

air would cool if it were thermally isolated and lifted against the

gravitational force. The adiabatic lapse rate, which is a critical

020      |      Vol_VII-0026                                                                                                                  
value for many processes, is expressed by the formula

Γ_a = g/C_p

where g is the acceleration of gravity and C_p the specific heat

of air at constant pressure. Substituting the numerical values for

g and C_p, it is found that Γ_a =1°C per 100 m. = 5.5°F per 1000 ft. for nonsaturated

air.

        Above the top of the inversion the lapse rate is normally about

1/2 to 2/3 of the adiabatic rate. Occasionally, the adiabatic rate

may be approached, but it is never exceeded by any appreciable

amount.

        In the inversion layer, the counterlapse may be very large;

numerical values as high as 5°C per 100 m. are quite common, and

close to the snow surface values as high as 1°C per meter are not

uncommon, particularly in calm and cloudless conditions in winter.

        In calm air or when the winds are light the base of the

inversion is found at the earth’s surface. However, when the wind

021      |      Vol_VII-0027                                                                                                                  
Fig. 10 is sufficiently strong, friction along the earth’s surface causes

the lower layer to be mixed, and a normal lapse rate is established

in the lower layer while an inversion may be present at some distance

above the surface. These elevated inversions are usually less

intense than the ground inversions. Sverdrup [ 43 ] investigated

the occurrence of inversions by the aid of kites carrying instruments.

Since kites could be used only when the wind speed was sufficiently

high, his results (Fig. 10) apply to elevated inversions. It will

be seen that the inversion is lower in winter than in summer.

        Fig. 11 The intensity of the inversion increases with decreasing could

cover, and the most intense inversions occur after spells of calm

and clear weather. An example of the dependence of the inversion

on wind speed and cloud cover is shown in Fig. 11, which is reproduced

from a recent publication by the Canadian Meteorological Service

[ 27 ] .

        The inversions are most strongly developed over land and ice.

When the arctic air streams over open water of appreciably higher

temperature (e.g., in winter), the inversion is destroyed through

022      |      Vol_VII-0028                                                                                                                  
heating of the surface layer. In such cases, an adiabatic, or

even superadiabatic, lapse rate develops above the water surface.

The same is true of arctic air that invades warm continents in

summer.

        From the foregoing discussion it follows that the central

arctic is characterized by a well - developed inversion layer, and

that along the fringe of the arctic extreme variations occur, with

changes from large counterlapses to the adiabatic or superadiabatic

lapses.

        The processes leading to the formation and maintenance of the

arctic winter inversions have been investigated by Petterssen [ 32 ]

and Wexler [ 53 ] . These involve the general circulation of the

atmosphere and the radiative and eddy flux of heat.

        The snow surface, being an efficient radiator, will lose heat

toward space, and the air in contact with the snow will cool faster

than the air aloft. The snow surface will, therefore, act as a cold

source relative to the overlying layer of air. Since the atmospheric

023      |      Vol_VII-0029                                                                                                                  
pressure over the arctic is higher than over the adjacent oceans

(heat sources), the distribution of heat and cold sources is such

as to constitute a hindrance to the circulation, and a layer of

stagnant air develops over the arctic snow and ice fields. Since

the air is stagnant, it becomes subjected to continued cooling from

below. As the surface layer becomes very much colder then the over–

lying air, downward radiative flux of heat will tend to balance

the cooling of the ground. The maximum difference in temperature

between the top and the base of the inversion, which depends upon

the contents of moisture and carbon dioxide of the air, has been

determined by Wexler to be about 30 °C ( 54 °F), and this

value agrees well with observation.

        In summer the conditions are largely similar to those in winter,

except that the cold source is due mainly to the melting of snow,

while the air at higher levels is heated by radiation.

        If the wind is sufficiently strong, the radiative cooling of

the surface layer will be offset by the downward eddy flux of heat,

024      |      Vol_VII-0030                                                                                                                  
and the inversions become weaker, or may disappear temporarily and

locally. If the sky is cloudy, the back - radiation from the clouds

will have a similar effect.

        The arctic inversions are of great importance in many ways,

notably in connection with propagation of sound and light.

025      |      Vol_VII-0031                                                                                                                  

       

ACOUSTIC PHENOMENA

        No one who has lived in the arctic can have failed to observe

the frequent occurrence of supernormal audibility and the wide

variation in the audible range. For example, Captain Perry [ 35 ] ,

on his third voyage, noted a case where conversation was carried on

over a distance of 1.2 miles, and Collinson [ 9 ] reported on a

case where spoken words were heard at a distance of 2 miles. The

most extraordinary case of abnormal sound effects in the arctic is,

perhaps, the one described by Wegener [ 52 ] . On the Danish Green–

land expedition, 1907-08, observers at Pustervig, on the northeast

coast of Greenland, heard a tone of deep pitch (estimated at about

30 c.p.s.) which lasted for several hours and appeared to emanate

from a closed fjord called Dove Bay. This sound was heard on several

occasions when the fjord was filled with cold stagnant air.

        These abnormal sound effects can readily be explained by

reference to the structure of the arctic atmosphere and the properties

of the snow and ice.

        The range at which sound can be heard depends upon the temperature

026      |      Vol_VII-0032                                                                                                                  
of the air, the speed and direction of the wind, and the rate at

which sound energy is absorbed by the earth’s surface.

        1. Influence of Snow and Ice . - It is well known that soft

snow falling through the air absorbs sound energy very effectively.

The same is true of soft snow on the ground. On the other hand,

a hard crusted snow surface absorbs but little energy, and a smooth

ice surface is an almost ideal reflector of sound. The rate at

which sound energy is absorbed depends upon the pitch. Kaye and

Evans [ 22 ] measured the absorbtion coefficient of newly fallen

snow in England and found the values reproduced in Table III. It

TABLE III. Absorbtion Coefficient of Newly Fallen Snow .

Snow depth inches	Frequency (c.p.s.)
	125	250	500	1000	4000
1	0.15	0.40	0.65	0.75	0.85
4	0.45	0.75	0.90	0.95	0.95

        will be seen that for a pitch higher than 500 cycles per second, a

snow cover 4 inches, or more, deep absorbs almost all sound energy.

Although comparable figures for hard snow surfaces are not available,

027      |      Vol_VII-0033                                                                                                                  
it is evident that the absorbtion coefficient decreases rapidly

with the hardness, and is almost negligible for a smooth ice sur–

face. The audible range will, therefore, be short over a soft snow

surface, relatively large over hard snow, and excessively large

over ice fields.

        2. Influence of air temperature . - One of the major causes of

the supernormal audible range in the arctic is due to the distribution

of temperature, and in particular to the inversion layers described

in the foregoing section. Let C denote the speed of propagation

of the sound, and T the absolute temperature of the air. In still

air, the velocity of sound is proportional to the square root of the

absolute temperature. We may, therefore, write

C = A√(T)

where A is a constant for any given composition of the air. The

minor variations in composition, discussed in a foregoing section,

are too small to have any noticeable effect on the speed of propa–

gation

028      |      Vol_VII-0034                                                                                                                  

        Although the air temperature may very vertically as well as

horizontally, the latter variation is usually negligible in com–

parison with the former, and as shall here be concerned to discuss

only the influence due to the variation along the vertical.

        We consider first the idealized case when the temperature is

uniform in all directions (isothermal conditions). The speed of the

sound would then be uniform, and the “sound front” would be a

spherical shell expanding with a constant speed.

        Fig. 12 Instead of the “sound front” it is more convenient to consider

the “sound beams” or “sound rays”. These are represented by lines

originating in the sound source and being everywhere perpendicular

to the sound front. The sound rays in an atmosphere of uniform

temperature are shown in Fig. 12A, where the sound source is at

the earth’s surface. The rays are straight lines through the source.

Since the energy of a sound impulse is distributed uniformly on a

spherical surface, it is evident that the sound intensity must be

inversely proportional to the square of the distance from the

source, or

029      |      Vol_VII-0035                                                                                                                  
I = I₁/R2

where I ₁ is the intensity at unit distance from the source, and

I is the intensity at the distance R from the source. In the fol–

lowing, we shall refer to eq. (2) as the inverse square law.

        Let us now consider the case when the temperature decreases

along the vertical, as it normally does in middle and low latitudes.

The sound will travel faster in the horizontal than in the vertical

direction. The sound front will no longer be spherical, and the

sound rays will be curved upward as shown in Fig. 12B. The beams

that leave the source horizontally will lose contact with the earth’s

surface, and in the space below these beams, a sound shadow will be

found. This shadow refers to the beams, or the direct sound. A

certain amount of sound is, however, diffracted across the beams

into the shadow, but the intensity of this sound is small and it

decreases at rate which exceeds the inverse square law.

        The conditions represented in Fig. 12B being typical of middle

and low latitudes, it is evident that most people’s experience

030      |      Vol_VII-0036                                                                                                                  
about sound from distant sources is based upon the rather faint

sound which is diffracted into the beam shadow. Above the beam

shadow, the beams are more concentrated in Fig. 12B than they are

in Fig. 12A, with the result the intensity of the sound is corre–

spondingly increased. It will, thus, be seen that when the tem–

perature decreases along the vertical, the sound tends to escape

upward, and but little energy is transmitted along the earth’s

surface.

        As was shown in the foregoing section, inversion layers are

almost always present in the arctic. We shall, therefore, consider

this case in some detail. Since the temperature increases upward

through the inversion layer, the sound will travel faster vertically

than horizontally; the wave front will now be elongated upward, and

the sound beams will be curved downward. Fig. 12C shows the rays

from a sound source ( ) at the earth’s surface when tempera–

ture distribution is as shown to the right of the beams. It can

easily be shown that a beam that leaves the source at certain

critical angle will become tangent to the top of the inversion

031      |      Vol_VII-0037                                                                                                                  
layer where it splits, one branch (b) being curved downward and

the other branch (c) being curved upward. This critical angle

depends entirely upon the temperature difference between the top

and the base of the inversion, and is independent of the depth of

the inversion layer. The space between the beams b and c in

Fig. 12C is silent as far as direct sound is concerned.

        The beams that leave the source at angles less than the critical

value, will be refracted toward the earth’s surface. A considerable

portion of this sound is, again, reflected from the earth’s surface,

and this together with sound that is diffracted across the beams

will penetrate into the part of the shadow that is below the top

of the inversion. On the other hand, beams that leave the source

at angles greater than the critical value, will penetrate the in–

version and escape into space.

        Referring again to Fig. 12C, it is of interest to note that

the concentration of the beams is larger in the inversion layer and

less above this layer than in the radial case shown in Fig. 12A.

032      |      Vol_VII-0038                                                                                                                  
From this it follows that the sound intensity below the top of the

inversion decreases more slowly than indicated by the inverse square

law; above the top of the inversion, the reverse is true.

        We shall next consider Fig. 12D which illustrates the con–

ditions when the sound source is above the top of the inversion.

The inversion layer will now act as a hindrance to the propagation

of sound toward the earth’s surface. Except where the sound source

is directly overhead, or nearly so, very little sound energy reaches

the earth’s surface. Thus, an aircraft flying above the top of

the inversion is not readily detected by acoustic means.

        From the foregoing discussion it follows that an inversion

layer acts as a duct for sound emanating from sources below its top,

and as a cushion against sound that emanates from sources above its

top. Neither the duct nor the cushion is perfect, and their

efficiency (in still air) depends upon the intensity of the inver–

sion.

        The sound intensity may become greatly supernormal when the

sound source is situated below an inversion in a fjord (or valley)

033      |      Vol_VII-0039                                                                                                                  
surrounded by steep walls. If the fjord is frozen and the mountain

sides covered by hard snow, an almost ideal sound channel is estab–

lished, sound being reflected from the ice, the mountain sides and

the top of the inversion. If the fjord has a local contraction, a

basin is formed which, when the dimensions are suitable, may form

a resonant box. The case described by Wegener (loc. cit.) apparently

belonged to this category of sound effects.

        Although the mean state of the lower arctic atmosphere is

characterized by one inversion layer (see Fig. 6), multiple inver–

sions occur quite frequently, particularly over and near arctic

land masses (e.g. Greenland). The sound effects associated with

multiple inversions are extremely complex, and several zones of

shadow and zones of maximum intensity may occur, depending upon the

position of the source. Fig.12E shows, as an example, the sound

pattern of a source situated between two inversions. It will be

seen that the sound tends to become trapped between the top of the

lower and the base of the upper inversion, and that several shadow

zones may result.

034      |      Vol_VII-0040                                                                                                                  

        3. Influence of wind . - If V denotes the speed of the wind,

the velocity of sound can be expressed by the formula

C = A√(T) + V

which is the same as the velocity in still air plus the velocity of the

medium through which the sound travels. Now the former of these

velocities is of the order of 300 m/sec. (700 mph) while the latter

is of the order of 10 m/sec. (20 mph). The direct influence of the

wind is, therefore, very small if the wind is uniform in all direc–

tions.

        Owing to friction along the earth’s surface, the wind increases

with elevation up to about 500-1000 m. (i.e., 1500-3000 ft.). Al–

though the increase varies with the roughness of the ground, the

wind speed over a snow surface will normally be twice as large at

about 600 m. as is at 10 m. above the ground. Above this layer,

which is called the friction layer, the wind may increase or de–

crease with elevation depending upon the horizontal temperature

gradient.

        The variation along the vertical of the wind has a marked

035      |      Vol_VII-0041                                                                                                                  
influence on the propagation of sound. To demonstrate the nature

of this influence, we consider Fig. 12F, in which it is assumed

that the temperature is uniform along the vertical, while the wind

distribution is as indicated to the left. The beams that go down–

wind will be curved toward the earth’s surface. A beam that leaves

the source at a certain critical angle, will just touch the level

where the wind becomes uniform, and at greater distance from the

source, a sound shadow will be found below this level. The beams

that go upwind will be curved away from the earth’s surface, above

which another sound shadow is found. The greatest concentration of

sound beams is found in the downwind direction in the layer where

the wind increases, and it is here that the supernormal audibility

is observed.

        In the arctic both the wind and the temperature will normally

increase with elevation through the friction layer, with the result

that both effects combine to give supernormal sound intensity down–

wind. In the upwind direction, the temperature effect is counter–

acted by the wind effect, and except when the wind is very light,

036      |      Vol_VII-0042                                                                                                                  
the wind effect predominates.

        4. Sound ranging . - From the foregoing discussion it follows

that for any given source intensity the audible range depends upon

the curvature of the sound beams in the vertical plane, and this

curvature is determined by the distribution along the vertical of

temperature and wind. Provided that soundings of temperature and

wind are available, the path of the sound beams can be reconstructed

and the position of the sound source identified. A convenient

method of sound ranging has been developed by Bedient [ ] .

        For further information on propagation of sound in the atmosphere,

reference is made to the works of Wa e lchen [ 50 ] , Rothwell [ 36 ] ,

Whipple [ 55 ] , Gutenberg [ 15 ] , and Saby and Nyborg [ 37 ] .

037      |      Vol_VII-0043                                                                                                                  

       

OPTICAL PHENOMENA

        In addition to the aurora borealis, the abode of which is in

the ionosphere (see pp ), the sojourner in the arctic

will observe a number of optical phenomena of great beauty and in–

tensity. Some of these, such as the rainbow, the corona and the

halo, are not essentially different from those observed in middle

latitudes and will not be described here. The optical phenomena

which are most typical of the arctic and of some importance to the

arctic traveler are the mirages which are due to abnormal bending

of the light rays, and the ice blinks and the water sky which are

due to reflection of light from ice and water surfaces by the lower

face of a cloud layer.

        The mechanism of the formation of mirages is readily explained

by reference to the fact that light travels slightly faster in thin

air than it does in denser air. Thus, since the air density decreases

with elevation (except in very rare cases), a slant beam of light

will be curved downward, and this curvature depends upon the rate

at which the density decreases across the beam. In the following

038      |      Vol_VII-0044                                                                                                                  
we shall be concerned to discuss the bending of light beams between

points on the surface. Since these beams are quasi-horizontal it

suffices to consider the lapse of density along the vertical.

        Using the equation of state and the hydrostatic relationship,

it is readily shown that the rate of decrease of density (p )

with height (z) is expressed by

-(∂p/∂z) = (p/RT2)((g/R) – Γ)

where p denotes pressure, T absolute temperature, Γ lapse rate

of temperature, R the gas constant, and g the acceleration of

gravity.

        Since g and R are physical constant and p varies but

little in any given place, it will be seen that the lapse rate of

density (and the refractive index) is determined almost exclusively

by the temperature conditions.

        Travelers in the arctic have noticed a marked annual variation

in the optical phenomena, and this can readily be explained by

reference to equation (1). Let us assume for the moment that the

039      |      Vol_VII-0045                                                                                                                  
lapse rate of temperature is the same in winter as in summer.

Under typical arctic conditions the absolute temperature would be

about 275°A in summer and about 230°A in winter. It is then readily

seen that the refractive index is normally about 40 per cent greater

in winter than in summer. In addition to this effect of the annual

variation of temperature there is a large annual variation in the

lapse rate of temperature (see Fig. ), with the result that

the refractive index may vary several hundred per cent during the

annual cycle. In fact, the largest variations are due to the change

in lapse rate of temperature.

        As was shown in a foregoing section (p. ) the temperature

of the troposphere normally decreases with elevation such that

= 0.6°C per 100 meters (or 3.3°F per 1000 ft.), and this

together with the first term within the parentheses of eq. (1)

accounts for the normal refraction of light in the atmosphere. In

the arctic, however, the lapse rate may vary within very wide limits,

thus giving rise to abnormal bendings of the light beams.

040      |      Vol_VII-0046                                                                                                                  

        1. The superior mirage occurs in connection with temperature

inversions (p. ). In the inversion layer the temperature in–

creases with elevation, and the lapse rate of temperature (i.e., )

is negative. It will then be seen from formula (1) that the den–

sity decreases along the vertical at an abnormally fast rate, with

a consequent abnormal downward refraction of the light beam. An ob–

ject seen through the inversion layer will become distorted so that

it appears elongated in the vertical direction. For example, a

relatively flat strip of coast land may appear as an erect strip

and give the false impression of being a steep cliff; irregulari–

ties in the coast line will appear like columns, and the distor–

tions produce a picture which resembles architectural pseudo–

prostyle. In pronounced cases, the erect image is surmounted by

an inverted image, and in rare cases the inverted image is, again,

surmounted by second erect image.

        Fig. 13 An example of a superior mirage is shown in Fig. 13. The

upper picture shows the natural shape of Gundahl’s Knold while the

lower picture shows strong vertical distortion due to the presence

041      |      Vol_VII-0047                                                                                                                  
of an intense inversion.

        The superior mirage may occur without inverted image and dis–

tortion, in which case objects which are actually below the obser–

ver’s true horizon will appear above his apparent horizon. This

phenomenon is called looming. This, together with the pronounced

purity of the arctic air (p. ), probably accounts for many

instances of erroneous estimates of distances and reports of dis–

covered land masses and mountains in places where none exist. In

1818 Captain John Ross saw snow-covered peaks in Lancaster Sound

(74°N, 85°W), at an estimated distance of thirty miles, which appeared

to bar his way into the Northwest Passage. Subsequent explorations

have made it evident that the peaks seen by Ross were those of

North Somerset Islands (73°N, 93°W) at a distance of about 200

miles. Pearly and his companions clearly saw on two occasions in

1906 an extensive mountainous snow-covered land northwest of Cape

Colgate (82°N, 91°W) in Grant Land at an estimated distance of 130

miles, and named it Crocker Land. In 1914 MacMilland and Green

042      |      Vol_VII-0048                                                                                                                  
sighted Crocker Land and sledged 130 miles in its direction, seeing

the mountains once on the journey but never reaching them. The

exact location of Crocker Land is still a mystery, and it appears

certain that the sightings were caused by looming of unusual in–

tensity.

        The distance over which an object may loom depends upon the

height of the inversion and the difference in temperature between

the top and the base of the inversion. In calm and cold weather

the inversions are likely to be deep and intense; distances esti–

mated in such conditions are likely to be much in error.

        It is of interest to note that looming is a local phenomenon;

at some point closer to the loomed object than the observer, the

object will not be visible. The effect may be likened to the

“skipping” of radio waves which permits reception close to the

transmitting station and at considerable distance from it, but not

at intermediate distances. As a consequence of this, it is readily

seen that for an aircraft that sees a loomed sun, there must be

points both above and below the aircraft for which the sun will

043      |      Vol_VII-0049                                                                                                                  
Fig. 14 have set, and twilight will prevail both above and below an

aircraft illuminated by the loomed sun. These conditions are shown

diagrammatically in Fig. 14.

        2. The inferior mirage forms when the temperature decreases

with elevation at an excessive rate. These mirage, which are

common occurrences is southern deserts, may be observed locally in

the arctic, particularly where cold air from the ice fields is

heated by streaming over open water, or where bare land adjacent

to ice, is heated in sunshine. The superheated layer is usually

quite shallow (4 to 10 ft.), and within it the lapse rate of tem–

perature is large and positive. It will be seen from formula (1)

above that the density decreases with elevation at a subnormal rate;

in extreme cases when

is greater than g/R, the lapse of

density is reversed, and the light beams may be curved away from

the earth’s surface. In such cases, the true horizon disappears,

and an apparent horizon is formed below the true horizon leaving

a gap between the apparent horizon and the inferior mirage of objects

044      |      Vol_VII-0050                                                                                                                  
Fig. 15 above the true horizon. An example of an inferior mirage is shown

in Fig. 15.

        As with the superior mirage, the inferior mirage results in

a change in the apparent distance of objects. In the case of in–

ferior mirage, the effect is that of disappearance over the apparent

horizon of previously seen objects which are known to be above the

true horizon. This phenomenon is called sinking.

        Fig. 16 Fig. 17 3. The Fata Morgana is a combination of superior and inferior

mirage occurring when a superheated layer is surmounted by a

single or multiple inversion. Two examples of these extraordinary

optical distortions are shown in Figs. 16 and 17. A most vivid

account of such deformations has been rendered by Koch [ 23 ] in

the description of his journey across Greenland on 12 April 1913.

        4. Optical haze , or shimmer, occurs in a layer of air next

to the ground within which the lapse rate of temperature is ex–

cessive. Within this layer small-scale convective currents develop

with the warmer lumps of air ascending and the colder descending.

045      |      Vol_VII-0051                                                                                                                  
The differences in the refractive index of these lumps cause a

blurring of objects seen through the layer. Optical haze occurs

quite frequently in the arctic in the same meteorological condi–

tions as the inferior mirage; it makes it difficult to identify

details in the landscape and is annoying for telescopic observa–

tions, particularly range finding by the aid of coincidence range–

finder.

        5. Ice blink and water sky . - In the summer season (when the

sun is above the horizon at a small angle of elevation) light is

reflected and scattered between the ice surface and the base of

low layers of clouds. The whitish glare that is often seen on low

clouds is due to refection of light from distant ice fields. Some–

times, these reflections are quite intense and are thus called ice

blink. Conversely, if there are patches or lanes of open water in

the ice, dark patches or lanes will be seen on the base of cloud

layers. This is called water sky. Observations on water sky and

ice blink are extremely useful for navigation on the ice, for they

indicate, as if seen in a mirror, what lies beyond the horizon.

046      |      Vol_VII-0052                                                                                                                  

       

AIR MASSES AND FRONTS

        The concept of air masses, introduced by Bergeron [ 3 ] ,

is much used in modern meteorology and denotes a vast body of air

whose physical properties are more or less uniform in the horizontal

direction. The air, being almost transparent relative to high–

temperature radiation, absorbs only a small portion of the direct

solar radiation, and the earth’s surface, which is an efficient

absorber, takes up a large portion of this radiation, converts it

into sensible heat and gives it back to the atmosphere, partly

through low-temperature radiation but mostly through eddy motion,

or mixing. Consequently, the physical properties of the earth’s

surface constitute a predominant factor in the formation of the air

masses.

        The air masses typical of the arctic region in winter are

characterized by low temperature at all levels, extreme absolute

dryness and excessively stable stratification. Some examples of

typical winter conditions are shown in Table IV. It will be seen

that the relative humidity at high levels is very low; this condition

047      |      Vol_VII-0053                                                                                                                  

TABLE IV. Typical Temperature (T) and Relative Humidity (R) of

Arctic Air Masses in Winter

	Eureka Sound (8 ft. above MSL) Jan. 19, 1949.		Fairbanks (440 ft. above MSL) Jan. 14, 1949		International Falls (1112 ft above MSL) Jan. 28, 1949.
Height	T(°C)	R (%)	T(°C)	R(%)	T(°C)	R(%)
Station level	−45.0	25	−32.8	42	−17.2	68
2,000 ft.	−25.4	50	−18.1	68	−17.2	67
4,000 ft.	−24.8	54	−17.5	75	−15.7	67
6,000 ft.	−23.4	35	−17.0	67	−14.0	32
8,000 ft.	−21.8	24	−20.6	53	−13.7	40
10,000 ft.	−24.9	-	−22.6	28	−14.0	31
15,000 ft.	−35.1	-	−31.4	-	−19.3	32
20,000 ft.	−44.7	-	−40.5	-	29.3	-

048      |      Vol_VII-0054                                                                                                                  
is due to the circumstance that the air, on account of radiative

cooling aloft, takes part in a sinking, or settling motion. As

a result of this prevailing sinking motion and relative dryness,

high clouds are extremely rare over the central arctic in winter

(see p. ).

        Fig. 18 The source region of arctic air masses in winter is shown in

Fig. 18. On the North American and on the Eurasian sides it borders

onto the source regions of polar continental air masses. These

latter air masses are in many respects similar to the arctic regions,

except that the air masses are more shallow and have less extreme

properties.

        It will be seen from Fig. 18 that warm air from the North

Atlantic (polar maritime air) normally invades the arctic in the

region between Iceland and Norway as far east as Novaya Zemlya.

Less frequently, warm air from the Pacific invades the arctic along

the west coast of Alaska. On the other hand arctic air invades the

midlatitude belt most frequently over the eastern parts of North

America and Siberia. On the whole, more arctic air is shed

049      |      Vol_VII-0055                                                                                                                  
southwards than warm air northwards at low levels, the differences

being made up by an excess of northward transport of warm air at

greater heights in the troposphere.

        The southward flow of arctic air is by no means a steady one;

it appears to occur in outbursts of considerable strength, at in–

tervals of 3 to 10 days, the outburst being associated with intense

traveling cyclones. These outbreaks of arctic air may sometimes

reach as far south as 25°N, and are the main cause of cold spells

in low latitudes. The preferred regions for these outbreaks of

arctic air are the eastern part of North America and the western

part of the North Atlantic, and the eastern part of Siberia and the

adjoining part of the North Pacific.

        Fig. 19 In summer the arctic source region is less effective, owing

to the sun’s being above the horizon, and the contrast between the

arctic and neighboring air masses is less extreme. The source region

of arctic air masses in summer is shown in Fig. 19 in relation to

neighboring sources. Some examples of typical arctic air masses in

050      |      Vol_VII-0056                                                                                                                  
summer are given in Table V. On the whole, the relative humidity

aloft is higher in summer than in winter, and, as a result, the

amount of high clouds reaches a maximum in the warm season.

        Fig. 20 Fig. 21 Fig. 22 The transition from the arctic to the neighboring air masses

is usually not continuous. The mean circulation of the atmosphere

is such that there is a tendency for the air masses from neighboring

source regions to be brought together along zones of convergence,

Along these zones of convergence, which are called fronts , or

frontal zones, more or less abrupt transition in wind, temperature,

humidity, and weather will be found. The mean positions of these

principal frontal zones are shown in Figs. 20 and 21 for winter

and summer respectively. It will be seen that, on the average,

the arctic front is not continuous around the pole; it is normally

absent in the preferred regions of outbreaks of arctic air. A

schematic meridional cross-section of the principal air mass sources

and frontal zones is shown in Fig. 22.

051      |      Vol_VII-0057                                                                                                                  

TABLE V. Typical Temperature (T) and Relative Humidity (R) of

Arctic Air Masses in Summer

	Eureka Sound (8 ft. above MSL) July 1, 1950.		Fairbanks (440 ft. above MSL) July 20, 1946		International Falls (1112 ft. above MSL) July 12, 1946.
Height	T(°C)	R (%)	T(°C)	R(%)	T(°C)	R(%)
Station level	7.2	61	14.0	88	17.0	70
2,000 ft.	3.5	62	10.2	88	17.6	59
4,000 ft.	−0.3	64	5.3	92	12.5	59
6,000 ft.	−4.2	59	1.8	92	10.5	22
8,000 ft.	−7.9	63	−0.6	98	8.3	-
10,000 ft.	−11.0	66	−2.9	100	5.3	-
15,000 ft.	−18.3	86	−10.8	16	−2.0	20
20,000 ft.	−28.1	62	−20.5	58	−11.6	-

052      |      Vol_VII-0058                                                                                                                  

       

CYCLONES AND ANTICYCLONES

        The frontal zones discussed in the foregoing section are

rarely stable. On account of the contrasts in energy stored along

frontal zones, perturbations (known as cyclones, depressions, or

lows) develop and travel along the frontal zones, generally from

the east to the west with a component toward the north. In the

areas between the cyclones, regions of high pressure, or anti–

cyclones, develop and travel, generally eastward with component

toward the south. Most of these traveling cyclones remain in the

sup-polar belt and affect the fringe of the arctic region; some

of them, however, move into and cross the arctic.

        Fig. 23 An example of such a chain of fronts, cyclones and anticyclones

around the arctic is shown in Fig. 23. It will be seen that, on

this occasion, the arctic front is well developed over North

America and over northern Siberia. The polar front, too, is well

developed, more or less in its normal position. A series of cy–

clones is associated with the frontal systems, with anticyclones

in between.

053      |      Vol_VII-0059                                                                                                                  

        Fig. 24 As compared with middle and low latitudes, the arctic region

is a relatively quiet area as far as traveling disturbances are

concerned. The mean meridional distribution of frequencies of

cyclogenesis (formation of cyclones), cyclones, anticyclogenesis

(formation of anticyclones), and anticyclones is shown in Fig. 24

as a mean for all longitudes.

        In summer most anticyclones form about 50°N and move southward

such that their mean position if about 38°N. There is, however,

a secondary maximum of anticyclogenesis at about 75°N and a rela–

tively large maximum north of this latitude. It will further be

seen that most cyclones form about in latitude 50°N and move such

that their mean latitude is about 60°N. It has been shown by

Petterssen [ 32 ] that this poleward tendency of cyclone move–

ment is due to the thermal structure of the atmosphere and the

rotation of the earth.

        In winter the frequency distribution is, in principle, the

same as in summer. In all seasons the arctic region as a whole

054      |      Vol_VII-0060                                                                                                                  
is characterized by a low frequency of cyclones and a relatively

high frequency of anticyclones.

        The low frequency of cyclones is not typical of the entire

arctic region. As has been shown by Petterssen [ 32 ] , general

dynamical principles require that cyclonic circulation (vorticity)

must be produced in the cold sources above cold land and ice fields

and exported along isentropic surfaces downward to sea level along

the arctic coast. Hence all the bays of open water along the

fringe of the arctic will be characterized by cyclonic activity.

These areas of maximum cyclonic activity are also regions of

generally bad weather.

        Fig. 25 Fig. 26 Figures 25 and 26 show the geographical distribution of

cyclone centers in winter and summer, respectively. The following

regions in arctic and subarctic latitudes are characterized by high

frequency of cyclones: The Gulf of Alaska and the Aleutian Chain

(winter and summer), the Baffin Bay and Davis Strait (winter and

summer), the waters south and west of Iceland (winter and summer),

the Norwegian Sea (winter and summer), the Barentz Sea (mostly winter).

055      |      Vol_VII-0061                                                                                                                  

        Fig. 27 Fig. 28 The corresponding frequencies of anticyclones are shown in Figs.

27 and 28. It will be seen that winter anticyclones are quite fre–

quent over the central arctic, with a maximum over the north coast

of Alaska. In summer (Fig. 28) anticyclones are rare on the out–

skirts of the arctic, but quite frequent over the ice pack.

056      |      Vol_VII-0062                                                                                                                  

       

ATMOSPHERIC PRESSURE

        Until seventy years ago, all theoretical considerations concerning

the general atmospheric circulation postulated a zonal system of westerly

winds circulating about a low-pressure area centered at the North Pole.

Subsequent expeditionary data on winds and pressures within the Arctic,

however, failed to verify this simple concept. Furthermore, as early as

1888, Helmholtz [ 18 ] had deduced from hydrostatic considerations that

the prevailing low Arctic temperatures should produce a shallow surface

anticyclone in polar regions. As a result of the mounting evidence from

Arctic observations, together with the general acceptance of the Helmholtz

theory, it became popular during the next four decades to consider the

existence of a permanent polar anticyclone even though the details of the

Arctic pressure distribution remained essentially undetermined.

057      |      Vol_VII-0063                                                                                                                  

        However, from charts published in 1929 depicting the monthly

averages of temperature, pressure, and cloudiness, Baur [ 1 ] was able to

show that the centers of high atmospheric pressure tended to correspond

closely to the regions of minimum hemispherical temperature. He traced

the movement of the principal Arctic center of maximum pressure (and

minimum temperature) from a winter position in Eastern Siberia to a

position north of the Canadian Archipelago in spring, i.e., at a time

when the sub-Arctic continental regions become relatively warm in comparison

to the Arctic Ocean. He then made note of a continued easterly movement

of the centers to a position northeast of Greenland and Spitzbergen in

early summer. In early autumn Baur found a secondary maximum in pressure

over the Polar Sea which he ascribed to the effects of rapid cooling in

the Canadian Archipelago and adjoining ice pack, but on his series of

charts this center is soon superceded by the Siberian high and a weaker

counterpart over the Yukon Territory.

058      |      Vol_VII-0064                                                                                                                  

        The next published series of charts showing the distribution of

pressure over the Arctic was prepared by Sverdrup, Peterson and Loewe

[ 42 ] and drew heavily upon the analyses of Baur, Birkeland and Føyn

[ 1 ] . Dorsey [ 12 ] has more recently revised Sverdrup’s charts upon the

basis of modern observational data. Dorsey also has considered the charts

prepared by Dzerdzeyevski [ 13 ] in 1945 - a series which had made use of

the pressure data obtained near the pole by the Russian North pole Expedition.

        The charts prepared by Dorsey are apparently the most up-to-date and

figs 29-32 here are the ones presented here as Figures 29 to 32 . While the accuracy of

the pressure field indicated for the Arctic Ocean, Greenland, and the

Canadian Archipelago may be open to some question, it is, nevertheless,

probable that the charts do contain the essential characteristics of the

true pressure field at the surface. The prevailing wind directions usually

agree with the isobars and the locations of the principal cyclone tracks

and frontal systems are in accord with the resulting wind distribution.

059      |      Vol_VII-0065                                                                                                                  

        In winter (January, Figure 29 ), the Arctic pressure field is

dominated by the extensive anticyclonic system centered over the Asiatic

Continent and extending as a ridge toward the Chukchi Peninsula and two

very large low-pressure areas - one centered southwest of Iceland and

extending northeastward over the Barents Sea and northwestward over Davis

Strait, and a second centered over the Aleutians and occupying the entire

Bering Sea and Gulf of Alaska. A secondary anticyclone with a central

pressure in excess of 1020 mb is centered over the Mackenzie River Valley.

        In spring (April, Figure 30 ), high pressure exists over the greatest

part of the Arctic Ocean and it is during this season that pressures reach

their annual maxima over the Canadian Archipelago and northern Greenland.

Meanwhile, the Siberian anticyclone has so weakened in intensity that it

can no longer be discerned in the mean isobaric pattern. The Aleutian

low weakens somewhat during this season but retains approximately the same

position as in winter. The Icelandic low, on the other hand, is very much

less intense and occupies its southernmost position of the year (south

of Greenland).

060      |      Vol_VII-0066                                                                                                                  

        During summer (July, Figure 31 ), the pressure gradients at

their weakest over the Arctic. This is to be expected when one considers

that summer is also the season of minimum thermal contrast between polar

and temperate zones. It is during this season that the so-called

circumpolar belt of low pressure is located at its highest latitude. The

Polar Sea during this season is occupied by a true anticyclone as a result

of the contrast between the low surface temperatures over the cold sea

and the relatively higher temperatures which exist at the same time over

surrounding coastal and inland regions. (see Figure 45 .)

        In autumn (October, Figure 32 ), there is a return to a pressure

distribution which is more typical of winter conditions. The Icelandic

and Aleutian lows increase in intensity as the deep cyclonic disturbances

over the northern North Atlantic and North pacific become more frequent.

Meanwhile, the Siberian high has begun to make its appearance, although

a closed anticyclone still remains over the Arctic Ocean north of Greenland

and the Canadian Archipelago as pointed out in a previous paragraph.

061      |      Vol_VII-0067                                                                                                                  

        At this point it should, perhaps, be mentioned that the details

of the pressure distribution over interior Greenland have little meaning

as shown on the sea-level pressure charts. It is possible, on the basis

of theoretical considerations and actual pressure data, to construct an

idealized picture of the pressure field which would obtain over the region

were Greenland not in existence. However, such a picture has no physical

or meteorological significance. Greenland is not merely a positive

topographic feature but it is, in itself, an important air-mass source

because of the altitude and extent of the Ice Cap and because of the

abnormally steep horizontal (and vertical) temperature gradients which

are produced by the temperature contrasts between ice fields and coasts

[ 42 ] . It is because of these facts that there is found to be so little

connection between the pressure field as charted and the wind speeds and

prevailing directions which are recorded for various points over Greenland

or along its coastline.

062      |      Vol_VII-0068                                                                                                                  

        Pressure Fluctuations . - The pressure variabilities observed from

day to day at any Arctic location are directly related to the number

and intensity of migratory cyclones and anticyclones which pass near

enough to affect the area (see pages to ). The extreme ranges

occur during winter in connection with intense cyclonic activity and at

most Arctic meteorological stations both the absolute maximum pressures

and the absolute minimum pressures have been recorded during one of the

colder months. For example, the absolute maximum pressure for a Kara Sea

location occurred at Ostrov Domashnii on February 17, 1933 (1058.5 mb),

while the absolute minimum pressure for the same area occurred at Ostrov

Belyi on November 19, 1933 (950.1 mb) [ 45 ] . The average daily variability

of pressure shows a characteristic annual course with the maximum values

in winter (8 to 10 mb) and the minimum values in summer. In some Arctic

areas there appears to be an additional secondary maximum in April. The

monthly pressure variations also show the same general trend as the daily

variations, as is illustrated by the following typical Arctic data [ 43 ] :

063      |      Vol_VII-0069                                                                                                                  

       

Monthly Pressure Variation (in mbs)

	Yrs
Location	Rec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Arctic Ocean Fram and Maud	5	52.9	53.0	41.0	40.5	32.6	28.1	32.9	27.5	42.8	41.0	44.1	49.4
Central Canadian Archipelago	15	42.7	45.7	39.6	35.5	30.8	26.8	26.1	27.7	33.2	34.1	37.6	42.0

        Extreme pressure changes of as much as 50 mb in 24 hours have been recorded

at some stations on the coasts of the Arctic Ocean in connection with the

passage of an intense cyclone or anticyclone.

        The mean monthly pressure values in individual years and even the

annual pressures for different years may deviate considerably from long–

term averages [ 45 ] . For example, the mean annual pressure at Yugossky

Shar was 1031.1 mb in 1933 and 994.3 mb in 1914. These differences are

completely accounted for by differences in the frequencies of cyclonic

activity between the individual months or years.

064      |      Vol_VII-0070                                                                                                                  

        The preceding discussion applies only to true Arctic conditions

In lower latitudes around the periphery of the Arctic, the non-periodic

variations in pressure are of greater magnitude.

        Pressures in the Upper Atmosphere Pressures in the Upper Atmosphere . - When Helmholtz [ 19 ] deduced the

existence of a polar anticyclone upon the basis of hydrostatic considera–

tions, by the same reasoning he also concluded that low pressure must exit

aloft over the Arctic to compensate for high pressure at the surface. Modern

information concerning pressures aloft over the Arctic verify the basic

concept of Helmholz but the relations between the surface pressure and the

pressure aloft are not as simple as was at first believed. The Siberian

high in winter appears to be a relatively shallow phenomenon and is probably

superceded by relatively low pressures at a comparatively low altitude.

Details concerning the vertical structure of the atmosphere at low levels

over this region are lacking, however. The essentials of the vertical

distribution of pressure elsewhere within the Arctic can probably best be

described by examining the pressure field at the 700-mb level.

065      |      Vol_VII-0071                                                                                                                  

        Namias [ 30 ] has recently prepared upper - level charts illustrating

the height of the 700-mb surface over the Northern Hemisphere. His (slightly revised)

January and July charts are given as Figures and , with the altitudes

Figs. 33 and 34 here of the pressure surface represented by isolines plotted for 100-ft

intervals. The January chart (Figure ) shows the pressure field to have

a rather simple structure with two closed low-pressure centers - one over

the southeast portion of the Canadian Archipelago and a second in the

sub-Arctic over the Kamchatka Peninsula. The July chart (Figure 34 ),

on the other hand, shows much weaker pressure gradients than the winter

chart, and the pressures are higher as would be expected on the basis of

the higher surface temperatures. Three closed low-pressure areas are

shown within the Arctic during this season, the most important of which

is centered very nearly over the Pole. This is also an expected condition

when it is considered that the Arctic Ocean is essentially a “cold sources”

during warmer months in the Northern Hemisphere.

066      |      Vol_VII-0072                                                                                                                  

       

SURFACE WIND

        It is extremely difficult to generalize upon the surface wind

field in the Arctic because of several circumstances which are of

peculiar importance at high latitudes. In the first place, the

character of the wind regime at most coastal points and at many

inland locations is largely determined by local factors which are

not amenable to regional generalization. Secondly, the periodic

changes and spa e t ial deformations in the general wind field are no

less variable than are the highly irresolute Arctic pressure distri–

butions which produce the winds in the first place. (See page .)

The third, but not the least important, difficulty is occasioned by

the fact that the scanty observational data available for analysis

do not represent a homogeneous period of record at all points of

observation. For this reason it is often difficult to ascertain

whether the differences in the wind conditions between two weather

stations represent true regional differences in the circulation or

whether they merely indicate that the observations were recorded

during different years — a difficulty which is particularly serious

when wind observations obtained on shipboard within the Polar Sea are

067      |      Vol_VII-0073                                                                                                                  

        The General Wind Circulation . - The Arctic circulation is, of course,

dominated by the polar anticyclone which, during all seasons except

winter, is centered somewhere over the Arctic Ocean. So far as can

be determined from the scanty observational materials available, the

prevailing wind directions over the Arctic Ocean and surrounding

coasts appear to correspond to the mean pressure distribution. It is

apparent that easterly winds prevail over the well-explored portions

of the Arctic Ocean, over Iceland, the northern portions of Greenland,

and Alaska, and that northeasterly winds prevail in interior Alaska

and Greenland, all of which fits the prescribed mean pressure field.

(See Figs. 29 to 32 .)

        Wind conditions over the interior and coastal portions of Arctic

Eurasia, however, appear to be less well-defined. The Siberian anti–

cyclone dominates the interior and coastal circulations during winter,

but during other seasons the winds are regionally highly irregular.

Along the Siberian coasts of the Arctic Ocean in summer there appears

to exist a large onshore wind component resulting from summer heating

over the interior.

068      |      Vol_VII-0074                                                                                                                  

        In the more southerly portions of the Arctic, and particularly

in the peripheral maritime regions of frequent cyclone activity, the

surface winds are highly variable and do not exhibit a pronounced

“prevailing” direction. At several stations, for example, the

frequency data show that during the course of a year the winds tend

to blow almost as often from one direction as from any other. In

such regions the non-periodic features of the circulation far outweigh

any periodic or permanent characteristics.

        The preceding generalization of the Arctic surface circulation

appears to be about as complete a description as possible of the

large-scale aspects of Arctic winds. The remaining periodic and

regional differences in the surface circulation are the result of

local factors which will be described in greater detail.

069      |      Vol_VII-0075                                                                                                                  

        Surface Wind Speeds . - A large proportion of the description given

by polar explorers have stressed the prevalence of high winds and have

almost invariably given the impression that the Arctic is indeed a

stormy and inhospitable place. One fairly recent publication on

Arctic weather conditions, for example, presents a 3 1/2 page

discussion of winds and storms and, of this discussion, at least 3

pages describe extreme winds reported by various Arctic expeditions

since 1836. It is true that in some restricted areas within the

Arctic the almost continuous high winds are the most noticeable

feature of the climate. It is also true that excessive winds have at

one time or another been reported from nearly every Arctic observing

station. These circumstances, however, do not suffice to ascribe an

unusual severity to Arctic wind conditions.

070      |      Vol_VII-0076                                                                                                                  

        According to Sverdrup / [ 42 ] / , relatively low wind velocities are

characteristic of the Arctic Ocean and Canadian Archipelago. The annual

mean wind speed as recorded over the Polar Sea was only 10 mph during

the Fram Expedition from 1893 to 1896, and 9 mph during the Maud

Expedition of 1922 to 1924. Summarizing the observed conditions,

Sverdrup states, “It is remarkable that very high wind velocities are

so rare.” The highest wind speed observed on Fram was 40 mph,

and on the Maud Expedition, 34 mph; the latter, however, is an hourly

mean value. The Russian North Pole Expedition of 1937 / [ 5 ] ] / found

that high winds occasionally do occur near the North Pole since they

reported from the Pole on June 8 and 9 to the effect that gusts had

attained speeds of 60 feet per second (41 mph).

        The relative frequencies of high wind speeds at various Arctic

points can be judged from the data on the average monthly number of

days with winds of gale, force, which are presented in Table VI . Table VI here

071      |      Vol_VII-0077                                                                                                                  

Table VI. Mean number of days with “gales”*

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
004	5	4	4	3	2	1	**	**	2	3	5	4	33	..
006	5	4	3	3	2	4	1	2	4	3	4	4	39	7
007	5	3	3	5	2	3	1	2	7	8	5	7	50	5-6
Alaska, Coastal and Insular:
100	2	1	**	1	1	0	1	1	2	5	3	2	19	5
101	8	9	8	1	1	..	1	4	5	11	18	14	..	0-2
103	14	19	13	7	4	9	9	7	7	10	13	12	121	2
104	4	2	3	3	1	**	**	1	1	2	1	4	21	10
106	1	2	4	4	7	6	4	6	3	6	4	2	50	6-7
Alaska, Inland:
155	0	2	2	0	0	0	0	0	1	0	1	1	7	1-3
156	1	0	**	**	**	**	0	0	0	0	0	0	1	10
Canada, Coastal and Insular:
222	4	2	2	4	3	1	2	1	2	6	4	7	38	2-3
224	3	1	2	2	1	**	1	1	1	1	4	3	17	2-3
225	8	8	7	5	4	3	3	3	4	5	8	8	66	5-6
228	3	4	5	4	3	1	1	3	5	8	5	7	50	3
Greenland, Iceland, Coastal and Insular:
301	1	1	1	**	1	2	1	2	2	1	1	**	12	5-6
302	4	4	1	1	3	2	3	3	4	2	2	**	28	2-3
304	1	2	1	1	2	1	2	1	1	2	2	**	15	10
305	10	11	10	6	8	2	5	3	6	10	7	5	82	3-4
306	2	2	1	1	**	1	**	1	1	3	1	1	14	5
308	10	6	9	10	6	4	6	3	8	10	8	6	84	2

* Wind Speed ≥ 32 mph. ** Less than 0.5 day.

072      |      Vol_VII-0078                                                                                                                  

Table VI. Mean number of days with “gales”* (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular (cont.):
309	4	**	2	**	**	**	**	1	1	2	2	2	15	4-5
310	4	5	6	3	2	**	1	**	5	5	5	8	43	2-3
311	4	2	1	1	1	**	**	**	**	1	2	1	11	2-3
312	4	2	2	1	2	2	1	1	2	2	2	2	22	6-7
313	21	22	24	17	9	5	5	5	8	15	15	20	167	3-4
314	4	1	2	3	**	5	2	2	3	2	2	2	29	4-5
315	6	2	2	2	1	1	**	1	**	1	3	5	23	4-5
316	10	15	15	9	10	4	3	3	13	5	12	21	121	2
317	7	5	4	2	1	1	**	1	3	2	4	5	36	10
318	4	5	1	3	1	1	1	1	1	2	3	2	22	8
319	9	7	6	6	1	2	1	1	3	3	6	10	54	2-3
320	12	10	8	7	4	4	3	4	6	9	10	8	84	10
321	19	17	19	15	12	11	4	8	8	10	12	19	153	4-5
330	2	2	1	1	1	1	**	1	1	1	2	2	14	16
331	3	2	1	1	**	**	0	**	**	1	2	3	13	16
332	3	2	1	2	1	1	**	1	2	2	1	1	17	9
334	3	2	2	1	**	**	0	**	1	2	2	2	15	14
335	1	1	1	**	**	0	0	**	**	**	1	1	5	15
337	**	0	0	**	0	0	0	0	0	0	**	**	1	11
339	2	1	1	**	**	**	0	**	1	1	1	**	9	10
340	0	0	1	0	0	0	0	0	1	0	0	0	2	1
Greenland, Iceland, Inland:
361	**	**	0	**	0	0	0	0	**	**	0	**	1	16

* Wind Speed ≥ 32 mph. ** Less than 0.5 day.

073      |      Vol_VII-0079                                                                                                                  

Table VI. Mean number of days with “gales”* (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular:
400	110	9	7	5	3	3	2	2	4	6	8	11	69	10
401	11	8	7	9	3	3	2	2	6	6	11	11	79	1
406	7	7	6	4	3	2	1	2	3	4	6	7	52	19
408	5	5	4	3	2	1	1	2	2	3	5	5	38	31
412	2	2	2	1	0	**	0	**	1	1	2	2	13	28
414	2 2	2	1	**	**	**	0	**	**	1	2	1	9	26
415	4	4	4	2	3	2	2	1	2	3	5	4	36	18
417	6	3	3	6	2	2	0	1	3	4	5	4	37	..
420	3	3	2	1	**	**	**	**	1	2	2	3	17	26
421	**	0	**	**	0	0	0	**	**	0	**	**	**	8
423	0	0	0	**	0	0	0	0	0	0	0	0	**	7
425	2	1	2	1	2	2	1	1	2	2	1	1	19	18
426	**	**	**	0	0	0	0	0	**	0	**	0	1	17
428	2	2	2	1	2	2	1	1	2	2	2	2	20	18
429	1	1	1	1	1	1	1	**	1	1	1	1	8	18
Europe, Inland:
450	**	**	**	1	0	1	0	0	**	**	**	1	3	7
451	**	**	**	**	1	**	0	**	1	1	1	**	4	14
455	0	0	0	0	0	0	**	0	0	0	0	0	**	8
456	**	**	0	**	**	**	**	0	1	**	0	0	1	7
Asia, Coastal and Insular:
500	14	8	11	11	7	11	10	10	8	9	13	14	126	7-8
502	9	8	6	8	6	6	6	5	4	3	8	8	76	4-5

* Wind Speed ≥ 32 mph. ** Less than 0.5 day.

074      |      Vol_VII-0080                                                                                                                  

Table VI. Mean number of days with “gales”* (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
503	8	4	4	2	2	4	3	2	3	3	6	6	47	7-8
506	6	5	5	5	5	3	1	2	3	6	7	5	53	24
507	11	10	13	13	10	11	8	6	8	6	8	11	114	17
508	4	3	5	4	3	2	1	2	4	5	5	4	41	6
509	5	6	6	6	7	2	2	4	4	8	10	5	65	6-7
510	11	19	8	7	5	3	1	3	5	6	9	8	75	19
513	1	1	0	1	**	2	3	2	2	2	1	2	18	4
515	**	**	2	1	1	2	2	2	1	2	1	1	15	5
517	8	3	6	2	3	3	1	2	8	7	8	4	55	3
518	10	9	8	8	7	5	3	2	5	7	10	9	82	26
519	6	6	5	6	6	2	1	2	5	7	8	8	60	22
521	4	4	5	4	5	2	1	3	4	5	4	4	46	13
522	1	**	1	1	1	1	**	2	1	0	0	1	9	5
523	10	6	8	5	5	4	2	4	5	7	4	8	68	3
525	5	5	5	5	5	3	6	6	6	6	8	8	68	9
526	3	2	3	2	1	1	1	1	1	2	2	2	21	14
527	4	4	4	2	1	**	2	1	2	2	4	3	29	12
531	1	**	2	**	0	1	0	0	0	2	2	3	11	4
Asia, Inland:
550	4	4	2	2	1	0	1	**	1	1	2	3	19	5
551	6	6	2	2	2	0	2	4	0	1	5	6	35	1
553	5	6	7	5	3	2	1	2	3	4	5	4	48	18
554	7	10	8	11	10	7	6	7	6	7	12	9	100	4
556	**	**	**	**	**	2	2	1	1	**	**	0	7	17

* Wind Speed ≥ 32 mph. ** Less than 0.5 day.

075      |      Vol_VII-0081                                                                                                                  

Table VI. Mean number of days with “gales”* (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
558	0	0	**	0	**	1	1	1	**	1	0	0	4	8
560	**	2	3	2	2	2	2	1	2	1	2	1	20	8
561	1	1	1	1	1	**	**	**	**	**	**	**	5	11
562	**	2	3	1	3	2	**	1	2	1	3	1	18	10
563	2	2	1	2	1	1	1	1	1	2	2	2	17	6
566	**	**	1	**	1	1	1	**	1	1	1	0	7	13
568	**	**	1	1	2	2	1	1	1	1	**	**	10	18
571	0	0	0	0	0	0	0	1	0	4	0	1	6	1
572	1	1	1	**	**	1	**	**	1	**	1	1	7	16
573	2	2	2	3	3	2	2	1	3	2	2	2	25	9
574	1	**	**	**	1	**	0	**	**	**	1	**	5	10
575	1	**	0	0	0	0	0	**	**	**	**	**	2	18
576	**	1	1	2	1	2	1	1	**	**	1	1	11	13

* Wind Speed ≥ 32 mph. ** Less than 0.5 day.

076      |      Vol_VII-0082                                                                                                                  

        Data from coastal stations along the Arctic Ocean indicate that

average wind speeds at most points are higher than over the ocean

areas, but even here the wind speeds are low except where strongly

influenced by local factors. In general, the average wind speeds at

coastal points are of the order of 10 to 15 mph except at more exposed

locations where averages of 15 to 20 mph are fairly common. (See

Table VII .) However, the coastal areas may also experience excessively Table VII here

high winds at times. For example, on February 8, 1909, Note: Possibility that this may be an incorrect date See Reference title, J.P.J. a temporary

weather station s at Winter Harbor, Melville Island, recorded a 1-hour

average wind speed of 86 mph and a speed of over 100 mph for a

20-minute period. The average speed for the 24-hour period was in

excess of 60 mph / [ 6 ] / .

        Wind speeds over inland areas at low elevations within the Arctic

are usually much lower than those over either the Polar Sea or its

coasts. The mean annual wind speed at Verkhoyansk, for example, is

only 3.2 mph and at Yakutsk, 3.9 mph.

077      |      Vol_VII-0083                                                                                                                  

Table VII. Average specified wind speed (mph)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
001	11	9	10	11	13	14	12	11	13	14	14	..	..	1
002	11	9	8	8	11	12	12	11	11	10	9	10	10	1
004	21	21	18	17	13	14	12	14	16	18	19	18	17	..
006	14	14	11	11	13	13	11	12	16	14	14	12	13	5-6
007	15	13	13	13	14	14	13	15	17	18	17	16	15	5-6
008	11	..	..	..	..	..	8	11	7	8	9	10	..	0-1
Alaska, Coastal and Insular:
100	10	10	11	12	11	11	13	13	14	15	12	10	12	3-17
101	15	18	18	11	11	12	13	15	15	17	22	19	16	1
103	22	24	21	17	15	16	18	15	17	17	22	20	19	1
104	9	9	9	9	7	7	8	8	9	9	9	9	8	18-30
106	4	5	6	6	6	5	4	4	4	5	5	5	5	8
Alaska, Inland:
155	6	8	8	8	7	7	8	7	7	7	7	6	7	3
156	3	4	5	6	7	6	6	6	5	5	4	4	5	8
Canada, Coastal and Insular:
206	12	11	10	13	14	12	9	13	12	15	15	14	13	6
207	3	4	2	3	4	4	3	3	3	4	3	4	3	4
209	5	4	3	3	5	3	2	2	1	3	3	3	3	6
211	4	4	4	4	6	8	9	8	7	7	7	3	5	4
216	8	8	7	7	7	7	8	9	10	10	10	8	8	8
221	15	15	14	14	14	12	8	13	15	17	15	16	14	8
222	3	3	2	3	3	2	3	4	4	4	3	2	3	1-2

078      |      Vol_VII-0084                                                                                                                  

Table VII. Average specified wind speed (mph) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada Coastal and Insular (cont.):
223	11	11	11	13	12	12	10	11	12	13	15	13	12	15
224	11	7	9	9	11	8	9	8	9	9	11	10	9	5-6
227	18	18	17	17	14	13	13	13	15	18	19	18	16	15
228	15	15	14	14	13	12	11	13	16	17	17	15	14	12
Canada, Inland:
251	3	3	3	3	4	4	5	3	3	3	3	3	3	3-7
253	9	9	10	8	9	8	8	9	9	11	8	8	9	5
254	5	4	7	7	10	10	10	8	6	7	5	4	7	6-21
255	2	3	6	6	6	6	6	6	6	6	3	2	5	7
Greenland, Iceland, Coastal and Insular:
301	2	2	3	1	..	6	3	2	4	6	2	2	..	5
302	7	10	10	9	6	6	6	7	10	10	9	8	8	2
304	5	4	4	4	5	6	4	4	5	6	6	6	5	30
307	10	8	6	5	5	6	7	6	8	9	11	9	7	..
308	5	5	5	4	3	3	3	3	3	4	4	4	4	12
314	14	14	13	11	9	9	8	9	4	11	12	12	11	30
317	6	6	5	3	3	3	3	3	3	4	5	5	4	30
318	4	4	3	2	2	2	1	1	2	2	3	2	2	30
320	13	12	12	11	8	10	8	7	9	10	11	11	10	23
330	12	11	10	9	6	6	5	6	8	9	10	10	8	16
331	14	14	13	12	11	11	9	9	10	12	12	13	12	4
338	9	10	9	9	9	8	7	7	8	8	9	9	7	15
340	6	6	4	4	4	4	3	3	4	4	5	5	5	19
Greenland, Iceland, Inland:
351	11	9	13	12	9	9	9	8	11	10	9	14	10	2

079      |      Vol_VII-0085                                                                                                                  

Table VII. Average specified wind speed (mph) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular:
400	16	15	12	12	11	10	8	9	13	15	15	17	13	10
401	20	17	14	15	13	11	8	10	13	15	18	18	14	1
407	10	10	9	7	5	6	5	4	5	7	8	9	7	10
408	22	21	21	19	16	16	13	14	17	19	21	21	18	28
412	17	16	16	13	11	11	10	10	13	13	14	16	13	28
415	10	9	9	8	9	10	9	7	8	9	10	9	9	10
417	18	17	15	15	16	16	14	14	15	15	16	17	16	..
421	8	8	8	8	9	9	7	8	8	7	7	7	8	8
423	10	11	11	11	12	12	10	10	11	11	11	11	11	8
424	10	9	9	8	8	8	8	8	9	10	10	10	9	26
425	11	9	10	9	11	10	9	10	11	10	12	10	10	10
426	10	10	10	9	9	9	9	9	10	10	10	11	10	10
428	12	10	11	9	10	9	10	10	11	11	12	10	10	25
429	8	9	9	9	10	9	9	8	8	8	8	8	9	6
Europe, Inland:
451	3	2	3	3	5	8	4	2	2	1	2	3	3	10
452	10	11	11	10	11	13	11	10	11	11	9	9	11	25
453	8	6	7	6	7	7	6	5	6	7	6	7	7	10
454	14	13	14	14	13	13	13	13	12	13	14	13	13	11
455	6	7	7	7	8	8	6	6	7	7	6	6	7	8
456	4	5	6	8	9	8	7	7	9	6	5	4	7	8
457	7	7	8	6	7	6	5	5	6	7	7	7	7	36
458	6	6	7	6	7	7	7	6	6	6	6	6	6	30

080      |      Vol_VII-0086                                                                                                                  

Table VII. Average specified wind speed (mph) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular:
500	21	16	18	19	17	18	18	18	19	19	21	21	19	7-8
501	16	14	12	12	13	13	12	14	17	15	17	16	14	5-6
502	15	16	14	15	16	15	13	17	18	14	15	15	15	4-5
503	16	13	13	12	13	14	13	13	14	13	14	15	14	7-8
505	26	25	23	21	18	17	16	13	17	20	22	20	20	13
506	17	16	14	15	14	13	12	12	15	16	19	17	15	24
507	15	16	16	18	16	17	14	13	15	13	15	17	15	17
509	14	16	15	17	17	15	14	15	15	17	18	13	15	6-7
510	19	19	16	17	16	16	15	16	17	16	18	17	17	19
511	12	9	8	11	14	14	17	14	15	15	13	10	13	4
512	14	11	8	8	11	10	9	11	12	11	11	9	10	7
513	6	6	6	8	9	11	12	10	10	9	7	9	8	4
514	12	10	10	11	12	13	11	11	13	12	12	12	12	7
515	8	8	9	9	9	12	12	12	11	9	9	9	10	9
517	12	11	11	9	9	7	9	8	13	15	15	12	11	10
518	18	18	16	16	15	14	12	12	15	17	20	18	16	26
519	17	18	16	16	16	15	12	13	16	17	19	17	16	22
520	9	10	11	13	13	15	12	12	12	11	12	8	11	12
521	15	14	14	16	17	15	14	14	15	16	17	15	15	13
523	13	11	12	11	11	11	10	13	14	17	14	12	12	2
525	11	11	12	13	11	10	12	12	11	13	15	16	12	7
527	13	14	12	11	9	10	11	11	11	12	13	13	12	14
528	12	14	11	11	10	6	6	7	13	15	12	13	11	3
530	23	25	22	19	17	11	12	12	14	16	20	18	17	10
531	7	5	6	4	4	4	4	4	4	6	7	8	5	4

081      |      Vol_VII-0087                                                                                                                  

Table VII. Average specified wind speed (mph) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland:
550	9	9	8	9	10	9	9	9	8	8	7	8	8	5
552	5	6	7	10	11	11	10	9	10	10	7	6	8	18
553	15	16	15	15	15	13	11	12	13	15	14	13	14	18
555	8	9	10	10	11	10	8	9	10	10	9	7	9	4
556	1	2	2	4	6	7	6	5	4	3	2	1	3	21
566	2	3	3	4	5	5	4	4	4	5	3	3	4	24
567	4	4	5	6	7	6	5	5	5	6	5	4	5	12
568	3	3	3	5	6	5	5	5	5	4	3	3	4	21
576	1	1	2	2	3	3	2	2	2	2	2	1	2	13

082      |      Vol_VII-0088                                                                                                                  

        In a discussion of the frequency distribution of various wind

speeds, Simpson / [ 39 ] / has pointed out that at a given locality the

frequency with which winds of different velocities occur is closely

associated with the type of pressure distribution characteristic of

the region, i.e., whether cyclonic or anticyclonic. He says:

        “In one type the relative frequency increases as the velocity

decreases right down to calms; this type is associated with

anticyclonic pressure conditions. In the other / [ type / ] the

frequency increases as the wind decreases down to a certain

velocity after which the frequency decreases as the wind

decreases and calms may have a very small frequency; this type

is associated with cyclonic pressure distribution.”

        This seems to be a reasonably useful method for classifying wind–

speed distributions at Arctic locations. It is not established,

however, that one is justified in assuming that a “cyclonic” type of

frequency distribution indicates a predominance of cyclonic curvature

to isobars over the region (or vice-versa).

083      |      Vol_VII-0089                                                                                                                  

        Sverdrup / [ 43 ] / has performed the Simpson type of analysis upon

the wind data obtained at several coastal points on the Arctic Ocean

as well as upon those recorded from the Maud over the Ocean proper.

He found the “cyclonic type” of velocity distribution most frequent

over the Polar Sea during all seasons, with a tendency toward an

“anticyclonic type” at coastal locations, particularly during winter.

Sverdrup / [ loc. cit. / ] also found a good agreement between the type of

wind-speed distribution and the annual variation of pressure, i.e.,

the higher the barometric pressure the more nearly the frequency

distribution approaches the “anticyclonic type.” A similar analysis

of data from inland Arctic locations has not been performed, but (from

the high frequency of calms and low wind speeds) it can be deduced

that the anticyclonic type would greatly predominate during the colder

months.

084      |      Vol_VII-0090                                                                                                                  

        Vertical Wind Distribution Within the Surface Layar . - It has already

been pointed out that the existence of a surface temperature inversion

is characteristic of the Arctic during all seasons except over areas

with a continental type of climate during the warmer months. The

altitude and magnitude of the surface inversion varies systematically

with season, remaining fairly uniform during colder months and

becoming more variable during warmer months. A consideration of these

variations from place to place and from season to season is of consid–

erable importance to conclusions regarding the variations of winds

within the surface layers of the atmosphere over the Arctic. It is

for this reason that the relationships between the vertical temperature

structure of the surface layer of air and the local wind conditions

will be discussed in some detail.

085      |      Vol_VII-0091                                                                                                                  

        It is a matter of common knowledge among meteorologists that

the atmospheric mixing rate (eddy conductivity) is small within a

surface inversion layer, and smallest when the temperature increase

within the inversion is greatest. A low inversion, therefore,

effectively “seals-off” the surface layer against frictional drag

by the atmospheric layer above the inversion. In other words, the

circulation below the surface inversion layer has a strong tendency

to act independently of the rest of the atmosphere. This circumstance

is one of the several reasons why it is so difficult to describe the

general Arctic surface circulation in broad regional terms. (See

page .)

086      |      Vol_VII-0092                                                                                                                  

        The wind velocity near the surface depends partly upon the

transport of kinetic energy from above (which serves to move

the surface layer of air) and partly upon friction at the ground

(which serves to slow down the movement of air near the surface).

Assuming the friction at the ground to be constant, the lowest wind

velocities at the surface occur when a sharp surface temperature

inversion is present because it is under these conditions that the

transport of kinetic energy from above is least. By identical

reasoning it can be pointed out that the highest velocities at the

surface will occur when the surface inversion is weakest or entirely

absent. In the presence of a strong surface inversion the ratio

between the wind speed at the surface and that, say at 1500 feet, is

large. When the inversion is weak or non-existent, the ratio is

small [ 43 ] . This circumstance is clearly indicated by the following

data which show the vertical distribution of wind velocity as related

to altitude of the base of the inversion, and which have been averaged

by Sverdrup for a number of Arctic points [ loc. Cit. / ] :

087      |      Vol_VII-0093                                                                                                                  

Altitude of Base of Inversion	Zero to 330 feet	330 to 660 feet	660 to 980 feet	Greater than 980 feet
Altitude of wind Measurement (ft)	Wind speed (mph)	Wind Speed (mph)	Wind Speed (mph)	Wind Speed (mph)
1970	23.7	25.3	29.1	28.4
1640	24.2	26.2	30.6	28.2
1310	25.1	25.9	30.2	27.3
980	25.9	26.9	29.5	27.5
660	25.9	25.9	25.9	24.2
330	22.1	20.1	22.8	21.3
20	10.5	13.2	13.4	15.7

        Over the pack-ice, Sverdrup found large ratios in winter

between the velocities at 1,600 feet and those on the surface, the

maximum ratio thus coinciding with the presence of a low and sharp

temperature inversion which is characteristic of this season. During

spring and autumn he found the ratio to be small because in these

seasons the inversion lies higher and is less pronounced. A secondary

maximum in the ratio was found to occur in summer over the pack-ice

but not at the coast. The reason for the difference here is that over

the pack-ice in summer the surface temperature cannot depart much from

freezing, whereas the temperatures can rise well above freezing at the

coast with a consequent destruction of the surface inversion. (See

page .)

088      |      Vol_VII-0094                                                                                                                  

        Details of the vertical structure of the surface wind field are

similar over the interior Arctic. The existence of exceedingly

strong surface temperature inversions during winter accounts for the

prevalence of calms at interior stations during this season, even

though winter is the period during which the arctic circulation reaches

its greatest intensity. Calms are much less frequent everywhere during

the warmer months when the inversion is either weak or absent.

        Sverdrup / [ loc. cit. / ] has also shown that under inversion conditions

there is a clockwise turning of the wind with altitude. The lower

(or stronger) the temperature inversion, the greater the degree of

turning. When the base of the inversion is at an altitude of less than

330 feet his data show an average deviation of 26 degrees between the

direction of the wind at the surface and the direction observed at

330 feet. When the base of the inversion is at an altitude greater

than 1,000 feed, the average turning is only 4 degrees.

089      |      Vol_VII-0095                                                                                                                  

        It should, perhaps, be pointed out here that the velocity

profiles described in this subsection are typical of conditions

found over more-or-less level surfaces and do not apply to conditions

as they occur within a “fallwind” or “katabatic” flow. This latter

phenomenon will be described in a subsequent section.

        Local Influences on Surface Winds . - No one can examine detailed

Arctic wind data from coastal and inland points without being

impressed by the fact that local surface wind speed and direction are

largely determined by exposure of the station (and wind instruments)

and by the location of the area with respect to land and water bodies

and to the regional orography. As an example of the influence of

exposure, Sverdrup [ 42 ] cites one case where a series of observations

made between 1900 and 1902 at a station on Kllesmere Island showed an

average wind speed of 11.2 mph, whereas a series of observations made

in the same area during the interval 1899 to 1900 gave an average

wind speed of only 2.1 mph. The reason for this marked difference

is that the winter lodgings were located in a more sheltered location

during the first year of observations than was the case during the

succeeding years. figs. 35 and 36 here

090      |      Vol_VII-0096                                                                                                                  

        At many coastal points, particularly along the costs of

Greenland and Iceland, the direction and speed of the surface winds

are so local in character that they may bear little or no relation–

ship to winds in the offing. In Iceland, the numerous fjords

indenting the west, north, and east sides of the island contribute

their quota of gorge and channel winds. Similarly, at many places

along coastal Greenland sheltering bluffs or the trend of fjords

largely determine the local wind directions. For example, there are

very few northerly and northwesterly winds at Godhavn, a fact which

is due to the location of the observing station on the shore below

the southerly bluffs of Disko Island. In the same manner, the wholly

different frequencies of north, northeast, and east winds at Godhavn

and Jakobshavn, stations quite near each other, are entirely the

result of different topographic influences. In contrast, at Jakobshavn

and Holsteinsborg, the latter a station much farther from Jakobshavn

than Godhavn, the distribution of wind directions is quite similar

because of a similarity in topographic features / [ 42 ] / .

091      |      Vol_VII-0097                                                                                                                  

        Regional Influences on Surface Winds . - All expeditions to the Ice

Cap region of Greenland have commented on the fact that the surface

winds ordinarily are directed from the interior toward the coast.

This wind regime is merely a large-scale example of a “gravitational”

or “katabatic” wind system. These downslope winds result from the

presence of the cold layer of stable air which forms over the Ice Cap

and which subsequently flows down the slopes of the Ice Cap under the

influence of gravity. The speed of the flow depends first upon the

steepness of the slope; secondly, upon the temperature (density)

contrast between the stable surface air and the warmer air above;

and, lastly, upon the pressure gradient between the inland ice and the

coast. Near the summits of the Ice Cap the winds are more variable,

since their direction and speed depend more upon the magnitude and

direction of the pressure gradient then upon the activity of the cold

air. These katabatic or downslope winds, while they are particularly

characteristic of the Greenland climate, are not limited to this

region. They are an important climatic feature in other Arctic regions

092      |      Vol_VII-0098                                                                                                                  
of diverse topography, such as along the coasts of northern Norway, Spitzbergen,

at Wrangle Island, and in parts of Alaska. Winds of this character

can occur in any part of the Arctic where there is sufficient area

at high elevation to allow the accumulation and downslope flow of

air which is very cold relative to air in the free atmosphere at the

same elevation. Williwaws , also known as Takus or kniks , are a form

of this katabatic wind that occurs along parts of the Alaskan coast.

They are most frequently encountered below along precipitous coastlines.

In many instances the cold air supply which initiates the fallwind

is of limited supply and, for this reason, williwaws are often of

short duration since they cease as soon as the cold air is exhausted.

093      |      Vol_VII-0099                                                                                                                  

        The depth of the katabatic wind is seldom more than five or

six hundred feet, even along the Greenland Ice Cap. These winds

are strongest and deepest when the temperature contrast between the

coast and the interior is greatest. For this reason they tend to

present a maximum frequency in the morning hours and a minimum in

the afternoon, although there are local exceptions to this general

rule, particularly nearer the centers of origin of the winds (as in

the interior of the Ice Cap). They are also somewhat stronger on

clear days than on cloudy days when interior temperatures are above

average. In contrast to the vertical distribution of wind speeds in

other types of Arctic wind systems (see page ), the maximum wind

speeds are found near the surface, i.e., winds are stronger below the

surface inversion than above.

094      |      Vol_VII-0100                                                                                                                  

        Another regional factor affecting the wind regime along Arctic

coasts is exactly opposite in both cause and effect to the fallwinds

just described. In this case the wind is directed inland from a

relatively cool ocean toward a heated continental interior. This

phase of a monsoonal (seasonal reversal of circulation) wind regime

occurs during summer, as would be expected, and is well-developed on

a fairly large scale in portions of Siberia and Alaska. This component

of the surface wind is seldom very great and at no times do the wind

speeds approach the extreme values found in the katabatic flow. Thermal

lows develop during the warmest months in the interiors of Siberia and

Alaska, replacing winter anticyclones in each case. This substitution

results in a tendency toward a reversal of the circulation between

winter and summer. Actually there are few localities where a complete

180-degree reversal of the circulation takes place between the seasons.

In most cases the effect is merely one of several factors which

influence the circulation and may only serve to deviate the wind

slightly from the direction which would prevail were there no marked

temperature contrasts between land and sea.

095      |      Vol_VII-0101                                                                                                                  

        Diurnal Variation of Wind . - The land- and sea-breeze effect is

seldom as well-developed in Arctic regions as in more southerly

latitudes — largely because there is no important diurnal variation

in surface heating and cooling. Nevertheless there is a tendency

toward a diurnal reversal in wind direction along Arctic coasts

during warmer months, particularly when pressure gradients are weak.

For example, in some parts of Greenland there is a tendency during

summer for winds to blow inward along the fjords during daytime and

outward during the night [ 42 ] .

        The wind speed at most Arctic stations also shows a diurnal

variation, both inland and at the coast. At locations surrounded

by moderate elevations the chan g es in wind speed are directly related

to changes in stability, i.e., velocities are least during night hours

when stability is greatest and greatest during afternoon hours when

surface heating is at a maximum. Along the Arctic coast, Sverdrup

[ 43 ] found that the maximum wind speeds occur generally between 1200h

and 1400h and the minima between 0400h and 0600h. The diurnal variation

over the pack-ice is similar but of smaller magnitude, as would be

expected from the smaller diurnal range in stability. (See Fig 37 .) fig. 37 here

096      |      Vol_VII-0102                                                                                                                  

        A diurnal period in the wind is also noticeable at higher

altitudes and on slopes (as along the Greenland Ice Cap) but in

these cases the phase is reversed, i.e., the minimum wind speeds

occur during the afternoon and the maximum speeds during night or

early morning hours. This type of diurnal variation in the case of

slope stations is related to the nighttime augmentation of the

katabatic-type flow through radiational cooling in the interior. At

locations on mountain ridges or peaks, a similar diurnal variation

takes place, but in these cases the cause is the lessened frictional

drag at the higher wind levels, lowered by increased stability at

the surface.

097      |      Vol_VII-0103                                                                                                                  

        Annual Variation of wind speed . - Most of the factors involved in the

annual variation of winds over the Arctic have, of necessity, been

discussed in preceding paragraphs. All that remains is to describe

the more important factors affecting the seasonal variations of wind

speed as they apply to various types of Arctic topographies.

        Wind speeds nearly everywhere along Arctic coasts and over the

polar sea are lowest during summer. At this time pressure gradients

are weakest because of the weakening of thermal contrasts between

high and middle latitudes and between continents and seas. However,

at locations within the continental interiors, winter is the period of

low wind speeds for the reasons that have already been pointed out on

page . The maximum wind speeds at interior stations tend to occur

in late spring or early summer (see data for Yakutsk and Verkhoyansk

in Table VII ), but, again, there are local exceptions. Elsewhere the

maximum wind speeds tend to occur during late autumn or winter at

times of maximum cyclonic activity.

098      |      Vol_VII-0104                                                                                                                  

       

UPPER-AIR WINDS

        It was pointed out in the section on upper-air pressures that the

Arctic anticyclones are relatively shallow phenomena, and hence there

is a tendency for the direction of the pressure gradient aloft to reverse

itself at comparatively low altitudes. (Compare Figures 29 to 32 and

33 to 34 .) Pilot balloon observations over the Arctic Basin have, in

all cases, confirmed this tendency toward reversal. Sverdrup [ 43 ] has

shown that the predominance of easterly winds at the surface is confined

largely to the levels below 10,000 feet, and that they are replaced by

prevailing westerly winds at higher altitudes above the region of his

observations. This general turning of the wind to a westerly direction

is dynamically in accordance with the observed fact that the average

temperature within the lower atmospheric layer s of the west winds decreases toward the

north from the region represented by the upper-air soundings. It is

admitted, however, that the average wind aloft over other portions of

the Arctic may be from directions other than westerly. (See Fig. 39 .)

099      |      Vol_VII-0105                                                                                                                  

        Variation of Wind with Altitude . — Some aspects of the vertical

distribution of winds in the lower layers of the Arctic atmosphere have

already been discussed in the section on surface winds. It was pointed

out that there exists a strong tendency for a clockwise turning of the

wind direction from the ground upward through a sharp surface temperature

inversion. The data show, however, that this turning is largely confined

to the lowest five or six hundred feet of the atmosphere. In the region

of Sverdrup’s observations [ 43 ] , it is found that for surface wind

directions of east, southeast, or south, a much less rapid clockwise

turning of the wind continues above the surface inversion layer. For

all other surface winds, the direction of turning is counterclockwise.

A very rapid turning between 26,000 and 30,000 feet is noted by Sverdrup

in the data which correspond to surface wind directions from southwest

(through west) to northeast. He concludes that this accelerated turning

marks the transition from a tropospheric to a stratospheric circulation.

100      |      Vol_VII-0106                                                                                                                  

        These results, however, cannot in any way be taken as representative

of average conditions over the entire Arctic. The degree and direction

of turning is locally dependent upon the average direction and magnitude

of the pressure gradient at all altitudes above the area represented by

vertical soundings. These qualities of the pressure gradients aloft in

the Arctic will be shown to be more complex than is the case in the region

of the lower-latitude westerlies.

        The wind speeds over the Arctic normally increase from the surface

upward to a level at or below the base of the stratosphere (tropopause)

above which they may decrease in intensity. The tendency for the height

of maximum wind speed to occur at or near the tropopause is clearly

illustrated by the following data from the Maud pilot balloon ascents [ 43 ] :

Altitude of Tropopause (feet)	26,200	29,500	32,800	36,100	39,400	42,600	45,900
Altitude of Wind Maximum (feet)	26,200	28,500	30,500	32,800	34,800	37,100	39,400

        Observations obtained during the Canadian Wordie Expedition of 1937 to northwest

Greenland and the Canadian Arctic [ 8 ] indicate further that the height

of the level of maximum wind speed and the height of the tropopause both

101      |      Vol_VII-0107                                                                                                                  
vary directly with surface pressure — a condition which is merely

another reflection of the well-know meteorological fact that the

stratosphere is lower over cyclone centers than over anticyclones. The

expeditionary data show that the altitude of the level of maximum wind

speed varies from about 26,000 feet to 37,000 feet, averaging about

10,000 feet lower in winter than in summer. The latter finding, again,

is in line with present knowledge concerning the annual variation of

the tropopause height. (See pages to .)

        In contrast to conditions in the westerlies, where the wind speeds

tend to increase with altitude throughout the troposphere, the easterly

winds of the Arctic Basin are strongest near the ground and, on the

average, decrease to their minima between 10,000 and 13,000 feet. As a

measure of the great degree of independence between the surface anti–

cyclonic circulation and the westerly circulation at higher altitudes,

Sverdrup [ 43 ] noted that, in many cases, the transition from easterly

to westerly winds was very sharp, almost as if the pilot balloon had

passed through a marked front. It thus appears that a characteristic

boundary surface is present over the Arctic, and that it exists at an

average altitude of between 10,000 and 13,000 feet.

102      |      Vol_VII-0108                                                                                                                  

        This systematic change with altitude of the average wind is well

illustrated by the following data from the Maud Expedition [ 43 ] :

Level (feet)	0	3,300	6,600	13,100	19,700
Wind resultant from:	s88° E.	s36° E.	s16° E.	s66° W.	s89° W.
Resultant velocity (mph)	2.0	4.0	3.4	4.3	6.0

        Regional and Seasonal Differences in Upper Winds . — The January and

July distributions of streamlines and the mean vector winds over Arctic

and temperate latitudes at the 10,000- and 20,000-foot levels are shown

by Figures 38 to 41 . In addition, the several available wind roses

which apply to the 40,000-foot level are entered on the 20,000-foot figs. 38 to 41 here

charts.

        These charts show that much of the westerly zonal flow characteristic

of the wind field at lower latitudes is lost within the Arctic where

closed circulations exist in the mean flow — circulations which are

assymmetrical with respect to the pole. This circumstance is to be

interpreted as meaning that the upper-air wind field is considerably

more complex over the Arctic than over temperate regions.

103      |      Vol_VII-0109                                                                                                                  

        The average upper winds north of the Arctic Circle are weaker than

are the midlatitude westerlies. At 10,000 fact, for example, the resultant

winds in the Arctic average about 20 knots compared to averages of 25 to 30

knots in midlatitudes. In the lower latitudes the westerly winds increase

with height throughout the troposphere, with average velocities at 40,000

feet probably exceeding 100 knots in some areas in winter. In the Arctic

the increase in the wind velocity with height is less rapid and, as has

already been shown, winds reach their maximum velocity (of about 30 knots) at

around 30,000 feet.

        The mean wind velocities show little seasonal variation at the higher

altitudes. For this reason the differences between the mean upper winds

over the Arctic and those over midlatitudes are small in summer and large

in winter. However, in this connection, it should be pointed out that the

“mean wind” values, whether scaled from upper-level pressure charts or

computed from upper-air soundings, do not have the same meaning as those

for “average wind speed.” The former are vector quantities and the fact

the mean wind is of low velocity may merely signify that the wind directions

and speeds are highly variable from day to day and tend to cancel one another.

104      |      Vol_VII-0110                                                                                                                  
A more representative picture of the regional differences in the upper

winds is obtained through an examination of the frequency distributions

of wind directions and speeds at individual weather stations. This is

at least true within the limits of reliability of the observational

samples and the adequacy of areal coverage.

       

figs. 42 and 43 here

        Unfortunately, upper-air wind data over the Arctic are very scanty

and probably not too representative. A large fraction of the data has

been obtained from pilot balloon soundings which must, of necessity, have

been carried out during intervals of favorable weather. In portions of

the Arctic, winds from one direction tend to bring the clearest skins and,

as a consequence, the winds-aloft data obtained during such situations may

extend to high altitudes. Winds from other quadrants may more often be

associated with low cloudiness, blowing snow, or other visibility-reducing

factors and observations will be limited in number and altitude. For

these reasons, the upper-air data obtained from pilot balloon soundings

tend to be heavily weighted by “fair weather” situations. These facts

should be kept in mind when making seasonal and regional comparisons of

the wind-rose data shown on Figures 38 to 43 .

105      |      Vol_VII-0111                                                                                                                  

        The most outstanding feature of the upper-air winds over the Arctic,

as shown by the wind roses, is their extreme day-to-day variability. It

is for this reason that the mean flow picture described in the preceding

paragraphs has a minimum of practical significance. Aerial reconnaissance

over the Arctic Basin has shown that the Arctic is subject to the incursion

of well-developed cyclones and migratory anticyclones, and is not a region

of continuously weak circulation as might be inferred from the streamline

pattern which describes the mean flow.

        Nevertheless, the maximum wind speeds observed in the Arctic seldom

equal those which are commonly observed in the lower-latitude westerlies.

North of the 70th parallel, wind speeds exceeding 100 knots are rare at

any altitude although the U. S. Air Force reconnaissance flights over

the Arctic have recorded 65-knot winds at the Pole at an altitude of

15,000 feet and 80-knot winds within 5 degrees of the Pole at approxi–

mately the same altitude (January 9, 1949) [ 49 ] .

        The greatest variability in the winds occurs nearly everwhere in

the Arctic during summer when the upper-level circulation is weakest.

Conversely, the winds exhibit their maximum directional constancy during

winter.

106      |      Vol_VII-0112                                                                                                                  

        Because of the great regional and seasonal variabilities in the

upper-wind frequencies over the Arctic, not further attempt will be made

here to describe the detail that is shown by the various station wind

roses. It should be noted that most of the summarized data apply to the

land areas, and even here they represent only the relatively lower altitudes.

These latter two limitations introduce the further complication of orographic

distortion of the pattern of wind frequencies. This distortion will be most

noticeable in the wind roses presented for stations in Greenland and Alaska,

where the elevated Ice Cap and interior high mountains, respectively, affect

the regional wind fields well above the 10,000-foot level.

107      |      Vol_VII-0113                                                                                                                  

       

AIR TEMPERATURE

        It has been shown previously that during most of the year the

Arctic is covered by a shallow layer of cold air which, because of

its great stability, is effectively isolated from the atmosphere

above. As a result, the air temperature is largely determined by

to local temperature of the ice, land, or snow surface. Over the

ice pack of the Arctic Ocean the local temperature of the ice is

primarily dependent upon the loss or gain of heat by radiation, upon

conduction of heat from the atmosphere, and upon the transport of

heat through the ice from the warm water below. Variations in

temperature caused by the transport of air from other regions occur

in every season, but the temperature at the ice surface is very

conservative and always tends to return to the equilibrium temperature

locally appropriate to the season. This tendency is particularly

pronounced over the Arctic Ocean in summer when the ice is melting.

During this season the air temperature seldom deviates far from the

freezing point, even near the coast where temperatures over the land

may be considerably higher.

108      |      Vol_VII-0114                                                                                                                  

        Over the land areas of the Arctic conditions are somewhat

different. During the colder months the cold layer may become

thicker than over the ocean; particularly at the bases of mountain

ranges where the surface “pool” of cold air is augmented by cold

air drainage from higher elevations. At times of strong winds the

surface air may become mixed to considerable altitudes, and, because

the transport of heat downward from the upper layers may be relatively

large, the temperature of the surface becomes a less dominating factor

than over the Arctic Ocean. During summer months the air temperature

over land may rise considerably above freezing because of the general

absence of a moderating snow cover and the effects of extended insolation

received during the long summer days of the Arctic.

109      |      Vol_VII-0115                                                                                                                  

        A very common misconception of the Arctic is that it is a

region of eternal ice and snow and an area of continual intense

cold. Greenland is a land possessing these qualities over much of

its surface, but the analogy has been incorrectly drawn when

Greenland is taken as typical of all Arctic regions. Greenland

consists almost entirely of a high plateau with occasional peaks

extending above 10,000 feet. Because of the high elevation and

relatively heavy precipitation, it is largely covered by ice. In

general, however, most Arctic lands possess neither of these

characteristics, and over much of the area the scanty snows melt

rapidly with the approach of summer.

110      |      Vol_VII-0116                                                                                                                  

        Moreover, the North Pole is not the coldest part of the

Northern Hemisphere. On the basis of separate considerations of

loss of heat by radiation from the ice and the amount of heat

conducted through the ice from below, (Sverdrup [ 43 ] ) has computed

that the most probable absolute minimum temperature over the pack-ice

is between the limits −58° and −62° F. It should be pointed out,

however, that the computations are based upon ice thicknesses

observed by Sverdrup and would not apply where the ice characteristics

depart markedly from those observed by him. On the Maud Expedition

(1918-1925) Sverdrup nowhere encountered temperatures below −46° F.

over the pack-ice, although Mohn [ 28 ] reports a minimum of −62° F.

recorded by the Fram , March 1894, at latitude 79°48′ N., longitude

135° E.

        Even though it is to be expected that coastal stations would

exhibit lower minima than should occur over the ocean areas, there

are several Arctic coastal stations that have never recorded temperatures

below −52° F. (Herschel Island, for example). This evidence indicates

that it is unlikely that temperatures near the Pole ever fall very

much below −60° F.

111      |      Vol_VII-0117                                                                                                                  

        In contrast to conditions over the Arctic Ocean, temperatures

over the continental portions of the Arctic may fall below −80° F.

during winter, and even regions well beyond the confines of the Arctic

may experience temperatures well below −60° F. The lowest official

temperature on record for North America, −81° F., occurred at Snag

Airport, Yukon Territory, February 3, 1947. There are points in the

United States (as at Havre, Montana) that have recorded temperatures

as low as −68° F. — eight degrees lower than is probably near the

Pole.

        The lowest temperature ever observed at the surface of the earth

is −93.6° F. (−69.8° C.), recorded prior to 1920 at Verkhoyansk,

Siberia, well over 1,500 miles from the geographic pole [ 54 ] . For

many years this station enjoyed the distinction of recording the

coldest winter weather of the globe, and the Verkhoyansk region came

to be known as the “Cold Pole of the Earth.” We now have reason to

believe, however, that temperatures at high elevations within the Ant–

arctic Continent are probably lower than any at the surface in the

Northern Hemisphere and that the true “Cold Pole” will be found some–

where near the South Pole.

112      |      Vol_VII-0118                                                                                                                  

        In 1929 a meteorological station was inaugurated in the Oimekon

River district of Siberia, some 400 miles southeast of Verkhoyansk

and, from the brief climate record available, it is noted that the

winter temperatures have consistently averaged lower than those recorded

at Verkhoyansk during the same period. It is quite possible, therefore,

that this station may establish a new record low temperature for the

Northern Hemisphere.

113      |      Vol_VII-0119                                                                                                                  

        It has been pointed out that the summer temperature in the pack–

ice never deviates much from the freezing point. In coastal waters

above-freezing summer temperatures are, therefore, found only within

ice-free areas, but even here the air temperature must remain near

freezing because the surface temperature of the water never rises

much above 32° and the air temperature seldom differs greatly from the

water temperature. Sverdrup’s observations show that warm air from

inland is often transported considerable distances from the coast,

but it is cooled so effectively in the lower layers by contact with

the ice or cold water that a strong temperature inversion is almost

immediately formed. During summer along the immediate coast relatively

high temperatures may be observed for short periods at times of

offshore winds, but when the wind reverses the temperature s almost

immediately falls to near 32°, confirming the conception that an abrupt

change in temperature at sea level takes place when one departs from

the coast.

       

figs. 44 and 45 here

114      |      Vol_VII-0120                                                                                                                  

        During the three summer months the mean maximum temperatures over

the Arctic pack-ice, as recorded on the Fram and Maud , are as follows:

	June	July	August
Fram	37.0° F.	37.0° F.	36.3° F.
Maud	37.0° F.	37.2° F.	36.5° F.

        The absolute maximum observed on the Fram expedition was 39.2° F.

(June 1896) and on the Maud expedition, 38.3° F. (June 1923). tables VIII to XIII here

        In contrast to summer conditions over the pack-ice, most coastal

stations regularly record temperatures above 50° F., and at some

stations temperatures as high as 85° F. have been observed. Even

higher temperatures are recorded at inland stations which are removed

from the moderating effects of water bodies. A maximum temperature of

100° F. has been recorded above the Arctic Circle, and there are a few

inland Arctic stations at lower altitudes that have not recorded

temperatures above 90°.

115      |      Vol_VII-0121                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	..	..	..	..	36	39	38	37	34	..	..	..	39	1-3
003	..	..	..	..	..	38	38	37	35	..	..	..	38	1-3
004	38	39	44	40	49	54	59	59	49	48	41	40	59	7
006	35	29	29	22	33	40	43	42	41	33	31	32	43	5-6
007	31	29	24	27	32	41	46	49	41	33	31	32	49	5-6
008	14	32	..	..	28	34	36	33	27	2	10	21	..	0-1
Alaska, Coastal and Insular:
100	33	35	33	42	45	65	78	73	59	42	39	34	78	25-30
101	31	32	21	35	45	59	57	55	53	43	27	32	59	1
102	32	34	40	47	64	81	82	75	65	57	38	33	82	12-18
103	25	39	35	35	43	55	63	63	57	45	29	39	63	2
104	42	45	44	60	66	79	84	80	66	58	50	40	84	33-35
105	33	33	37	45	50	64	71	68	62	53	54	42	71	4-8
106	56	55	56	63	71	92	81	82	73	63	62	53	92	22-25
Alaska, Inland:
150	39	35	37	47	81	81	85	75	57	47	41	37	85	3-4
151	27	19	13	37	45	67	83	67	57	37	29	21	83	1-2
152	35	34	49	59	75	88	89	86	72	51	34	36	89	5-7
153	40	41	50	60	85	100	93	87	79	61	40	37	100	22-27
154	47	51	53	59	76	90	79	84	76	62	60	49	90	16-18
155	40	43	53	64	82	90	89	90	78	67	42	46	90	35-37
156	41	47	56	65	86	95	99	90	80	67	54	58	99	35
157	41	45	56	68	85	92	95	87	79	68	48	42	95	30-35
Canada, Coastal and Insular:
204	14	21	26	32	50	60	61	52	54	40	34	21	54	4-5

116      |      Vol_VII-0122                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
211	28	36	27	34	51	63	75	64	56	44	23	34	75	10
213	9	26	40	26	41	60	68	63	49	37	32	15	68	6-8
214	23	38	23	25	39	48	65	62	51	41	31	17	65	5
216	10	11	20	33	47	72	78	71	58	42	24	14	78	15
221	12	4	15	31	39	63	75	68	55	39	28	14	75	16
222	26	30	22	27	43	61	77	70	55	39	31	27	77	5
223	30	31	34	39	44	65	73	67	55	41	32	29	73	8-10
225	34	24	25	38	44	60	70	67	55	42	36	34	70	4
226	48	53	43	42	55	69	70	66	62	56	52	36	70	7-8
227	34	33	35	36	42	58	63	58	49	40	34	32	63	5-8
228	39	31	41	62	87	88	96	87	84	62	45	34	96	30
Canada, Inland:
250	44	49	45	53	77	85	87	88	71	55	44	46	86	8
252	15	24	40	57	74	83	84	80	68	52	33	21	84	44
253	41	50	48	59	79	84	82	83	80	59	46	47	83	6
254	11	22	32	52	72	85	84	80	69	47	27	20	84	13
255	34	38	46	55	74	79	81	81	72	59	37	26	84	9
256	37	47	52	68	86	94	92	92	81	73	43	35	94	32
258	23	28	40	61	76	83	86	84	74	63	36	22	86	17
259	32	33	38	60	76	81	84	82	67	63	38	24	84	11
260	37	36	40	60	70	82	82	86	67	63	41	37	86	…
262	25	31	42	62	78	82	88	83	75	63	40	33	88	29
263	31	35	49	66	81	85	87	85	78	67	44	33	87	32

117      |      Vol_VII-0123                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular:
302	37	37	35	37	41	59	59	55	45	41	39	35	59	2-3
304	50	50	48	50	55	63	68	64	61	51	52	47	68	30
305	55	49	53	47	63	71	71	61	53	51	59	55	71	4-5
306	45	50	48	44	56	61	64	59	59	63	48	49	64	5
307	34	41	36	45	53	66	69	59	50	47	35	38	69	5
308	48	41	47	45	49	60	63	54	62	47	52	40	63	12
309	53	47	50	48	57	63	63	62	60	51	47	47	63	13
310	45	41	45	41	49	61	63	65	49	39	39	39	65	2-3
311	41	40	43	50	56	65	74	59	52	44	38	38	74	6
312	49	51	49	51	67	73	71	71	63	57	59	47	73	6-7
313	55	51	45	43	55	69	63	59	61	57	47	49	69	4-5
314	61	51	58	62	64	69	76	71	69	65	56	55	76	30
315	43	45	45	57	61	71	69	63	71	53	45	41	71	4-5
316	29	45	37	39	47	65	61	55	61	31	35	39	65	1
317	46	50	46	49	61	69	73	68	66	55	56	49	73	10
318	54	58	60	59	68	72	74	71	69	67	64	60	74	30
319	49	47	49	53	57	69	65	63	61	59	55	49	69	1-2
320	52	48	44	50	62	68	64	62	62	58	57	54	68	10
321	39	51	43	55	61	63	65	63	59	55	45	43	65	4-5
331	49	50	51	59	63	66	72	67	63	58	52	52	72	14
334	49	50	49	56	64	70	75	79	65	59	53	50	79	56
337	48	47	53	65	70	83	71	67	62	58	49	48	83	4
Greenland and Iceland, Inland:
351	6	−9	4	10	16	23	27	22	17	8	−2	−3	27	1
361	45	50	49	66	67	75	83	74	70	60	51	48	83	16

118      |      Vol_VII-0124                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular:
400	35	32	33	33	41	50	51	53	45	53	45	39	53	10
401	33	31	32	31	32	46	53	45	41	35	33	31	53	1
406	45	50	48	60	73	83	86	83	68	56	50	47	86	49
407	42	42	41	50	68	81	80	74	70	54	45	44	81	10
408	42	41	46	56	69	78	76	77	61	53	44	42	78	55
412	49	49	51	64	74	80	85	79	71	65	52	51	85	55
414	44	46	46	57	66	79	82	76	67	57	50	46	82	55
415	45	41	46	58	83	86	90	85	67	56	44	42	90	38
417	35	34	34	36	54	61	67	68	54	46	38	36	68	6
420	48	50	55	70	76	84	87	81	74	66	55	51	87	55
421	50	54	64	70	84	98	91	86	75	68	55	50	98	50
424	47	43	53	67	77	84	88	64	74	59	49	46	88	44
425	41	42	50	64	81	88	90	94	73	63	51	44	94	44
426	42	43	55	72	86	94	97	93	85	69	56	46	97	157
428	41	39	54	67	83	90	94	89	77	65	60	39	94	95
429	37	36	44	69	80	88	87	86	74	59	45	38	88	33
Europe, Inland:
450	45	46	51	60	75	86	90	84	75	59	45	44	90	46
451	42	43	46	57	78	85	90	85	69	57	46	44	90	44
453	41	41	45	53	73	83	87	83	77	56	42	42	87	10
454	51	53	57	70	79	87	95	86	84	67	58	56	95	20
455	54	54	59	72	82	90	97	88	79	70	56	49	97	53
456	43	45	52	59	66	77	82	84	79	66	61	46	84	44
457	44	46	52	78	84	90	95	88	74	66	51	45	95	44
458	42	43	51	74	82	84	89	87	72	58	46	45	89	27

119      |      Vol_VII-0125                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular:
500	35	35	33	39	52	49	62	59	56	42	39	35	62	7-8
501	30	31	20	28	34	50	71	71	58	33	31	33	71	5-6
502	27	25	15	29	37	52	66	58	58	32	33	29	66	4-5
503	28	24	30	26	36	48	67	63	56	35	31	29	67	7-8
504	15	9	12	25	40	69	66	64	43	32	17	22	69	4
505	34	35	34	41	56	71	76	73	65	46	41	37	76	38
506	34	32	34	37	45	74	79	67	63	50	43	35	79	24
507	41	42	40	41	55	56	66	68	55	53	42	43	68	17
508	34	32	29	33	35	66	74	62	57	38	33	33	74	5
509	29	28	33	33	38	80	79	72	62	42	33	33	80	6-7
510	31	32	27	32	45	67	73	69	56	40	32	33	73	19
511	26	6	−1	24	38	60	69	72	52	31	14	5	72	2
512	25	13	22	36	74	75	91	81	68	45	25	18	91	7
513	−7	11	21	30	68	85	84	80	68	35	21	12	85	7
514	17	7	14	21	50	60	68	72	54	38	18	22	72	11
515	4	−1	12	27	64	85	89	87	67	41	17	10	89	12
516	26	16	18	27	42	60	64	63	49	37	26	30	64	3
517	22	29	30	33	49	63	65	62	47	38	35	32	65	10
518	35	33	34	40	53	78	78	77	68	50	38	36	78	26
519	33	31	34	40	49	74	80	76	66	47	37	33	80	22
520	33	34	38	48	70	82	85	81	68	57	49	35	85	33
521	32	29	33	36	34	72	73	78	59	48	35	33	78	4
522	11	22	31	36	60	77	88	84	58	38	34	19	88	11
523	28	13	24	34	52	61	75	66	51	36	24	38	75	3

120      |      Vol_VII-0126                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular: (cont.)
524	33	31	30	32	38	63	75	77	58	50	36	30	77	4
525	43	39	35	38	45	59	67	58	55	44	43	36	67	7
526	34	35	38	40	65	77	82	80	67	53	38	32	82	12
527	34	35	35	42	46	70	75	71	62	46	41	34	75	15
529	37	35	37	39	46	64	73	61	58	50	44	40	73	4
530	35	31	30	37	52	66	74	69	55	47	36	34	74	7
531	35	36	35	47	54	68	77	68	59	53	33	28	77	4
Asia, Inland;
550	26	26	35	44	53	76	85	83	68	40	43	31	85	4-5
551	−3	16	18	35	48	81	84	78	69	39	15	19	84	3
552	24	14	28	43	58	85	86	83	67	48	23	23	86	18
553	30	28	34	38	52	79	85	77	66	47	34	35	85	14
554	27	24	31	41	50	76	83	84	66	48	32	29	84	17
556	2	14	38	52	71	94	93	88	72	48	33	32	94	33
558	8	17	30	42	74	94	92	85	67	51	24	9	94	13
559	−11	−10	30	37	64	91	86	87	66	49	20	6	91	3
560	30	32	46	58	77	84	86	84	76	64	39	36	86	10
561	32	33	44	61	82	88	92	87	81	63	38	35	92	9
562	32	32	41	60	81	85	90	85	77	62	38	35	92	9
563	29	33	49	54	71	84	91	86	74	56	38	32	91	46
565	24	34	53	62	72	95	103	88	83	62	32	24	103	13
566	26	35	48	57	85	92	95	92	80	59	39	30	95	23
567	21	30	41	60	78	93	96	93	78	64	34	22	96	25
568	16	15	40	55	82	90	100	92	78	58	35	26	100	33

121      |      Vol_VII-0127                                                                                                                  

Table VIII . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
570	10	23	40	59	70	86	99	89	77	59	26	5	99	17
571	14	..	14	32	54	..	..	72	68	52	23	14	..	0-1
572	37	35	38	46	58	82	84	80	70	47	40	34	84	21
573	37	35	47	76	89	90	95	91	81	60	44	37	95	21
574	37	41	52	69	86	95	96	91	79	66	47	37	96	37
576	28	31	51	60	79	91	100	96	79	58	35	32	100	25

122      |      Vol_VII-0128                                                                                                                  

Table IX . Absolute minimum temperature (°F.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	−59	−58	−62	..	..	..	..	..	..	..	..	−50	−62	3
003	−46	−46	−43	..	..	..	..	..	..	..	..	−41	−46	2
004	0	−2	−1	5	15	23	31	30	23	11	8	−1	−2	7
006	−52	−53	−50	−40	−16	13	24	17	0	−24	−32	−43	−53	5-6
007	−41	−37	−39	−26	−2	13	24	24	13	−6	−28	−39	−41	5-6
008	−48	−12	..	..	2	18	28	18	−11	−32	−32	−32	..	0-1
Alaska, Coastal and Insular:
100	−52	−56	−52	−42	−18	8	22	20	4	−25	−43	−55	−56	25-30
101	−25	−37	−31	−17	−5	22	28	30	28	2	−11	−29	−37	1
102	−55	−50	−58	−29	−15	20	30	26	18	−17	−37	−49	−58	12-18
103	−31	−39	−37	−21	−11	24	34	32	22	0	−13	−25	−39	2
104	−47	−41	−38	−30	−6	20	28	23	16	−4	−26	−42	−47	34-35
105	−27	−31	−31	−18	3	25	30	32	21	15	0	−25	−31	4-9
106	−33	−32	−19	−15	20	29	34	31	19	−6	−18	−36	−36	22-25
Alaska, Inland:
150	−50	−58	−58	−32	−14	31	39	23	15	−28	−50	−52	−58	3-5
151	−53	−63	−53	−37	−17	24	32	26	14	−21	−53	−51	−63	1-2
152	−62	−55	−47	−39	−4	32	32	21	−2	−12	−48	−58	−62	5-8
153	−67	−70	−50	−41	−3	25	25	22	7	−30	−61	−71	−71	23-27
154	−46	−40	−34	−25	3	28	30	30	18	−5	−27	−40	−46	17-18
155	−76	−68	−57	−40	−4	23	29	18	3	−27	−55	−68	−76	36-40
156	−66	−54	−44	−25	4	32	34	28	12	−28	−38	−59	−66	11
157	−75	−74	−56	−38	2	23	25	16	2	−28	−54	−69	−75	32-36

123      |      Vol_VII-0129                                                                                                                  

Table IX . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular:
204	−49	−45	−43	−37	−19	12	29	22	5	−9	−31	−41	−49	4-5
211	−51	−57	−49	−37	−14	11	22	24	9	−12	−42	−41	−57	10
213	−56	−56	−55	−43	−22	16	28	27	13	−13	−41	−50	−56	6-8
214	−41	−47	−45	−28	−12	15	27	25	16	−5	−25	−40	−47	5
216	−45	−44	−40	−33	−9	21	34	30	18	−9	−29	−39	−45	15
221	−47	−46	−39	−28	−7	20	33	34	21	−2	−30	−38	−46	16
222	−57	−52	−51	−35	−20	13	30	28	8	−13	−32	−43	−57	5
223	−40	−42	−32	−26	−8	10	25	26	20	4	−21	−34	−42	8-10
225	−40	−43	−39	−29	−9	19	31	30	20	−6	−32	−36	−43	4
226	−46	−46	−45	−32	−15	24	30	31	20	2	−22	−42	−46	7-8
227	−30	−32	−22	−14	2	16	27	27	14	−2	−10	−18	−32	5-8
228	−57	−52	−52	−26	−14	13	22	25	15	−17	−53	−47	−57	30
Canada, Inland:
250	−56	−56	−50	−44	−14	20	30	29	12	−22	−50	−54	−56	8
252	−52	−45	−34	−9	21	32	36	30	18	−1	−30	−43	−52	44
253	−60	−57	−31	−14	19	28	29	17	20	1	−43	−54	−60	6
254	−54	−51	−44	−28	8	31	35	27	15	−13	−41	−52	−54	13
255	−44	−42	−29	−5	22	34	37	30	23	7	−29	−37	−44	9
256	−65	−64	−50	−45	−11	22	26	18	4	−27	−47	−64	−65	32
258	−49	−44	−34	−14	22	33	39	32	24	2	−24	−41	−49	17
259	−46	−44	−37	−16	15	28	41	35	25	3	−25	−42	−46	11
260	−53	−55	−40	−23	4	31	44	38	19	3	−30	−41	−55	…
262	−51	−46	−40	−18	16	28	34	28	20	0	−25	−45	−51	29
263	−54	−50	−36	−9	19	28	35	30	19	3	−28	−45	−54	32

124      |      Vol_VII-0130                                                                                                                  

Table IX . Absolute maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular:
302	−33	−39	−35	−23	−9	22	30	24	6	−11	−29	−37	−39	2-3
304	−37	−40	−38	−26	8	10	24	24	14	0	−17	−4	−40	30
305	−9	−21	−11	1	8	28	33	30	26	16	−3	−3	−21	4-5
306	−20	−24	−17	−15	2	25	35	36	24	10	4	−6	−24	5
307	−39	−48	−41	−36	−10	21	27	23	4	−23	−31	−36	−48	5
308	−37	−38	−42	−30	0	22	28	26	10	−13	−27	−38	−42	12
309	−28	−27	−24	−14	1	24	31	34	20	11	−1	−11	−28	13
310	−15	−25	−21	−9	4	24	32	34	26	18	−3	0	−25	2-3
311	−28	−35	−32	−16	10	30	35	35	25	−1	−10	−22	−35	23
312	−35	−37	−37	−17	4	30	32	24	12	−13	−35	−33	−37	6-7
313	−9	−21	−17	−3	8	28	33	30	26	18	−1	1	−21	4-5
314	−10	−16	−10	−5	10	22	29	30	22	11	2	−9	−16	30
315	4	−11	2	10	18	24	28	30	28	18	14	6	−11	4-5
316	0	−7	−7	1	3	24	22	28	28	14	6	2	−7	1
317	−4	−10	−8	−1	13	25	29	28	25	10	3	−4	−10	10
318	−12	−16	−12	−5	14	28	33	31	16	9	0	−7	−16	30
319	0	−7	4	12	26	30	30	34	26	10	6	−3	−7	1-2
320	5	10	6	8	20	28	30	31	29	23	15	8	5	10
321	8	1	4	14	14	24	30	28	28	24	14	12	1	4-5
331	6	8	8	13	24	32	39	34	27	18	10	10	6	14
334	−23	−13	−22	−11	10	20	27	27	23	12	1	−5	−23	51
337	9	12	14	25	23	31	38	35	31	22	15	15	9	4
Greenland and Iceland, Inland:
351	−84	−84	−85	−74	−46	−22	−19	−31	−42	−79	−74	−83	−85	1
361	−36	−14	−20	−11	3	21	27	26	10	1	−13	−22	−36	16

125      |      Vol_VII-0131                                                                                                                  

Table IX . Absolute minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular:
400	−38	−39	−39	−29	−4	15	30	22	2	−19	−38	−33	−39	10
401	−35	−45	−35	−33	−5	17	24	21	−8	−27	−34	−32	−45	1
406	1	−2	−3	9	15	27	33	31	26	14	7	2	−3	49
407	−5	−5	−1	5	20	30	36	36	29	16	8	−5	−14	10
408	−8	−11	−2	6	14	25	30	30	24	8	6	−3	−11	55
412	3	−4	3	11	20	31	35	36	30	10	5	−4	−4	55
414	0	−1	3	6	17	23	34	30	24	8	3	2	−1	55
415	−45	−36	−38	−18	3	27	30	29	17	−10	−23	−39	−45	27
417	−23	−29	−33	−21	−4	15	30	25	17	3	−5	−23	−33	6
420	3	2	8	14	25	33	38	36	30	19	12	0	0	55
421	−31	−26	−20	0	18	28	37	35	25	5	−9	−24	−31	50
424	−23	−21	−16	12	25	34	42	32	28	14	−5	−18	−23	44
425	−41	−41	−32	−16	10	26	30	24	16	−5	−24	−34	−41	44
426	−28	−38	−19	1	22	33	43	37	28	9	1	−39	−39	37
428	−49	−41	−35	−18	8	26	34	33	20	−5	−22	−45	−49	37
429	−47	−43	−47	−25	4	23	28	25	13	−14	−45	−52	−52	38
Europe, Inland:
450	−50	−50	−44	−25	−7	22	30	25	9	−18	−33	−44	−50	46
451	−59	−59	−46	−34	−6	23	27	19	3	−27	−43	−52	−59	44
453	−43	−43	−34	−23	0	25	30	28	16	−9	−21	−37	−43	10
454	−8	−15	−10	6	14	31	35	35	27	9	1	−10	−15	20
455	−26	−27	−24	−6	14	28	34	33	23	0	−16	−29	−29	53
456	−45	−49	−36	−17	0	23	28	25	19	−8	−29	−40	−49	44
457	−37	−35	−25	2	18	29	38	32	20	6	−12	−35	−37	44
458	−36	−37	−25	−12	10	25	33	31	20	2	−13	−32	−37	27

126      |      Vol_VII-0132                                                                                                                  

Table IX . Absolute minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular:
500	−33	−30	−31	−26	−3	13	23	26	11	−4	−20	−29	−33	7-8
501	−55	−46	−48	−39	−15	15	25	24	16	−17	−48	−46	−55	5-6
502	−53	−50	−49	−41	−13	11	28	26	14	−23	−37	−45	−53	4-5
503	−50	−45	−44	−43	−14	10	26	23	2	−21	−39	−46	−50	7-8
504	−46	−44	−43	−35	−18	19	27	25	16	−5	−24	−41	−46	4
505	−42	−39	−47	−25	−10	1	14	30	9	0	−29	−32	−47	37
506	−45	−40	−43	−30	−11	13	24	22	18	4	−22	−37	−45	24
507	−38	−39	−41	−28	−10	13	25	27	7	−12	−23	−41	−41	17
508	−52	−54	−43	−32	−10	11	26	28	14	−6	−38	−43	−54	5
509	−60	−49	−45	−32	−10	12	28	27	14	−20	−40	−46	−60	6-7
510	−52	−55	−46	−35	−13	6	27	26	11	−18	−39	−49	−55	19
511	−54	−64	−54	−35	−17	9	31	29	10	−21	−40	−57	−64	2
512	−54	−57	−47	−30	−14	18	29	27	18	−27	−49	−50	−57	7
513	−63	−60	−52	−39	−19	20	31	27	−1	−34	−50	−58	−63	5
514	−54	−48	−42	−37	−15	11	26	24	12	−16	−40	−46	−54	11
515	−63	−61	−55	−49	−22	11	30	23	2	−30	−47	−58	−63	12
516	−46	−41	−42	−25	−10	22	28	28	19	−12	−30	−40	−46	3
517	−43	−43	−50	−34	−13	14	23	24	6	−10	−28	−34	−50	10
518	−47	−46	−44	−33	−12	5	25	24	14	−7	−28	−43	−47	26
519	−50	−58	−47	−32	−15	10	23	25	18	−16	−39	−51	−58	22
520	−63	−65	−53	−28	−14	20	33	30	15	−18	−53	−61	−65	18
521	−55	−50	−49	−33	−20	11	30	28	20	−19	−37	−52	−55	4
522	−60	−60	−55	−37	−24	27	33	27	12	−24	−52	−55	−60	7
523	−44	−46	−42	−31	−19	10	28	28	10	−22	−29	−33	−46	3

127      |      Vol_VII-0133                                                                                                                  

Table IX . Absolute minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont):
524	−43	−39	−39	−29	−24	19	27	27	23	−1	−27	−35	−43	4
525	−48	−48	−43	−22	−13	17	27	27	20	−12	−36	−39	−48	7
526	−59	−52	−52	−23	−3	28	35	25	8	−21	−39	−50	−59	12
527	−50	−48	−43	−39	−10	21	35	30	14	−9	−34	−49	−50	15
528	−39	−48	−35	−27	−12	14	29	29	23	1	−20	−28	−48	3
529	−24	−38	−31	−26	−8	23	32	36	26	12	−3	−38	−38	4
530	−38	−37	−40	−21	−5	16	31	28	16	0	−24	−31	−40	7
531	−53	−58	−25	−16	5	18	32	27	17	−22	−37	−49	−58	4
Asia, Inland:
550	−72	−65	−54	−37	−14	19	34	29	8	−30	−60	−57	−72	4-5
551	−61	−66	−60	−42	−18	8	32	31	7	−29	−49	−56	−66	3
552	−72	−75	−61	−43	−10	17	30	25	−4	−36	−59	−72	−75	12
553	−63	−62	−52	−39	−17	11	31	22	4	−24	−53	−55	−63	14
554	−70	−67	−56	−39	−25	8	31	29	−4	−29	−54	−64	−70	17
556	−90	−94	−77	−66	−30	19	28	18	2	−48	−72	−84	−94	33
558	−71	−72	−61	−42	−16	22	33	24	9	−30	−53	−72	−72	9
559	−66	−67	−54	−41	0	28	35	20	7	−30	−46	−55	−67	3
560	−55	−44	−48	−17	1	25	38	32	18	12	−41	−57	−57	10
561	−49	−41	−39	−14	5	29	34	30	20	−21	−42	−52	−52	9
562	−60	−56	−47	−27	−9	22	39	28	13	−20	−57	−67	−67	18
563	−75	−78	−63	−39	−16	20	29	22	5	−46	−68	−78	−78	13
565	−75	−70	−56	−37	−11	17	31	21	2	−39	−60	−74	−75	13
566	−76	−72	−50	−31	3	28	36	28	13	−26	−59	−69	−76	23
567	−76	−68	−58	−34	−9	28	32	21	−3	−32	−60	−72	−76	11

128      |      Vol_VII-0134                                                                                                                  

Table IX . Absolute minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont):
568	−81	−84	−56	−39	−1	24	36	27	13	−31	−64	−76	−84	33
570	−76	−76	−56	−31	−3	26	34	26	11	−34	−60	−73	−76	17
571	−51	−56	−54	−34	..	..	..	..	..	3	−56	−54	..	0-1
572	−75	−72	−57	−40	−14	23	27	22	4	−34	−61	−65	−75	17
573	−51	−36	−40	−8	6	30	39	32	21	−4	−40	−49	−51	16
574	−65	−58	−46	−20	4	30	39	32	8	−16	−49	−60	−65	34
576	−66	−63	−49	−30	−5	23	31	23	4	−29	−49	−59	−66	26
577	−72	−66	−54	−32	7	26	30	22	7	−33	−53	−72	−72	9

129      |      Vol_VII-0135                                                                                                                  

Table X . Mean temperature (°F.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
001	−19	−24	−23	−9	11	24	29	26	17	4	−5	..	…	0-1
002	−32	−32	−23	−9	12	29	32	29	16	−7	−20	−26	−3	2-3
003	−27	−22	−23	−7	10	29	32	31	21	6	−12	−21	1	2
004	23	22	21	25	30	36	41	42	38	32	27	24	30	11
005	15	12	12	18	28	35	40	39	35	29	21	19	25	..
006	−14	−13	−18	−8	14	29	34	32	26	13	−2	−13	7	5-6
007	−9	−8	−15	−1	17	30	33	33	31	19	3	−5	11	5-6
008	−16	8	..	..	14	28	32	30	10	−5	−12	−7	…	0-1
Alaska, Coastal, and Insular:
100	−17	−17	−15	0	20	35	40	39	31	17	0	−12	10	26-31
101	−1	−7	−11	13	24	35	42	42	38	27	8	1	23	1
102	−10	−6	−1	14	30	44	53	51	41	24	6	−4	20	13-19
103	−4	−2	−5	12	26	36	46	44	39	30	11	5	5	2
104	3	6	9	20	34	46	50	50	42	29	16	8	26	34-36
105	1	2	7	20	30	39	46	48	43	32	26	11	25	4-8
106	12	19	24	35	45	54	57	56	48	36	22	13	35	23-26
Alaska, Inland:
150	−2	−2	−4	16	36	52	59	48	39	22	2	−5	20	3-5
151	−23	−45	−15	−4	20	42	52	43	37	9	−9	−16	13	1-2
152	−11	−7	0	21	40	57	56	52	41	22	0	−7	22	7-8
153	−21	−16	0	22	43	58	61	55	42	21	−6	−20	20	21-27
154	7	9	12	27	40	53	54	53	45	31	17	8	30	17-19
155	−12	−4	6	25	44	57	58	53	41	24	1	−10	24	34-41

130      |      Vol_VII-0136                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Alaska, Inland: (cont.)
156	−11	−1	10	29	47	58	60	55	44	27	3	−7	26	36-38
157	−13	−4	8	27	45	56	59	54	42	25	4	−11	24	30-34
Canada, Coastal and Insular:
200	−34	−37	−28	−11	16	32	37	35	15	−9	−22	−27	−3	8
201	−37	−43	−24	−12	16	33	37	34	15	−9	−26	−30	−4	3
202	−34	−20	−26	−11	13	34	37	33	20	−2	−15	−23	1	5
203	−36	−26	−30	−13	11	33	40	34	15	−2	−15	−26	−1	2
204	−21	−23	−14	−2	17	34	41	38	28	12	−5	−18	7	5
205	−26	−26	−23	−9	17	37	41	38	26	5	−7	−23	4	3
206	−15	−14	−12	2	24	37	49	40	28	15	−3	−16	11	3
207	−32	−32	−24	−3	16	34	39	35	23	1	−12	−22	2	3
209	−32	−30	−21	−4	16	34	38	35	22	7	−8	−26	3	5
210	−18	−26	−18	−5	16	32	41	36	26	9	−9	−17	6	5
211	−20	−27	−17	−4	20	36	43	41	30	14	−6	−17	8	10
213	−26	−29	−21	−2	20	36	42	41	32	15	−5	−21	7	18
214	−14	−16	−12	−2	20	33	39	39	32	21	3	−9	11	5
215	−19	−14	−10	2	20	36	44	42	32	15	−4	−15	11	9
216	−19	−19	−16	0	22	38	50	46	36	18	−6	−16	11	13
217	−23	−25	−22	−5	14	37	49	44	33	11	−11	−23	7	13
219	−24	−25	−18	2	23	30	40	35	28	13	−7	21	7	4
220	−20	−25	−9	8	28	36	42	42	36	21	3	−10	13	2
221	−27	−25	−16	2	21	37	49	47	38	22	−2	−17	11	18
222	−25	−20	−14	2	19	35	46	46	32	18	1	−17	10	8

131      |      Vol_VII-0137                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular: (cont.)
223	−14	−14	−4	9	25	35	42	42	35	25	9	−6	15	14
224	−15	−12	−3	11	28	38	46	44	36	25	12	−4	17	22
225	−11	−19	−10	6	24	36	45	43	34	24	12	−5	15	3
226	−16	−16	−7	8	25	37	45	44	37	25	11	−8	15	12
227	−1	−2	8	16	27	33	38	39	35	29	21	7	21	15
228	−19	−17	−6	14	30	43	54	52	42	27	6	−11	18	30
Canada, Inland:
250	−19	−16	−10	9	31	49	56	50	38	20	−4	−17	16	20
251	−21	−15	−7	10	34	53	58	53	39	19	−7	−16	17	28
252	−21	−12	4	29	46	57	60	55	42	26	1	−14	23	41
253	8	13	22	33	46	55	56	54	46	36	14	7	32	6
254	−24	−19	−10	14	38	54	59	56	40	21	−6	−20	17	31
255	−4	3	16	33	46	55	58	55	46	34	7	−4	29	9
256	−19	−13	−2	19	41	55	59	54	42	25	−1	−15	20	30
257	−19	−13	−2	19	41	55	59	54	42	25	−1	−15	20	31
258	−18	−11	1	26	45	56	62	57	46	29	4	−12	24	42
259	−16	−10	0	23	40	50	59	57	46	32	9	−7	24	45
260	−13	−13	1	21	38	54	61	58	45	34	8	−9	24	..
261	−17	−10	−2	21	41	52	60	54	45	31	10	−9	23	24
262	−16	−9	3	26	45	54	60	56	45	30	10	−9	25	25
263	−13	−5	8	31	48	56	61	57	46	32	10	−6	27	30
Greenland, Iceland, Coastal and Insular:
300	−33	−36	−30	−11	15	33	38	35	17	−7	−19	−24	−2	..

132      |      Vol_VII-0138                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular: (cont.)
301	−11	−12	−7	5	..	35	39	38	28	13	2	−11	…	5
302	−7	−12	−10	−1	22	35	41	38	27	15	5	−9	12	3-4
303	−7	−17	−8	−3	19	34	40	36	25	6	−5	−6	9	2
304	−4	−6	−1	10	27	37	43	42	35	25	16	6	19	30
305	19	14	18	23	33	40	45	43	38	32	25	23	30	4-5
306	7	8	13	20	33	42	49	46	37	29	22	18	27	5
307	−4	−6	−7	3	21	35	39	38	30	13	6	0	14	15
308	1	−2	2	10	24	35	40	38	32	19	9	4	18	5
309	11	7	12	20	33	42	46	45	39	29	23	18	27	13
310	13	3	6	13	27	38	42	42	36	27	20	17	24	2-3
311	3	3	10	19	36	44	48	48	39	27	18	9	25	23
312	4	2	4	16	36	49	50	46	37	24	13	8	24	6-7
313	18	12	12	20	32	41	44	43	38	30	25	21	28	4-5
314	16	16	21	27	37	42	47	46	40	31	24	19	31	30
315	23	21	24	28	35	41	45	45	40	33	27	27	25	4-5
316	13	16	18	22	27	38	42	39	40	22	21	20	26	1
317	18	16	19	25	34	41	45	43	38	30	23	20	29	36
318	19	20	24	32	41	46	50	48	42	35	27	22	34	30
319	25	24	27	31	39	45	45	46	40	33	27	25	35	1-2
320	22	23	26	31	37	41	43	42	39	35	29	25	33	37
321	25	24	27	30	36	41	44	44	41	35	30	27	34	4-5
330	34	35	35	36	43	49	52	51	45	38	35	35	41	17
331	32	33	35	39	44	49	52	51	46	39	35	33	41	14

133      |      Vol_VII-0139                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular: (cont.)
334	28	27	26	26	35	42	45	45	42	36	31	29	35	21
336	30	30	31	36	43	49	52	51	46	37	33	33	39	10
337	32	33	36	40	45	49	52	51	48	40	36	35	41	11
340	33	33	33	36	42	48	51	50	46	39	36	34	40	18
Greenland, Iceland, Inland:
350	−24	−33	..	..	..	..	..	..	1	−17	−28	−24	…	0-1
351	−42	−53	−40	−24	−5	4	12	1	−8	−32	−46	−37	−22	1
361	22	24	24	29	36	45	50	46	40	33	25	25	33	17
Europe, Coastal and Insular:
400	1	2	7	2	18	30	34	33	28	18	8	2	14	10
401	−4	−5	−10	−1	16	29	33	32	23	13	3	−2	10	1
403	3	1	2	7	23	35	42	41	32	21	11	7	19	19
404	11	4	5	16	27	35	40	39	32	24	14	12	21	15
405	4	−7	−5	9	21	32	38	37	28	16	10	8	16	15
406	26	24	26	30	37	44	50	51	44	36	29	26	35	50
407	24	22	24	29	39	47	54	53	44	36	31	28	36	10
408	21	20	23	28	35	42	48	48	44	34	28	24	33	20
409	33	32	33	38	43	50	54	54	50	43	38	33	42	60
410	34	33	33	36	41	46	50	51	47	42	38	35	41	60
411	30	29	30	35	42	50	55	54	47	40	34	31	40	60
412	29	28	20	36	42	50	55	54	48	40	34	29	39	60
413	30	28	29	33	39	46	50	51	46	39	33	30	38	60
414	26	25	26	32	39	47	52	51	44	36	30	27	36	60

134      |      Vol_VII-0140                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular: (cont.)
415	11	11	17	29	38	48	55	51	43	31	20	13	31	35
416	17	15	18	25	32	40	47	47	42	33	26	20	30	21
417	13	9	6	16	28	36	45	48	41	32	25	18	26	6
418	−1	1	6	19	31	42	54	50	41	28	13	5	24	17
419	12	11	18	28	37	47	53	51	44	32	21	14	31	60
420	32	31	32	38	44	51	55	55	50	42	36	32	41	60
421	21	20	26	35	45	55	60	58	50	39	31	23	39	26
423	11	10	16	28	40	53	58	55	45	34	23	14	32	33
424	21	20	25	34	46	57	62	60	51	42	32	25	40	92
425	12	12	18	30	41	51	58	54	45	34	24	16	33	35
426	18	18	25	37	49	58	64	60	51	41	30	22	39	35
428	8	10	17	30	41	53	60	55	46	34	21	12	32	35
429	6	7	15	28	38	50	57	52	43	31	19	10	30	40
Europe, Inland:
450	5	6	12	24	36	49	54	50	41	27	16	8	27	22
451	4	5	12	25	37	49	55	51	42	28	14	5	27	60
453	12	7	16	27	40	52	58	53	42	30	22	18	31	30
454	26	28	32	39	46	52	58	55	48	40	32	28	40	20
455	20	21	27	37	48	59	61	58	49	39	30	22	40	29
456	9	9	17	29	41	51	55	51	43	31	22	12	31	20
457	16	15	24	35	47	56	63	58	49	37	28	21	37	20
459	3	8	19	33	46	56	62	56	45	31	18	7	32	35
460	−1	4	13	27	26	49	58	53	43	29	14	4	28	35

135      |      Vol_VII-0141                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular:
500	3	2	−5	5	19	30	35	36	32	24	13	5	17	7-8
501	−15	−12	−19	−4	17	31	38	37	32	15	−3	−11	9	5-6
502	−19	−14	−19	−6	15	32	40	37	32	13	−6	−14	8	4-5
503	−17	−13	−19	−7	15	30	35	34	29	14	−2	−12	7	7-8
505	13	8	5	15	25	35	44	44	38	29	23	15	24	17
506	8	3	0	12	23	34	43	43	39	30	23	13	23	24
507	6	2	−3	10	24	34	42	43	36	27	19	9	21	17
508	−5	−7	−11	2	19	31	39	41	36	23	11	0	15	5
509	−12	−11	−12	2	20	28	48	46	37	20	2	−10	14	6-7
510	−10	−7	−12	2	19	33	40	41	35	20	3	−7	13	19
511	−30	−34	−29	−8	13	32	42	42	32	5	−16	−29	2	2
512	−20	−18	−20	−1	24	39	48	47	36	14	−10	−16	10	7
514	−22	−23	−20	−7	15	33	37	37	32	15	−7	−18	6	11
515	−34	−32	−23	−8	19	40	52	43	33	10	−14	−27	5	12
517	−11	−13	−10	1	17	33	37	35	29	18	4	−5	11	10
518	5	0	−1	12	24	35	44	45	40	29	20	8	22	26
519	−1	−4	−5	10	23	35	43	44	39	26	14	1	19	22
520	−14	−8	0	13	28	45	57	52	41	24	2	−7	19	33
521	−7	−9	−7	9	23	38	51	50	40	24	7	−7	18	13
522	−39	−33	−16	3	28	51	54	48	35	10	−10	27	9	10
523	−20	−15	−10	−4	18	34	39	37	30	17	−1	−8	10	3
524	−14	−18	−12	14	18	34	40	41	36	21	3	−9	12	4
525	−5	−8	−3	8	22	35	42	40	35	24	10	1	17	7

136      |      Vol_VII-0142                                                                                                                  

Table X . Mean temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular: (cont.)
526	−11	−9	1	15	33	49	56	52	41	22	3	−8	20	16
527	−10	−6	−4	5	25	41	51	49	39	23	5	−7	17	23
529	6	3	6	18	29	39	45	44	38	28	16	11	24	4
530	1	−3	1	13	25	38	45	43	37	26	13	5	20	7
531	−5	−6	11	22	33	44	51	53	45	26	5	−5	23	4
Asia, Inland:
550	−22	−13	−14	5	22	42	54	48	38	13	−11	−18	12	4-5
551	−28	−22	−20	−5	22	39	54	48	35	13	−12	−16	9	3
553	−14	−10	−9	4	21	40	54	49	39	20	−3	−13	15	14
556	−58	−48	−24	9	36	56	60	52	36	6	−34	−51	3	38
557	−49	−34	−20	7	29	50	53	50	38	9	−22	40	6	3
559	−40	−32	−17	−9	34	55	58	50	39	14	−18	−34	10	10
560	−10	−4	6	22	35	50	60	53	42	28	4	−8	23	9-10
563	−18	−10	2	15	31	48	61	55	41	20	−4	−17	19	46
565	−33	−21	−3	21	41	60	67	58	42	21	−11	−31	18	13
566	−32	−19	−1	23	43	60	67	58	44	23	−6	−26	20	25
567	−38	−24	−4	18	40	59	65	58	42	17	−15	−35	15	25
568	−46	−33	−9	17	41	60	66	59	43	17	−20	−40	13	77
569	−21	−19	−13	5	21	42	47	42	33	12	−12	−14	10	1
570	−44	−31	−8	25	41	58	65	58	44	19	−11	−34	15	17
572	−20	−14	−10	5	28	50	57	50	37	17	−4	−15	15	25
576	−23	−14	1	21	39	56	63	55	41	21	−3	−18	20	33
577	−14	−9	3	24	43	57	62	55	40	23	1	−20	22	9

137      |      Vol_VII-0143                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
004	27	27	25	28	32	38	43	44	39	33	28	26	33	7
006	−5	−6	−13	−1	18	32	36	35	29	19	4	−5	12	5-6
007	1	0	−8	4	20	32	35	36	33	22	8	3	15	5-6
Alaska, Coastal and Insular:
100	−11	−11	−7	8	25	40	47	44	35	22	6	−5	16	25-29
101	5	−1	−6	20	30	39	46	45	42	31	13	6	28	1
102	−1	0	4	23	36	50	58	56	46	30	12	3	26	8-12
103	2	5	2	19	31	41	50	49	43	34	17	13	29	2
104	11	13	17	27	41	53	56	55	48	35	21	14	32	33-35
105	7	9	9	22	33	42	48	48	43	35	25	12	27	6-7
106	19	27	33	44	54	62	65	64	57	44	30	20	..	22-25
Alaska, Inland:
150	6	6	8	26	45	62	69	57	46	29	11	2	28	3-4
151	−16	−18	−7	8	28	50	63	51	39	17	−2	−11	21	1-2
152	−2	1	14	35	51	70	67	63	51	30	8	1	32	6-7
153	−11	−6	13	35	56	70	72	66	52	28	2	−11	30	19-21
154	16	17	22	36	50	63	63	61	53	38	24	15	38	16-18
155	−4	5	18	36	56	70	71	65	51	31	8	−2	34	33-38
156	−2	5	22	42	58	70	71	64	53	35	12	0	36	11
157	−6	6	21	40	58	70	72	67	52	34	11	−3	35	26-32
Canada, Coastal and Insular:
204	−13	−16	−6	8	25	39	48	42	32	16	0	−12	14	7
205	−20	−19	−16	−1	24	43	48	43	32	10	−1	−18	10	3
206	−9	−7	−6	9	30	43	56	45	32	19	4	−11	17	3

138      |      Vol_VII-0144                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
210	−12	−20	−10	2	22	37	47	41	30	14	−3	−11	11	5
211	−13	−20	−9	5	27	41	51	47	34	20	−1	−10	14	10
212	−11	−14	−3	8	28	40	47	43	36	20	6	−5	16	3-4
213	−19	−22	−13	7	28	42	48	46	35	20	1	−14	13	18
214	−6	−9	−4	6	27	38	46	46	36	26	9	−2	18	5
215	−13	−8	−3	9	26	42	51	47	36	20	2	−10	17	9
216	−12	−12	−8	9	30	45	58	52	42	23	1	−9	18	13
217	−15	−17	−14	4	27	43	57	50	36	17	−4	−17	14	13
221	−21	−19	−9	9	27	43	57	53	42	27	5	−11	17	18
222	−17	−12	−5	12	27	41	54	53	37	24	8	−10	18	8
223	−8	−8	3	16	30	40	49	48	39	29	15	0	21	14
224	−8	−5	5	19	34	44	53	50	41	30	17	2	23	22
225	−5	−12	−1	14	30	42	51	49	39	29	16	4	21	3
226	−9	−9	2	17	32	42	52	49	42	30	17	−2	22	12
227	5	4	14	21	31	37	42	43	38	32	24	12	25	15
228	−11	−8	4	24	38	52	65	62	49	34	13	−3	26	30
Canada, Inland:
250	−11	−9	−2	19	40	59	66	59	44	25	3	−10	24	20
251	−13	−6	4	22	44	64	68	63	46	25	0	−8	26	28
252	−14	−4	16	41	59	70	73	67	52	33	7	−8	33	41
253	15	23	31	43	58	67	67	65	55	42	21	15	42	6
254	−14	−10	3	27	50	67	72	70	49	29	2	−11	28	31
255	5	15	29	44	59	67	70	67	56	41	14	4	39	9
256	−12	−4	9	31	53	68	71	65	51	31	5	−8	30	30

139      |      Vol_VII-0145                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland (cont.):
257	−12	−4	9	31	53	68	71	65	51	31	5	−8	30	31
258	−10	0	13	38	56	68	74	68	56	36	11	−4	34	42
259	−6	1	12	34	50	60	70	67	55	40	17	2	34	45
260	−5	−4	12	32	46	63	69	66	50	39	15	−1	32	…
261	−11	−3	7	31	51	62	70	65	52	36	15	−4	31	24
262	−8	1	15	38	56	67	74	69	55	38	18	0	35	26
263	−1	10	24	45	61	70	75	71	59	43	21	5	40	30
Greenland and Iceland, Coastal and Insular:
302	1	−4	−2	9	28	41	46	43	33	23	13	−1	19	3-4
304	2	0	7	18	34	43	49	48	40	29	21	11	25	30
305	24	19	23	28	37	46	50	49	42	35	29	29	35	4-5
306	13	16	18	26	38	46	54	50	41	32	26	22	32	5
307	26	28	27	32	41	59	61	56	46	39	28	27	39	5
308	12	12	14	22	33	43	49	45	39	25	19	15	27	12
309	16	14	18	26	39	48	51	50	42	33	28	23	32	13
310	18	9	12	20	31	43	47	46	39	31	24	21	29	2-3
311	26	15	24	26	40	49	50	50	44	32	26	18	38	2-3
312	11	10	13	24	45	57	58	55	44	30	21	14	32	6-7
313	22	18	17	25	37	47	50	48	42	34	28	25	33	4-5
314	21	21	27	34	44	50	55	53	45	35	29	24	36	30
315	27	26	30	35	42	47	51	50	45	37	31	29	38	4-5
316	18	23	23	29	32	45	49	47	45	26	26	25	32	1
317	25	26	30	36	44	50	55	52	46	35	31	28	38	10
318	25	27	32	39	48	54	57	55	48	40	33	28	40	30

140      |      Vol_VII-0146                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
319	31	30	33	36	45	53	52	52	45	38	32	31	41	1-2
320	31	33	32	41	46	50	52	52	48	42	36	33	41	10
321	29	28	31	34	40	47	50	50	46	39	33	31	38	4-5
331	38	38	40	44	49	54	57	56	51	44	39	38	46	14
334	33	32	31	35	40	47	49	50	46	40	36	34	39	21
337	36	38	42	46	51	57	57	57	54	47	41	38	47	4
Greenland and Iceland, Inland:
361	29	31	30	36	42	54	58	54	47	39	31	29	40	15
Europe, Coastal and Insular:
400	10	5	1	8	22	34	38	37	30	22	14	9	19	10
401	6	2	−4	5	20	32	36	36	27	18	10	6	16	1
406	26	25	28	34	40	49	55	54	46	37	31	27	37	20
407	39	36	39	44	56	67	74	67	57	47	42	41	51	10
408	23	23	26	31	38	44	51	51	46	36	30	26	35	20
412	30	30	33	39	46	52	58	58	51	41	35	30	42	20
414	26	26	30	35	43	51	57	56	47	37	31	27	39	20
415	12	11	23	35	43	52	57	55	47	34	22	14	34	18
420	32	33	36	42	48	53	60	59	52	44	37	33	44	20
421	28	28	35	43	54	65	69	66	58	45	37	29	46	26
423	19	18	25	36	48	62	66	63	52	39	29	21	40	33
424	26	26	32	43	55	63	71	66	57	45	37	31	46	20
425	13	13	24	37	47	55	62	59	50	38	25	16	36	18
426	19	20	28	42	55	63	68	64	54	44	31	22	42	18
428	9	11	22	36	47	57	64	59	49	36	23	12	35	18
429	7	8	20	33	44	53	61	57	47	33	19	8	33	18

141      |      Vol_VII-0147                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Inland:
450	14	15	23	35	44	57	62	59	48	33	24	17	36	22
451	5	8	23	33	43	55	63	59	48	32	17	8	33	20
454	29	32	37	44	52	57	63	61	53	44	35	30	45	20
455	27	29	36	46	59	70	71	66	58	46	36	29	48	29
456	17	19	27	39	50	60	64	59	51	37	28	20	39	20
457	22	22	32	44	56	65	72	66	55	42	33	26	45	20
458	19	18	29	40	51	62	70	64	54	39	29	23	41	20
Asia, Coastal and Insular:
500	11	9	1	10	23	33	40	40	35	28	18	11	22	7-8
501	−4	−3	−12	3	21	35	43	41	36	20	3	−3	15	5-6
502	−8	−5	−14	1	19	35	45	42	35	18	1	−6	14	4-5
503	−8	−5	13	0	19	33	40	37	32	18	3	−6	13	7-8
505	19	14	11	20	29	39	49	49	41	33	37	20	29	17
506	15	9	7	18	27	37	49	48	42	33	27	18	28	24
507	12	8	4	16	28	39	48	48	39	31	24	15	26	17
508	4	1	−4	10	24	33	44	45	38	27	17	7	20	5
509	−3	−1	−5	10	25	41	55	51	41	25	9	−2	20	6-7
510	0	2	−4	9	24	36	45	45	38	24	10	1	19	19
511	−28	−30	−23	1	20	37	47	47	35	10	−11	−22	7	2
513	−42	−29	−10	3	25	47	54	47	35	10	−17	−25	8	4
514	−16	−17	−13	−1	21	36	43	41	34	19	−4	−12	11	6
515	−35	−32	−21	−2	24	43	55	45	36	10	−14	−28	7	8
517	−4	−7	−2	8	22	37	42	40	32	21	7	1	16	11

142      |      Vol_VII-0148                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
518	12	7	6	19	28	39	51	50	43	32	25	14	27	26
519	8	4	2	17	28	40	51	49	42	30	20	8	25	22
522	−39	−31	−10	11	34	54	58	51	38	11	−10	−24	12	5
523	−13	−8	−4	4	25	39	46	42	33	23	6	−2	16	3
525	2	0	4	14	27	38	47	45	29	28	16	8	22	7
526	−10	−7	6	21	37	53	61	57	47	26	5	−5	24	10
527	−9	−5	1	10	31	44	55	52	41	25	5	−5	20	9
531	1	1	17	30	38	49	55	57	50	32	10	0	28	4
Asia, Inland:
551	..	−9	−19	5	31	47	59	46	41	18	0	..	..	0-1
553	−5	0	−1	13	27	45	61	55	44	24	4	−5	22	18
554	−18	−17	−3	9	24	45	63	57	41	18	−1	−14	17	4
556	−58	−40	−10	19	43	61	66	58	44	12	−30	−51	10	15
558	−42	−29	−8	12	35	57	62	53	41	15	−16	−34	12	12
559	−39	−28	−7	19	42	62	67	56	44	16	−13	−33	15	8
560	−3	4	15	30	42	57	67	59	49	31	9	−1	30	9
562	−9	1	16	29	44	57	67	63	51	31	9	−5	29	18
563	−19	−6	10	21	38	53	66	61	46	24	−3	−17	23	13
566	−26	−10	12	33	50	67	75	66	51	28	0	−24	27	11
567	−37	−18	6	25	45	63	69	53	47	22	−11	−35	20	11
568	−45	−28	1	26	50	68	73	67	50	22	−15	−38	19	17
570	−39	−22	−5	31	47	66	71	65	51	24	−6	−40	21	9
572	−17	−10	−2	12	33	55	63	60	43	20	1	−13	20	14
573	−2	9	23	39	56	66	71	67	56	37	18	4	37	15

143      |      Vol_VII-0149                                                                                                                  

Table XI . Mean daily maximum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
574	−5	6	23	38	52	66	73	69	55	35	15	−2	35	18
575	−14	0	22	38	53	69	74	69	53	33	11	−9	33	17
576	−20	−6	14	32	47	65	72	66	51	29	4	−15	28	18

144      |      Vol_VII-0150                                                                                                                  

Table XII . Mean daily minimum temperature (°F.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
004	22	22	20	24	27	33	38	39	35	29	24	22	28	7
006	−23	−25	−25	−15	10	27	31	30	22	4	−10	−22	1	5-6
007	−13	−16	−21	−7	12	27	30	31	28	16	−3	−12	6	5-6
Alaska, Coastal and Insular:
100	−23	−24	−22	−8	14	29	34	33	27	12	−6	−18	4	25-28
101	−7	−13	−16	7	19	30	38	38	35	23	4	−5	19	1
102	−14	−14	−15	7	25	38	46	46	37	21	2	−9	14	8-11
103	−9	−9	−12	4	22	27	41	40	36	26	6	−2	19	2
104	−4	−2	1	12	28	38	44	44	36	24	10	1	20	34-35
105	−7	−3	1	17	26	35	43	43	39	30	21	6	21	2-6
106	5	9	13	27	36	44	49	47	39	29	16	6	27	23-25
Alaska, Inland:
150	−10	−11	−15	5	27	42	49	40	32	15	−6	−12	11	3-4
151	−30	−31	−24	−16	13	34	42	35	26	2	−16	−22	5	1-2
152	−21	−17	−12	5	28	43	45	41	31	16	−9	−17	11	6-8
153	−27	−26	−12	8	32	47	51	45	33	13	−12	−28	10	19-21
154	−1	0	3	18	31	43	46	45	38	24	11	0	21	16-18
155	−21	−13	−6	12	32	44	46	42	32	17	−6	−16	14	34-40
156	−21	−17	−6	20	35	46	48	44	34	20	−4	−15	15	11
157	−23	−14	−6	12	31	43	46	41	31	17	−4	−19	13	27-33
Canada, Coastal and Insular:
204	−30	−30	−23	−12	8	28	35	34	25	8	−11	−24	1	5
205	−33	−33	−30	−18	9	31	35	33	19	0	−12	−29	−2	3

145      |      Vol_VII-0151                                                                                                                  

Table XII . Mean daily minimum temperature (°F.) (cont.) ✓

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec.
Canada, Coastal and Insular (cont.) :
206	−21	−22	−18	−6	18	32	41	36	24	12	−10	−21	5	3
210	−25	−33	−25	−13	9	28	35	32	21	3	−15	−23	0	5
211	−27	−34	−26	−13	12	30	36	35	26	9	−12	−23	1	10
212	−25	−30	−18	−9	15	30	36	34	29	11	−4	−18	4	3-4
213	−32	−35	−29	−11	12	30	36	36	28	10	−11	−27	1	16
214	−21	−24	−20	−11	12	28	33	33	28	16	−4	−15	5	5
215	−25	−20	−18	−5	15	30	37	36	28	11	−10	−21	5	9
216	−26	−27	−23	−8	15	32	42	40	31	12	−13	−22	4	13
217	−31	−33	−31	−14	6	31	41	38	28	5	−17	−30	−1	13
221	−33	−31	−23	−6	15	32	40	41	33	17	−9	−24	4	18
222	−33	−28	−23	−9	11	28	38	39	27	11	−7	−24	3	8
223	−19	−21	−12	2	20	30	35	36	31	23	4	−11	10	14
224	−21	−19	−10	3	22	33	38	37	32	21	6	−10	11	22
225	−18	−25	−19	−3	18	32	38	37	30	19	7	−13	9	3
226	−23	−24	−15	−1	18	31	39	39	32	20	−6	−15	9	12
227	−7	−7	3	11	24	30	33	34	32	26	17	3	17	15
228	−27	−25	−16	4	22	34	43	43	35	20	−2	−19	9	30
Canada, Inland:
250	−27	−24	−19	−2	23	40	47	42	32	16	−10	−24	8	20
251	−30	−23	−18	−1	24	42	49	43	32	13	−13	−23	8	28
252	−28	−20	−8	16	34	43	46	42	32	19	−4	−20	13	41
253	1	4	12	24	34	43	45	43	38	29	7	−1	23	6
254	−33	−29	−22	0	27	42	47	41	31	14	−14	−29	6	31

146      |      Vol_VII-0152                                                                                                                  

Table XII . Mean daily minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec.
Canada, Inland (cont.):
255	−14	9	2	22	34	44	47	43	36	26	0	−12	18	9
256	−27	−22	−14	7	29	42	47	43	33	18	−7	−22	11	30
257	−27	−22	−14	7	28	42	47	42	33	18	−7	−22	10	31
258	−27	−21	−11	14	33	45	50	46	36	21	−3	−20	14	42
259	−25	−21	−12	11	29	40	49	47	37	24	2	−16	14	45
260	−22	−23	−9	9	29	44	52	50	39	29	2	−17	15	…
261	−23	−16	−11	12	31	43	51	44	38	26	5	−15	15	24
262	−25	−20	−9	14	32	42	47	43	34	22	3	−17	14	26
263	−24	−19	−8	17	34	42	47	43	32	22	0	−17	14	30
Greenland and Iceland, Coastal and Insular:
302	−16	−21	−19	−10	16	30	36	33	21	8	−3	−17	5	3-4
304	−10	−12	−9	1	21	31	36	36	31	21	12	1	13	30
305	15	9	13	19	28	35	39	38	24	28	21	18	25	4-5
306	−3	−3	7	13	27	36	43	42	34	26	19	14	22	5
307	−33	−41	−32	−29	−1	24	29	26	12	−10	−19	−30	−9	5
308	−3	−5	−4	6	21	31	35	33	29	15	6	1	14	12
309	6	1	5	13	27	37	41	41	35	25	19	13	22	13
310	8	−2	−1	7	22	33	37	38	34	24	17	13	19	2-3
311	6	2	9	15	31	42	46	44	36	26	17	10	24	6
312	−3	−6	−5	8	26	40	41	38	30	17	6	−1	16	6-7
313	13	7	8	16	27	35	39	38	34	27	21	17	23	4-5
314	11	10	15	21	30	35	39	39	35	27	20	15	25	30
315	19	15	18	22	29	35	38	39	35	29	24	22	27	4-5

147      |      Vol_VII-0153                                                                                                                  

Table XII . Mean daily minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
316	8	10	12	15	22	33	36	34	34	17	16	14	21	1
317	14	14	17	20	30	36	39	38	34	26	21	18	26	10
318	14	13	17	25	34	39	42	41	36	29	22	16	27	30
319	19	19	21	26	33	38	39	40	35	28	22	19	29	1-2
320	21	22	22	29	34	36	37	39	37	33	27	24	30	10
321	22	21	23	26	31	36	38	38	36	31	26	24	29	4-5
331	27	29	30	34	39	44	48	46	41	35	31	29	36	14
334	23	22	21	25	31	37	40	41	37	32	27	24	30	21
336	25	25	26	31	38	43	47	46	41	32	29	28	34	10
337	26	29	31	35	39	43	46	46	43	36	32	29	36	4
340	32	33	29	35	40	47	49	49	44	38	36	33	39	4
Greenland and Iceland, Inland:
361	16	18	17	22	30	36	41	38	32	27	19	17	26	19
Europe, Coastal and Insular:
400	−6	−10	−14	−5	14	27	31	31	24	14	2	−5	9	10
401	−11	−13	−18	−9	11	26	30	29	19	7	−4	−9	5	1
406	21	20	23	27	33	41	46	46	40	32	26	22	31	20
407	3	3	6	13	26	32	41	39	32	22	14	8	23	10
408	18	17	20	25	32	39	45	45	41	31	26	21	30	20
412	24	24	25	30	38	44	51	50	43	35	30	25	35	20
414	22	20	22	27	35	42	47	46	40	31	27	23	32	20
415	4	1	8	21	31	40	46	44	37	27	14	10	23	18
420	27	28	29	34	40	45	51	51	45	37	32	28	37	20
421	13	12	17	26	35	45	51	49	42	33	24	16	30	26
423	4	2	7	19	32	44	50	47	39	28	17	6	25	33
424	17	15	22	31	41	49	57	54	47	36	30	22	35	20

148      |      Vol_VII-0154                                                                                                                  

Table XII . Mean daily minimum temperature ( ° F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
425	5	3	9	22	33	41	48	46	38	29	18	10	25	35
426	12	12	18	30	42	51	56	53	45	37	26	17	33	18
428	1	0	8	23	35	44	51	48	41	30	16	4	25	18
429	−1	−1	6	20	31	40	47	45	37	26	13	2	22	25
Europe, Inland:
450	−4	−4	1	13	28	40	45	42	33	21	8	−1	19	22
451	−6	−9	0	14	29	40	45	41	34	20	7	−3	18	20
454	23	24	26	33	40	46	52	50	43	35	29	25	36	20
455	12	12	17	27	37	48	51	49	42	32	23	15	30	29
456	0	−1	6	19	31	41	45	43	35	25	15	3	23	20
457	10	9	17	27	37	47	53	50	42	33	24	16	30	20
458	6	5	13	24	34	44	51	48	40	29	21	12	27	20
Asia, Coastal and Insular:
500	−3	−6	−12	−2	15	27	32	33	29	19	8	0	11	7-8
501	−20	−20	−27	−12	10	28	33	33	29	9	−10	−18	3	5-6
502	−25	−22	−28	−15	9	28	36	34	28	8	−13	−21	2	4-5
503	−23	−21	−26	−14	9	27	32	31	26	8	−9	−19	2	7-8
504	−28	−29	−26	−13	9	29	33	33	28	10	−14	−24	1	4
505	−2	−1	−1	6	19	30	29	40	34	23	10	2	17	30
506	1	−3	−8	4	19	30	37	39	36	27	18	6	17	24
507	−2	−5	−10	2	19	30	37	38	33	23	12	2	15	17
508	−14	−17	−21	−7	13	28	35	37	32	18	3	−9	8	5
509	−20	−19	−21	−7	14	31	40	40	32	14	−5	−19	7	6-7
510	−17	−14	−19	− 5	14	29	36	37	32	15	−4	−14	8	19

149      |      Vol_VII-0155                                                                                                                  

Table XII . Mean daily minimum temperature (°F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular, (cont.)
511	−33	−39	−36	−16	6	26	38	36	30	0	−21	−35	−4	2
512	−24	−26	−28	−9	14	32	41	41	32	7	−17	−26	3	7
513	−48	−37	−25	−14	12	36	42	37	26	0	−23	−32	−2	4
514	−29	−30	−26	−13	9	32	33	33	29	11	−14	−24	1	11
515	−40	−40	−31	−19	10	34	42	35	27	3	−18	−33	−2	14
517	−18	−20	−17	−6	11	29	32	32	26	13	−3	−11	6	11
518	−2	−8	−9	4	19	31	37	39	35	23	15	0	15	26
519	−9	−11	−13	2	13	31	37	39	35	20	6	−7	12	22
520	−21	−18	−8	5	22	38	49	46	37	20	−5	−17	12	18
521	−13	−13	−15	−1	16	30	41	43	36	24	0	−12	10	3
522	−43	−32	−26	−12	13	39	44	40	30	4	−16	−37	0	10
523	−27	−22	−17	−12	12	29	33	32	27	12	−7	−15	4	3
524	−20	−20	−18	−5	10	30	35	36	31	17	−1	−13	7	4
525	−12	−15	−9	2	17	31	37	36	32	20	5	−6	11	7
526	−19	−14	−7	6	26	38	44	43	32	15	−7	−18	12	5
527	−18	−15	−11	−5	18	34	46	43	32	18	1	−13	11	9
529	0	−5	−2	12	23	34	41	39	35	24	11	5	18	4
530	−6	−9	−7	6	19	32	38	37	31	21	8	−2	14	7
531	−16	−20	−1	10	24	38	45	45	36	16	−6	−15	13	4
Asia, Inland:
551	...	−17	−36	−12	15	39	48	37	31	2	−14	−26	…	0-1
552	−45	−40	−25	−6	17	38	46	42	29	6	−27	−39	0	12
553	−23	−18	−17	−5	14	35	46	42	34	14	−11	−21	7	18

150      |      Vol_VII-0156                                                                                                                  

Table XII . Mean daily minimum temperature ( ° F.) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.)
554	−29	−26	−17	−4	15	35	48	44	33	10	−13	−24	6	12
556	−65	−56	−39	−12	22	43	47	39	27	−4	−40	−58	−8	14
558	−49	−40	−29	−11	18	43	48	41	30	5	−23	−40	−1	9
559	−45	−39	−25	−2	27	47	48	38	27	4	−26	−34	2	3
560	−17	−12	−3	14	29	44	53	48	37	22	0	−15	17	10
561	−14	−7	0	19	47	47	56	51	41	24	5	−10	23	9
562	−20	−12	0	14	31	46	54	51	40	24	0	−15	18	18
563	−28	−19	−7	2	23	41	52	47	36	16	−13	−26	10	13
565	−65	−60	−49	−28	3	27	34	27	14	−23	−53	−63	−20	13
566	−28	−27	−11	11	31	47	55	49	37	16	−12	−34	11	9
567	−45	−32	−18	2	28	46	52	46	34	10	−22	−43	5	11
568	−54	−40	−20	6	32	48	54	48	34	11	−24	−46	4	17
570	−51	−41	−22	8	32	46	50	43	33	14	−18	−48	4	7
571	−6	−20	−36	−15	..	..	..	..	..	18	−23	−31	..	0-1
572	−29	−34	−19	−8	19	40	47	41	33	9	−10	−22	6	12
573	−13	−3	7	23	40	50	55	51	41	26	8	−6	23	13
574	−17	−11	2	18	34	49	55	51	39	26	5	−13	20	18
575	−28	−22	−6	15	32	45	51	48	35	20	−3	−22	14	17
576	−33	−26	−12	7	28	41	48	43	34	14	−11	−26	9	18

151      |      Vol_VII-0157                                                                                                                  

Table XIII. Mean number of days with minimum temperature ≤ 32° F. ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
003	31	28	31	30	31	30	25	19	29	31	30	31	346	1-2
004	28	29	30	27	26	13	*	1	9	22	26	29	238	..
006	31	28	31	30	31	27	20	27	27	31	30	31	343	5-6
007	31	28	31	30	31	29	23	22	24	31	30	31	340	5-6
Alaska, Coastal and Insular:
100	31	28	31	30	30	23	13	16	27	31	30	31	321	22
101	31	28	31	30	30	21	1	1	9	29	30	31	272	1-2
102	31	28	31	30	25	6	*	*	6	28	30	31	246	8-12
103	31	28	31	30	29	20	0	1	7	27	30	31	265	2
104	31	28	31	29	22	5	1	2	11	25	29	31	245	33
105	31	28	31	30	30	11	0	0	2	23	28	31	245	2-6
106	31	28	29	24	9	*	0	*	6	19	29	31	200	23
Alaska, Inland:
150	31	28	31	30	21	2	0	4	17	28	30	31	253	3-4
151	31	28	31	30	31	16	1	12	28	31	30	31	300	1-2
152	31	28	31	30	19	1	*	3	18	30	30	31	252	5-8
153	31	28	31	29	16	1	0	2	15	30	30	31	244	23
154	31	28	31	28	18	1	*	*	7	25	27	31	227	17
155	31	28	31	29	15	1	1	4	14	29	30	31	244	31-36
156	31	28	31	28	13	1	0	1	14	28	28	30	233	5-6
157	31	28	31	29	18	3	1	6	16	28	30	31	252	5-6

* Less than 0.5 day.

152      |      Vol_VII-0158                                                                                                                  

Table XIII. Mean number of days with minimum temperature ≤ 32° F. (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular:
222	30	28	31	30	31	24	1	2	23	31	30	31	292	2
224	30	28	31	30	29	15	1	0	18	31	30	31	273	1
Canada, Inland:
256	30	28	31	28	10	0	0	0	9	26	30	31	224	1-2
Greenland, Iceland, Coastal and Insular:
306	31	28	30	30	22	5	0	0	11	27	30	31	245	5
314	31	28	30	28	21	8	1	1	8	26	29	31	240	31
317	30	28	30	28	20	9	3	4	14	26	28	29	249	30
318	30	27	29	24	11	2	0	*	6	21	27	30	206	28
331	25	20	17	15	5	1	0	*	3	11	12	17	126	3-4
Europe, Coastal and Insular:
400	31	28	31	30	31	28	22	23	29	31	30	31	345	10
407	30	27	30	25	11	1	0	0	2	19	28	30	203	10
415	31	28	30	25	18	4	0	*	5	21	27	31	220	13
425	31	28	31	25	13	2	*	1	5	18	27	30	212	18
426	30	28	29	18	4	0	0	0	1	8	22	28	169	18
428	31	28	31	24	11	2	0	0	2	16	28	31	203	18
429	31	28	31	24	18	5	*	1	7	21	30	31	225	13
Europe, Inland:
451	31	28	31	28	19	3	*	3	11	25	29	31	239	55
453	31	28	31	27	17	3	*	3	13	22	27	30	232	10
Asia, Coastal and Insular:
500	31	28	31	30	31	29	18	11	22	31	30	31	323	7-8
501	31	28	31	30	31	23	13	15	21	31	30	31	315	5-6
503	31	28	31	30	31	28	20	25	27	31	30	31	343	7-8

* Less than 0.5 day.

153      |      Vol_VII-0159                                                                                                                  

Table XIII. Mean number of days with minimum temperature ≤ 32° F. (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
507	31	28	31	30	30	19	2	1	13	30	30	31	275	17
508	31	28	31	30	31	27	9	2	15	31	30	31	295	6
509	31	28	31	30	31	17	2	1	15	30	30	31	276	6-7
510	31	28	31	30	30	24	6	6	15	31	30	31	292	19
511	31	28	31	30	31	23	2	8	18	31	30	31	294	5
512	31	28	31	30	29	17	5	1	10	31	30	31	274	4
513	31	28	31	29	25	12	1	6	22	31	30	31	279	6
514	31	28	31	30	31	25	15	13	23	31	30	31	319	8
515	31	28	31	30	31	13	1	9	24	31	30	31	291	7
518	31	28	31	30	31	20	5	3	8	24	30	31	271	26
519	31	28	31	30	30	20	5	2	9	27	30	31	275	22
521	31	28	31	30	29	23	5	2	12	28	30	31	280	3
522	31	28	31	30	30	3	0	2	20	31	30	31	267	4
523	31	28	31	30	30	21	11	14	24	31	30	31	312	3
525	31	28	31	30	30	19	1	2	15	29	30	31	277	7
526	31	28	30	28	23	3	0	1	14	26	30	31	245	12
527	31	28	31	30	30	10	0	0	13	29	30	31	263	12
531	31	28	31	28	26	4	*	1	8	29	30	31	247	4
Asia, Inland:
551	31	28	31	30	29	0	0	0	12	31	30	31	253	1
552	31	28	31	30	29	7	0	2	20	31	30	31	270	14
553	31	28	31	30	29	10	*	2	9	30	30	31	261	18

* Less than 0.5 day.

154      |      Vol_VII-0160                                                                                                                  

Table XIII. Mean number of days with minimum temperature ≤ 32° F. (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
554	31	28	31	30	29	8	*	1	12	29	30	31	260	17
556	31	28	31	25	7	*	0	0	3	27	30	31	214	34
558	31	28	31	30	25	1	0	2	20	31	30	31	260	9
559	31	28	31	30	16	1	0	4	20	30	30	31	252	3
560	31	28	31	27	18	2	0	0	8	27	30	31	233	10
561	31	28	31	26	13	*	0	*	4	24	30	31	219	9
562	31	28	31	28	15	1	0	*	5	21	30	31	221	11
563	31	28	31	30	23	3	0	1	9	29	30	31	245	9
565	31	28	30	17	2	0	0	0	1	19	30	31	189	..
566	31	28	31	29	13	*	0	1	1	28	30	31	223	23
567	31	28	31	30	21	1	*	1	13	30	30	31	247	12
568	31	28	31	31	30	15	1	0	1	12	30	30	238	33
570	31	28	31	29	16	0	0	3	14	30	30	31	243	7
571	31	28	31	30	..	..	..	..	..	29	30	31	..	0-1
572	31	28	31	30	28	3	0	3	18	30	30	31	263	14
573	31	28	31	25	8	0	0	0	4	23	29	31	211	9
574	31	28	31	26	13	*	0	0	5	23	30	31	219	11
575	31	28	31	28	15	1	0	*	10	28	30	31	233	18
576	31	28	31	30	21	2	*	2	14	30	30	31	250	13

* Less than 0.5 day.

155      |      Vol_VII-0161                                                                                                                  

        Temperatures at moderate elevations in the Arctic differ

markedly from those recorded at lowland locations, primarily because

of the existence of the surface temperature inversion described in

previous sections. Temperatures at moderate elevations tend to

average considerably higher than those at lowland locations except

at inland points during summer when the surface inversion is non–

existent. At the highest Arctic elevations, however, temperatures

average lower than at most lowland locations, the differences being

most pronounced during the summer months. For example, over the

northern portion of the Greenland Ice Cap above 7,000 feet, July

temperatures may average between zero and 10° F. with extreme minima

as low as −20°. In winter, temperatures below −70° are probably

common. The lowest Greenland temperature on record, −84.6° F., was

obtained by the Wegener Expedition [ 54 ] at the Eismitte station

(70°54′ N.; 40°42′ W.; elevation 9,842 feet).

156      |      Vol_VII-0162                                                                                                                  

        Annual Variation of Temperature . - An examination of the annual

temperature curves for various locations reveals the existence of

three well-defined types, i.e., 1) maritime, 2) coastal, and 3)

continental.

        (1) Maritime . - The very small temperature variation during

June, July, and August produces a flat curve in the graph of the

monthly mean temperatures (see Fig. Table X ). There is a similar tendency

toward a flat curve during the winter months without pronounced

monthly minima in the mean temperature. There is a definite tendency,

however, for the seasonal minima to occur in late winter or early

spring. (Over the Polar Sea the average winter temperature is of

the order of −30° F.)

        (2) Coastal . - The coastal climate closely resembles the maritime,

the year consisting primarily of a long, cold winter and a short,

cool summer. There is a tendency toward a delayed seasonal maximum in

July or August. The mean summer temperature, while higher than over

the Arctic Ocean, remains below 50° F. The coldest month of the year

on the average is February, but in individual years the seasonal minima

may be delayed until March.

157      |      Vol_VII-0163                                                                                                                  

        (3) Arctic Continental . - The interior arctic climate is

characterized by very low winter temperatures with a pronounced

winter minimum in January or February. Summer temperatures are

relatively very high and show pronounced monthly maxima in July with

a tendency toward higher temperatures in June than in August. The

annual ranges of mean temperature for individual localities may

exceed 100°. (The absolute range in temperature at Verkhoyansk is

188°.)

        From the preceding discussion it is evident that the annual

range in temperature (difference in temperature between warmest and

coldest month) is directly related to topography and the degree of

maritime influence. Stations at high elevation exhibit a smaller

annual range in temperature than do low-level stations in the vicinity.

Maritime locations similarly show a smaller range in temperature than

do continental locations at the same latitude. In fact, as shown by

Fig. 46 , there is a close relation between the magnitude of the annual

range in mean temperature and distance from the seacoast.

158      |      Vol_VII-0164                                                                                                                  

        Non-Periodic Changes in Temperature . - The day-to-day variations in

temperature depend primarily upon the nearness of the region to the

major storm tracks and the temperature contracts between air masses

associated with passing frontal systems. Dynamic heating effects in

the lee of mountain ranges and the local effects of differences in

surface cover (water or ice versus land) are secondary causes of such

non-periodic variations. In general the magnitude of the interdiurnal

temperature variations throughout the Arctic is at a maximum in winter

and at a minimum in summer. The variations are at a minimum over the

open Arctic Ocean, where air-mass contrasts are lacking and dynamic

heating effects are exceptional. The variations are particularly

large in peripheral continental areas and in Alaska and coastal

Greenland, where considerable dynamic heating (chinook or foehn

effects) can occur in leeward locations during periods of strong

circulation.

159      |      Vol_VII-0165                                                                                                                  

        Diurnal Variation of Temperature . - The daily range in temperature

throughout the Arctic reflects the general characteristics of the

climatic picture. District insolational differences between day and

night, a dry-land cover, clear skies, low humidity, and an absence of

wind coupled with the presence of a shallow temperature inversion, are

all conducive to a large diurnal variation of temperature. Conversely,

long periods of daylight or darkness, snow, ice or water surface,

cloudy skies, and high surface winds coupled with a deep temperature fig. 47 here

inversion (or no inversion), are all conducive to a small diurnal range

in temperature. In the period of winter darkness there are almost no

daily fluctuations in temperature on land; over the Arctic Ocean in

summer fluctuations are negligible since the temperature remains close

to freezing. In most maritime and coastal Arctic regions the

combination of circumstances, is such as to produce the maximum variation

in April. At this time there exists only a thin layer of cold air

below the inversion level, and it is only this layer that shares in

the daily temperature fluctuations. At the same time, the increased

insolation has begun to exert its diurnal effect. At inland locations

160      |      Vol_VII-0166                                                                                                                  
farther south in the Arctic there is a tendency toward a secondary

maximum of variation in summer, after the land is free from snow and

the surface inversion has completely disappeared.

161      |      Vol_VII-0167                                                                                                                  

        Geographic Distribution of Temperature . - It is beyond the scope of

the present chapter to discuss in detail the regional and geographical

differences in temperature over the Arctic. Much of the geographical

distribution can be inferred from what has already been discussed;

additional generalized information will be found in the figures,

while more detailed local information is presented in the tables.

        The general features of the Arctic temperature distribution are,

of course, determined by the general circulation of the atmosphere

in its relation to latitude, season, and the distribution of land

and sea. Of more specialized interest are the details of the circu–

lation in relation to major ocean currents and to important orographic

features.

162      |      Vol_VII-0168                                                                                                                  

        It is clear from the isothermal chart for January (see Figure 44 )

that the deviations of the trend of isotherms from parallelism with

the latitude circles is closely related to the location of the

principal land and water masses. It can be noted that the low

temperature isotherms bend Equatorward over the continental land masses

and Greenland and bend Poleward over the Bering and Norweigian Seas

and Davis Strait where there is significant Poleward transport of

warm water. The effects of the Gulf Stream system can be noted in

the relatively high temperatures over European Arctic lands. The

effects of the transport of warm water through Bering Straits

similarly can be noted by comparing the higher temperatures along the

north coasts of Alaska and Siberia near the Straits with the relatively

low temperatures that exist at the same time farther westward along

the coasts of the East Siberian Sea and eastward over the Beaufort Sea

region.

163      |      Vol_VII-0169                                                                                                                  

        A good example of the influence of a major topographic feature

on the temperature distribution is given by the steep temperature

gradient that can be noted along the southern Alaska coast on the

January isothermal chart. Here the mountain ranges close to the

coast act effectively as barriers between the stable Arctic air masses

to the north and east and the relatively warm maritime air over the

Gulf of Alaska. Those Arctic air masses which do arrive at the coast

after moving southward over the barrier have had much of their Arctic

“sting” removed through dynamical heating resulting from descent to

sea level pressures.

        In contrast to the winter situation, the isotherms on the summer

chart (see Fig. 45 ) are arranged more nearly parallel to the latitude

circles and the temperature gradients are less steep. If the low

temperatures found at higher altitudes on the Greenland Ice Cap and

elsewhere are disregarded, and only sea level temperature are considered,

it may be seen that in this season the cold pole of the Northern

Hemisphere actually exists over the Polar Sea.

164      |      Vol_VII-0170                                                                                                                  

       

PRECIPITATION, SNOWFALL, THUNDERSTORMS

        Before entering into a detailed discussion of precipitation

characteristics of Arctic regions, it should be pointed out that observa–

tions regarding precipitation are, perhaps, the most unsatisfactory of

all Arctic meteorological records. During snowstorms it is often difficult

to determine whether snow is falling or is being whirled up from the surface.

The “dry” Arctic snow usually begins to drift at wind speeds of from 10 to

12 mph, and with high wind speeds the air is as thick with snow as would be

expected during a heavy snowstorm in extra-Arctic regions. Under these

circumstances, either driven snow will be blown into the recording gauge

or newly fallen snow will be blown out of the gauge. Over the Greenland

Ice Cap, observational difficulties are even more extreme because the

heavier precipitation is almost i nvariably associated with strong winds.

Nor can the accretion of snow cover be used as a measure of the actual

amounts of precipitation because of excessive drifting of surface snow

and concurrent ablation through evaporation or melting. The observational

difficulties known to exist in the Arctic caused the earlier permanent

meteorological stations to give up all attempts at direct measurement of

precipitation [ 42 ] .

165      |      Vol_VII-0171                                                                                                                  

        Another complication arises in attempting to record the number of days

with measureable precipitation. Because of the exceedingly small moisture

concentration possible at very low temperatures (see Table II ), the falling

snow during cold weather is very “fine” and there are many occasions when

precipitation is so slight as to defy measurement. The records for one

April at Goose Fjord, Ellesmere Island, for example, indicated that, while

precipitation fell on 11 days during the month, the precipitation amounts

for the 11 days totaled only 0.2 mm (less than 0.01 inch). At North

American Arctic stations a day with precipitation is considered as a

24-hour period during which 0.01 inch or more of rain or snow (melted) is

collected. Elsewhere a value of 0.1 mm is usually considered the limiting

amount, although some stations have recorded all days when precipitation

occurred, regardless of amount. These limitations of the data should be

kept in mind when attempting to make regional comparisons.

166      |      Vol_VII-0172                                                                                                                  

        Precipitation over most of the Arctic is very light and the annual

amounts are so small that the region would be described as desert or

semi-desert were it located in southerly latitudes. Available data

indicate that over much of the Polar Basin the annual precipitation

amounts average less than 10 inches, while over the Siberian-American

portion of the Arctic Ocean and the whole northern part of the Canadian

Archipelago, the amounts are generally of the order of 4 inches or less

[ 42 ] . The greatest portion of the annual precipitation falls in the

summer and as rain; snow, however, appears in every month, and sleet,

occasionally. Farther southward, near the regions of most frequent

frontal activity around the peripheral portions of the Arctic, the annual

precipitation amounts are more respectable. Some points in Greenland and

the European Arctic, for example, present an annual precipitation in excess

of 40 inches.

167      |      Vol_VII-0173                                                                                                                  

        Form of Precipitation . - Snow is the most frequent form of precipitation

but, as mentioned previously, it does not always account for the major

part of the measured quantity of precipitation. Over much of the Polar

Basin snow may be expected during all months of the year, and in the far

north the number of days with snow may exceed the number of days with rain

even during June. During July and August rain is normally the most

frequent form of precipitation in these regions, but by September snow

again predominates. On the other hand, many high latitude stations have

recorded rain during winter. During January 1937, for example, Domashnii

Ostrov (at approximately 80° N.) recorded 4 days with liquid precipitation

[ 45 ] . Strictly speaking, the precipitation in nearly all of these

instances is more properly described as drizzle than as rain. The situa–

tions occur with temperatures which are unseasonably high but not always

above freezing. On February 10, 1939, for example, drizzle was observed

at Yugorsky Shar (on the Kara Sea) although the maximum temperature for

the date was −4° F. [ 45 ] .

168      |      Vol_VII-0174                                                                                                                  

        Along the immediate coasts in the more southerly latitudes and in

some insular locations, rain is by far most frequent form of

precipitation, and even in January and February sleet or rain is common.

        Days with precipitation occurring simultaneously in the forms of

rain and snow are comparatively rare over the true Arctic. Such days,

when they do occur, are characterized by unstable weather conditions and

are observed primarily in the transitional seasons of spring and autumn.

However, in the far north such occurrences are most frequent in summer,

while in the more southerly portions of the Arctic they are most frequent

in winter.

        Sleet, which is precipitation in the form of small grains of ice and

which occurs when rain falls through a significant layer of air below 32° F.,

is of frequent occurrence along portions of the coasts of the Arctic Ocean.

It occurs most frequently during winter although it may be observed during

any month except July and August. The phenomenon appears to be particularly

prevalent in the coastal Kara Sea area. Ostrov Nedeneniia, for example,

records an average of 104 days a year with sleet, Gyao-Youro, 74 days, and

Russkii Ostrov and Mys Chelyuskin, each 66 days [ 45 ] .

169      |      Vol_VII-0175                                                                                                                  

        Rime, a deposit of granular ice which is caused by the impingement

and freezing (without shattering) of sub-cooled for droplets on solid

surfaces and objects exposed to fog-laden winds, is observed over most

northern Arctic coastal regions throughout the year. In some locations

the phenomenon may occur on as many as 60 days per year (as at Tikaya

Bukhta) but averages of 15 to 20 days are probably more typical. Upon

occasion the rough deposit of ice may accumulate to rather impressive

amounts; Wiese [ 56 ] recorded 3 cm (1.2 inches) of accumulated rime

during a 24-hour period in March at a point along the coast of Novoya

Zemlya.

170      |      Vol_VII-0176                                                                                                                  

        Hoarfrost is another form of precipitation of importance in the

Arctic, particularly in region where the total precipitation is low.

It is caused through direct condensation of atmospheric water vapor on

solid objects which are below freezing or on snow or ice surfaces. It

differs from rime in having a crystalline rather than a granular structure.

It also has a considerably lesser rate of accumulation. According to

measurements on the Maud Expedition, hoarfrost accounted for 15 percent

of the total precipitation collected over the Polar Sea. In general, the

amount of hoarfrost increases with increasing wind speed providing the

relative humidity of the air (with respect to ice) is greater than 100

percent. Over the Arctic pack-ice, however, the probability that hoarfrost

will occur decreases with increasing wind speed in agreement with the fact

that the humidity over the ice tends to decrease at higher wind velocities

[ 43 ] . The probability of hoarfrost increased regularly with decreasing

temperature but the rate of accretion also decreases because of lessened

water vapor, and at very low temperatures the amount become too small to

measure.

171      |      Vol_VII-0177                                                                                                                  

        Conditions are particularly favorable for hoarfrost formation over

the Greenland Ice Cap. Since the strong winds over the inland ice bring

large volumes of supersaturated air into surface contact, all conditions

are favorable for an increase in the deposit of crystals on the ice.

However, calculations by Sverdrup indicate that the total annual amounts

do not exceed 1.25 inches of water a year - a finding that does not permit

the conclusion that frost formation on the interior Ice Cap furnishes the

principal part of the ice accretion.

        Still another form of precipitation fairly common in the Arctic is

one which is variously referred to as glaze, glaze ice, freezing rain or

simply as “ice storm”. It occurs when rain (or drizzle) falls on objects

or surfaces which are below freezing. The raindrops shatter on impact and

immediately freeze, forming a layer of clear ice on all objects exposed to

the rain. Glaze differs from rime and hoarfrost in presenting a clear,

glassy appearance instead of a rough and opaque granular or crystalline

structure. It becomes a phenomenon of considerable practical concern when

the deposits on telephone lines, antenna e , poles, or other structural objects

are heavy enough to cause structural failure.

172      |      Vol_VII-0178                                                                                                                  

        Glaze is formed most frequently with surface air temperatures

between the limits of about 23° and 32° F. Under such conditions

temperatures a short distance over the surface are frequently above

freezing (see pages ) , a requisite for rainfall formation. At air

temperatures much above 32° F. there is little opportunity for surface

freezing; at temperatures much below 20° the precipitation is almost

invariably snow although there are exceptions. (See page .)

Glaze occurs most frequently during spring and autumn except in the far

northern portions of the Arctic where summer is the season of maximum

frequency. At most coastal stations on the Polar Sea the number of days

with glaze is usually less than 10 but in some years a few localities

may record as many as 45 such days [ 45 ] .

173      |      Vol_VII-0179                                                                                                                  

        From the standpoint of aviation activities in the Arctic, the

formation of rime, hoarfrost, and glaze is of considerable practical

concern. Any amount of frost or glassy ice on wings or stabilizers

of aircraft, however small it may be, should be removed before take-off

is attempted. A take-off into a fog of sub-cooled water droplets

(rime-forming condition) or into a rain at sub-zero temperatures (glaze

situation) can be particularly dangerous. Several cases of severe

prop-icing have been reported when running-up the engines in sub-cooled

fog, and severe wing icing has occurred not only during take-offs and

landings but even during taxiing for take-offs [ 33 ] . The rapidity with

which glaze ice or rime can accumulate on aircraft should never by

underestimated by those flying under Arctic conditions.

174      |      Vol_VII-0180                                                                                                                  

        Annual Variation of Precipitation . - Data from the Arctic Ocean indicate

that the probability of precipitation has a double annual period with

maxim in spring and autumn, a principal minimum in winter and a secondary

minimum in summer. This march of precipitation probability corresponds

to the annual variation of cloudiness at the coast but not to the varia–

tion of cloudiness over the pack-ice [ 43 ] . This lack of association table XIV and XV here

merely reflects the fact that the stratus clouds characteristic of the

pack-ice are largely the result of local processes. They are in no way

related to the circulations forming a part of cyclonic systems which affect

the Arctic. Conversely, it must be assumed that coastal cloudiness is

essentially frontal phenomenon.

        Sverdrup (loc. cit.) found that May has the greatest number of days

with precipitation and the midwinter months the smallest. The contrast

between summer winter precipitation frequencies appears to be greater

over the Polar Sea than in coastal areas.

175      |      Vol_VII-0181                                                                                                                  

Table XIV . Mean number of days with precipitation ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	c	11	11	13	13	20	20	21	19	22	14	9	9	180	2
003	c	2	8	6	6	19	17	14	17	16	13	6	6	130	2
004	c	19	19	15	15	11	9	11	9	15	15	17	18	174	…
005	c	14	14	14	10	12	7	7	8	14	13	14	13	139	…
006	e	13	8	7	7	6	8	11	14	12	10	9	9	114	24
007	e	18	14	13	11	7	11	13	16	20	17	13	16	169	21
Alaska, Coastal and Insular:
100	c	3	3	2	3	2	3	8	8	8	7	4	3	54	22-25
101	c	6	5	5	9	6	4	9	9	14	17	4	6	94	1-2
102	c	5	2	3	2	1	2	7	7	5	4	3	4	45	6-10
103	c	3	13	6	5	15	8	12	16	16	13	2	3	112	2-3
104	c	9	7	8	8	8	9	14	17	14	10	8	9	121	23-36
105	c	11	11	8	16	7	6	12	10	13	13	17	18	156	2-5
106	c	7	6	5	4	5	6	10	15	14	12	7	6	97	23-25
Alaska, Inland:
150	c	14	12	18	11	14	15	14	13	18	20	12	17	178	2-5
151	c	..	8	21	18	15	22	19	25	23	26	21	28	…	0-2
152	c	5	5	4	3	4	7	10	7	8	6	5	4	68	5-8
153	c	5	4	3	2	3	6	7	9	6	5	5	3	58	20-27
154	c	9	6	8	7	8	11	16	20	18	10	8	9	130	17-19
155	c	8	7	7	4	7	10	14	15	13	9	8	7	109	30-31
156	c	10	6	6	4	9	10	13	15	10	11	10	7	111	11

c - 0.01 inch or more. e - Not defined.

176      |      Vol_VII-0182                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Alaska, Inland (cont.):
157	c	7	5	5	5	8	11	13	13	11	8	7	7	100	33-36
Canada, Coastal and Insular:
204	c	5	3	5	4	6	7	6	8	7	9	8	4	72	4-5
206	c	6	6	7	6	8	5	8	14	10	9	6	2	87	5
208	a	4	8	19	9	19	9	6	..	17	24	6	2	…	1
210	c	6	3	4	4	7	6	6	14	10	8	4	5	77	5
211	c	6	3	6	6	6	6	7	10	8	8	6	5	77	7
213	c	3	1	2	2	2	4	6	6	4	5	3	3	41	4-5
214	c	4	1	2	1	5	4	5	5	8	15	6	3	59	2-3
216	c	8	6	7	6	7	6	10	15	10	10	10	8	103	10
217	c	3	3	6	4	5	6	10	13	10	6	5	3	74	6
221	c	6	5	6	9	8	7	12	11	12	9	9	8	102	10
223	c	6	6	6	11	12	10	10	11	11	13	15	11	122	10
224	c	5	5	6	6	8	9	9	8	8	10	9	7	91	4-7
226	c	6	3	4	7	5	7	9	9	7	8	8	7	81	6-8
227	c	10	8	11	9	12	11	12	11	14	14	15	14	141	10
228	c	5	6	6	6	7	9	10	12	11	12	9	8	101	10
Canada, Inland:
250	c	4	5	4	4	4	5	9	10	10	8	8	5	76	10
252	c	8	6	8	5	9	11	13	14	11	11	11	10	117	10
253	c	7	7	8	3	5	9	13	11	10	11	12	8	104	5
254	c	7	7	8	6	8	6	9	14	10	12	12	7	106	10
255	c	9	7	5	7	9	12	12	14	12	12	15	13	127	8

a - Trace or more. c - 0.01 inch or more.

177      |      Vol_VII-0183                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland (cont.):
257	c	6	7	7	6	7	8	10	12	8	8	8	6	93	10
258	c	6	5	8	5	7	7	10	9	6	7	8	8	86	10
259	c	8	8	9	5	8	7	9	9	9	10	12	9	103	10
260	c	8	8	8	5	6	6	11	7	9	10	8	9	99	…
262	e	11	8	9	5	7	6	11	7	9	11	8	11	103	…
Greenland and Iceland, Coastal and Insular
302	a	17	10	11	14	13	13	16	12	15	17	17	15	170	3
303	b	18	10	11	6	9	6	3	6	6	8	12	14	107	…
304	b	4	4	6	5	7	6	7	8	10	11	10	6	84	50
305	e	13	14	15	12	14	6	10	10	18	18	15	17	162	3
307	d	7	4	5	3	4	3	4	5	5	4	6	6	56	5
308	b	9	8	7	4	..	4	5	1	7	6	5	6	…	9
309	b	8	8	7	8	5	5	7	8	9	11	12	11	100	13
310	c	9	12	16	9	8	5	10	7	20	11	16	13	139	2
312	c	4	4	3	2	3	5	11	8	7	6	6	5	55	7
313	c	14	14	14	12	14	7	11	5	17	12	12	12	146	5
314	c	8	8	7	6	7	8	8	10	11	11	9	6	97	45
317	b	14	12	12	10	10	9	8	9	10	13	11	12	131	29
318	b	12	10	12	10	10	10	9	10	13	12	12	11	131	45
321	c	19	17	18	17	13	14	14	13	12	16	14	19	187	2-3
330	e	21	20	19	18	16	17	14	20	22	20	19	20	226	11

a - Trace or more b - 0.004 inch or more. c - 0.01 inch or more. d - 0.04 inch or more. e - Not defined.

178      |      Vol_VII-0184                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
331	b	21	19	18	16	14	14	14	19	19	17	19	21	211	16
333	e	21	17	18	15	17	16	15	21	21	19	20	20	220	11
334	a	10	10	10	9	8	6	8	10	11	12	12	11	117	…
335	e	14	11	12	12	9	10	13	14	13	17	14	14	153	15
336	e	11	12	11	9	5	7	10	12	12	13	11	12	125	11
337	e	18	16	17	16	17	15	17	19	23	19	18	21	216	11
338	b	13	13	13	10	10	11	8	11	14	12	14	14	142	15
339	e	14	10	12	11	8	9	10	12	13	13	10	11	133	7
340	c	19	16	16	15	13	11	11	16	16	18	16	18	186	14
341	e	19	13	18	13	13	10	15	13	16	14	18	21	183	8
Greenland and Iceland, Inland:
350	e	7	4	..	..	..	..	..	..	..	11	13	10	…	…
351	e	19	13	18	21	19	15	20	17	15	18	15	13	203	1
360	e	17	15	15	15	17	14	15	21	18	17	14	16	194	7
361	e	14	10	11	10	5	7	12	13	10	14	10	10	126	11
Europe, Coastal and Insular:
400	e	13	14	11	10	10	9	12	15	13	16	13	12	147	1
401	e	9	7	8	9	12	12	13	18	18	15	13	9	144	2
403	c	12	12	12	10	7	6	6	6	9	11	11	12	114	…
406	b	14	16	15	13	13	12	12	10	16	17	16	13	167	12
408	b	14	16	12	11	10	9	10	11	15	15	16	15	155	…

a - Trace or more b - 0.004 inch or more. c - 0.01 inch or more. e - Not defined.

179      |      Vol_VII-0185                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
411	d	20	19	15	13	14	12	12	13	19	20	20	16	194	50
412	b	12	11	13	11	11	11	12	13	17	15	16	13	155	20
414	b	16	15	13	13	11	12	11	13	17	16	17	14	170	20
415	c	13	13	12	13	16	15	15	16	18	17	17	14	179	25
417	e	25	21	19	18	18	14	11	16	22	22	22	23	231	…
420	b	15	11	13	11	12	11	12	13	15	15	15	14	157	20
421	b	12	11	12	9	11	10	12	13	11	14	12	15	142	36
422	b	15	13	12	10	11	10	13	17	17	18	16	15	166	30
423	b	15	12	12	9	9	9	12	12	12	14	14	14	144	27
424	b	19	16	14	13	12	13	12	16	15	17	18	19	184	36
425	c	14	13	11	12	13	12	16	16	16	16	16	17	170	18
426	a	22	19	14	12	14	13	16	19	16	16	19	22	203	18
427	a	13	13	11	11	11	10	11	13	16	16	15	15	155	25
428	a	16	15	13	11	12	12	12	14	15	17	17	17	171	25
429	b	8	7	5	7	10	9	11	12	14	11	10	7	112	17
Europe, Inland:
450	b	13	11	10	8	10	10	16	16	13	12	13	12	144	32
451	d	5	5	6	5	6	8	9	9	7	8	8	6	82	…
452	c	5	5	5	7	8	9	10	12	8	9	7	6	91	…
453	b	19	16	15	14	13	15	15	17	17	18	18	18	195	30

a - Trace or more b - 0.004 inch or more. c - 0.01 inch or more. d - 0.04 inch or more. e - Not defined.

180      |      Vol_VII-0186                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Inland (cont.):
454	c	21	17	17	17	20	19	21	23	22	20	19	18	234	31
455	b	12	10	10	9	12	12	14	15	12	13	12	13	144	38
456	c	14	12	13	10	10	11	15	18	13	15	14	15	160	26
457	b	19	16	15	14	14	16	15	18	16	19	19	19	200	36
458	b	19	17	15	14	14	15	15	17	17	19	19	20	201	35
Asia, Coastal and Insular:
500	e	8	7	9	10	11	12	13	17	18	14	10	9	138	3
501	e	13	9	7	9	11	13	14	18	19	16	10	12	151	18
502	e	14	14	9	13	16	16	19	24	23	17	11	11	186	19
503	e	8	9	6	4	6	10	12	14	13	13	12	10	116	22
505	e	17	15	13	12	13	12	11	15	18	17	16	14	173	14
506	c	14	12	11	11	9	9	12	13	15	17	14	14	151	18
507	e	12	10	12	9	8	8	9	11	16	16	13	14	134	6
508	e	19	18	15	13	11	10	11	19	21	22	18	16	192	13
509	e	21	16	15	13	14	15	12	20	22	23	18	16	204	15
510	e	13	12	12	10	9	13	12	20	20	18	15	14	169	17
511	c	4	6	1	2	10	8	2	8	12	4	11	7	75	2
512	c	9	9	7	5	4	10	11	12	14	12	9	6	108	3
513	c	8	12	9	9	8	12	14	14	17	13	12	12	141	7
514	f	0	0	*	0	*	2	2	2	1	*	0	0	8	11

b - 0.004 inch or more. c - 0.01 inch or more. e - Not defined. f - 0.08 inch or more. * - Less than 0.5 day.

181      |      Vol_VII-0187                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
515	c	4	6	5	4	11	13	12	13	13	9	9	6	107	9
517	b	8	7	7	6	8	8	9	12	10	10	7	7	99	11
518	e	14	11	13	11	12	12	11	16	21	19	17	17	175	9
519	e	13	11	9	11	13	12	11	17	21	19	16	14	167	12
520	d	8	8	7	5	8	8	10	11	11	10	10	10	107	…
521	e	15	11	12	12	15	14	10	16	18	18	15	14	171	25
522	b	8	10	8	8	6	6	13	14	14	14	12	9	120	5-8
523	c	6	10	11	9	8	6	10	14	18	12	9	7	120	3
525	c	8	7	8	8	5	4	10	12	14	12	12	10	110	8
526	b	8	8	9	6	7	9	10	12	9	10	9	8	106	16
527	b	10	10	9	7	9	9	11	12	10	8	10	9	115	14
531	c	3	3	6	4	7	11	9	12	13	10	7	4	88	4
Asia, Inland:
550	e	14	13	13	13	13	15	16	20	17	20	15	15	185	28
551	c	8	12	13	14	14	13	15	16	13	20	11	15	167	3
552	c	12	10	11	8	7	10	12	12	13	18	13	12	138	13
553	e	15	13	13	10	12	14	12	17	19	20	16	14	173	26
554	b	14	13	11	12	10	12	12	13	18	17	16	14	162	18
556	b	5	5	4	4	4	7	8	8	6	7	8	7	73	30
557	c	8	7	6	6	4	7	11	12	9	4	9	6	99	5
558	c	8	9	7	5	6	8	10	11	12	11	11	10	107	5

b - 0.004 inch or more. c - 0.01 inch or more. d - 0.04 inch or more. e - Not defined.

182      |      Vol_VII-0188                                                                                                                  

Table XIV . Mean number of days with precipitation (cont.) ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
559	c	17	15	10	6	7	10	14	15	13	16	18	19	161	10
560	c	8	7	9	9	11	13	12	12	11	13	11	11	127	8
561	c	14	10	10	7	11	12	11	15	15	16	17	15	154	10
562	c	14	11	11	7	14	15	12	14	16	15	16	15	159	10
563	c	12	12	12	11	12	13	12	14	17	19	16	14	164	42
565	e	14	12	9	8	10	9	6	7	9	15	19	16	134	12
566	b	8	8	7	7	9	11	9	10	10	10	11	10	110	26
567	c	11	10	9	7	8	9	10	9	11	14	14	11	122	25
568	b	9	8	5	5	6	8	9	10	9	12	12	10	104	31
569	e	3	6	4	5	12	15	8	14	7	10	6	4	94	1
570	e	6	5	5	7	7	8	8	11	9	9	6	4	85	18
572	e	8	8	8	6	6	7	12	12	8	10	11	9	105	21
573	c	8	7	7	6	8	10	10	11	10	11	10	10	107	18
574	c	11	9	9	10	12	14	12	14	13	16	15	13	146	21
575	c	16	15	15	11	12	13	12	13	14	16	19	17	173	10
576	b	17	14	14	11	11	12	14	12	14	16	21	19	176	13
577	e	16	13	12	12	12	13	13	14	13	18	17	16	167	…

b - 0.004 inch or more. c - 0.01 inch or more. e - Not defined.

183      |      Vol_VII-0189                                                                                                                  

Table XV . Mean precipitation (inches) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
003	0.1	0.3	0.2	0.1	0.3	0.4	0.7	1.0	0.3	0.2	0.2	0.2	3.9	2
004	1.5	1.7	1.1	0.9	0.5	0.6	0.8	1.1	2.5	2.2	1.4	1.0	15.3	7
005	1.1	1.4	1.2	0.7	0.7	0.8	0.7	0.9	1.6	1.4	1.0	1.1	12.6	15
006	0.2	0.2	0.1	0.1	0.2	0.3	1.1	0.5	0.6	0.2	0.1	0.2	3.7	24
007	0.2	0.2	0.1	0.1	*	0.7	1.1	1.0	0.3	0.2	0.1	0.2	4.5	21
Alaska, Coastal and Insular:
100	0.2	0.2	0.1	0.1	0.1	0.3	0.9	0.7	0.5	0.6	0.3	0.3	4.2	25-27
101	0.1	0.1	0.2	0.1	0.1	0.1	0.3	0.3	0.4	0.5	*	0.4	2.6	…
102	0.7	0.2	0.2	0.4	0.1	0.4	1.3	1.1	0.6	0.5	0.3	0.3	6.1	11
103	1.3	1.3	0.9	0.6	0.5	1.0	1.4	2.5	2.6	1.1	0.6	1.3	14.9	3-6
104	1.1	0.8	0.8	0.7	0.6	1.1	2.5	3.2	2.7	1.6	1.0	1.1	17.3	35-37
105	1.1	1.5	0.5	1.4	0.6	0.4	1.5	1.4	2.4	2.1	1.0	1.0	14.8	2-5
106	0.8	0.7	0.6	0.4	0.5	0.7	1.6	2.6	2.6	2.2	1.0	0.9	14.6	24-26
Alaska, Inland:
150	*	*	1.0	1.7	1.0	1.6	2.6	5.0	3.7	1.5	*	*	18.8	2-5
151	…	…	…	*	*	1.0	1.0	2.7	*	1.0	*	*	…	1-2
152	0.6	0.2	0.2	0.5	0.6	0.7	1.5	0.9	1.8	0.6	0.6	0.6	8.2	6-8
153	0.4	0.4	0.3	0.3	0.5	0.8	1.1	1.2	0.6	0.6	0.4	0.3	6.8	21-27
154	1.0	0.6	0.8	0.5	0.7	1.1	2.4	3.9	3.3	1.6	1.0	0.8	17.7	18-19
155	0.8	0.7	0.6	0.2	0.8	1.2	2.4	2.5	1.7	1.1	0.7	0.6	13.3	36-43
156	1.0	0.5	0.7	0.3	0.6	1.4	1.9	2.0	1.3	0.8	0.7	0.6	11.7	35-38
157	0.5	0.4	0.4	0.4	0.8	1.5	1.8	2.0	1.3	0.8	0.5	0.4	10.7	33-36
Canada, Coastal and Insular:
201	0.4	0.1	0.4	0.2	0.4	0.2	0.7	0.5	0.4	0.2	0.2	0.3	3.9	3

*Less than 0.05 inch.

184      |      Vol_VII-0190                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
204	0.4	0.2	0.5	0.5	0.5	0.8	0.9	1.8	0.5	1.4	0.8	0.2	8.6	5
208	0.9	0.8	0.9	0.4	1.5	…	…	…	0.9	0.4	0.3	0.2	…	0-1
211	0.4	0.2	0.4	0.3	0.6	0.6	0.6	1.5	0.7	0.7	0.4	0.4	6.8	10
212	0.1	0.2	0.4	0.2	0.4	1.0	1.1	1.8	1.5	1.7	0.7	0.2	8.6	4
213	0.2	0.1	0.1	0.3	0.4	0.4	1.3	1.0	0.9	0.6	0.5	0.4	6.2	5
214	0.2	0.2	0.1	*	0.4	0.2	0.9	1.2	0.4	1.1	0.8	0.1	5.7	5
215	0.2	…	…	…	0.5	1.2	0.8	1.1	0.6	0.8	0.1	0.3	…	0-6
216	0.6	0.4	0.6	0.8	0.6	0.8	1.3	1.9	1.0	1.2	0.8	0.6	10.7	13
217	0.7	…	…	…	…	…	2.0	1.2	0.9	…	0.1	0.1	…	0-1
220	0.3	0.3	0.6	0.5	0.7	2.3	3.4	1.2	2.2	0.6	0.9	0.7	13.6	4
221	0.4	0.5	0.5	0.9	0.7	1.0	1.8	1.5	1.4	1.3	0.8	0.9	10.9	20
222	0.2	0.4	0.2	0.5	0.6	0.5	1.5	1.7	1.5	0.7	0.5	0.1	8.5	6
223	0.6	0.6	0.6	1.1	0.8	1.0	1.7	1.9	1.7	1.3	1.5	0.8	13.6	14
224	0.7	0.7	0.6	1.0	1.3	1.5	1.8	1.7	1.5	1.5	1.2	0.5	14.1	6
225	0.3	0.3	0.2	0.5	1.2	0.6	1.6	1.4	1.7	0.7	0.4	0.5	9.5	3½
226	0.9	1.5	1.0	1.8	0.7	1.1	1.2	1.9	1.0	1.6	2.2	2.1	17.0	7
227	1.0	1.1	1.0	0.9	1.3	1.3	1.9	1.5	2.3	1.3	1.2	1.0	16.0	15
228	0.5	0.6	0.9	0.9	0.9	1.8	2.2	2.7	2.3	1.4	1.0	0.7	16.0	54
Canada, Inland:
250	0.6	0.5	0.4	0.5	0.6	0.8	1.3	1.3	0.9	0.8	0.8	0.5	9.0	20
251	0.6	0.5	0.4	0.6	0.5	1.l	1.3	1.6	1.3	0.9	0.7	0.6	10.1	28
252	0.9	0.7	0.5	0.5	1.0	1.2	1.5	1.6	1.4	1.2	1.1	1.0	12.6	41
253	0.5	0.4	0.7	0.3	0.6	1.3	1.8	1.2	1.6	1.0	1.1	0.6	11.1	6
254	0.5	0.5	0.5	0.5	0.7	1.0	1.5	1.7	1.2	1.1	0.8	0.6	10.6	31

*Less than 0.05 inch.

185      |      Vol_VII-0191                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland (cont.):
255	1.1	0.7	0.6	0.6	1.2	2.4	1.9	1.6	1.4	1.3	1.7	1.3	15.8	9
256	0.5	0.5	0.4	0.4	1.2	1.3	2.0	1.9	1.1	0.8	0.6	0.5	11.2	30
257	0.5	0.5	0.4	0.4	1.2	1.3	2.0	1.9	1.1	0.8	0.6	0.5	11.2	31
258	0.7	0.7	0.5	0.7	1.4	1.5	2.0	1.5	1.3	1.1	0.9	0.8	13.0	42
259	0.6	0.5	0.5	0.7	0.9	1.3	1.3	1.8	1.5	1.0	0.9	0.8	11.8	45
260	0.8	0.5	0.6	0.5	0.7	0.9	1.2	0.9	0.7	1.1	0.7	0.6	10.3	…
261	0.6	0.6	0.5	0.5	0.9	1.2	1.1	1.4	1.6	1.1	1.4	0.7	11.6	27
262	0.5	0.6	0.5	0.5	1.0	1.8	2.2	1.8	1.7	0.9	0.8	0.7	13.0	26
263	0.6	0.4	0.6	0.6	1.1	1.8	2.0	1.7	1.3	0.7	0.6	0.5	12.1	30
Greenland and Iceland, Coastal and Insular:
302	0.1	0.1	0.1	0.1	0.1	0.2	0.5	0.5	0.4	0.1	0.1	0.2	2.6	3
303	1.2	0.7	0.7	0.1	0.2	0.2	*	0.3	0.3	0.2	1.0	0.7	5.8	2
304	0.4	0.4	0.6	0.6	0.6	0.6	1.0	1.1	1.0	1.1	1.1	0.5	9.0	50
305	1.6	2.5	1.8	1.6	2.8	1.0	3.4	3.7	5.4	4.1	2.3	2.2	32.4	3-4
306	1.0	0.7	0.3	0.5	0.2	0.6	0.2	0.7	0.5	0.6	0.8	0.8	6.9	4-6
307	1.1	0.6	0.6	0.3	0.5	0.5	0.6	1.4	1.3	0.8	0.8	0.9	8.7	5
308	1.8	1.7	0.6	1.5	0.3	1.0	0.6	0.4	1.1	1.1	1.0	1.5	12.5	10
309	0.6	0.5	0.7	0.6	1.5	1.2	2.7	2.0	1.7	1.4	1.3	1.0	15.2	8
310	0.2	0.9	0.7	0.2	0.7	0.6	1.3	0.6	2.4	0.5	0.8	0.4	9.3	2-3
312	0.2	0.3	0.1	0.1	0.3	0.4	1.0	0.7	0.8	0.6	0.4	0.3	5.1	6-8
313	2.1	1.8	2.4	2.0	3.9	6.7	4.1	1.8	5.6	1.8	1.3	1.7	35.4	4-5
314	1.4	1.7	1.7	1.2	1.7	1.4	2.2	3.1	3.3	2.5	1.9	1.5	23.5	50
317	3.3	2.0	2.4	2.4	2.4	2.1	1.9	2.4	3.7	5.7	3.3	2.8	34.3	28
318	3.3	2.6	3.3	2.5	3.5	3.2	3.1	3.8	5.8	5.7	4.6	3.2	44.6	50

*Less than 0.05 inch.

186      |      Vol_VII-0192                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
319	1.4	1.5	2.5	1.0	2.8	1.8	2.6	3.8	4.1	4.6	1.6	0.8	28.5	2-3
321	7.3	8.2	11.9	7.9	9.5	8.2	6.2	6.5	7.9	9.5	5.8	10.9	99.7	4-6
331	3.9	3.3	2.7	2.4	1.9	1.9	1.9	2.0	3.5	3.4	3.7	3.5	34.3	50
333	7.5	6.4	6.2	5.2	5.0	5.9	5.8	7.0	10.3	8.4	8.7	9.5	85.9	10
334	0.6	0.7	0.5	0.4	0.7	1.4	1.4	2.3	2.0	2.5	1.8	0.9	15.3	13
335	1.4	0.9	1.3	0.9	0.7	1.7	2.1	2.6	2.4	4.0	2.2	1.9	22.0	12
336	5.0	2.6	3.1	3.5	2.3	2.4	3.2	3.7	3.8	5.1	3.3	4.5	25.0	12
337	6.9	6.7	7.7	4.5	5.6	5.4	3.8	5.9	7.7	6.0	7.5	8.7	76.4	11
338	8.6	6.9	6.2	5.2	4.4	4.5	4.3	4.3	7.5	7.5	7.2	7.6	74.2	15
339	1.7	0.9	0.9	0.8	0.9	1.6	2.0	2.6	2.6	2.6	2.0	2.5	21.1	10
340	8.6	5.4	3.8	1.9	2.3	2.6	2.3	2.7	11.9	3.9	5.4	6.8	57.6	3
341	4.1	3.8	4.1	2.4	3.9	3.2	4.3	4.6	6.4	4.8	5.9	6.0	53.5	8
Greenland and Iceland, Inland:
360	5.0	4.5	3.3	2.6	2.6	3.4	2.9	5.6	4.3	5.6	4.0	3.9	47.7	7
361	1.0	0.6	0.7	0.4	0.6	1.1	1.6	2.5	1.6	1.0	0.8	0.9	12.7	5
Europe, Coastal and Insular:
400	0.2	0.3	0.2	0.2	0.2	0.3	0.7	1.1	0.7	0.3	0.2	0.2	4.6	1
401	0.2	0.1	0.1	0.1	0.2	0.4	0.8	0.6	0.7	0.3	0.2	0.1	3.8	2
402	1.1	1.1	0.9	1.1	0.4	0.5	0.6	1.6	1.3	1.0	1.5	1.3	12.3	…
403	1.3	1.2	1.1	0.9	0.5	0.5	0.7	0.8	0.9	1.2	1.0	1.6	11.7	14
406	2.6	3.1	2.8	2.2	2.1	2.2	2.8	2.6	3.9	3.5	3.4	2.9	34.1	50
407	1.4	1.4	1.3	0.6	0.8	1.3	1.5	1.6	2.7	1.5	1.5	1.4	17.0	10
408	2.7	2.6	2.1	1.6	1.4	1.5	1.8	2.1	2.4	2.5	2.5	2.6	25.8	…
409	4.9	4.6	3.6	2.7	2.8	2.7	2.9	3.7	5.5	5.0	5.2	4.5	48.1	50

187      |      Vol_VII-0193                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
410	2.1	1.9	1.4	1.1	1.1	1.2	1.5	1.9	2.6	2.6	2.7	2.0	22.1	50
411	6.2	7.5	4.5	2.9	3.7	3.1	3.2	3.2	7.0	7.2	7.5	5.5	61.5	50
412	2.8	2.9	2.4	1.7	2.7	2.7	2.4	2.0	4.0	4.3	3.8	2.4	34.1	50
413	3.0	2.7	2.2	1.7	1.6	1.5	1.7	2.1	3.7	3.5	3.7	2.8	30.2	50
414	4.3	4.4	3.1	2.3	1.9	2.2	2.2	2.8	4.7	4.6	4.4	3.8	40.7	50
415	0.5	0.8	0.5	0.6	1.2	1.2	2.3	1.9	1.7	1.3	1.3	0.9	14.4	18
417	0.3	0.3	0.3	0.3	0.5	0.7	1.0	1.8	2.0	1.5	0.8	0.4	9.9	…
419	0.7	0.8	0.6	0.6	0.8	1.5	2.3	1.9	1.9	1.5	1.2	0.9	14.7	50
420	3.5	3.0	2.5	2.2	2.5	2.5	3.0	3.3	5.1	4.6	4.7	3.2	40.1	50
421	1.5	1.2	1.5	1.0	1.7	1.7	2.4	3.2	2.7	2.7	2.1	1.7	23.3	50
422	1.7	1.5	1.3	1.4	1.7	2.0	2.4	2.8	2.6	2.3	2.1	1.7	23.5	30
423	1.5	1.1	1.0	0.9	1.1	1.3	1.8	2.1	2.2	2.2	1.9	1.3	18.4	51
424	1.8	1.5	1.4	1.4	1.8	1.8	2.2	2.9	2.5	2.6	2.5	2.0	24.4	40
425	0.8	0.6	0.7	0.9	1.2	2.0	2.6	2.9	2.7	1.9	1.2	0.9	18.9	25
426	1.1	1.0	1.0	1.3	1.8	2.3	2.3	3.3	2.4	1.9	1.6	1.2	21.2	50
427	0.7	0.7	0.8	1.0	1.5	1.7	2.3	2.3	1.8	1.1	0.8	0.7	15.4	25
428	0.9	0.8	0.9	0.8	1.4	2.0	2.4	2.5	2.2	1.8	1.3	1.0	18.0	45
429	0.5	0.3	0.4	0.6	1.0	1.7	1.8	2.0	1.9	1.3	0.8	0.6	15.4	20
Europe, Inland:
450	0.5	0.4	0.3	0.3	0.8	1.3	2.8	2.4	1.3	0.9	0.7	0.4	12.1	32
451	0.7	0.5	0.4	0.5	0.7	1.6	2.0	1.9	1.8	0.9	0.9	0.5	12.4	30
452	0.7	0.5	0.6	0.9	1.3	2.1	2.4	2.7	1.4	1.3	1.0	0.7	15.6	…
453	1.1	0.9	0.9	1.2	1.4	2.3	2.5	2.6	2.1	2.0	1.6	1.2	19.8	30
454	3.4	2.9	2.2	1.8	1.5	1.7	2.2	3.0	3.3	3.4	2.1	2.6	30.1	50

188      |      Vol_VII-0194                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Inland (cont.):
455	1.2	1.0	1.0	0.9	1.2	1.2	1.4	1.5	1.2	1.3	1.2	1.3	14.4	38
456	1.0	0.7	0.7	0.8	1.3	1.7	2.7	2.9	2.0	1.6	1.1	0.9	17.3	51
457	1.6	1.2	1.3	1.3	1.7	2.6	2.6	3.2	2.7	2.4	1.9	1.7	24.3	51
458	1.5	1.3	1.1	1.3	1.7	2.4	3.1	3.2	2.5	2.3	1.8	1.5	23.7	50
Asia, Coastal and Insular:
500	0.1	0.1	0.1	0.1	0.2	0.5	1.0	1.5	0.9	0.3	0.1	0.1	5.1	3
501	0.3	0.1	0.1	0.2	0.2	0.9	1.5	1.2	0.9	0.4	0.2	0.2	6.2	18
502	0.2	0.1	0.1	0.2	0.2	0.8	1.5	2.0	0.9	0.3	0.1	0.2	6.5	19
503	0.1	0.1	0.1	0.1	0.1	0.7	1.1	1.1	0.4	0.3	0.2	0.1	4.5	22
504	0.1	0.1	0.1	*	0.2	0.4	1.2	1.0	0.5	0.2	0.1	0.2	4.0	4
505	0.7	0.6	0.5	0.4	0.5	0.7	1.0	1.5	1.4	1.1	0.6	0.6	9.6	24
506	0.3	0.2	0.2	0.2	0.3	0.8	1.1	1.3	1.3	0.8	0.4	0.4	7.3	18
507	0.3	0.2	0.2	0.2	0.2	0.5	1.5	1.2	1.5	0.6	0.4	0.3	7.0	6
508	0.3	0.3	0.2	0.2	0.2	0.6	0.6	1.6	1.1	0.5	0.4	0.2	6.2	13
509	0.4	0.2	0.2	0.2	0.5	0.9	0.9	2.0	1.7	0.6	0.3	0.3	8.3	15
510	0.2	0.1	0.2	0.2	0.2	0.7	0.8	1.6	1.6	0.5	0.3	0.2	6.6	17
511	0.1	0.1	0.0	0.0	0.2	0.4	0.3	1.4	0.4	0.1	0.2	0.2	3.4	2
512	0.1	0.1	0.1	0.1	0.1	1.3	1.2	1.1	0.8	0.2	0.2	0.1	5.4	7
513	0.2	0.2	0.1	0.2	0.3	1.2	1.1	1.1	0.8	0.4	0.4	0.3	6.0	7
514	0.1	0.1	0.1	0.1	0.2	0.4	0.6	0.6	0.4	0.2	0.1	0.1	3.0	4
515	0.2	0.2	0.2	0.1	0.4	0.8	1.1	1.1	0.7	0.3	0.3	0.3	5.7	14
516	0.2	0.2	0.1	0.1	0.1	1.1	0.9	0.6	0.8	0.2	0.1	0.2	4.2	3
517	0.2	0.2	0.2	0.2	0.2	0.4	0.6	0.9	0.5	0.4	0.1	0.2	4.1	11
518	0.2	0.2	0.2	0.2	0.4	0.9	1.1	1.8	1.8	0.9	0.4	0.4	8.2	9

*Less than 0.05inch.

189      |      Vol_VII-0195                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
519	0.2	0.2	0.2	0.2	0.4	0.9	1.0	1.7	1.5	0.9	0.3	0.2	7.8	12
520	0.3	0.3	0.2	0.3	0.7	1.3	1.8	2.0	1.5	0.7	0.5	0.4	10.0	30
521	0.3	0.2	0.3	0.4	0.8	1.9	1.3	2.3	2.0	0.6	0.4	0.3	10.7	25
522	0.5	0.2	0.2	0.2	0.2	0.7	1.5	1.2	0.9	0.5	0.4	0.3	6.8	7
523	0.1	0.4	0.5	0.5	0.2	0.4	0.8	1.8	0.8	0.7	0.2	0.2	6.7	3
524	0.2	0.2	0.2	0.2	0.3	0.3	0.9	1.1	0.7	0.4	0.2	0.1	4.9	4
525	0.6	0.6	0.4	0.5	0.4	0.5	1.6	1.8	2.1	1.9	0.5	1.0	11.8	8
526	0.3	0.3	0.4	0.3	0.4	0.7	1.7	1.8	1.2	1.0	0.6	0.4	9.2	16
527	0.3	0.3	0.2	0.2	0.4	0.9	1.3	1.6	1.1	0.5	0.3	0.4	7.5	14
528	0.4	0.9	0.3	0.4	0.3	0.9	2.0	2.7	2.0	0.2	0.2	0.2	10.4	3
529	0.9	0.7	0.8	0.9	0.3	0.7	1.7	1.9	2.7	1.8	1.3	0.6	14.3	4
530	1.1	0.2	0.6	0.6	0.5	0.7	1.6	1.5	2.6	1.8	0.5	0.8	12.5	7
531	0.1	0.2	0.1	0.2	0.3	1.1	2.1	2.6	1.3	1.0	0.9	0.1	10.0	4
Asia, Inland:
550	0.4	0.6	0.3	0.9	0.5	1.4	1.8	2.7	1.5	1.2	0.7	0.4	11.8	28
551	0.2	0.3	0.3	0.5	0.7	0.8	1.6	1.8	1.1	0.8	0.4	0.6	9.1	3
552	0.3	0.2	0.3	0.3	0.5	1.0	1.5	1.6	1.5	0.9	0.4	0.3	8.9	18
553	0.2	0.2	0.2	0.2	0.4	1.5	1.5	2.5	1.9	1.0	0.5	0.2	10.1	26
554	0.2	0.2	0.2	0.3	0.4	1.2	1.3	1.7	1.7	0.7	0.3	0.2	8.4	17
556	0.2	0.1	0.1	0.2	0.3	0.9	1.1	1.0	0.5	0.3	0.3	0.2	5.1	31
557	0.4	0.2	0.3	0.2	0.4	1.2	1.4	2.4	0.8	0.6	0.4	0.2	8.4	3
558	0.3	0.3	0.2	0.2	0.2	0.9	1.3	1.2	0.8	0.5	0.5	0.4	6.8	13
559	0.6	0.4	0.2	0.2	0.5	0.9	2.4	1.7	1.1	0.4	0.8	0.6	9.8	10
560	0.5	0.3	0.4	0.6	1.5	2.2	2.5	2.0	1.5	0.9	0.6	0.5	13.5	8

190      |      Vol_VII-0196                                                                                                                  

Table XV . Mean precipitation (inches) (cont.) ✓

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
561	0.8	0.6	0.7	0.5	2.0	2.3	2.4	3.0	2.2	1.6	1.0	1.0	18.0	10
562	0.6	0.4	0.5	0.5	1.3	2.5	2.4	3.2	1.9	1.3	0.8	0.7	16.1	28
563	0.5	0.4	0.4	0.6	1.0	1.6	2.0	2.3	2.0	1.1	0.8	0.6	13.2	40
564	0.7	0.6	0.4	0.7	1.5	2.2	3.2	1.7	1.6	0.9	1.0	0.8	15.3	5
565	0.3	0.3	0.2	0.3	0.7	1.5	1.0	1.3	1.0	0.6	0.6	0.4	8.2	…
566	0.4	0.3	0.3	0.4	0.9	1.7	1.6	2.1	1.2	0.7	0.7	0.5	10.7	26
567	0.3	0.3	0.3	0.3	0.9	1.3	1.3	1.6	1.0	0.7	0.6	0.4	9.0	…
568	0.2	0.2	0.1	0.3	0.5	1.1	1.3	1.6	0.9	0.5	0.4	0.3	7.4	35
569	*	*	*	0.1	0.7	1.6	1.1	1.7	0.4	0.6	0.1	0.1	6.5	1
570	0.1	0.2	0.1	0.3	0.4	0.8	1.2	1.4	0.8	0.3	0.2	0.2	6.1	17
571	0.2	0.1	0.2	0.1	0.2	0.6	1.2	1.2	0.5	0.3	0.4	0.3	5.3	4
572	0.3	0.3	0.3	0.2	0.3	0.8	1.5	1.9	1.1	0.5	0.5	0.4	7.9	21
573	0.6	0.6	0.6	0.7	1.5	2.3	2.9	2.7	1.7	1.3	1.1	0.9	16.9	35
574	0.8	0.5	0.5	0.7	1.4	2.4	2.4	2.6	1.7	1.5	1.2	1.0	16.9	48
575	0.8	0.5	0.5	0.5	1.0	1.8	2.1	2.0	1.7	1.0	1.0	1.0	13.8	18
576	0.7	0.4	0.5	0.7	0.9	1.7	2.5	2.1	1.5	0.9	1.1	0.9	13.8	30
577	0.4	0.3	0.2	0.3	0.7	1.3	1.4	1.4	1.2	0.7	0.5	0.5	8.8	…

*Less than 0.05 inch.

191      |      Vol_VII-0197                                                                                                                  

        As shown by the data on the average number of days with precipitation

(Table XIV ), the monthly frequencies are more uniform in continental

locations and in the more southerly Arctic latitudes. There is a

tendency toward summer maxima at high-latitude continental locations and

toward autumn and winter maxima in the maritime locations near the major

winter storm tracks, particularly over the Norwegian and Barents Seas.

        The annual variation of precipitation amounts over the Arctic Basin

presents a somewhat different picture than the annual variation of

precipitation probabilities. Most locations show decided summer maxima,

usually in July or August. However, between the east coast of Greenland

and Novaya Zemlya the averages are greater in winter than in summer.

(See Table XV .)

       

fig. 48 here

192      |      Vol_VII-0198                                                                                                                  

        Diurnal Variation of Precipitation . - Because of the general absence of

important diurnal insolational effects in winter at the higher latitudes,

no diurnal variation in precipitation is observed during this season over

the pack-ice. In other seasons, however, the probability of precipitation

appears to be greater at night than in daytime, a difference which is

especially great in spring. During the warmer months in the lower Arctic,

and particularly at inland points, it is to be expected that precipitation

will be most frequent during daylight hours when thermal convection is

most pronounced. Specific Arctic data by which to verify this conclusion

are lacking however.

193      |      Vol_VII-0199                                                                                                                  

        Snowfall . - Snowfall in Arctic regions is, on the average, very light.

However, heavy snows do occur in the more mountainous regions and also

in the areas under maritime influence near the major winter cyclone paths.

On the plains or steppes of Arctic continental regions, the average annual

snowfall does not often exceed 2 feet. This snowfall, however, does not

result in a uniform snow cover over the interior. The more exposed ridges

and plateaus are free from snow throughout most of the year because they

are swept clean by winds. At the same time, a fairly deep snow cover may

be experienced in valleys and river courses which are more or less protected

from the scouring action of the wind.

       

tables XVI to XVIII here

        In regions with a more maritime influence, as around Hudson Bay,

Labrador, southern Greenland and Baffin Bay, average snow depths between

5 and 10 feet are common. In these regions the heaviest precipitation of

the year is often recorded in November and December, with the result that

snowfall constitutes a large percentage of the total annual precipitation.

194      |      Vol_VII-0200                                                                                                                  

Table XVI . Mean number of days with snow ✓

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	e	11	11	13	13	19	17	14	14	13	17	9	9	156	2
003	e	2	8	6	6	19	7	4	9	16	13	6	6	102	1
004	c	15	17	15	11	10	3	1	*	6	9	15	17	118	..
005	e	11	12	13	8	8	2	*	*	3	8	12	11	87	..
006	e	12	8	7	5	6	7	4	8	9	10	9	8	93	..
007	e	13	11	8	6	7	9	5	7	14	15	10	12	115	..
Alaska, Coastal and Insular:
100	a	2	2	2	3	3	1	2	3	8	9	5	6	46	5
101	a	11	14	13	16	13	6	..	3	8	18	17	15	…	0-2
104	a	14	15	15	15	9	1	0	0	2	12	15	17	115	1-2
106	a	17	12	14	5	1	*	..	..	1	7	13	15	…	0-7
Alaska, Inland:
153	a	5	4	4	2	1	0	0	0	1	6	6	4	33	10
154	a	10	9	9	8	4	0	0	*	1	7	11	10	69	10
155	a	8	9	9	6	2	*	0	0	2	11	11	10	68	11
156	a	13	9	9	7	3	1	0	0	3	12	13	10	80	10
157	a	10	8	8	7	2	0	0	*	2	8	11	10	66	10
Canada, Coastal and Insular:
204	d	5	3	5	4	6	3	0	1	5	9	8	4	53	5
206	b	6	6	7	6	8	2	0	3	6	8	6	2	60	5
208	a	14	8	19	9	19	7	0	..	17	24	6	2	…	0-1

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

195      |      Vol_VII-0201                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular: (cont.)
210	b	6	3	4	4	7	4	1	0	8	8	4	5	54	5
211	b	6	3	6	6	6	4	*	1	7	8	6	5	58	7
213	d	3	1	2	2	2	*	0	*	2	5	3	3	24	5
214	d	3	..	..	11	10	11	..	..	..	9	..	2	…	0-1
216	b	8	6	7	5	7	1	*	*	3	9	10	8	64	10
217	d	2	..	4	..	..	..	0	0	..	..	..	4	…	..
221	b	6	5	6	8	6	1	0	0	3	8	9	8	60	10
223	b	6	6	6	11	10	6	*	*	5	11	15	11	87	10
224	d	5	5	5	6	7	2	*	0	1	9	8	7	54	6
226	d	6	3	4	7	4	2	0	0	2	7	8	7	51	7
227	b	10	8	11	9	10	4	0	*	1	11	14	14	92	10
228	b	5	6	6	5	2	1	*	0	1	8	9	8	51	10
Canada, Inland:
250	b	4	5	4	4	2	1	0	*	4	7	8	5	44	10
251	d	4	4	3	4	3	2	0	1	4	8	3	3	40	9
252	b	8	6	8	2	*	0	0	0	1	7	11	10	53	10
253	b	7	7	8	2	1	0	0	0	1	5	11	8	50	5
254	b	7	7	8	6	4	*	0	0	2	9	11	7	61	10
255	b	9	7	5	4	*	0	0	0	1	8	13	13	60	8
257	b	6	7	7	6	2	0	0	0	1	6	8	6	49	10
258	b	6	5	8	3	1	0	0	0	*	5	8	8	44	10

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

196      |      Vol_VII-0202                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland: (cont.)
259	b	8	8	9	4	1	*	0	0	1	6	12	9	58	10
260	e	8	8	8	4	0	0	0	0	1	4	8	9	50	..
262	b	7	6	7	3	1	0	0	0	1	6	9	9	49	10
Greenland, Iceland, Coastal and Insular:
304	c	4	4	6	5	6	3	1	1	6	10	10	6	63	..
307	c	7	4	5	3	3	1	*	1	3	4	6	6	44	5
308	c	8	8	7	4	..	1	*	0	5	5	5	6	…	9
309	c	8	8	7	8	4	1	*	0	4	8	11	11	70	13
314	d	8	7	7	6	4	2	*	*	2	7	7	6	56	26
317	c	13	12	11	9	6	1	0	*	3	9	10	11	84	28
318	e	11	9	10	8	5	1	*	*	2	6	9	10	70	..
330	e	17	14	12	9	3	1	*	*	2	3	10	12	87	16
331	c	15	12	9	5	2	*	0	0	1	4	8	12	69	19
332	e	12	11	12	8	3	1	0	0	1	5	6	8	67	9
333	e	12	10	8	4	2	*	*	0	1	3	6	9	55	11
334	e	8	7	7	6	2	1	0	0	1	5	4	5	45	14
335	e	12	10	10	9	3	1	*	*	1	8	8	10	73	15
336	e	9	9	8	8	2	*	0	*	1	6	7	8	59	16
337	e	8	6	4	3	1	0	0	0	*	*	4	5	31	11
338	e	8	5	5	3	1	*	0	0	*	2	3	5	31	15
339	e	11	8	10	9	3	2	*	0	1	6	4	6	60	10

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

197      |      Vol_VII-0203                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular: (cont.)
340	e	14	12	13	11	5	1	0	0	1	8	7	10	82	14
341	e	9	8	7	6	1	*	0	0	0	2	3	6	42	8
Greenland, Iceland, Inland:
360	e	10	9	8	3	1	*	0	0	0	3	4	5	43	7
361	e	12	10	10	10	4	3	*	1	4	10	9	10	83	16
Europe, Coastal and Insular:
400	e	12	11	8	8	9	7	5	7	11	15	13	11	117	10
401	e	7	7	7	8	11	10	9	13	16	14	10	8	120	1
406	a	12	12	14	12	8	4	*	*	3	9	11	11	96	12
408	a	16	17	16	12	10	4	0	*	3	11	15	17	121	44
411	a	14	15	12	8	4	1	0	0	1	6	11	10	81	..
412	a	11	11	10	6	3	*	0	0	1	5	8	8	63	44
414	a	13	14	13	10	7	1	0	0	2	8	11	11	90	44
415	e	11	12	10	9	9	4	*	*	3	9	15	15	94	18
416	c	11	12	13	10	5	2	0	0	2	7	9	10	81	10
417	e	24	20	19	17	16	6	0	0	1	12	17	22	154	..
420	a	12	11	11	7	3	*	0	0	*	4	8	9	65	44
421	a	11	11	11	6	2	*	0	0	*	3	7	13	64	36
423	a	15	12	12	7	3	*	0	0	*	5	10	13	77	27
424	e	17	16	13	7	2	*	0	0	*	4	10	15	84	36
425	e	14	13	11	8	4	1	0	0	1	7	15	16	91	18

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

198      |      Vol_VII-0204                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular: (cont.)
426	e	20	18	12	7	2	*	0	0	*	5	13	19	97	18
428	e	8	9	8	4	3	1	0	0	1	6	10	10	60	25
429	e	8	7	5	5	6	2	1	1	3	7	10	7	60	17
450	a	13	11	10	8	5	2	*	*	3	8	12	12	84	32
451	a	9	8	9	7	6	2	*	*	2	7	9	7	66	44
452	c	12	9	11	10	6	3	*	0	1	8	10	10	80	..
454	c	15	14	13	9	4	*	0	0	1	5	10	13	84	44
455	a	12	10	10	5	2	*	0	0	*	2	7	11	59	38
456	a	14	12	13	9	4	1	*	0	2	8	12	15	90	26
458	c	18	17	15	10	4	*	0	0	1	8	16	18	107	35
Asia, Coastal and Insular:
500	e	10	8	8	10	10	9	4	6	13	13	9	8	108	7-8
501	e	12	6	6	8	11	9	4	7	11	14	10	11	107	5-6
502	e	13	9	7	11	14	8	7	4	13	14	11	11	122	4-5
503	e	6	8	5	4	6	7	4	6	10	13	11	8	88	7-8
505	e	16	14	13	12	12	7	1	1	5	12	14	14	121	14
506	e	14	10	9	10	8	5	*	*	5	13	15	16	106	24
507	e	12	10	11	9	7	5	1	1	8	14	12	13	104	17
508	e	16	14	13	12	10	6	2	1	10	18	17	15	133	5
509	e	19	13	14	13	14	8	0	1	10	18	15	12	136	6-7
510	e	12	11	11	10	10	9	9	3	10	17	14	12	122	19

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

199      |      Vol_VII-0205                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular: (cont.)
511	e	4	5	1	2	8	4	0	2	7	4	10	6	53	2
512	e	20	13	12	11	7	1	0	0	1	6	12	12	95	7
514	e	15	12	14	13	13	2	0	*	3	12	14	14	112	11
515	e	4	4	4	2	9	6	2	4	11	7	8	6	67	4
517	e	8	7	7	6	8	4	1	5	8	8	7	7	76	9
518	e	13	10	12	11	11	6	1	*	6	15	16	16	115	26
519	e	12	11	9	11	12	5	1	1	7	15	14	12	110	22
520	e	8	9	7	7	7	1	*	0	3	10	10	9	72	10
521	e	13	9	10	11	11	4	*	*	4	15	14	10	102	4
522	e	8	9	8	8	6	1	1	4	10	13	10	10	88	4
523	e	11	8	13	10	10	3	4	1	8	13	17	12	110	3
524	e	13	11	14	10	10	0	0	0	2	10	12	10	92	4
525	e	7	6	8	8	5	1	1	1	5	10	11	9	72	7
526	e	8	8	8	7	6	*	0	*	2	8	10	8	65	13
527	e	9	10	8	7	7	2	*	*	2	6	9	9	66	14
529	a	12	12	7	8	4	0	0	0	0	2	7	7	69	4
530	e	12	13	15	13	6	0	0	0	0	3	8	12	82	7
531	e	3	3	6	4	4	*	0	*	0	7	7	3	37	4
Asia, Inland:
550	e	22	..	21	..	16	7	0	0	10	23	..	12	…	0-1
551	e	25	15	8	13	12	7	0	5	8	19	14	16	142	1
552	e	10	7	9	9	8	2	*	1	9	16	10	8	89	..

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

200      |      Vol_VII-0206                                                                                                                  

Table XVI . Mean number of days with snow (cont.)

Station	Amt	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland: (cont.)
553	e	13	12	12	9	10	5	*	*	7	19	17	14	118	14
554	e	8	7	9	10	7	5	0	*	6	12	13	10	85	4
556	e	7	6	4	4	3	1	*	1	4	8	8	8	54	18
558	e	3	5	4	3	1	1	*	1	4	8	8	4	42	5
559	e	17	14	10	5	4	1	*	1	5	15	18	20	111	9
560	e	10	12	12	10	7	2	0	*	3	14	14	13	96	8
561	e	12	7	7	7	5	1	*	0	1	8	9	11	667	3
562	e	15	12	13	8	7	1	*	*	3	12	16	16	104	10
563	e	10	9	10	9	9	4	*	*	7	16	15	14	103	15
566	e	9	8	6	6	3	*	0	0	2	9	10	9	62	16
567	e	12	11	9	7	4	*	0	*	3	13	15	12	86	12
568	e	9	6	4	4	1	0	0	0	1	10	9	9	53	14
570	e	3	4	5	6	3	0	0	0	2	9	7	3	42	8
571	e	11	2	3	8	6	0	0	0	4	12	12	7	65	0-1
572	e	7	7	7	5	4	*	0	*	3	9	10	8	62	16
573	e	8	6	7	4	2	*	0	0	1	6	10	10	54	18
574	e	11	9	9	8	4	*	0	0	2	13	15	13	83	21
575	e	17	15	14	9	4	*	0	0	3	13	19	18	112	18
576	e	16	14	14	11	6	*	0	*	5	15	21	18	120	13

a Trace or more b Measurable amounts c 0.004 inches or more d 0.1 inch or more e Not defined * Less than 0.5 day.

201      |      Vol_VII-0207                                                                                                                  

Table XVII. Mean monthly snowfall (inches)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Alaska, Coastal and Insular:
100	2.6	2.7	2.0	2.7	1.8	0.4	1.0	0.7	3.0	7.9	4.3	3.9	33.0	21-33
102	15.6	5.4	5.7	5.2	0.5	0.4	0.0	*	1.4	5.2	3.5	3.8	46.7	6-11
104	10.8	8.9	10.2	5.1	1.3	0.2	0.0	*	0.4	3.6	8.5	10.8	59.8	29-34
105	0.9	0.7	0.1	0.7	0.5	0.2	1.2	0.6	1.0	1.1	0.3	0.2	7.5	2-5
106	12.1	8.7	7.7	2.9	0.2	0.0	0.0	0.0	*	5.2	11.2	10.4	58.4	21-25
Alaska, Inland:
152	9.4	11.3	4.5	5.1	1.8	0.0	0.0	0.0	*	7.1	11.2	11.7	62.1	6-8
153	7.8	6.9	3.8	1.6	0.5	0.0	0.0	0.1	1.3	7.2	7.7	5.1	42.0	21-27
154	7.2	4.9	8.0	3.3	0.5	0.0	0.0	0.0	0.2	3.3	5.2	9.3	41.9	16-18
155	10.0	9.5	8.1	2.5	0.5	*	*	0.0	0.9	7.6	5.8	8.6	53.5	33-37
156	11.7	7.2	8.1	2.7	0.4	*	0.0	0.1	0.7	6.5	7.4	8.7	53.5	31
157	8.4	5.4	5.5	3.6	0.5	*	0.0	0.2	1.7	8.1	9.2	10.1	52.7	28-31
Canada, Coastal and Insular:
204	3.8	2.4	5.4	5.1	4.5	5.3	0.0	0.6	3.5	14.1	8.7	2.4	55.8	5
205	1.7	4.6	1.1	1.0	0.0	0.0	0.0	0.0	4.5	7.5	7.2	0.5	28.1	3
206	2.3	3.2	2.5	1.2	4.0	1.4	0.0	5.3	5.5	3.8	2.2	1.2	32.6	1-4
210	9.7	2.1	3.7	4.5	6.2	8.7	0.1	*	17.8	17.6	10.5	3.5	84.4	4
211	3.9	2.3	3.9	2.7	5.3	3.5	0.1	1.6	5.7	7.0	4.3	3.9	44.2	10
212	1.1	2.3	4.2	2.1	4.3	5.5	0.0	0.2	4.5	16.8	6.6	2.2	40.8	4
213	2.5	0.8	0.9	2.6	3.6	0.5	0.0	0.4	1.3	5.6	4.7	3.9	26.8	5
214	2.4	2.3	0.8	0.4	3.8	1.5	1.0	*	1.0	11.0	8.0	1.1	33.3	5
215	2.2	…	1.5	3.5	5.2	0.4	0.0	0.0	4.2	3.2	1.3	2.6	…	0-6
216	5.7	4.4	6.3	5.2	4.9	1.8	*	0.2	3.9	9.9	8.4	6.3	57.0	13
217	3.4	5.0	2.0	3.6	4.8	6.2	0.0	T	2.5	3.9	5.8	3.6	40.8	13

* Less than 0.05 inch. T Trace

202      |      Vol_VII-0208                                                                                                                  

Table XVII. Mean monthly snowfall (inches) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular: (cont.)
221	3.5	5.5	5.0	8.8	6.1	0.8	0.0	*	1.2	9.1	8.0	9.1	57.0	20
222	1.7	3.8	2.4	5.1	6.3	1.6	0.0	0.0	3.4	7.2	4.6	1.3	37.4	6
223	5.7	5.5	5.9	11.2	6.7	4.0	0.9	0.6	3.1	10.6	14.7	8.4	77.3	14
224	7.2	7.1	4.8	10.0	5.7	2.0	0.0	0.0	1.0	12.3	9.6	4.9	64.8	6
225	3.0	3.4	1.7	5.4	8.8	2.3	0.0	0.0	4.1	5.2	4.3	4.8	43.0	3
226	8.8	14.6	9.2	18.0	4.5	1.6	0.0	0.0	2.1	13.1	22.1	21.0	115.0	7
227	10.2	11.1	9.4	8.7	9.0	3.0	*	0.1	2.2	8.2	12.1	10.3	84.3	15
228	4.8	6.1	8.5	7.7	1.8	1.4	0.0	*	1.7	8.1	10.3	6.6	56.9	30
Canada, Inland:
250	5.8	5.3	4.3	5.0	2.4	2.2	*	0.8	3.3	7.3	8.1	4.8	49.3	20
251	6.0	4.7	3.9	6.2	2.7	1.2	0.0	*	3.1	8.0	6.8	6.0	48.6	28
252	8.7	7.0	5.1	3.5	0.6	0.1	0.0	*	1.8	7.9	11.3	10.2	56.2	41
253	4.5	4.3	7.1	2.7	1.2	0.0	0.0	0.0	0.5	5.0	10.8	6.3	42.4	6
254	5.3	4.9	4.9	4.8	3.8	0.4	0.0	0.2	2.8	8.9	8.2	5.8	50.0	31
255	11.1	7.0	6.3	4.0	0.8	0.0	0.0	0.0	0.3	9.2	15.5	13.2	67.4	9
256	4.6	4.9	3.5	4.1	2.5	0.2	0.0	0.1	2.8	7.0	6.1	4.5	40.3	30
257	4.6	4.9	3.5	4.1	2.5	0.2	0.0	0.1	2.8	7.0	6.1	4.5	40.3	31
258	7.2	7.0	4.8	5.8	4.1	*	0.0	0.1	0.7	8.1	8.5	8.3	54.6	42
259	6.2	5.4	5.3	4.9	1.8	0.3	0.0	0.1	0.5	5.0	8.4	8.0	45.6	45
260	8.1	5.0	5.8	3.4	0.2	*	0.0	0.0	0.1	2.3	6.9	5.9	37.7	..
261	6.3	5.6	5.3	2.9	1.2	0.5	0.0	0.0	1.8	6.8	14.2	7.3	51.9	27
262	5.4	6.0	4.9	4.1	1.3	0.1	0.0	*	0.8	4.7	8.3	6.7	42.3	26
263	6.1	3.7	5.9	3.1	1.0	0.1	0.0	0.0	0.5	3.0	5.1	5.2	33.7	30

* Less than 0.05 inch.

203      |      Vol_VII-0209                                                                                                                  

Table XVII. Mean monthly snowfall (inches) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular:
302	0.6	0.5	1.5	2.3	1.1	0.8	0.0	0.0	2.2	1.5	2.5	1.9	14.9	3
331	3.0	3.4	1.7	0.8	0.2	0.0	0.0	0.0	*	0.5	1.4	2.1	13.1	15
Europe, Coastal and Insular:
425	8.4	6.7	8.3	8.6	5.0	0.8	0.0	0.1	1.2	5.8	8.6	8.4	60.1	..

* Less than 0.05 inch.

204      |      Vol_VII-0210                                                                                                                  

Table XVIII Mean snow depth (inches)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Alaska, Coastal and Insular:
100	8	7	8	6	3	*	0	*	1	3	5	6		8
101	1	2	4	9	5	1	0	0	*	2	3	1		1
104	3	13	16	11	4	0	0	0	*	*	2	6		11
105	6	8	7	7	1	*	0	0	0	3	8	10		1-4
Alaska, Inland:
153	18	26	23	3	0	0	0	0	*	7	13	16		10
156	18	17	20	11	1	0	0	0	*	1	4	11		14
Canada, Coastal and Insular:
214	13	22	15	24	24	16	2	*	*	9	16	18		2-3
216	3	4	6	6	3	2	*	*	4	8	6	3		7
223	16	15	19	14	7	0	0	0	0	3	6	11		8
226	13	15	16	13	4	0	0	0	1	8	10	13		3
227	5	8	16	*	0	0	0	0	0	*	7	5		8
Canada, Inland:
252	23	25	4	0	0	0	0	0	0	1	9	13		10
254	18	20	19	14	0	0	0	0	*	5	11	20		2-21
263	20	19	17	0	0	0	0	0	3	13	15	20		10
Greenland and Iceland, Coastal and Insular:
302	3	1	1	2	1	*	0	0	*	*	1	2		2-3
305	19	19	21	19	12	*	0	0	*	2	8	16		3-5
308	24	25	28	40	39	8	*	0	*	5	11	22		..
310	8	8	11	10	7	*	0	0	*	1	6	11		2-3
312	3	2	2	2	*	*	0	*	*	1	3	3		5-7
317	11	10	12	14	9	3	*	0	*	5	12	10		3
318	6	8	13	11	2	*	*	0	*	1	3	5		3-5
319	2	3	4	2	*	*	0	0	*	1	2	1		3-7
321	36	33	60	65	44	6	*	*	*	3	6	20		3-5

* - Less than 0.5 inch.

205      |      Vol_VII-0211                                                                                                                  

Table XVIII Mean snow depth (inches) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular: (cont.)
330	4	4	4	2	1	0	0	0	0	2	3	4		11
331	4	2	2	1	0	0	0	0	0	1	2	2		10
Greenland and Iceland, Inland:
361	18	19	21	15	7	1	0	0	1	5	11	8		11
Europe, Coastal and Insular:
408	21	28	34	30	14	*	0	0	*	1	5	15		..
411	9	13	17	4	1	0	0	0	0	*	4	9		..
415	16	22	25	23	8	0	0	0	0	2	5	10		..
424	12	16	12	*	0	0	0	0	0	1	1	7		20
425	12	16	18	10	*	0	0	0	0	*	4	8		..
428	18	24	27	11	*	0	0	0	0	*	4	11		4
Europe, Inland:
451	12	15	16	13	2	0	0	0	0	1	6	11		..
452	19	25	28	23	6	0	0	0	0	*	7	15		..
454	3	5	4	1	*	0	0	0	0	*	1	2		15
455	10	12	11	3	0	0	0	0	0	0	2	5		25
457	16	19	15	1	0	0	0	0	0	2	3	9		36
458	16	21	20	4	0	0	0	0	0	1	4	11		18
Asia, Coastal and Insular:
503	7	7	8	8	8	5	*	0	1	3	5	6		7
506	10	11	13	12	11	3	0	0	0	1	3	8		..
508	11	12	12	13	15	8	0	0	*	3	6	8		6
510	16	21	25	29	27	9	0	0	0	4	11	14		18

* - Less than 0.5 inch.

206      |      Vol_VII-0212                                                                                                                  

Table XVIII Mean snow depth (inches) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular: (cont.)
513	2	1	5	6	..	0	0	0	0	5	5	3		3
515	18	21	23	24	24	3	0	0	1	6	10	15		..
517	8	12	12	9	10	4	0	0	0	2	6	3		11
518	7	8	11	13	12	2	0	0	0	1	3	6		26
519	5	5	4	5	4	*	0	0	0	1	4	4		22
522	13	17	19	19	12	*	0	0	*	3	9	12		..
523	9	10	12	14	14	5	0	0	0	2	5	6		6
526	13	18	22	25	13	..	0	0	0	2	4	9		3-4
527	13	18	20	22	18	2	0	0	*	2	5	9		..
Asia, Inland:
552	4	5	4	8	6	0	0	0	1	3	4	4		..
554	44	50	58	6	*	0	0	0	0	5	25	36		..
556	9	11	11	11	4	0	0	0	0	3	6	8		6
558	15	18	19	16	8	*	0	0	*	4	9	13		..
559	15	17	19	19	7	0	0	0	*	2	7	12		..
562	20	27	32	27	8	..	0	0	*	1	5	12		11
563	38	41	40	33	27	..	0	0	0	2	10	23		3
566	11	13	12	6	0	0	0	0	*	1	7	9		..
568	10	13	15	8	0	0	0	0	*	1	4	6		..
572	33	38	44	48	40	..	0	0	0	3	14	26		6
573	20	25	28	13	1	0	0	0	0	1	5	12		9
575	14	17	17	7	*	0	0	0	0	1	5	10		..
576	23	24	24	19	1	0	0	0	0	3	11	17		8

* - Less than 0.5 inch.

207      |      Vol_VII-0213                                                                                                                  

        It is to be noted that the water equivalent of Arctic snow is often

considerable. With the low winter temperatures which occur in the Arctic,

the precipitated snow (plus hoarfrost) is most often in the form of small

ice spicules which form so compact a mass that 2 inches of the snow may

be equivalent to 1 inch of liquid water. The average density of snow

cover over the Arctic Basin area is least at the beginning of winter and

increases to its maximum value in spring (average densities of snow cover

are of the order of 0.30 to 0.45).

       

fig. 49 here

        Snow depths probably reach a maximum in March or April over much

of the Arctic. In some of the more maritime regions which experience

heavy snows, the maximum snow depth may not be reached until May. Over

some of the drier continental portions of the Arctic, on the other hand,

the period of maximum snow depth may occur as early as February.

208      |      Vol_VII-0214                                                                                                                  

        The snow cover disappears at some time during spring or summer

everywhere in the Arctic except at elevations above the permanent snow

line and in local protected locations nearer sea level. Near the Pole

the snow begins to melt in June, and by the end of July the snow cover is

almost gone. The Russian North Polar Expedition (1937), for example,

reported that it was difficult in late July to find enough

snow to use as ballast for the tents [ 5 ] .

209      |      Vol_VII-0215                                                                                                                  

        The average thickness of snow cover by months for selected

Siberian arctic locations is given in Table XVIII . Comparing these data with

the data on monthly snowfall (Table XVII ), it is seen that the thickness

of the snow cover is not completely determined by snowfall alone. Other

factors such as melting, drifting, evaporation and the accretion of rime,

etc., serve to alter the relationship. Topographical conditions also

exert their influence on the snow depths, since larger amounts of

snowfall occur on windward slopes than in leeward locations. This effect

is particularly noticeable in Greenland where the data show considerably

less accretion in the eastern portions than is observed at western

stations in the same latitude. The amount of accretion in the border

regions of the Greenland Ice Cap must also decrease sharply from south to

north, as is evidenced by the comparatively higher elevation of the

permanent snow line in the north (1400 m) compared to the south — a

difference which exists in spite of the temperature decrease toward the

north.

210      |      Vol_VII-0216                                                                                                                  

        Thunderstorms . - Thunderstorms have never been recorded over the Arctic

pack-ice but they do occur infrequently at coastal and inland locations

above the Arctic Circle. In Jakobshaven 3 thunderstorms were experienced

in the course of 62 years. In all Arctic regions their frequency

increases rapidly toward the south. For example, Ivigtut has had 24

thunderstorms in 45 years of record; Nanortalik, 77 in 42 years. At

inland locations in more southerly Arctic latitudes, thunderstorms are

fairly frequent and probably occur at least several times each year. at

some inland stations the average annual number is as high as 9 (as at

Fairbanks). Thunderstorms have been recorded in all months [ 43 ] but their

occurrence is most probable in July and August.

211      |      Vol_VII-0217                                                                                                                  

       

HUMIDITY

        Some of the facts concerning humidity conditions within the Arctic

have already been discussed in the section on the composition of the

atmosphere. There it was emphasized that a clear distinction must be

made between humidity as expressed in terms of the actual moisture

content (by vapor pressure, specific humidity, or mixing ratio) and as

expressed in terms of the degree of saturation (by relative humidity or

by saturation deficit). In the latter case a further distinction must

be made between the expression of relative humidity in terms of percent

of saturation with respect to ice and its expression in terms of

saturation with respect to water. (See Table II.) For example, the

observations on the Fram [ 28 ] over the pack-ice during February 1894

gave a mean temperature for the month of −32.1°F. and a mean relative

humidity with respect to ice of 129 percent. The corresponding relative

humidity computed with respect to water for the same month is only 92

percent.

212      |      Vol_VII-0218                                                                                                                  

        It should be mentioned that humidity computations at low

temperatures in the Arctic are highly questionable partly because of

the importance of small instrumental or observational errors at these

temperatures and also because of the difficulty in obtaining a sample

unaffected by a local source of moisture (such as the observer himself).

        As a very generalized statement for the entire Arctic it can be said

that it is essentially a region of high relative humidities but, because

of low temperatures, it is also a region which presents very small absolute

amounts of atmospheric moisture. Relative humidities average generally

between 75 and 100 percent, even over continental areas, except where

foehn (dynamical heating) effects are persistent. Over glaciers, elevated

snowfields, and the pack-ice, however, the relative humidities with respect

to ice are frequently above 100 percent. From 150 observations on about

120 different days in the winters of 1923-24 and 1924-25, Malmgren [ 26 ]

found that over the Polar Sea in winter the relative humidity always

remains near 100 percent. The smallest observed value was 83 percent and

the greatest, 122 percent. In 77 percent of all cases the relative

humidity with respect to ice was between 93 and 107 percent. During

213      |      Vol_VII-0219                                                                                                                  
summer the relative humidities were lower over the Polar Sea but even

in July the average (with respect to a water surface) was 95 percent.

        Malmgren [ 26 ] points out that in calm weather over the pack-ice

there exists a sharp decrease in relative humidity from the surface

upward due to the presence of the surface temperature inversion. When

the wind blows, however, the mixing processes bring air of higher

temperature, i.e., lower relative humidity, down to the ice. For this

reason the surface humidity decrease as the wind speed increases and

becomes progressively lower as the wind extends the mixing to greater

altitudes. Changes in cloudiness have a similar effect. Under clear

sky conditions (in winter), the increased radiative loss of heat from

the ice lowers the surface air temperature with a resulting increase in

relative humidity. The relations between relative humidity (with respect

to ice) and temperature, wind speed, and cloudiness in winter as found

by Malmgren [ 26 ] are as follows:

Wind Speed (mph)	1.3	4.5	8.9	13.2	20.6
Relative Humidity (%)	105.7	103.2	101.1	98.7	96.5

214      |      Vol_VII-0220                                                                                                                  

Temperature (°F.)	10.4	–0.6	–8.9	–17.9	–25.2	–35.9
Relative Humidity (%)	97.1	98.1	98.9	101.1	103.2	103.9
Cloudiness (0-10)	0.9	3.9	7.2	9.9
Relative Humidity (%)	104.3	101.6	99.2	97.9

        When a marked surface temperature inversion is present, the humidity

usually decreases from a maximum at the surface to a value between 50 and

60 percent at the top of the inversion. Above the inversion the humidity

remains fairly constant with altitude unless warm, moist air is being

advected aloft from lower latitudes, in which case a marked maximum in

humidity may occur even at altitudes of 15,000 or 20,000 feet.

        The only circumstances that allow low relative humidities to occur

in the Arctic are offered by strong offshore or downslope winds such as

occur at the foot of a glacier or a mountain range. An example of the

lowering of humidity during periods of offshore (downslope) winds is

given by the following average relative humidity data for Foka Bay,

Novaya Zemlya:

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann
Onshore wind	…	82.0	92.1	92.2	92.4	93.8	94.1	94.2	91.9	83.3	83.3	84.8	91.0
Offshore wind	…	79.8	81.5	87.1	78.5	81.3	83.5	82.2	82.9	77.6	74.7	74.6	79.5

215      |      Vol_VII-0221                                                                                                                  

        Annual Variation of Humidity . — In most inland Arctic regions the

annual variation of relative humidity follows very closely the annual

variation in temperature as would be expected on the basis of the

functional dependence of relative humidity upon air temperature. Inland,

the maximum humidity values are found in winter and the minima, in summer.

In the more maritime regions, the reverse is generally true. In Greenland,

however, the interior ice locations show summer maxima and the coastal

regions, winter maxima. This circumstance can be accounted for by the tables XIX to XXI here

fact that the free air at 8,000 to 10,000 feet is exceedingly dry in

winter compared to its state in summer. On the northern coasts of

Greenland, however, the prevailing downslope winds of summer give

humidities which are lower than those recorded during winter when the

katabatic circulation from the Ice Cap is at its weakest.

216      |      Vol_VII-0222                                                                                                                  

Table XIX . Mean relative humidity (%) by seasons

at continental and coastal stations

	Continental Stations			Coastal Stations
Station	Summer	Winter	Station	Summer	Winter
Fairbanks	48	78	Nome	83	76
Chesterfield	87	92	Barrow	87	81
Meanook	74	85	Coppermine	81	73
Hopes Advance	85	89	“Fram”	94	82
Olekminsk	67	80	“Maud”	96	78
Verkhoyansk	60	72	“Sedov” Foka Bay	91	80
West Station*	83	76	Danmarkshavn**	79	84
Eismitte*	86	79	Angmagssalik**	73	82

*Stations on Greenland Ice Cap. **Stations on northeast Greenland coast.

217      |      Vol_VII-0223                                                                                                                  

Table XX . Mean relative humidity (%)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	81	85	..	..	..	..	..	..	..	..	80	81	..	..
003	74	75	75	80	87	93	96	96	93	85	79	75	84	2
004	84	83	81	82	82	86	90	86	83	82	81	83	84	..
005	86	83	80	82	84	88	85	83	84	82	85	86	84	..
007	89	84	83	89	88	93	96	96	93	88	88	86	89	5-6
008	76	..	..	..	..	..	95	94	86	79	77	75	..	0-1
Alaska, Coastal and Insular:
100	84	80	80	80	84	87	86	88	88	86	83	80	84	2
Alaska, Inland:
156	81	76	62	55	53	56	63	69	67	74	81	82	68	9
157	92	85	81	67	56	61	65	76	77	80	86	91	76	1-2
Canada, Coastal and Insular:
201	..	..	..	..	79	79	80	79	84	83	..	..	..	..
204	85	84	87	86	90	89	86	87	86	84	88	86	87	2-5
211	..	..	..	..	83	77	79	83	83	82	..	..	..	4
216	..	..	..	..	..	89	90	92	93	93	..	..	..	2-3
221	..	..	..	..	..	90	84	85	89	..	..	..	..	5
Canada, Inland:
250	..	..	..	..	..	73	76	85	85	..	..	..	..	5
252	..	..	..	..	67	69	76	81	86	..	..	..	..	5
253	90	84	78	65	56	64	64	69	75	79	88	91	75	5
255	93	89	76	70	61	65	66	68	75	78	88	91	77	4
256	90	84	83	73	67	61	64	71	80	85	93	89	78	3

218      |      Vol_VII-0224                                                                                                                  

Table XX . Mean relative Humidity (%) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland, (cont.):
258	83	83	76	67	62	59	62	65	71	82	87	80	73	4
260	..	..	..	..	80	68	71	74	80	90	..	..	..	5
Greenland and Iceland, Coastal and Insular:
303	84	81	88	78	80	80	80	76	70	74	86	87	80	2
304	73	74	72	78	87	86	82	81	85	89	84	78	75	24
306	..	..	..	..	72	73	69	68	69	..	..	..	..	5
314	89	89	89	89	88	84	87	87	86	88	90	88	88	7
317	83	82	81	79	77	74	73	72	73	80	80	81	77	35
320	75	76	74	72	72	73	76	78	76	75	74	75	75	16
331	81	80	80	74	70	75	75	74	74	78	81	81	77	3
Greenland and Iceland, Inland:
351	80	77	78	81	86	84	88	84	84	80	79	78	82	1
Europe, Coastal and Insular:
403	81	80	80	77	76	82	81	83	82	80	79	82	80	..
408	82	81	81	82	82	83	84	85	85	85	85	83	83	15
412	68	69	71	70	68	71	74	73	75	76	73	69	71	18
414	77	76	74	71	69	71	74	80	80	80	80	78	75	18
415	86	85	80	75	71	70	75	80	83	86	88	88	81	24
420	75	73	73	69	60	74	76	75	76	75	76	74	74	18
421	83	84	81	71	62	61	67	73	66	81	87	88	76	7
423	86	85	83	77	64	65	61	73	78	88	91	87	78	7
424	87	87	82	78	71	72	73	80	83	86	88	89	81	26
425	88	87	83	81	75	73	80	86	88	88	90	90	84	21

219      |      Vol_VII-0225                                                                                                                  

Table XX . Mean relative humidity (%) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular, (cont.):
426	86	85	79	71	63	63	67	74	79	82	86	87	77	25
428	88	87	83	76	73	68	74	86	85	87	90	89	82	25
429	87	85	81	75	72	69	73	80	85	87	89	88	81	25
Europe, Inland:
450	85	85	84	74	67	63	63	73	77	83	88	87	77	7
454	73	70	70	65	65	66	70	72	77	78	75	76	72	18
455	79	81	78	68	55	55	61	71	73	82	86	84	73	7
456	90	87	79	70	61	56	63	72	76	85	90	92	77	7
Asia, Coastal and Insular:
500	87	84	90	88	88	92	93	92	90	86	87	88	90	7-8
501	82	80	80	84	86	90	90	91	90	87	82	82	85	5-6
502	85	82	82	73	71	70	72	73	80	81	82	85	78	8
503	86	85	82	84	86	90	90	94	90	87	84	82	87	7-8
507	80	82	80	80	78	78	79	80	82	81	82	82	80	17
508	85	84	83	86	87	92	92	91	91	90	88	86	88	6
509	88	87	84	87	89	88	81	87	90	90	87	84	87	6-7
510	89	88	85	88	88	91	90	90	89	88	88	86	88	19
511	85	85	86	87	89	92	92	90	90	88	87	84	87	2
513	81	83	80	80	78	77	76	77	82	80	82	79	80	..
515	81	82	86	86	88	85	78	84	89	90	87	85	85	6
518	89	89	86	87	89	90	87	90	88	88	89	85	89	26
519	87	88	84	84	88	89	88	92	90	90	89	86	88	22
520	86	90	88	84	83	81	78	82	88	91	87	88	85	4-8
522	80	78	79	70	72	67	69	80	82	87	84	79	77	1

220      |      Vol_VII-0226                                                                                                                  

Table XX . Mean relative humidity (%) (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland:
553	84	81	81	82	85	83	74	82	85	89	84	82	83	18
554	79	72	74	79	79	73	71	81	87	84	80	75	78	2
556	72	71	67	60	55	53	59	69	75	77	76	74	67	9
558	78	78	76	71	70	65	68	78	78	83	84	82	76	6
562	81	80	75	70	67	69	71	77	82	82	83	81	77	10
566	81	80	73	67	61	64	64	72	75	76	81	80	73	7-15
567	81	81	72	62	60	60	61	69	74	80	83	79	72	12
573	84	80	73	67	63	64	66	77	77	81	85	89	76	9

221      |      Vol_VII-0227                                                                                                                  

Table XXI . Average vapor pressure (mbs)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
003	0.3*	0.3*	0.4*	0.8*	2.0*	5.2	5.9	6.0	4.2	1.8	0.6*	0.3*	…	1-2
007	1.5	1.2	0.7	1.3	2.9	5.2	6.0	6.1	5.5	3.3	1.7	1.3	3.1	5-6
Asia, Coastal and Insular:
500	2.2	1.9	1.1	1.9	3.2	5.1	6.4	6.7	5.6	4.0	2.7	2.1	3.6	7-8
501	1.2	1.1	0.7	1.3	2.8	5.6	7.2	6.9	5.9	2.9	1.5	1.1	3.2	5-6
503	1.1	1.1	0.7	1.1	2.7	5.1	6.5	6.1	5.2	2.7	1.5	0.9	2.9	7-8
507	2.1	1.7	1.2	2.1	3.5	5.2	7.1	7.6	5.9	4.3	3.2	2.4	3.9	17
508	1.7	1.3	0.8	1.7	3.5	5.2	7.5	8.0	6.5	4.0	2.4	1.9	3.7	6
509	1.5	1.1	0.9	1.7	3.9	6.3	9.1	9.3	6.8	3.7	1.9	1.3	4.0	6-7
510	1.3	1.3	0.9	1.7	3.2	5.7	7.5	7.9	6.4	3.5	1.9	1.3	3.6	19
518	2.4	1.9	1.7	2.4	4.5	5.9	8.4	9.3	7.5	4.9	3.7	2.7	4.7	26
519	2.0	1.3	1.5	2.1	4.4	5.7	8.8	9.3	7.3	4.5	2.9	2.1	4.4	22
Asia, Inland:
553	1.2	1.2	1.2	1.9	3.5	6.7	10.3	9.9	7.1	3.5	1.5	1.1	4.4	18

* - The values for November through May were obtained from plot of annual

course of vapor pressure, page 253, “Scientific Results of the Maud

Expedition: by Sverdrup.

222      |      Vol_VII-0228                                                                                                                  

        Data concerning the annual course of vapor pressure over the Arctic

are not available in any regional detail. However, the values nearly

everywhere should be lowest in winter (0.1 to 0.4 mb near sea level) and

highest in July or August (4.0 to 6.5 mb near sea level). These values

are approximately of the same order of magnitude as the saturation vapor

pressures at the observed seasonal temperatures. (See page .)

Diurnal Variation of Humidity . Table XXII shows the diurnal variation

of relative humidity as observed on the Fram in South Ellesmere Land.

Average humidity is highest between midnight and 0400h and lowest between

noon and 1600h in all months except January, when the diurnal maxima and

minima are reversed. The January reversal in humidity appears to correspond

to a similar reversal in the diurnal temperature variation during this month

at most stations on the Arctic Ocean and in the Canadian Archipelago.

Sverdrup [ 43 ] found the diurnal variation in humidity to be very small

over the pack-ice but the hours of maxima and minima appear to correspond

quite closely to those recorded at the coast by the Fram .

223      |      Vol_VII-0229                                                                                                                  

Table XXII . Diurnal range in relative humidity (%) in South

Ellesmere Land, 1898-1902

Hour	2h	4h	6h	8h	10h	12h	14h	16h	18h	20h	22h	24h	Ra.*
Jan	83.0	83.0	83.4	83.1	83.1	83.3	83.3	83.7	83.6	83.3	83.1	83.1	0.7
Feb	85.1	84.8	84.3	84.4	84.3	84.0	83.8	83.7	84.6	84.8	84.8	84.4	1.4
Mar	80.6	81.0	80.9	80.6	80.6	79.3	79.0	79.6	79.7	80.3	80.3	80.1	2.0
Apr	83.5	83.0	82.5	81.0	79.5	78.6	78.5	78.4	79.2	81.2	82.8	83.4	5.1
May	82.1	81.3	79.6	78.7	77.4	76.1	76.3	76.8	77.8	79.0	80.2	81.4	6.0
Jun	82.2	81.9	80.8	79.4	78.2	76.8	78.2	75.9	77.4	78.5	79.9	82.0	6.3
Jul	84.4	84.4	84.6	83.4	82.4	80.5	79.1	79.1	79.7	81.3	82.6	84.1	5.7
Aug	89.3	89.4	89.1	89.3	86.9	85.2	84.3	82.6	85.2	86.4	88.0	88.7	6.8
Sep	86.3	86.7	85.2	84.0	83.3	83.0	83.0	83.6	85.8	86.4	85.7	86.3	3.7
Oct	82.3	81.7	81.5	80.6	81.2	80.0	80.5	80.2	82.5	82.3	82.8	83.0	3.0
Nov	81.7	81.4	81.7	81.4	81.9	81.2	80.6	80.9	80.5	80.8	81.1	81.2	1.4
Dec	84.1	84.3	83.8	83.8	84.0	83.4	83.3	83.2	83.8	83.6	83.6	84.2	1.1

*Mean diurnal range.

224      |      Vol_VII-0230                                                                                                                  

        Sverdrup also found that the vapor pressure in the surface air over

the pack-ice has a regular diurnal variation in all months in which the

relative humidity varies regularly but that the phase is reversed. (See

Fig. 50 .) The maximum vapor pressure occurs at the hour of minimum

relative humidity and the minimum vapor pressure occurs near midnight fig. 50 here

when the relative humidity is at its maximum.

       

table xxiii here

        Non-Periodic Variations in Humidity . While the annual and diurnal variations

in the actual moisture content of the atmosphere are quite considerable over

the Arctic, the corresponding variations in relative humidity are very

slight. The principal variations in relative humidity appear to be non–

periodic in nature and the result of several causative factors. In some

coastal areas and in regions which exhibit a local diversity in the character

of the land surface, large changes in humidity can accompany rapid changes

in wind direction. This is particularly true during summer along the coasts

of the Polar Sea, where a sudden change in the wind from an offshore to an

onshore direction will produce an immediate rise in relative humidity. This

change is primarily caused by the sudden change in temperature (see page )

rather than by any large difference in the actual moisture content between

225      |      Vol_VII-0231                                                                                                                  

Table XXIII. Diurnal variation of relative humidity (%)

(with respect to water)

Station	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Ayon Island (69°52′N., 167°52′E.)
Mean		82.8	86.9	83.7				86.0	84.2
Max.		83.9	88.7	89.0				86.7	84.5
Hour of Max.		0100	0200	0400				1900	0800
Min.		81.2	84.8	79.1				85.5	84.0
Hour of Min.		1500	1600	1200				1200	0100
Amplitude		2.72	3.84	8.95				1.20	0.56
Cape Serdze Kamen (66°53′N., 188°22′E.)
Mean	79.4	84.5	86.4	91.1*			90.7	86.6	83.0
Max.	80.0	86.6	91.1	93.1*			92.1	89.0	84.5
Hour of Max.	0700	0200	2400	0100*			2200	0400	2400
Min.	78.4	82.2	81.7	89.3*			88.8	84.7	81.8
Hour of Min.	1200	1300	1100	1000*			1500	1300	0700
Amplitude	1.59	4.45	9.39	3.80*			3.31	4.31	2.75
Pack Ice 1922 (Approx. 71°N., 185°E.)
Mean						95.0	95.4	84.5
Max.						97.0	96.1	85.2
Hour of Max.						2300	0800	1500
Min.						91.3	91.7	84.1
Hour of Min.						1500	1400	2300
Amplitude						5.66	1.35	1.12

* Four Pillar Island (74°43′N., 165°25′E.)

226      |      Vol_VII-0232                                                                                                                  

Table XXIII. Diurnal variation of relative humidity (%)

(with respect to water) (cont.)

Station	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Pack ice 1923 (Approx. 75.5°N., 165°E.)
Mean				95.5	97.0	97.3	91.1	86.0
Max.				97.7	98.3	98.2	91.5	86.3
Hour of Max.				0200	0100	0600	2000	0300
Min.				93.5	95.7	95.8	90.1	85.7
Hour of Min.				1600	0900	1300	1400	1100
Amplitude				4.17	2.60	2.38	1.40	0.63
Pack Ice 1924 (Approx. 76.5°N., 145°E.)
Mean			81.8	91.3	94.7
Max.			83.4	92.7	96.1
Hour of Max.			0200	0100	2300
Min.			79.7	89.7	92.5
Hour of Min.			1300	1400	1100
Amplitude			2.73	3.06	3.60

227      |      Vol_VII-0233                                                                                                                  
offshore and onshore winds. Large variations in relative humidity can

also occur with increases in the wind to speeds which are sufficient to

break down the surface temperature inversion or upon the initiation of

winds which exhibit a considerable dynamical heating because they possess

a large downslope component.

        At lower latitudes in the Arctic the changes in air mass accompanying

frontal passages are probably the most important among the several factors

which account for rapid and sizeable changes in the atmospheric moisture

content. Such changes in air mass are reflected in the observations by

corresponding changes in both the specific humidity (vapor pressure) and

the relative humidity terms.

228      |      Vol_VII-0234                                                                                                                  

       

CLOUDINESS AND CEILINGS

        The general character of cloud cover over the Arctic differs

considerably from that considered typical for most temperate regions.

The uniform and contourless stratus clouds which are by far the most

frequent type observed give to the Arctic its reputation for a dull and

monotonous appearance. Over the Arctic Ocean during summer the low

stratus type of cloud constitutes from 70 to 80 percent of all clouds

observed. In winter and spring they are not so frequent, but they still

constitute from 45 to 60 percent of all cloud types present. Along the

coast in more southerly locations, the stratus clouds are proportionately

less frequent. In these regions the cloud decks tend to be more often

broken up by convective currents, with a resulting increase in the

proportion of stratocumulus cloud reported.

        Sverdrup [ 43 ] has shown that there is no direct relation between

air temperature and the occurrence of stratus over the maritime Arctic

regions. However, he does show that the occurrence of low stratus is

closely associated with the presence of a surface temperature inversion.

229      |      Vol_VII-0235                                                                                                                  
Along the coasts of the Arctic Ocean in summer the surface inversion

exists only when there is an onshore wind, but with offshore winds and

when the temperature is high at the ground, the temperature decreases

regularly with altitude. Conditions are then unfavorable for the

formation of low cloud. These processes probably account for the

secondary minimum in cloudiness that is observable during one or more

of the summer months at a number of Arctic coastal stations (see Table XXIV ).

       

table XXIV here

        Over nearly all of the Arctic cloudiness is most extensive in summer

and autumn and least extensive in winter and spring. Over the Arctic

Ocean during summer the low stratus overcast may persist for weeks at a

time without once offering a glimpse of blue sky or upper cloud. Days

with clear sky occur rarely if ever. It is significant to note that

average sky conditions computed from observations on both the Fram and

the Maud indicate that no clear days (cloudiness, 2-tenths or less) are

to be expected during any of the months from June through August.

       

tables XXV to XXVII here

        The Arctic Ocean proper and those adjacent coastal regions with a

preponderance of onshore winds show a maximum cloud cover in midsummer.

Those localities more often subject to offshore winds present a maximum

230      |      Vol_VII-0236                                                                                                                  

Table XXIV . Mean monthly cloudiness (%)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	36	41	56	48	76	87	91	85	91	63	39	36	62	2⅓
003	36	42	34	47	73	85	88	88	82	80	51	40	62	2
004	84	83	79	83	82	84	90	85	81	83	83	81	83	…
005	82	80	82	86	90	89	87	89	90	86	86	81	86	4
006	60	69	52	56	82	82	84	88	89	83	62	49	71	4
007	68	62	50	64	90	95	88	92	95	82	74	65	78	5
008	53	..	..	..	..	..	82	82	80	65	50	57	..	0-1
Alaska, Coastal and Insular:
100	47	57	53	53	80	80	83	97	90	91	70	60	70	2½
102	53	53	57	57	70	67	73	87	73	77	53	63	63	2½
104	54	52	50	64	62	62	79	75	68	70	52	58	62	10
105	52	53	49	50	69	63	66	75	72	69	61	50	61	10
106	70	60	50	63	83	70	70	77	80	87	70	67	67	8
Alaska, Inland:
150	53	47	70	57	67	70	70	87	73	70	53	70	63	2½
151	63	53	67	57	80	77	73	87	87	87	80	80	73	2
152	40	47	70	40	60	57	53	73	77	70	47	43	57	2
153	44	43	42	37	40	41	45	52	57	60	50	40	46	10
154	60	47	57	77	80	80	87	83	80	77	63	70	70	2½
156	63	53	60	60	70	70	70	73	80	80	57	60	63	7
157	48	50	54	56	61	56	62	68	72	66	57	48	58	10
Canada, Coastal and Insular:
201	34	28	50	35	60	66	70	78	63	44	28	36	49	2
202	20	41	34	45	62	66	62	78	81	57	33	33	51	2-5

231      |      Vol_VII-0237                                                                                                                  

Table XXIV . Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
204	39	42	50	54	60	72	62	76	78	70	56	34	58	3
213	36	36	40	30	48	58	48	60	70	76	52	30	49	5
216	46	46	45	53	62	58	58	74	78	68	56	47	58	6
217	30	26	29	36	74	58	48	82	79	67	40	..	..	1
218	32	25	27	42	68	69	58	68	83	68	56	27	52	2
220	50	55	64	62	70	82	80	78	84	71	74	58	69	…
223	49	48	55	66	81	76	60	68	79	85	76	52	66	8-11
224	48	50	48	57	67	68	64	51	64	70	65	51	59	2
226	36	44	26	50	64	56	62	65	63	66	40	53	53	2
227	68	63	68	74	80	74	70	67	74	79	85	76	73	6
228	45	52	38	53	56	52	50	48	59	68	56	50	52	5
Canada, Inland:
250	41	42	43	44	45	51	60	74	70	67	58	49	54	8
252	57	49	44	48	49	53	58	58	59	63	62	63	55	15
253	70	70	75	57	66	76	86	65	78	69	81	71	71	…
254	44	44	38	44	46	42	43	51	63	64	53	41	48	…
257	37	34	38	46	48	49	56	62	62	70	58	46	50	4
259	52	47	49	45	54	50	45	44	66	67	62	47	52	18
260	43	47	39	41	50	41	58	56	66	73	67	51	53	…
Greenland, Iceland, Coastal and Insular:
301	37	46	62	42	..	66	69	65	68	59	60	36	62	5
302	47	47	40	57	63	60	70	60	67	67	63	43	57	2
303	63	44	50	32	43	52	51	48	48	46	56	54	49	…

232      |      Vol_VII-0238                                                                                                                  

Table XXIV . Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland, Iceland, Coastal and Insular (cont.):
304	49	45	47	54	66	72	66	68	68	70	71	62	62	31
307	42	48	50	41	50	64	60	65	56	49	56	49	52	…
308	59	71	50	68	53	58	51	55	51	54	53	62	57	…
310*	73	68	67	71	71	71	69	71	72	73	76	76	71	15
314	75	72	69	70	68	69	66	70	70	69	68	67	69	31
317	67	61	61	61	63	62	56	54	63	68	67	66	62	30
318	64	63	59	58	60	61	59	62	62	61	58	58	61	29
320	68	68	64	62	64	66	64	68	64	63	64	64	65	2
330	73	74	70	70	60	63	68	72	74	72	72	71	70	16
331	67	68	71	62	65	71	72	72	66	67	66	67	68	10
332	78	78	76	77	74	78	81	86	80	72	70	79	77	9
333	76	73	74	72	78	74	78	75	79	68	74	76	75	11
334	73	70	71	71	66	66	73	73	70	77	77	74	72	14
335	68	64	64	70	64	71	76	80	74	76	69	66	70	…
336	75	74	75	74	70	72	74	79	75	79	72	72	74	20
337	67	67	66	67	74	72	78	75	74	62	69	66	70	11
339	85	80	84	84	80	82	85	83	83	86	84	82	83	10
340	66	67	69	69	71	69	75	76	72	72	66	65	70	18
341	71	70	79	72	71	68	82	69	76	73	75	67	73	8
Greenland, Iceland, Inland:
351	66	49	54	60	61	54	77	60	53	54	52	57	58	1
360	73	70	70	76	79	74	78	80	78	75	75	74	75	7
361	75	71	72	75	68	70	74	79	75	81	74	73	74	15

* - Data for Agto, 67° 57′ N., 53° 44′W.

233      |      Vol_VII-0239                                                                                                                  

Table XXIV . Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular:
400	70	67	61	71	86	85	87	92	92	90	73	64	78	10
401	64	56	52	76	87	91	91	96	82	85	67	72	77	4
403	62	59	58	56	66	75	70	73	76	72	61	59	66	14
406	70	73	73	74	75	73	69	69	77	73	74	65	72	…
407	70	70	75	74	77	74	68	73	82	75	74	69	73	10
408	76	74	72	71	76	74	72	75	77	77	80	77	75	44
410	78	76	72	68	68	69	71	69	75	75	77	76	73	…
412	65	63	58	55	58	59	61	59	67	66	65	59	61	44
414	65	64	60	62	68	68	66	67	76	70	70	60	66	…
415	70	70	60	69	72	68	75	77	77	81	77	76	73	10
417	82	77	73	81	89	83	80	83	84	86	86	85	82	7
420	72	71	68	65	66	68	70	70	75	71	71	68	70	…
421	62	60	59	56	55	50	53	68	61	63	60	69	59	20
423	66	62	55	54	61	55	57	62	63	68	70	71	62	20
424	80	75	67	64	58	55	53	62	63	74	81	83	68	…
425	73	70	67	68	75	66	64	72	75	77	82	75	72	21
426	84	78	68	62	60	60	61	64	69	79	83	88	71	10
428	88	87	83	76	73	68	74	80	85	87	90	89	82	25
429	79	82	73	75	79	69	73	78	82	85	86	78	78	13
Europe, Inland:
450	62	57	54	56	68	64	68	72	69	68	66	67	64	…
451	66	63	61	64	70	66	66	71	73	71	70	66	67	44
453	76	65	61	71	67	66	67	70	71	80	79	76	71	9

234      |      Vol_VII-0240                                                                                                                  

Table XXIV . Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Inland (cont.):
454	77	76	73	71	73	73	77	79	79	77	77	75	76	44
455	66	62	56	54	52	52	55	56	56	63	66	69	59	…
456	66	59	59	59	63	60	65	68	69	72	71	70	65	20
457	76	70	60	59	55	56	53	61	62	75	82	81	66	36
458	76	71	64	62	61	63	59	66	70	78	84	82	70	35
Asia, Coastal and Insular:
500	63	61	63	77	89	91	85	89	91	92	81	69	79	8
501	57	47	46	62	81	88	80	89	89	80	58	62	70	5
502	58	53	60	59	81	84	80	94	88	78	58	57	70	4
503	57	60	46	63	86	87	86	93	90	85	64	55	73	7
504**	30	45	34	62	71	85	84	95	90	81	66	44	66	2½
505	80	77	71	73	82	76	75	81	84	82	83	75	78	14
506	76	68	61	70	82	81	71	80	83	85	81	74	76	14
507	69	69	65	68	80	75	70	78	82	83	80	72	74	16
508	68	64	60	67	86	82	79	90	90	88	80	70	77	6
509	71	66	61	68	86	84	79	92	88	85	72	62	76	7
510	65	69	59	70	85	91	81	90	88	85	75	64	77	18
511	40	36	32	53	77	80	76	85	90	72	60	51	63	1½
513	40	48	43	53	66	71	73	79	78	70	55	50	60	7
515	34	36	33	36	65	76	68	78	85	73	60	46	58	9
517	55	58	50	54	79	74	72	79	81	74	67	64	67	9
518	74	67	66	72	88	83	76	82	88	87	87	79	79	26
519	69	64	57	69	84	80	68	81	86	86	88	80	76	22

** - Data from station approximately 75° N., 147° E.

235      |      Vol_VII-0241                                                                                                                  

Table XXIV. Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
520	63	65	59	62	72	75	68	75	79	80	70	67	70	33
521	64	59	59	68	84	78	72	79	81	83	76	66	72	13
522	47	43	40	46	54	53	61	70	73	65	65	51	56	3-6
523	57	69	68	60	77	84	80	86	91	83	78	75	76	3
525	53	64	61	74	86	74	77	82	85	79	78	63	73	10
526	55	53	53	64	68	73	76	72	67	70	64	56	64	14
527	52	63	54	55	68	69	75	74	72	71	65	60	65	14
531	64	59	62	53	73	77	79	67	56	64	68	62	65	4
Asia, Inland:
551	42	54	49	64	80	74	74	77	81	79	55	48	65	3
552	60	46	56	63	68	75	79	79	81	90	73	59	69	12
553	64	66	65	64	77	80	70	83	84	86	71	62	73	18
554	65	70	59	69	75	81	70	75	85	82	72	65	72	17
555	71	58	68	58	67	75	64	74	80	85	76	56	69	4
556	34	31	33	48	61	64	64	66	66	64	46	39	51	33
557	52	54	29	36	40	64	64	68	74	71	65	48	55	4
558	40	42	32	34	51	57	62	72	70	68	54	48	53	9
559	53	48	44	52	63	65	61	75	74	71	62	56	60	10
560	67	54	52	51	67	62	58	65	69	70	65	62	62	11
561	55	49	43	47	60	58	55	61	67	69	68	61	58	9
562	66	59	54	58	70	69	62	68	72	80	72	69	67	24
563	63	60	58	59	68	68	63	70	79	81	70	63	67	46
564	59	64	63	67	75	75	73	76	77	81	72	62	70	5
565	61	51	58	67	79	60	50	53	67	78	69	70	64	13
566	56	60	49	53	68	65	58	63	70	74	63	68	63	23

236      |      Vol_VII-0242                                                                                                                  

Table XXIV. Mean monthly cloudiness (%) (cont.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
567	66	63	56	65	72	71	67	69	75	79	70	63	68	25
568	52	45	37	49	59	56	56	60	63	73	61	56	56	30
569	34	41	41	57	69	63	50	67	69	68	54	34	54	1
570	23	20	24	34	46	38	36	42	48	59	42	22	36	16
572	53	54	50	56	67	65	68	71	71	72	65	56	62	21
573	64	65	58	56	61	65	60	62	67	71	76	71	65	9
574	67	58	57	56	65	64	58	64	63	78	75	65	64	20
575	61	57	60	64	68	63	62	65	71	76	75	65	66	18
576	73	64	58	63	67	67	68	68	74	75	79	77	69	13

237      |      Vol_VII-0243                                                                                                                  

Table XXV. Mean number of clear days

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	g	14	12	9	8	7	0	0	0	0	4	11	15	80	2 1/2
003	g	14	9	12	10	2	0	0	0	1	1	7	9	65	2
004	g	*	*	1	0	*	*	*	*	0	*	*	*	2	…
005	c	1	1	1	1	*	1	*	*	*	0	0	1	6	…
006	c	6	2	7	6	1	2	2	1	1	1	6	9	43	4
117	c	5	3	8	5	*	0	1	1	0	*	2	5	31	5
Alaska, Coastal and Insular:
100	g	17	18	18	14	7	9	8	4	4	6	12	13	130	10
102	g	15	13	15	12	12	13	7	6	7	8	11	12	132	11-13
104	g	10	11	12	9	9	8	5	4	6	7	10	11	102	19
105	g	13	8	7	4	5	8	3	4	3	2	2	2	61	2-4
106	g	9	8	10	9	7	8	6	4	6	6	7	9	89	24-26
Alaska, Inland:
152	g	15	14	18	16	12	10	4	5	6	7	15	15	137	8-10
153	g	15	16	17	18	15	15	15	11	10	9	10	13	164	10
154	g	11	10	12	9	6	9	4	5	5	7	11	11	100	18-19
156	g	10	9	11	10	4	4	5	3	4	5	8	11	84	10
157	g	12	10	10	10	6	8	7	6	5	7	8	12	101	10
Canada, Coastal and Insular:
201	c	16	14	8	12	5	4	4	1	4	12	17	16	113	2
202	c	20	11	13	9	6	5	6	1	1	7	15	14	108	3
204	c	16	13	13	9	8	6	8	4	3	7	11	18	117	3-5

c – 2-tenths of less total cloud cover. g – Undefined. * - Less than 0.5 day.

238      |      Vol_VII-0244                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
213	c	17	21	20	20	15	13	14	6	6	7	12	16	168	3-5
220	g	14	16	16	8	4	4	6	2	0	2	5	10	87	2
223	g	11	12	12	6	5	4	9	6	3	3	5	14	90	5-7
224	g	15	18	19	10	5	5	6	10	4	6	7	12	116	4-5
226	c	13	18	17	15	7	6	6	7	4	9	7	18	125	2
227	c	11	7	7	6	4	6	6	10	4	5	6	8	80	2-5
Canada, Inland:
250	c	16	13	20	13	10	12	8	6	4	7	13	15	136	2-4
Greenland and Iceland, Coastal and Insular:
301	g	13	10	3	..	..	4	4	2	2	4	5	9	..	0-3
302	g	12	11	16	11	8	9	6	10	6	7	8	15	119	2
304	g	9	10	10	8	5	3	5	5	4	3	3	6	71	31
307	g	12	10	9	11	8	5	6	4	4	9	4	11	93	…
308	g	7	2	8	7	7	6	7	5	7	7	8	7	78	19
310**	g	1	2	2	1	2	2	2	1	1	1	1	2	18	15
314	g	1	1	2	2	3	2	2	2	2	3	2	2	24	31
317	g	4	4	5	6	6	6	6	8	6	4	4	5	64	30
318	g	5	7	7	9	9	7	8	7	7	7	7	7	87	28
320	g	2	2	4	3	4	2	3	2	3	4	4	3	35	19
330	g	2	2	3	2	5	4	4	3	2	2	2	3	32	16
331	g	2	2	2	2	2	1	2	1	1	1	2	2	20	16
332	g	1	1	1	1	2	1	1	*	1	*	1	*	10	16

c – 2-tenths of less total cloud cover. g – Undefined. * - Less than 0.5 day. ** - Data for Agto, 67° 57' N., 53° 44' W.

239      |      Vol_VII-0245                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.)
333	g	1	2	2	2	11	1	1	1	2	2	1	1	16	11
334	g	1	1	2	1	2	2	1	1	1	*	*	1	13	14
335	g	3	4	4	3	5	3	2	1	2	3	3	3	34	15
336	g	1	1	1	2	3	2	1	1	1	1	2	1	17	16
337	g	3	2	3	3	1	2	1	*	1	2	2	2	22	11
339	g	*	1	1	1	*	*	*	0	*	*	*	1	4	10
340	g	4	3	2	3	3	3	1	1	1	1	3	4	30	14
341	g	7	3	2	3	4	4	1	4	2	2	2	5	39	8
Greenland and Iceland, Inland:
360	g	4	3	1	2	1	2	2	1	1	3	2	2	24	7
361	g	1	1	2	2	2	2	1	1	1	*	1	1	15	16
Europe, Coastal and Insular:
400	c	3	3	6	3	1	1	1	*	0	*	3	6	28	10
401	c	4	5	7	2	1	1	1	0	0	0	2	8	30	4
403	c	6	6	7	7	4	3	3	2	2	3	6	7	56	…
406	a	3	3	3	3	3	3	4	4	1	2	2	4	35	12
407	c	1	1	1	1	1	1	3	2	0	1	1	2	15	10
408	a	2	2	3	2	2	2	2	2	1	1	1	0	22	29
412	a	3	5	5	4	5	6	5	3	3	4	3	4	50	28
414	c	5	4	6	5	5	5	5	4	3	4	4	7	57	25
415	c	1	1	3	2	1	2	1	*	*	1	1	1	14	18

a – Less than 1-tenth total cloud cover. c – 2-tenths of less total cloud cover. g – Undefined. * - Less than 0.5 day.

240      |      Vol_VII-0246                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
417	c	1	2	1	1	0	1	2	0	1	0	0	1	10	7
420	c	4	5	5	5	5	5	4	3	2	3	3	3	47	27
421	c	11	7	8	10	12	11	10	7	10	6	6	5	103	8
423	c	4	5	6	5	4	5	6	4	4	4	2	3	52	8
424	c	2	2	5	4	5	5	5	3	3	2	2	2	40	36
425	c	4	3	5	5	3	4	3	1	3	2	2	2	35	13
426	c	2	2	4	5	4	4	4	2	3	2	1	1	33	18
428	c	1	2	3	3	1	3	1	1	1	1	1	1	19	18
429	c	4	2	3	3	1	3	2	1	1	1	1	2	21	13
Europe, Inland:
450	c	5	4	5	6	4	2	3	4	2	4	2	4	45	8
451	a	3	3	4	3	2	3	3	2	1	2	2	3	31	18
453	c	3	3	4	3	3	3	2	2	1	1	1	2	28	9
454	c	2	2	3	3	2	2	1	1	1	2	2	2	23	31
455	c	7	6	6	9	10	8	8	5	6	5	4	2	76	8
456	c	5	4	5	5	5	4	5	4	3	3	3	4	50	8
457	c	3	3	6	6	5	5	5	4	4	2	1	2	46	36
458	c	2	3	5	5	3	3	4	3	2	2	1	1	34	35
Asia, Coastal and Insular:
500	c	4	3	4	2	*	*	2	1	*	*	2	4	21	8
501	c	7	7	9	5	2	*	2	1	*	2	7	5	46	5
502	c	8	6	6	6	1	1	2	1	*	2	5	6	43	4

a – Less than 1-tenth total cloud cover. c – 2-tenths of less total cloud cover. * - Less than 0.5 day.

241      |      Vol_VII-0247                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
503	c	7	4	8	5	1	*	1	0	1	1	5	7	40	7
505	b	2	2	2	2	2	3	3	1	0	1	3	2	24	13
506	c	3	4	5	2	1	2	3	1	0	1	1	2	25	14
507	c	3	3	3	4	2	3	3	2	1	1	1	2	26	16
508	c	3	3	5	3	1	1	2	*	*	1	1	3	23	6
509	c	4	3	5	3	*	1	1	0	*	1	2	6	26	7
510	c	5	4	5	4	1	*	2	*	*	1	2	5	29	18
511	c	15	15	17	11	5	4	5	2	2	6	7	13	102	2-3
512	g	6	7	12	10	6	4	7	5	2	4	5	13	81	2-3
513	c	13	8	12	8	4	3	2	1	2	3	6	7	69	4
514	c	11	12	14	10	6	4	5	2	3	2	8	10	86	11
515	c	17	14	15	13	4	2	4	2	1	3	7	11	93	5
516	c	16	11	9	12	7	7	6	5	3	6	9	8	98	4
517	c	6	4	6	5	2	2	1	0	1	1	2	4	34	9
518	c	3	4	4	3	0	1	2	1	*	1	1	3	21	26
519	c	3	4	6	3	1	1	3	1	0	*	2	3	27	22
520	g	4	3	4	3	2	2	3	2	1	1	2	4	31	10
521	c	4	4	6	3	1	2	2	1	*	1	2	5	33	13
522	c	10	9	11	9	7	5	5	2	3	3	3	8	75	4
523	c	8	6	7	6	2	2	2	1	1	1	2	3	41	3
525	c	6	6	5	2	1	1	2	1	1	2	2	5	34	8

b – 1-tenths or less total cloud cover. c – 2-tenths of less total cloud cover. g – Undefined. * - Less than 0.5 day.

242      |      Vol_VII-0248                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
526	c	7	6	8	4	3	2	1	2	3	3	4	6	48	13
527	c	8	17	10	12	7	10	5	6	4	12	11	11	110	4
531	c	3	3	4	6	1	1	1	3	5	5	2	2	35	4
Asia, Inland:
551	d	3	9	18	7	7	3	4	1	3	5	8	12	81	2
552	c	11	12	12	10	8	5	5	6	4	3	7	11	94	20
553	c	6	5	5	4	2	1	3	1	1	2	4	7	40	18
554	c	11	4	13	6	5	2	4	6	1	3	6	11	72	3
555	g	2	6	4	8	6	1	4	2	1	1	3	7	45	4
556	c	12	11	12	9	4	2	3	2	3	5	9	9	81	8
557	c	10	6	8	7	4	3	1	2	2	3	4	6	56	14
558	c	14	11	13	15	8	5	5	2	3	4	8	10	98	9
559	c	6	7	7	5	1	5	3	*	2	2	3	3	44	4
560	c	10	10	11	9	7	4	6	5	5	7	9	10	93	8
561	d	8	9	12	9	8	9	9	7	5	6	8	9	99	6
562	c	5	3	5	6	3	2	3	3	1	2	3	3	39	…
563	c	6	6	7	7	4	3	3	3	2	2	5	6	54	11
566	c	5	1	4	4	1	2	5	3	2	1	3	4	35	8
567	c	5	5	9	6	3	2	2	3	3	2	4	8	50	11
568	c	10	9	14	9	5	5	5	5	5	3	6	7	86	24
570	c	19	19	17	14	7	11	10	11	9	6	8	17	148	8

c – 2-tenths or less total cloud cover. d – 3-tenths or less total cloud cover. g – Undefined. * - Less than 0.5 day.

243      |      Vol_VII-0249                                                                                                                  

Table XXV. Mean number of clear days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
572	c	9	8	9	7	4	3	2	3	2	4	5	6	53	10
573	c	9	11	13	11	8	7	8	7	7	6	7	7	101	9
574	d	9	13	11	9	6	9	10	7	5	5	5	6	95	6
575	c	6	6	6	4	3	3	4	3	2	2	3	5	47	18
576	c	3	3	6	4	3	3	3	2	2	3	1	2	35	13

244      |      Vol_VII-0250                                                                                                                  

Table XXVI. Mean number of partly cloudy days

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	g	9	10	8	13	6	4	4	7	3	15	13	10	102	2 1/2
003	g	13	13	16	12	13	14	9	5	9	23	19	18	164	2
004	g	10	8	13	10	13	9	7	9	11	11	11	13	125	…
005	c	13	11	12	9	7	7	8	8	5	11	12	13	116	…
006	c	16	17	16	15	11	8	7	8	6	10	14	14	144	4
007	c	12	16	16	13	6	4	6	3	3	7	13	12	109	5
Alaska, Coastal and Insular:
100	g	4	4	5	5	5	7	7	6	5	6	5	5	64	10
102	g	5	5	6	7	9	8	5	7	8	7	5	5	77	11-13
104	g	7	6	6	7	10	9	7	8	8	8	6	5	87	19
105	g	5	5	5	4	4	6	4	4	5	6	8	9	67	2-4
106	g	8	7	7	8	11	10	9	9	9	9	7	7	101	24-26
Alaska, Inland:
152	g	6	6	5	7	11	13	13	10	8	7	4	6	95	8-10
153	g	5	3	5	5	8	8	8	8	7	4	5	5	71	10
154	g	6	5	7	7	9	8	6	7	7	7	6	6	81	18-19
156	g	6	6	7	9	11	14	9	6	7	6	6	6	96	10
157	g	4	4	6	5	7	6	6	5	5	4	5	5	62	10
Canada, Coastal and Insular:
201	d	11	12	17	15	14	11	19	14	15	12	10	11	151	2
202	d	9	11	15	15	11	11	11	11	11	13	12	13	143	3
204	d	4	6	7	9	9	8	9	6	7	6	5	4	79	3-5

c – 3- to 8-tenths total cloud cover. d – 3- to 7-tenths total cloud cover. g – Undefined.

245      |      Vol_VII-0251                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
213	d	3	3	5	3	5	4	4	6	5	4	4	5	52	3-5
218	d	12	12	14	14	13	10	17	16	10	16	13	20	167	2
223	d	10	6	7	8	5	5	7	6	6	6	5	7	76	5-7
224	d	4	3	2	5	5	4	5	8	4	5	5	3	52	4-5
226	d	6	6	4	5	7	8	7	8	4	5	7	5	71	2
227	d	8	7	8	7	6	5	7	7	6	6	4	7	77	2-5
Canada, Inland:
250	d	4	5	4	4	8	6	9	8	6	4	2	5	61	2-4
Greenland and Iceland, Coastal and Insular:
301	g	12	12	3	..	..	11	17	14	16	17	14	18	..	1-3
302	g	5	5	5	3	4	5	5	4	7	6	4	4	57	2
304	g	13	11	13	12	12	11	12	11	11	13	13	12	144	31
307	g	11	10	14	14	14	13	13	17	20	14	20	10	170	…
308	g	12	12	14	13	13	14	15	19	15	14	12	11	164	19
310*	g	16	14	16	16	15	14	16	16	16	16	14	12	181	15
314	g	15	15	16	16	15	16	17	15	15	14	15	17	186	31
317	g	14	13	14	13	13	13	16	14	14	14	13	14	165	30
318	g	13	9	12	10	12	12	11	11	12	11	11	14	138	28
320	g	16	15	15	16	17	17	17	16	16	15	14	18	192	19
330	g	14	12	13	15	15	15	13	12	13	14	13	13	163	16
331	g	15	12	14	13	17	15	14	15	16	19	15	15	100	16
332	g	13	11	13	11	15	13	10	10	11	12	12	15	146	16

d - 3- to 7-tenths total cloud cover. g - Undefined. * - Data for Agto, 67° 57′ N., 53° 44′ W.

246      |      Vol_VII-0252                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
333	g	12	11	12	12	14	14	12	13	11	15	15	13	154	11
334	g	16	16	15	17	18	16	15	17	17	16	16	16	194	14
335	g	14	13	13	12	13	12	12	11	11	11	13	15	151	15
336	g	16	14	12	12	14	13	14	11	13	11	14	16	157	16
337	g	15	15	15	15	15	14	13	14	13	16	15	14	174	11
339	g	10	10	9	8	13	12	9	12	11	10	10	12	125	10
340	g	15	13	15	12	13	13	14	14	15	15	15	15	169	14
341	g	8	11	9	11	11	11	9	10	11	12	11	10	124	8
Greenland and Iceland, Inland:
360	g	9	10	13	10	10	13	11	11	11	11	12	13	134	7
361	g	15	16	15	13	16	15	15	13	15	13	15	17	178	16
Europe, Coastal and Insular:
400	d	13	13	13	13	7	7	7	5	5	8	11	12	114	10
401	d	16	14	17	12	6	4	5	4	6	10	16	14	124	4
403	d	12	10	13	13	14	10	12	12	12	12	12	13	145	…
406	a	13	10	11	10	10	10	11	12	12	13	12	14	138	12
407	d	17	16	14	14	13	14	15	14	12	16	15	17	177	10
408	a	13	13	14	13	11	12	13	12	14	13	12	12	152	29
412	a	14	11	14	15	16	14	14	16	13	14	12	13	166	28
414	d	12	11	12	11	12	11	13	14	11	13	13	12	145	25
415	d	14	13	16	13	12	14	13	14	13	12	12	13	160	18
417	d	12	10	17	11	7	9	27	9	9	10	9	9	139	7

a - 1- to 9-tenths total cloud cover. d - 3- to 7-tenths total cloud cover. g – Undefined.

247      |      Vol_VII-0253                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
420	d	13	11	13	13	14	14	15	14	13	14	12	13	158	27
421	d	10	10	11	11	14	14	17	16	14	12	11	8	148	8
423	d	13	9	12	15	17	15	17	15	12	9	10	8	152	8
424	g	9	10	12	14	17	17	19	18	17	12	8	7	160	36
425	d	12	11	15	14	15	17	16	16	13	12	11	11	163	13
426	d	10	9	14	13	16	17	16	18	15	11	8	8	154	18
428	d	10	10	14	13	16	15	16	14	11	10	8	10	147	18
429	d	8	9	13	10	12	14	14	14	11	9	10	10	132	13
Europe, Inland:
450	d	16	14	15	15	13	12	15	10	12	11	11	10	154	8
451	a	16	14	16	15	12	13	15	12	15	11	13	14	166	18
453	d	11	14	15	12	16	15	18	16	16	10	10	12	165	9
454	d	11	11	14	12	14	13	12	12	11	13	11	13	146	31
455	g	11	9	11	12	15	15	17	16	17	9	10	9	151	8
456	d	14	11	14	12	14	12	14	14	13	10	11	8	147	8
457	d	10	11	13	13	18	17	19	17	16	12	9	9	164	36
458	d	12	10	13	13	18	17	19	16	15	10	8	10	161	35
Asia, Coastal and Insular:
500	d	15	16	17	11	7	6	7	5	5	8	9	12	119	8
501	d	14	16	16	15	10	8	8	5	6	11	13	15	138	5
502	d	12	15	19	14	10	8	9	3	7	10	15	16	141	4
503	d	13	15	17	13	8	8	7	5	5	9	13	15	129	7

a - 1- to 9-tenths total cloud cover. d - 3- to 7-tenths total cloud cover. g – Undefined.

248      |      Vol_VII-0254                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
505	b	12	10	14	14	9	11	13	11	9	11	9	13	136	13
506	d	11	12	15	14	10	9	12	12	8	7	7	10	127	14
507	d	14	13	17	12	11	11	13	10	10	12	12	15	150	16
508	d	14	14	15	15	9	10	10	7	6	8	12	15	136	6
509	d	11	12	15	14	9	8	12	6	7	9	13	14	131	7
510	d	12	11	16	11	8	6	8	6	7	9	12	13	119	18
511	d	4	3	5	3	3	4	2	4	3	4	4	6	45	2-3
512	g	2	3	3	4	3	3	3	2	4	4	6	4	41	2-3
513	d	4	3	4	4	4	6	6	4	5	5	5	5	55	7
514	d	3	2	3	4	3	2	3	2	2	2	2	3	30	11
515	d	9	9	13	12	13	12	12	8	5	10	9	11	123	5
516	d	9	6	8	6	9	8	6	4	3	5	5	5	77	4
517	d	18	18	18	16	11	13	16	14	14	15	17	17	187	9
518	d	12	12	15	12	8	9	12	10	7	7	8	9	123	26
519	d	14	14	17	15	9	10	15	12	10	9	10	13	149	22
520	g	12	12	16	13	10	11	14	15	13	12	12	12	152	10
521	d	17	16	16	14	9	11	15	12	13	9	11	15	156	13
522	d	14	14	17	14	16	19	16	16	12	15	17	15	185	4
523	d	15	12	11	10	11	9	10	8	6	10	12	14	128	3
525	c	15	11	16	12	10	16	11	11	8	10	8	14	142	…
526	c	15	12	13	15	13	14	13	17	15	14	16	17	174	13

b - 2- to 8-tenths total cloud cover. c - 3- to 8-tenths total cloud cover. d - 3- to 7-tenths total cloud cover. g – Undefined.

249      |      Vol_VII-0255                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
527	e	3	1	2	2	4	3	2	2	5	3	1	1	28	4
531	a	10	6	8	6	9	8	6	4	3	5	6	6	77	4
Asia Inland:
551	c	11	4	4	6	6	3	7	5	6	5	5	2	64	2
552	d	4	4	5	5	5	5	5	4	4	2	4	4	51	20
553	d	12	10	14	15	11	11	14	9	9	6	10	11	133	18
554	d	13	7	9	10	9	12	12	10	8	9	11	13	123	3
555	g	14	12	13	12	11	13	17	14	10	7	10	14	147	4
556	d	15	13	15	13	16	15	17	15	14	14	14	16	177	8
557	c	11	9	12	13	13	14	14	13	14	13	14	13	154	14
558	c	11	11	14	10	14	16	15	13	12	14	12	15	157	9
559	d	18	13	19	18	15	14	18	12	12	17	17	15	188	4
560	e	4	2	4	4	4	7	8	6	5	4	4	3	55	8
561	f	2	1	2	3	3	4	4	2	2	1	2	2	28	6
562	d	12	16	17	16	17	18	19	19	14	13	12	13	188	…
563	d	13	11	14	13	13	15	18	14	12	9	10	12	154	11
566	d	13	17	19	17	15	17	17	16	13	14	12	15	185	8
567	d	20	15	15	14	17	17	20	17	14	13	14	18	194	11
568	d	14	13	14	15	18	19	19	17	16	16	16	15	192	24

a - 1- to 9-tenths total cloud cover. c - 3- to 8-tenths total cloud cover. d - 3- to 7-tenths total cloud cover. e - 3- to 6-tenths total cloud cover. f - 4- to 6-tenths total cloud cover. g - Undefined.

250      |      Vol_VII-0256                                                                                                                  

Table XXVI. Mean number of partly cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
570	c	11	8	12	12	20	16	18	16	14	15	15	10	167	16
572	g	12	10	13	14	13	17	17	15	13	12	13	13	162	10
573	e	4	3	2	5	5	7	8	7	6	3	3	3	56	9
574	f	1	0	2	2	3	3	3	2	1	1	0	2	20	6
575	c	13	13	14	15	16	17	17	16	14	11	10	12	168	18
576	c	12	14	15	16	17	17	18	17	14	12	12	11	172	13

c - 3- to 8-tenths total cloud cover. e - 3- to 6-tenths total cloud cover. f - 4- to 6-tenths total cloud cover. g - Undefined.

251      |      Vol_VII-0257                                                                                                                  

Table XXVII. Mean number of cloudy days

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
002	g	8	6	14	9	18	26	27	24	27	12	6	6	183	2 1/2
003	g	4	6	3	8	16	16	22	26	20	7	4	14	136	2
004	g	21	20	18	20	18	21	24	22	19	20	19	18	238	…
005	c	17	16	18	20	24	22	23	23	25	20	18	17	243	…
006	c	9	9	8	9	19	20	22	22	23	20	10	8	178	4
007	c	14	9	7	12	25	26	24	27	27	24	15	14	225	5
Alaska, Coastal and Insular:
100	g	10	6	8	11	19	14	16	21	21	19	13	13	171	10
102	g	11	10	10	11	10	9	19	18	14	15	14	14	156	11-13
104	g	14	11	13	14	12	13	19	19	16	16	14	15	176	19
105	g	13	15	18	22	22	16	24	22	22	22	20	20	237	2-4
106	g	14	13	14	13	14	12	16	18	16	16	16	15	177	24-26
Alaska, Inland:
152	g	10	8	9	7	8	7	15	16	16	17	10	10	134	8-10
153	g	11	9	9	7	8	7	8	12	13	18	15	13	130	10
154	g	14	13	12	13	16	13	21	19	19	17	14	14	185	18-19
156	g	15	13	13	11	16	12	17	22	19	20	16	14	188	10
157	g	15	14	15	15	18	16	18	20	20	20	17	14	202	10
Canada, Coastal and Insular:
201	c	4	2	6	3	12	15	18	16	11	7	3	4	101	2
202	c	2	6	3	6	14	14	14	19	18	11	3	4	114	3
204	c	11	9	12	12	14	16	14	21	20	18	14	10	170	3-5
213	c	10	4	6	8	11	13	12	19	19	20	14	9	146	3-5

c - 8-tenths or more total cloud cover. g - Undefined.

252      |      Vol_VII-0258                                                                                                                  

Table XXVII. Mean number of cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular (cont.):
218	c	5	0	1	8	14	16	8	13	20	13	12	1	111	2
223	c	11	10	12	16	22	21	16	18	21	23	20	10	199	5-7
224	c	12	8	10	15	21	20	21	13	23	21	18	16	198	4-5
226	c	13	5	9	10	17	17	19	16	22	17	16	9	169	2
227	c	12	14	16	17	21	19	18	15	20	20	20	17	208	2-5
Canada, Inland:
250	c	11	10	9	13	13	13	15	17	20	20	16	11	168	2-4
Greenland and Iceland, Coastal and Insular:
301	g	6	6	22	..	..	15	10	15	12	10	11	4	…	1-2
302	g	14	12	10	16	19	16	20	17	17	18	18	12	189	2
304	g	9	7	8	10	14	16	14	15	15	15	14	13	150	31
307	g	8	8	8	5	9	12	12	10	6	8	6	10	102	…
308	g	12	14	9	10	11	10	9	7	8	10	10	13	123	19
310*	g	14	12	13	13	14	14	13	14	13	14	15	17	166	15
314	g	15	12	13	12	13	12	12	14	13	14	13	12	155	31
317	g	13	17	12	11	12	11	9	9	10	13	13	12	136	30
318	g	13	12	12	11	10	11	12	13	11	13	12	10	140	28
320	g	13	11	12	11	10	11	11	13	11	12	12	11	138	19
330	g	15	14	15	13	11	11	14	16	15	15	15	15	170	16
331	g	14	14	15	15	12	14	15	15	13	11	13	14	165	16
332	g	17	16	17	18	14	16	20	21	18	19	17	16	209	16
333	g	18	15	17	16	17	15	18	17	17	14	14	17	195	11

c - 8-tenths or more total cloud cover. g - Undefined. * - Data for Agto, 67° 57′ N., 53° 44′ W.

253      |      Vol_VII-0259                                                                                                                  

Table XXVII. Mean number of cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
334	g	14	11	14	12	11	12	15	13	12	15	14	14	158	14
335	g	14	11	14	15	13	15	17	19	17	17	14	13	180	15
336	g	14	13	18	16	14	15	16	19	16	19	14	14	191	16
337	g	13	11	13	12	15	14	17	17	16	13	13	15	169	11
339	g	21	17	21	21	18	18	22	19	19	21	20	19	236	10
340	g	12	12	14	15	15	14	16	16	14	15	12	12	166	14
341	g	16	14	20	16	16	15	21	17	17	17	17	16	202	8
Greenland and Iceland, Inland:
360	g	18	15	17	18	20	15	18	19	18	17	16	16	207	7
361	g	15	11	14	15	13	13	15	17	14	18	14	13	172	16
Europe, Coastal and Insular:
400	c	15	12	12	14	23	22	23	26	25	23	16	13	225	10
401	c	11	9	7	16	24	25	25	27	24	19	14	9	208	4
403	c	13	12	11	10	13	17	16	17	16	16	12	11	164	…
406	a	15	15	17	17	18	17	16	15	17	16	26	13	202	12
407	c	13	11	16	15	17	15	13	15	18	14	14	12	173	10
408	a	16	13	14	15	18	16	16	17	15	17	17	17	191	29
412	a	14	12	12	11	10	10	12	12	14	13	15	14	149	28
414	c	14	13	13	14	14	14	13	13	16	14	13	12	163	25
415	c	16	14	12	15	18	15	17	16	17	18	18	17	191	18
417	c	18	16	13	18	24	20	2	22	20	21	21	21	216	7
420	c	15	12	13	12	12	11	12	14	15	14	15	15	160	27

a - 10-tenths total cloud cover. c - 8-tenths or more total cloud cover. g - Undefined.

254      |      Vol_VII-0260                                                                                                                  

Table XXVII. Mean number of cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
421	c	10	11	12	9	5	5	4	8	6	13	13	18	114	8
423	c	14	14	13	10	10	10	8	12	14	18	18	20	161	8
424	c	20	16	14	12	9	8	7	10	10	17	20	22	165	36
425	c	16	14	11	12	13	9	12	14	14	17	17	18	168	13
426	c	20	17	13	12	11	10	11	11	12	19	20	22	178	18
428	c	20	16	14	14	14	12	14	16	18	20	21	20	199	18
429	c	20	18	16	17	18	14	14	17	19	21	20	19	212	13
Europe, Inland:
450	c	10	10	11	9	14	16	13	17	16	16	17	17	166	8
451	a	12	11	11	12	17	14	13	17	14	18	15	14	168	18
453	c	17	11	12	15	12	12	11	13	13	20	19	17	172	9
454	c	18	15	14	15	15	15	17	19	18	17	17	16	196	31
455	c	13	13	14	9	6	7	6	10	7	17	16	20	138	8
456	c	12	13	12	13	12	14	12	13	13	14	18	16	162	8
457	c	18	14	12	11	8	8	7	10	10	17	20	20	155	36
458	c	17	15	13	12	10	10	8	12	13	19	21	20	170	35
Asia, Coastal and Insular:
500	c	12	9	10	17	24	24	22	25	25	23	19	15	225	8
501	c	10	5	6	10	19	22	21	25	24	18	10	11	181	5
502	c	11	7	6	10	20	21	20	27	23	19	10	9	181	4
503	c	11	9	6	12	22	22	23	26	24	21	12	9	196	7
505	b	17	16	15	14	20	16	15	19	21	19	18	15	205	13

a - 10-tenths total cloud cover. b - 9-tenths or more total cloud cover. c - 8-tenths or more total cloud cover.

255      |      Vol_VII-0261                                                                                                                  

Table XXVII . Mean number of cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
506	c	17	12	11	14	20	19	16	18	22	23	22	19	213	14
507	c	14	12	11	14	18	16	15	19	19	18	17	14	189	16
508	c	14	11	11	12	21	19	19	24	24	22	17	13	206	6
509	c	16	13	11	13	22	21	18	25	23	21	15	11	208	7
510	c	14	13	10	15	22	24	21	25	23	21	16	13	217	18
511	c	12	10	9	16	23	24	24	25	25	21	19	12	218	2-3
512	g	23	18	16	16	22	23	21	24	24	23	19	14	243	2-3
513	c	10	12	11	14	19	19	20	23	21	19	24	13	95	7
514	c	17	14	15	16	22	24	24	27	25	27	20	18	249	11
515	c	5	5	3	5	14	16	15	21	24	18	14	9	149	5
516	b	6	11	14	12	15	15	19	22	24	20	16	18	190	4
517	c	7	6	7	9	18	15	14	17	15	15	11	10	144	9
518	c	16	12	12	15	23	20	17	20	23	23	21	19	221	26
519	c	14	10	8	12	21	19	13	18	20	22	18	15	189	22
520	g	15	13	11	14	19	7	14	14	16	18	16	15	182	10
521	c	10	8	9	13	21	17	14	18	17	21	17	11	176	13
522	c	7	5	3	7	8	6	10	13	15	13	10	8	105	4
523	c	8	10	13	14	18	19	19	22	23	20	16	14	196	3
525	b	10	11	10	16	20	13	18	19	21	19	20	12	189	8
526	b	10	10	10	11	14	14	17	13	12	14	11	8	143	13
527	d	21	10	20	16	21	17	23	23	22	16	18	20	227	4
531	c	12	8	11	8	16	16	17	13	10	13	12	9	144	4

b - 9-tenths or more total cloud cover. c - 8-tenths or more total cloud cover. d - 7-tenths or more total cloud cover. g - Undefined.

256      |      Vol_VII-0262                                                                                                                  

Table XXVII . Mean number of cloudy days (cont.)

Station		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland:
551	b	17	15	8	17	18	24	20	25	21	21	17	17	220	…
552	c	16	12	14	15	18	20	21	21	22	26	19	16	220	20
553	c	13	13	12	11	18	18	14	21	20	23	16	13	192	18
554	c	7	11	9	14	17	16	15	15	21	19	13	7	170	3
555	g	15	10	14	10	14	16	10	15	19	23	17	10	173	4
556	c	4	4	4	8	11	13	11	14	13	12	7	6	107	8
557	b	10	13	11	10	14	13	16	16	14	14	12	12	155	14
558	b	6	6	4	5	9	9	11	16	15	13	10	3	110	9
559	c	7	8	5	7	5	11	10	19	16	12	10	13	133	4
560	d	17	16	16	17	20	19	17	20	20	20	17	18	217	8
561	d	21	18	17	18	20	17	18	22	23	24	20	20	238	6
562	c	14	9	9	8	11	10	9	9	15	16	15	15	138	…
563	c	12	11	10	10	14	12	10	14	16	20	15	13	157	…
566	c	13	10	8	9	15	11	9	12	15	16	15	12	145	8
567	c	6	8	7	10	12	11	9	11	13	16	12	6	121	11
568	c	7	6	3	6	8	6	7	9	9	12	8	9	90	24
570	b	1	1	2	4	4	3	3	4	7	10	7	4	50	8
572	g	20	10	9	9	4	10	12	13	15	15	12	12	141	10
573	d	18	14	16	14	18	16	15	17	17	22	20	21	208	9
574	d	21	15	18	19	22	18	18	22	24	25	25	23	250	6
575	b	12	9	11	11	12	10	10	12	14	18	17	14	150	18
576	b	16	11	10	10	11	10	10	12	14	16	17	18	158	13

b - 9-tenths or more total cloud cover. c - 8-tenths or more total cloud cover. d - 7-tenths or more total cloud cover. g - Undefined.

257      |      Vol_VII-0263                                                                                                                  
cloudiness in early autumn, with a secondary maximum in early summer

immediately preceding the summer minimum of stratus just described.

The cause of the double maximum is therefore obvious. At more southerly

coastal locations nearer the winter storm tracks (as over northern

Scandinavian areas), the annual variation in cloudiness is less than is

true for the Arctic generally and some stations show maxima during one

of the winter months.

       

figs. 51 and 52 here

        At the more northerly locations the average amount of cloud cover

is relatively small in winter and also during the early spring, the

latter period being the most favorable for air operations within the

Arctic. The average cloud cover during winter is about 4-tenths over

the pack-ice and from 2- to 3-tenths at northerly land stations. These

figures are to be compared with summer averages of about 9- and 8-tenths,

respectively.

        During the winter and early spring months the proportion of high

clouds increases but the stratiform types still predominate. The

cumuliform types of cloud are exceedingly rare anywhere over the Arctic

Ocean and are infrequent elsewhere except over interior Arctic locations

258      |      Vol_VII-0264                                                                                                                  
during summer. The excessive cloudiness prevalent during the warmer

months does not affect temperatures as significantly as might be expected

from experiences in lower latitudes. In the Arctic insolation is not

affected as much by clouds as in locations farther south, partly because

the layers of clouds in the Arctic are thinner than in lower latitudes

and partly because the incoming radiation is doubly reflected from snow–

covered ground and clouds. On account of the relatively strong insolation

on overcast days, the diurnal temperature range is much greater than on

corresponding overcast days in lower latitudes. This condition is

particularly true during spring months.

        Diurnal Variation of Cloudiness . — The hourly cloud data available for

a few localities over the Arctic Ocean and adjacent coasts show that

there is an apparent and regionally consistent diurnal variation during

the dark season and in the months when the night is longer than the day.

At this time there appears to be a definite maximum cloudiness during

the day (so-called) and a minimum cloudiness during the night. Simpson

[ 39 ] ascribes this feature to the fact that the observer’s estimate of

cloud cover tends to be too low when the sun is more than 10° below the

259      |      Vol_VII-0265                                                                                                                  
horizon. Other observers have subsequently verified Simpson’s conclusion

as to the non-reality of the diurnal variation in Arctic cloudiness during

the winter half-year.

        During the summer half-year, when the sun is either continuously

above the horizon or the day is longer than night, the character of the

diurnal variation is regionally complex and appears to change from one

month to the next. Sverdrup [ 43 ] suggests that the maximum at night

occurs when there is a prevalence of stable fog situations, and that a

daytime maximum is associated with convection currents. The type of

diurnal variation which results depends upon which factor dominates

the local weather.

        Cloud Altitudes and Ceilings . — Cloud heights are lower in the Arctic

than in temperate latitudes. Over the Arctic Ocean and adjacent coasts,

for example, the bases of stratus clouds will be found anywhere between

the surface and 5,000 feet [ 43 ] but most frequently below 1,500 feet.

The following data from the Maud Expedition give the ranges and averages

of ceilings described by the bases of the various cloud types over the

Arctic Basin (as determined from pilot balloon observations):

260      |      Vol_VII-0266                                                                                                                  

Cloud Form	Altitude of Bases (feet)	Greatest Frequency at Altitude (feet)
Cirrus	Up to 19,000	…
Cirrostratus	15,000 to 16,000	…
Cirrocumulus	15,000 to 16,000	…
Altostratus	8,000 to 15,000	11,500 to 13,000
Altocumulus	8,000 to 15,000	About 10,000
Stratocumulus	1,600 to 8,000	About 1,600
Fractostratus	650 to 6,500	…
Stratus	0 to 5,000	Below 1,600

        These data indicate that low ceilings unfavorable for air operations

over the Arctic Basin should be closely associated with the prevalence

of the stratus type of cloud formation. It is difficult to generalize

in similar fashion for inland areas because of the almost inseparable

relation between cloud altitudes and orography. In general, the period

of the greatest frequency of low ceilings will correspond to the period

of most frequent cloud cover, but there are important local exceptions

to this rule.

261      |      Vol_VII-0267                                                                                                                  

        According to Rigby [ 34 ] , low ceilings are most frequent nearly

everywhere in the Arctic during summer and early autumn, particularly

over the Kara and Barents Sea areas. Only in the more southerly Arctic

areas, nearer the major winter cyclone tracks, is there a general

reversal of this seasonal pattern.

        The vertical extent of cloudiness over the Arctic also averages

considerably less than at the lower latitudes where the atmospheric

moisture content is relatively high and where convective and frontal

activity is more vigorous. The weather reconnaissance flights which

have been conducted by the U. S. Air Force since 1947 show very clearly

that summer is the season of the greatest vertical development of cloud

systems over the Arctic. (See Table XXVIII .) During this season the average

altitude of the tops of the lower cloud layers is of the order of 11,000 table XXVIII here

to 12,000 feet, with the higher forms of clouds extending well above

20,000 feet. In late autumn, winter, and early spring, on the other

hand, the tops are normally below 6,000 feet — easily topped by aircraft

cruising at relatively low flight altitudes.

262      |      Vol_VII-0268                                                                                                                  

Table XXVIII. Cloud cover* data from USAF reconnaissance flights

July 1948 to June 1949

Route — Fairbanks to Barrow to North Pole to Prince Patrick Island to

Aklavik to Fairbanks, or vice versa, depending on winds

Month	Below 18,280 Feet				Above 18,280 Feet
	Ovc	Bkn	Sct	Clr	Ovc	Bkn	Sct	Clr
Frequency (%) of Specified Cloud Conditions
January	29	5	7	59	0	0	4	96
February	36	6	8	50	0	0	6	94
March	23	6	8	63	1	4	15	80
April	17	13	19	51	7	5	11	77
May	46	19	12	23	4	2	5	89
June	54	29	17	0	3	7	43	47
July	64	29	6	1	5	4	37	54
August	64	23	7	6	14	4	28	54
September	45	35	16	4	1	4	26	69
October	43	16	14	27	2	1	27	70
November	48	16	13	23	0	0	5	95
December	28	8	14	50	0	1	7	92

* Ovc - >. 9 to 1 . 0 cloud cover

Bkn - >. 5 to <. 9 cloud cover

Sct - >. 1 to <. 5 cloud cover

Clr - 0 <. 1 cloud cover

263      |      Vol_VII-0269                                                                                                                  

        The preceding figures apply principally to conditions over the

Arctic Ocean and contiguous coastal areas. In more southerly locations

on the fringes of the true Arctic, the vertical cloud structures are

more nearly typical of those found in temperate regions. At times of

strong convective or frontal activity, the cloud tops in these areas

may often exceed 30,000 feet.

264      |      Vol_VII-0270                                                                                                                  

       

FOG AND VISIBILITY

        With the possible exception of blowing snow, fog is the most

important weather factor limiting aviation in the Arctic regions.

Over a large portion of the Arctic seas fog may be expected to occur

on at least 90 days each year, and in many maritime areas the average

number is greater than 160. Fog frequencies are usually much lower

at inland locations, but at some points the annual figure may run

as high as 120 to 130 days. (See Table XXIX .) table XXIX here

265      |      Vol_VII-0271                                                                                                                  

Table XXIX . Mean number of days with fog

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
003	15	8	12	5	17	19	27	27	15	6	7	10	167	2
004	2	3	3	5	3	6	13	10	6	3	2	2	58	…
005	1	2	3	5	7	9	19	15	12	4	3	1	82	…
006	3	6	7	7	4	6	20	20	13	4	2	1	92	4
007	2	4	3	4	3	14	26	23	14	5	3	3	105	5
Alaska, Coastal and Insular:
100	5	10	2	5	7	10	15	16	5	3	3	1	83	4
101	2	1	2	5	6	12	14	6	6	4	*	1	59	2
102	1	2	3	3	3	4	2	2	2	1	1	1	25	9-10
103	2	3	5	10	10	16	15	7	5	2	1	1	77	1-3
104	5	5	5	4	5	11	8	6	4	4	3	7	67	8
105	2	3	3	5	9	12	15	12	5	4	3	4	76	6-7
106	*	1	0	0	0	0	0	0	1	*	1	1	3	6-7
Alaska, Inland:
150	1	2	1	*	1	1	1	2	2	1	1	*	14	4-5
151	13	13	8	10	6	6	8	10	7	5	7	12	105	2-3
152	1	1	2	1	1	*	1	3	3	1	1	1	16	6-7
153	4	4	1	0	*	0	*	*	2	2	2	4	20	5-10
154	2	1	3	2	4	2	5	7	6	3	2	3	40	7-8
155	1	1	0	*	0	*	*	1	1	1	*	*	5	10
156	17	11	12	1	1	1	2	4	3	7	6	13	78	8-9
157	1	1	*	0	*	0	*	*	2	*	*	1	6	7-10

* - Less than 0.5 day.

266      |      Vol_VII-0272                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Coastal and Insular:
204	0	1	0	*	*	1	2	2	1	1	*	1	7	6-7
205	0	0	*	0	0	1	2	1	10	2	0	0	16	1-3
206	4	1	0	1	0	1	10	12	13	1	2	1	44	1-3
210	1	2	1	2	*	1	6	7	1	1	1	1	26	3-4
211	0	0	1	*	*	1	4	8	2	1	1	0	22	3-4
212	00	1	0	1	1	3	5	2	2	0	1	0	16	3
213	1	2	2	2	1	1	1	1	1	1	1	1	14	14-18
214	1	1	*	1	*	2	3	4	1	1	1	1	16	2-3
215	*	*	*	1	3	6	7	6	3	*	*	0	26	7-10
216	*	1	*	1	2	1	2	3	1	1	*	*	12	10-11
217	1	1	*	1	2	2	2	3	2	1	1	1	17	4-8
221	*	1	1	1	2	2	3	4	2	1	1	1	17	20
222	2	3	2	1	1	2	4	4	3	5	4	2	34	2½
223	*	1	1	1	2	7	9	9	6	1	*	0	37	12-13
224	1	1	*	1	1	2	3	2	3	1	1	1	16	16-17
225	1	2	2	*	1	2	3	3	3	1	1	1	20	5
226	*	*	1	1	1	1	1	1	1	**	0	*	8	10-12
228	4	3	3	2	2	3	6	7	4	2	2	4	42	2½
Canada, Inland:
250	1	1	*	0	*	*	1	*	1	1	*	1	5	11-16
251	6	1	0	0	0	0	0	1	2	1	2	1	15	1-5
254	2	2	1	1	*	*	*	1	2	2	2	2	16	17-21
256	*	1	*	*	*	*	*	*	*	1	1	*	3	1½

* - Less than 0.5 day.

267      |      Vol_VII-0273                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Canada, Inland (cont.):
259	1	1	1	*	1	*	*	*	1	1	2	1	9	1½
261	0	0	0	*	0	0	*	0	0	*	1	*	1	1
Greenland and Iceland, Coastal and Insular:
301	1	0	3	2	..	6	7	11	5	3	1	1	..	5
304	2	1	1	2	5	9	11	7	2	1	*	1	42	31
306	7	5	8	9	10	13	10	5	3	2	2	2	76	5
307	0	1	1	1	2	6	6	7	4	0	..	..	..	..
308	4	6	6	8	15	14	11	8	9	5	4	6	96	11
309	9	9	11	12	15	15	17	17	8	8	3	5	125	..
311	1	*	0	2	3	5	5	5	2	*	0	1	24	6
314	1	1	2	4	8	11	14	14	8	2	1	1	67	31
315	3	2	9	4	9	9	11	6	6	9	4	6	78	5
316	8	5	14	18	26	23	28	26	26	3	8	10	195	25
317	1	1	2	4	9	11	11	9	5	3	2	1	59	30
318	*	*	1	1	1	3	5	6	3	1	*	*	21	28
330	1	1	1	2	2	1	1	1	1	*	1	1	12	16
331	1	1	1	1	1	2	2	2	2	2	2	1	18	16
332	2	2	2	1	6	5	10	9	4	2	1	2	46	9
333	1	2	3	4	7	7	8	7	5	2	3	2	51	11
334	*	1	2	2	5	5	9	6	3	*	1	1	35	14
335	1	*	1	2	4	5	8	6	3	2	*	1	34	15
336	*	*	1	1	2	2	3	3	2	1	1	1	17	16
337	*	*	1	*	*	1	1	*	*	*	*	*	4	11

* - Less than 0.5 day.

268      |      Vol_VII-0274                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Greenland and Iceland, Coastal and Insular (cont.):
339	1	*	2	1	4	4	5	3	2	*	1	*	23	10
340	1	1	2	1	2	3	5	3	2	1	1	*	23	14
341	1	1	2	2	4	5	10	7	4	2	2	1	41	8
Greenland and Iceland, Inland:
351	15	14	4	1	6	1	2	13	15	26	16	20	133	1
360	*	1	1	1	*	1	1	*	1	1	1	1	9	7
361	2	1	1	1	2	2	4	2	2	2	2	1	20	16
Europe, Coastal and Insular:
400	6	7	9	9	9	10	15	16	6	5	4	5	100	10
401	2	*	4	8	5	13	24	24	14	5	2	2	104	4
403	*	1	*	*	*	3	4	3	1	1	0	0	13	7
405	2	5	4	5	3	2	11	3	5	1	1	2	44	9
406	0	0	0	*	1	3	6	5	1	*	0	0	16	12
407	*	0	0	0	*	*	2	1	1	0	*	*	4	10
408	*	*	0	*	1	3	7	5	1	*	*	*	17	44
410	*	1	*	1	3	4	5	2	2	1	*	*	19	..
412	*	*	0	*	*	*	1	*	*	*	0	*	1	44
414	1	1	1	1	1	1	2	2	2	1	1	1	14	46
415	1	*	*	*	1	1	3	4	2	1	2	1	16	10
417	2	3	3	5	6	12	14	12	5	3	4	2	71	..
420	*	*	1	1	2	3	3	2	1	1	*	*	14	44
421	2	2	3	4	3	2	2	3	4	5	3	2	35	50
422	1	1	1	2	1	1	*	1	2	2	2	1	14	14

* - Less than 0.5 day.

269      |      Vol_VII-0275                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Europe, Coastal and Insular (cont.):
423	2	2	2	2	2	1	1	1	2	3	3	2	23	50
424	9	8	9	8	4	2	2	2	7	10	8	8	77	36
425	1	1	2	1	2	1	2	3	2	2	1	1	17	10
426	3	4	4	4	2	1	1	3	7	6	5	5	46	10
428	3	3	3	2	1	*	1	2	2	4	3	3	27	10
429	*	*	0	0	*	0	*	1	1	1	0	0	3	7
Europe, Inland:
450	4	3	3	2	2	0	0	1	2	5	5	4	31	50
451	5	2	1	*	*	*	*	1	2	2	3	2	16	44
453	3	3	2	2	1	1	2	7	6	6	7	5	45	10
454	3	2	2	2	2	1	2	3	5	6	4	4	36	44
455	5	3	2	1	0	0	0	2	5	5	4	4	31	50
456	4	3	2	2	2	1	2	3	4	6	5	5	39	50
457	2	2	2	2	1	1	*	2	4	5	3	2	26	35
458	2	2	2	1	1	*	*	1	3	2	2	1	17	35
Asia, Coastal and Insular:
500	1	2	3	4	5	12	17	17	10	3	1	1	76	8
501	4	3	4	3	7	14	19	18	8	4	1	1	86	5
502	4	5	6	6	6	9	13	16	6	8	4	3	85	4
503	2	4	7	7	6	11	21	21	11	5	4	1	99	7
505	2	3	2	2	4	8	12	11	8	5	3	2	62	14
506	6	5	7	6	9	15	17	16	11	5	3	4	106	14
507	2	2	2	1	3	4	6	6	5	3	2	2	39	16
508	5	8	8	6	6	15	18	12	8	6	4	5	101	6
509	6	4	3	5	8	9	8	8	8	6	4	3	73	7

* - Less than 0.5 day.

270      |      Vol_VII-0276                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Coastal and Insular (cont.):
510	3	6	6	6	5	14	17	15	8	6	4	4	94	18
512	3	3	3	5	5	14	12	8	5	4	2	1	65	7
513	3	1	*	2	4	6	4	8	2	1	2	2	35	4
514	4	7	8	8	8	15	18	15	6	3	3	6	101	10
515	0	0	0	1	3	2	*	2	*	2	2	0	11	5
516	2	1	3	3	10	16	21	23	10	3	2	2	95	3
517	2	2	3	5	7	12	14	14	6	3	4	3	75	10
518	4	5	6	7	10	14	16	14	8	7	5	4	99	26
519	2	2	3	4	7	15	14	16	8	6	2	2	80	22
520	0	1	*	1	1	*	1	2	4	3	*	*	14	9
521	3	2	4	4	5	7	5	6	5	5	3	2	51	13
522	0	0	0	0	1	1	1	1	1	1	0	*	6	5
523	5	2	4	4	10	14	16	15	10	3	5	3	91	3
524	1	1	4	6	11	10	13	9	9	10	4	3	81	4
525	5	5	6	5	8	14	17	13	11	4	4	3	95	8
526	1	*	*	1	2	6	7	7	3	1	*	1	29	14
527	2	2	1	2	5	7	3	2	1	1	2	1	29	14
529	1	2	1	3	4	10	10	12	3	1	1	1	49	3
530	5	2	4	7	5	8	12	10	8	6	3	7	77	5
531	0	0	0	1	5	9	12	9	4	1	0	0	41	4
Asia, Inland:
550	2	2	1	1	2	4	3	6	4	4	4	3	35	5
551	1	0	0	0	0	0	1	2	1	1	0	0	5	2
552	10	12	7	6	4	7	6	6	9	13	9	11	100	8

* - Less than 0.5 day.

271      |      Vol_VII-0277                                                                                                                  

Table XXIX . Mean number of days with fog (cont.)

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Asia, Inland (cont.):
553	7	4	5	7	7	4	3	5	5	8	7	4	66	18
554	4	2	3	1	3	6	2	1	3	3	4	3	32	4
555	5	4	2	0	1	2	4	3	4	5	2	6	38	3
556	3	2	1	*	1	*	1	5	4	1	2	4	24	9
558	3	2	1	*	1	*	1	3	2	2	1	2	18	8
559	0	1	*	0	0	0	1	4	2	1	1	*	10	4
560	2	1	1	1	1	*	*	1	2	2	1	2	12	8
561	0	0	0	0	*	0	0	0	1	1	0	0	2	5
562	0	*	*	*	1	*	*	1	2	1	*	0	6	10
563	*	*	*	0	1	*	*	*	1	1	1	2	6	7
566	7	2	1	*	0	*	1	3	2	1	1	4	22	8
567	4	2	1	*	*	*	*	1	1	1	1	5	16	10
568	12	7	1	*	0	*	*	1	2	2	2	10	38	25
570	0	0	*	*	*	1	2	3	3	1	0	0	10	7
572	0	*	0	*	1	*	*	1	1	1	1	0	5	14
573	2	1	1	1	1	1	1	3	3	4	2	3	23	9
574	2	1	*	0	*	*	1	3	3	*	*	*	10	9
575	2	*	*	0	1	1	4	6	6	1	*	2	23	11
576	8	3	*	*	*	*	1	1	1	1	1	7	23	11

* - Less than 0.5 day.

272      |      Vol_VII-0278                                                                                                                  

        It is quite probable that the frequency of fog over the Arctic

Ocean decreases from the coasts toward the Pole. According to

Stefansson [41] , the zone of most frequent fog formation is a belt

parallel to the coast line of the Polar Sea. This belt does not

extend more than twenty or thirty miles seaward or more than a

corresponding distance inland. However, regional comparisons

concerning the number of days with fog are somewhat unreliable,

partly because the observations have been made at a variety of hours

and partly because fog has not always been recorded in accordance with

international procedures. For these reasons, and for the additional

reason that fog is essentially a phenomenon governed by local rather

than regional factors, caution should be exercised in attempting to table XXX here

distinguish small regional and areal differences in the frequencies

of fog occurrence on the basis of the observational materials presented

in the several figures and tables. The data, however, are probably

entirely adequate for purposes of noting in time differences in fog

occurrence at the locations for which data are available and for

pointing out the large and more important regional differences in

prevalence of the phenomenon.

273      |      Vol_VII-0279                                                                                                                  

Table XXX. Prevailing wind direction during fog occurrence

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Yrs Rec
Oceanic:
006	SW	SW	E	N	SW	S	NW	NW	S	W	SE	SW	5-6
		E		E
Asia, Coastal and Insular:
500	SE	SE	SE	NW	NW	NW	NW	NW	SE	NW	W	SE	7-8
	SW
503	E	W	E	SW	NE	E	E	E	W	NE	E	E	7-8
	S
	SW
506	S	S	S	NE	NE	NE	NE	NE	SW	SW	SW	SE	20
507	NE	E	NE	NE	NE	NE	SE	E	NE	SE	NE	NE	17
	E			E								SE
510	S	S	S	S	S	N	N	NE	S	S	S	S	19
512	W	SW	W	NE	E	E	N	E	E	SW	SW	SW	..
517	..	..	..	..	..	E	E	E	NE	..	..	..	..
518	S	S	S	SW	SW	SW	N	SW	SW	SW	S	S	26
523	..	..	..	..	..	SE	SE	SE	SE	..	..	..	..
525	..	..	..	..	..	N	N	N	N	..	..	..	..
530	..	..	..	..	..	SE	SE	SE	SE	..	..	..	..
Asia, Inland:
552	SW	SW	SW	N	N	SW	N	SW	SW	SW	SW	SW	..

274      |      Vol_VII-0280                                                                                                                  

        Fog Types . - Four types of fog are of common occurrence in the Arctic.

The most common type is an advection fog formed primarily during

warmer months when relatively warm, moist air moves over a cold surface.

A further condition is the existence of a surface temperature inversion

which serves to retard turbulent dissipation of the fog. The areas

which are most favorable for the formation of this type of summer fog

are the open waters of the Kara, Laptev, East Siberian, and Chukchi

Seas. Fifteen to twenty days per month with fog is a normal condition

for these areas during the summer. Because of the influx of warm

water from the Gulf Stream system, this type of fog is less frequent

over the Barents and Norwegian Seas. The frequency of the summer

advection fogs decreases rapidly from the coast line inland and

diminishes less rapidly over the pack-ice.

275      |      Vol_VII-0281                                                                                                                  

        The second type of fog of importance in the Arctic is the

radiation fog of winter. These fogs form readily under a sharp

surface temperature inversion during very cold weather and are

caused by reduction in temperature of the moist surface air by

contact with the radiationally-cooled ground or ice surface. Because

the heat conduction from subsurface layers is larger over oceanic ice

than over land or snow surfaces, the radiational cooling is more

effective in producing fog over coastal and inland points than over

the ice of the Arctic Ocean.

276      |      Vol_VII-0282                                                                                                                  

        According to Petterssen / [ 31 ] / , the fogs are also less frequent

over snow surfaces than over snow-free regions because of the

depression of the saturation vapor pressure over ice. Even when the

air is clear and calm so that radiational cooling is most rapid,

fogs do not easily form over cold snowfields. The following fog

data obtained on the Maud Expedition ( Sverdrup / [ 43 ] / ) show that there

is a conspicuous minimum in fog frequencies between the temperatures

of +5° and −13°:

Temperature	41°	41°	32°	23°	14°	5°	4°
		to	to	to	to	to	to
Interval (°F.)		32°	23°	14°	5°	−4°	−13°
Probability of dense through light fog (mist)	0.114	0.317	0.224	0.110	0.061	0.027	0.020
Temperature	−13°	−22°	−31°	40°
	to	to	to
Interval (°F.)	−22°	−31°	−40°
Probability of dense through light fog (mist)	0.046	0.095	0.076	0.210

277      |      Vol_VII-0283                                                                                                                  
The minimum in fog probability in the temperature range +5° to −22°

appears to be associated with the vapor pressure depression which

is noted to be at a maximum in the temperature ranges +5° to −15°

(see Table II). The data also show a secondary maximum probability

in the temperature range −22° to −31°. This appears to be associated

with the prevalence of ice fog, which is to be discussed in succeeding

paragraphs.

        Because radiation fog is essentially a surface phenomenon, the

fog layers are usually shallow. They are also of light density, since

they tend to occur at the lowest temperatures when the quantity of

water vapor available for condensation is of necessity low. They

occur most frequently along river bottoms open to cold air drainage

and where there is sluggish air movement. They appear to be most

common in the lower Lena River Valley in Siberia and the lower

Mackenzie River Valley in North America. They are also quite frequent

in the Yukon Valley and in the valleys of the principal northward–

flowing rivers of Siberia, as well as over the pack-ice during cold

weather.

278      |      Vol_VII-0284                                                                                                                  

        The third type of fog, one of minor importance, is “steam fog”

or “Arctic smoke.” These fogs occur over open water which is subject

to invasion by very cold air. They occur only when the contrast

between air temperature and water temperature is very great. Under

such conditions the rate of evaporation from the water surface remains

relatively high, but the capacity of the surface air to hold moisture

is limited by its low temperature. As a result, the excess moisture

quickly condenses into fog, giving a “steaming” appearance to the water

surface. These fogs occur most frequently over rivers, unfrozen lakes,

open leads or polynias in the Arctic ice, and over coastal waters

which are adjacent to a local cold-air source. Such “steam” fogs are

generally shallow and are quickly dissipated by wind. However, they

may be sufficiently dense at times to obscure coastal landmarks and

landing strips adjacent to open water. Over the Arctic Ocean they

serve the very important purpose of advising the traveler of the

presence of open water.

279      |      Vol_VII-0285                                                                                                                  

        Similar to the “steam” fogs are the “animal” or “human” fogs

which are possible at Arctic temperatures of −40° F. or below. At

such temperatures the small amount of moisture given off by humans

or animals is sufficient to cause light fog in the immediate vicinity.

Persistent fog, however, occurs only under calm, or nearly calm,

conditions. At times such fog may be sufficiently dense to obscure

a herd of reindeer or caribou or a dog team. The effect probably

also adds to the frequency and density of fog within villages and

towns of the Arctic under very cold and calm conditions.

280      |      Vol_VII-0286                                                                                                                  

        The fourth type of fog, ice fog, is classified as a separate

form because of its composition rather than because is possesses

unique processes of formation. Ice fog is formed when temperatures

are low enough to cause direct atmospheric sublimation of moisture

in the form of ice crystals rather than in the form of sub-cooled

water droplets as in ordinary radiation or advection fogs. This

type of fog is particularly prevalent in and near inhabited areas

where there is a local source of moisture and where local combustion

products supply an abundance of condensation nuclei. The fog layers

vary in thickness from 50 to 500 feet and, while vertical visibilities

are usually good, horizontal visibility may be reduced to zero in

some cases. Ice fog which is dense enough and persistent enough to

seriously affect aircraft operations rarely occurs with temperatures

above −20°F. and with wind speeds in excess of 3 mph. This type of

fog is prevalent at all interior Arctic installations and at coastal

areas under distinct continental influence.

281      |      Vol_VII-0287                                                                                                                  

        Annual Variation of Fog . - While there is a tendency for Arctic

locations to show a maximum frequency of fog in summer, autumn, or

late spring, almost any month of the year will be represented as a

maximum month at some Arctic point. Inland areas which show a

preponderance of the radiation type of fog tend to present maxima

during one of the cooler months and particularly during autumn.

Maritime locations most frequently affected by advection fogs present

decided summer maxima.

        At higher elevations, as on the Greenland Ice Cap and in the

Alaskan mountains, fog is most often simply surface-lying cloud. This

fact is attested by the parallel curves shown when frequencies of days

with precipitation and days with fog are plotted together. In such

locations the period of maximum fogginess then merely coincides with

the period of maximum frontal activity. An example of such a fog–

precipitation regime is given by the following data for West Station

located at a moderate elevation (3,130 feet) on the edge of the

Greenland Ice Cap:

282      |      Vol_VII-0288                                                                                                                  

       

West Station (Lat. 71°11′ N.; Long. 51°07′ W.)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann
No. days with
Precipitation	13	19	11	12	9	6	4	15	8	10	10	13	130
Fog	11	16	13	11	7	4	3	15	5	12	10	16	123

        Diurnal Variation of Fog . - During the summer months over the Arctic

Ocean and adjacent coasts the probability of fog is much greater in

the night hours than during the early afternoon. This tendency is

shown clearly by the following data obtained on the Maud Expedition

during the months of June through August:

Local Hour	2	4	6	8	10	12	14	16	18	20	22	24
Probability of Fog	0.36	0.37	0.33	0.27	0.22	0.19	0.18	0.19	0.22	0.24	0.28	0.32

        The Maud data also show a somewhat similar diurnal variation in fog

frequencies during the colder months, but Sverdrup / [ 43 ] / assumes that

this variation is largely spurious and suggests that darkness has, to

some extent, influenced the accuracy of the fog observations.

283      |      Vol_VII-0289                                                                                                                  

        Data from inland Arctic stations show a diurnal variation in

fog similar to that noted over the maritime Arctic regions, with a

definite tendency for the phenomenon to occur more frequently in the

early morning than at noon or in the evening. It is common practice

in these regions to limit aviation activities during early morning

hours because of the prevalence of visibility-restricting fog.

284      |      Vol_VII-0290                                                                                                                  

        Other Visibility-Reducing Factors . - During the warmer months in the

Arctic, fog is the most important visibility-reducing factor. During

the winter months, however, blowing snow is the most common cause of

reduced visibilities, particularly in the more unprotected continental

and insular locations. Observations at Coppermine recorded by the

Canadian Polar Year Expedition / [ 7 ] / show that there were 79 hours

during the winter (1932-33) when blowing snow reduced the visibility

to 1,000 yards or less. At Chesterfield Inlet, blowing snow was

reported on 99 days from October to May inclusive. During November

1949, Pt. Barrow, Alaska, reported 265 hours with blowing snow, and

in December of the same year, Barter Island, Alaska, reported 241 table XXXI here

such hours. Other Arctic Alaskan stations show monthly averages of 65

to 120 hours during the winter season. Conditions over interior

Greenland and portions of Siberia are probably much more severe. The

frequency and severity of blowing snow is, of course, related directly

to the frequency of high winds and the presence of new or powdery snow

cover.

285      |      Vol_VII-0291                                                                                                                  

Table XXIX. Mean number of days with blowing snow

Station	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann	Yrs Rec
Oceanic:
006	9	6	11	8	9	5	0	0	4	8	8	8	75	5-6
007	13	11	15	14	15	5	0	*	3	12	11	11	110	5-6
Europe, Coastal and Insular:
400	9	10	15	13	10	1	*	*	4	10	8	11	94	10
Asia, Coastal and Insular:
500	12	12	16	16	12	4	0	0	2	8	11	10	103	7-8
501	11	13	13	12	11	3	0	0	2	9	6	11	89	5-6
502	14	13	15	18	15	4	0	0	2	8	11	9	107	4-5
503	18	14	19	16	18	9	0	1	7	14	16	18	150	7-8
507	11	10	11	11	9	1	0	0	1	6	10	11	82	17
508	11	9	11	14	14	3	*	0	*	7	10	12	91	6
509	16	15	16	17	12	1	0	0	1	6	13	11	108	6-7
510	13	15	16	18	14	3	0	0	2	12	13	14	120	19
518	12	13	16	13	9	*	0	0	0	3	8	13	88	26
519	8	8	10	8	4	*	0	0	*	3	6	4	51	22

* Less than 0.5 day.

286      |      Vol_VII-0292                                                                                                                  

        The best visibility conditions in the Arctic occur in April and

May when the summer fogs are not yet manifest, and when the slight

ice-crystal turbidity is not so frequent as in winter [ 42 ] .

        From the preceding discussion it is apparent that the Arctic is

not a region of consistently good visibilities. At first glance it

might appear that such a statement is in disagreement with the one

previously made (on page ___) to the effect that Arctic air masses

are characterized by exceptionally good visibilities (because of low

values of turbidity). Actually, the two conclusions are not in dis–

agreement. Arctic visibilities can be described as either poor or

very good depending upon whether or not hydrometeors are present in

the surface atmosphere. Such a statement implies that moderate visi–

bilities are comparatively rare in the Arctic. This latter conclusion

is verified for at least one Arctic area by Hovmøller [ 20 ] who points

out that visibilities in the range 1 to 12 miles are rare along the

northeastern coasts of Greenland, i.e., the greatest number of visibili–

ties are either less than 1 mile or greater t h an 12 miles.

287      |      Vol_VII-0293                                                                                                                  

       

SUNSHINE, ILLUMINATION

        The duration of sunshine has seldom been included among the

records of Arctic observations. Over the Arctic Ocean such data

are available only from the Maud Expedition [ 43 ] . These obser–

vations show that during March and April the duration of sunshine,

both in actual hours and in percent of possible sunshine hours, is

greater over the Arctic Ocean than over any region in southern Europe.

The values are much less during summer, however.

        Duration of Sunshine over the Arctic Ocean (from the Maud )

	Mar	Apr	May	Jun	Jul	Aug
Hours	204	309	269	98	117	70
% of possible hours	69	64	38	14	16	14

288      |      Vol_VII-0294                                                                                                                  

        During the year 1932-33, records of sunshine were obtained by

the Canadian North Polar Year Expeditions to Coppermine, Chesterfield

Inlet, and Capes Hopes Advance. Here, the greatest number of hours

of sunshine and also the greatest percentage of possible sunshine were

recorded during July and August when the duration of sunshine amounted

to 40 or 50 percent of the total possible. The minimum was reached in

December when less than 10 percent of the possible was recorded.

289      |      Vol_VII-0295                                                                                                                  

        In Arctic regions the quality of light is often a more practical

consideration than is the duration of sunlight or darkness. The

amount of light reflected from the snow surfaces is much greater than

in lower latitudes because of the lower angle of incidence of the

sun’s rays. As a result, the useful illumination is much greater

than under similar conditions of sunlight in lower latitudes. One

disadvantage, however, is that the light reflected from the snow surface

may be so intense as to obliterate definitive shadows. The resulting

lack of contrast may make it impossible to distinguish outlines of

terrain features or even of fairly large surface objects at close

range. Dark mountains may be seen for great distances, while a

crevasse immediately ahead of the traveler may be unseen. Moreover,

because of the high reflectivity of the snow cover, the danger of

severe sunburn is more likely than in southern latitudes, and snow

glasses are a necessary part of the equipment of every Arctic

traveler.

290      |      Vol_VII-0296                                                                                                                  

        In winter, however, the high reflectivity of the snow cover

is a valuable asset. Pilots have reported that the light of a half–

moon over a snow-bounded airfield is sufficient for landing purposes.

Most surface activities can be carried on under moonlight conditions

in the Arctic and the light of the stars alone is sufficient for some

purposes. It is only during periods of heavy overcast that the Arctic

darkness begins to approach the darkness of temperate latitudes.

        The total illumination throughout the year is greatest over the

Arctic pack-ice and the Greenland Ice Cap and least over open water

surfaces in winter and over snow-free land areas in summer.

       

Fig. 53 here

       

Table XXXII here

291      |      Vol_VII-0297                                                                                                                  

Table XXXII. Locations of Arctic weather stations

Station Number	Station Name		Latitude ° ′ N	Longitude ° ′	Elevation (ft.)
Oceanic:
001	“Sedov” (Drifting Ship) (1939)	Jan	84 55	124 12 E	Sea level
		Feb	85 55	119 26
		Mar	86 24	110 05
		Apr	86 13	89 32
		May	85 45	78 27
		Jun	85 50	68 08
		Jul	85 33	62 13
		Aug	86 11	54 46
		Sep	86 05	37 59
		Oct	84 49	25 54
		Nov	84 09	13 31
		Dec	82 35	81 15
002	“Fram” (Drifting Ship) (1893-1896)		Mean Position 82° 42′ N., 89° 36′ E		Sea level
003	“Maud” (Drifting Ship) (1922-1924)		Mean Position 74° 36′ N., 164° 00′ E.		Sea level
004	Jay Mayen		70 59	08 20 W.	76
005	Bear Island		74 28	19 17 E.	133
006	Ostrov Domashnii		79 30	91 08	10
007	Ostrov Uedineniia		77 30	82 12	30
008	Papanin North Polar Expedition (Drifting Ice) (1937-1938)	Jan	77 00	10 W.	Sea level
		Feb	73 00	17
		Mar	..	..

292      |      Vol_VII-0298                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name		Latitude ° ′ N	Longitude ° ′	Elevation (ft.)
Oceanic: (cont.):
008 (cont.)	Papanin North Polar Expedition (Drifting Ice) (cont.)	Apr	..	..
		May	89 20	60 W.
		Jun	88 50	10
		Jul	88 20	05
		Aug	87 30	00
		Sep	86 20	00
		Oct	84 40	05 E.
		Nov	83 30	05 W.
		Dec	81 30	07
009	Foka Bay		76 00	60 12 E.	Sea level
Alaska, Coastal and Insular:
100	Barrow		71 18	156 47 W.	13
101	Point Hope		68 20	166 48	19
102	Kotzebue		66 52	162 38	11
103	Wales		65 36	168 04	3
104	Nome		64 30	165 24	17
105	Gambell		63 51	171 36	30
106	Anchorage		61 13	149 52	118
Alaska, Inland:
150	Shungnak		66 55	157 05 W.	142
151	Umiat		69 26	151 50	..
152	Wiseman		67 26	150 13	675

293      |      Vol_VII-0299                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N	Longitude ° ′	Elevation (ft.)
Alaska, Inland (cont.):
153	Fort Yukon	66 34	148 18 W.	417
154	Bethel	60 48	161 45	35
155	Tanana	65 10	152 06	220
156	Fairbanks	64 51	147 43	440
157	Eagle	64 46	141 12	804
Canada, Coastal and Insular:
200	Lady Franklin Bay	82 00	63 06 W.	..
201	Fort Conger	81 44	64 45	..
202	Ellesmere Land	76 36	87 06	..
203	Goose Fiord	76 44	88 39	..
204	Craig Harbor	76 12	79 35	12
205	Bache Peninsula	79 10	76 45	10
206	Holman Island	70 30	117 38	30
207	Banks Strait	73 48	114 54	..
208	Winter Harbor	74 47	110 48	..
209	Barrow Strait	74 06	93 34	..
210	Fort Ross	72 02	94 03	50
211	Arctic Bay	73 16	84 17	36
212	Dundas Harbor	74 34	82 10	18
213	Pond Inlet	72 43	78 30	13
214	Clyde	70 20	68 30	26
215	Herschel Island	69 30	139 15	..
216	Coppermine	67 49	115 10	13

294      |      Vol_VII-0300                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N	Longitude ° ′	Elevation (ft.)
Canada, Coastal and Insular (cont.):
217	Cambridge Bay	69 05	105 00 W.	15
218	King William Land	68 37	95 53	..
219	Foxe Channel	67 12	84 42	..
220	Cumberland Sound	66 30	67 06	..
221	Chesterfield Inlet	63 20	90 43	13
222	Coral Harbor	64 11	83 21	193
223	Nottingham Island	63 07	77 56	54
224	Lake Harbor	62 50	69 55	54
225	Upper Frobishcher Bay	63 45	68 32	54
226	Pangnirtung	66 09	65 30	50
227	Resolution Island	61 18	64 53	127
228	Churchill	58 47	94 11	44
Canada, Inland:
250	Aklavik	68 14	134 50	25
251	Fort McPherson	66 58	134 55	..
252	Dawson	64 04	139 29	1,062
253	Whitehorse	60 43	135 05	2,289
254	Fort Good Hope	66 15	128 38	214
255	Watson Lake	60 07	128 48	2,248
256	Norman Wells	65 17	126 47	290
257	Fort Norman	64 54	125 40	..
258	Fort Simpson	61 52	121 13	572
259	Hay River	60 51	115 58	..

295      |      Vol_VII-0301                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude (ft.)	Elevation (ft.)
Canada, Inland (cont.):
260	Yellowknife	62 28	114 27 W.	660
261	Fort Resolution	61 10	114 00	..
262	For Smith	60 00	111 52	680
263	Fort Vermilion	58 23	115 59	..
Greenland and Iceland, Coastal and Insular:
300	Robeson Channel	82 00	63 42 W.	Sea level
301	Inglefield Bay	77 20	67 30	Sea level
302	Thule	76 34	68 48	129
303	Danmarkshavn	76 46	18 45	20
304	Upernivik	73 47	56 09	59
305	Marrak	70 30	54 15	136
306	Umanak	70 41	52 09	..
307	Myggbukta	73 30	21 35	13
308	Scoresbysund	70 28	21 58	56
309	Gothavn	69 14	53 31	36
310	Edgesminde	68 43	52 50	106
311	Holstensborg	66 56	53 39	89
312	Sondrestromfjord	66 30	52 15	190
313	Cruncher Island	66 02	53 33	51
314	Godthaab	64 11	51 45	66
315	Skjoldungen	63 21	41 39	297
316	Atterbury Dome	65 20	40 18	1,186
317	Angmagssalik	65 30	37 33	95

296      |      Vol_VII-0302                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Greenland and Iceland, Coastal and Insular (cont.):
318	Ivigtut	61 12	48 10 W.	82
319	Narsaq Point	60 54	46 00	95
320	Nanortalik	60 10	45 17	23
321	Prince Christian Sound	60 03	43 12	250
330	Lambavtn	65 30	24 06	5
331	Reykjavik	64 09	21 57	167
332	Kollsa	65 21	21 11	39
333	Vik	63 25	19 01	20
334	Grimsey	66 30	18 01	72
335	Husavik	66 02	17 21	..
336	Akureyri	65 41	18 05	23
337	Fagurholsmyru	63 54	16 37	131
338	Holar	64 18	15 11	..
339	Hofn	66 02	14 48	20
340	Seydisfjorder	65 16	14 00	26
341	Vattarnes	64 56	13 41	66
Greenland and Iceland, Inland:
350	Watkins Ice Station	67 03	41 49 W.	8,200
351	Eismitte	70 54	40 42	9,938
360	Haell	64 04	20 13	427
361	Grimsstadhir	65 36	16 12	1,247
Europe, Coastal and Insular:
400	Bukhta Tikhaya	80 19	52 48 E.	20

297      |      Vol_VII-0303                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Europe, Coastal and Insular (cont.):
401	Ostrov Rodol’fa	81 48	57 57 E.	157
402	Quade Hook	78 57	12 30	33
403	Green Harbor	78 02	14 15	36
404	Storo	76 30	16 30	..
405	Mossel Bay	79 54	16 27	..
406	Gjesvaer	71 06	25 22	20
407	Kistrand	70 28	25 15	5
408	Vardo	70 22	31 06	39
409	Nordoyan	64 48	10 33	102
410	Skomvaer	67 30	11 54	65
411	Svolvaer	68 14	14 37	3
412	Bodo	67 17	14 26	56
413	Andenes	67 20	16 08	23
414	Tromso	69 39	18 57	335
415	Kola	68 53	33 01	23
416	Swayatoi Nos	68 09	39 49	246
417	Kolquev Island	68 46	48 18	22
418	Pusstoserssk	67 35	52 11	39
419	Kirkenes	62 02	04 59	135
420	Bronnoysund	65 28	12 12	17
421	Harnösand	62 38	17 57	29
422	Vaasa	63 05	21 37	30
423	Haparanda	65 50	24 09	13

298      |      Vol_VII-0304                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Europe, Coastal and Insular (cont.):
424	Helsingfors	60 10	24 57 E.	39
425	Kem	64 57	34 39	30
426	Leningrad	59 56	30 16	20
427	Solovets	65 01	35 45	56
428	Archangel	64 28	40 31	20
429	Mezen	65 50	44 16	66
Europe, Inland:
450	Karesuando	68 26	22 30	1,091
451	Karasjok	69 28	25 31	443
452	Inari	68 57	26 49	502
453	Sodankyla	67 22	26 39	591
454	Trondheim	63 26	10 25	210
455	Falun	60 37	15 38	399
456	Stenselle	65 04	17 11	1,076
457	Jyvaskyla	62 14	25 44	387
458	Kajaani	64 13	27 46	479
459	Ust Ssyssolssk	61 40	50 51	332
460	Ust Zylma	65 27	52 10	220
Asia, Coastal and Insular:
500	Mys Zhelaniia	76 57	68 34	26
501	Mys Sterlegova	75 25	88 54	33
502	Ust’e R. Taimyry	76 12	99 04	30
503	Mys Cheliuskina	77 43	104 17	16

299      |      Vol_VII-0305                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Asia, Coastal and Insular (cont.):
504	Ostrov Kotel’nyy	76 02	138 06 E.	..
505	Malye Karmakuly	72 23	52 44	52
506	Ostrov Vaigach	70 24	58 48	36
507	Matochkin Shar	73 16	56 24	59
508	Ostrov Belyi	73 20	70 02	20
509	Gydo-Yamo	70 55	79 33	26
510	Ostrov Diksona	73 30	80 24	66
511	Ostrov Sagastyr’	73 23	126 36	16
512	Tiksi Bay	71 35	128 56	33
513	Kazach’ye	70 45	136 16	56
514	Shalaurova	73 11	143 14	26
515	Russkoye Ust’ye	71 00	149 05	6
516	Mys Medvezhiy	69 38	162 24	..
517	Wrangell Island	70 58	178 33 W.	10
518	Yugorski Shar	69 49	60 46 E.	43
519	Mare-Sale	69 43	66 48	56
520	Obdorsk	66 35	66 31	86
521	Novy Port	67 42	72 57	16
522	Wizhne-Kolymsk	68 32	160 59	16
523	Mys Shmidta	68 55	179 29 W.	30
524	Mys Van Karem	67 28	175 17	..
525	Uelen	66 10	169 50	23
526	Gizhiga	62 03	160 30 E.	33

300      |      Vol_VII-0306                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Asia, Coastal and Insular (cont.):
527	Anadyr’	64 45	177 35 E.	16
528	Zaliv Kresta	66 10	178 59 W.	13
529	Providence Bay	64 24	173 13	13
530	Lawrence Bay	65 35	170 40	Sea level
531	Ola	59 33	151 13 E.	16
Asia, Inland:
550	Volochanka	70 58	94 30 E.	..
551	Khatanga	72 00	102 09	230
552	Bulun	70 40	127 12	115
553	Ust ‘Yeniseiskii Port	69 40	84 24	20
554	Dudinka	69 24	86 04	66
555	Igarka	67 30	86 50	..
556	Verkhoyansk	67 35	133 30	400
557	Abyy	68 26	145 11	59
558	Sredne-Kolymsk	67 27	153 34	98
559	Rodchevo	66 18	152 44	33
560	Berezovo	63 56	65 04	138
561	Samorova	60 58	69 04	544
562	Surgut	61 17	75 20	135
563	Turukhansk	65 55	87 38	13
564	Taimba	60 19	98 55	551
565	El’gyay	62 29	117 31	443
566	Olekminsk	60 24	120 24	499

301      |      Vol_VII-0307                                                                                                                  

Table XXXII. Locations of Arctic weather stations (cont.)

Station Number	Station Name	Latitude ° ′ N.	Longitude ° ′	Elevation (ft.)
Asia, Inland (cont.):
567	Viliusk	63 45	121 35	394
568	Yakutsk	62 01	129 43	354
569	Semenowskij Rodnik	64 00	132 00	3,346
570	Ust’-Maya	60 25	134 29	581
571	Olmyaken	63 28	142 30	2,625
572	Markovo	64 41	170 25	85
573	Tobolsk	58 12	68 14	355
574	Yeniseysk	58 27	92 10	256
575	Kirensk	57 47	108 07	865
576	Blagoveshchensk Priisk	58 10	114 17	1,608
577	Bur	58 57	106 31	1,414

302      |      Vol_VII-0308                                                                                                                  

       

THE METEOROLOGY OF THE ARCTIC

       

INFORMATION ON DIAGRAMS

Figs. 1-3	Supplied.
Fig. 4	Same as Fig. 18 (p. 90) in Haurwitz and Austin: “Climatology.” Copyright by McGraw-Hill, New York
Figs. 5-12	Supplied.
Fig. 13	Upper figure same as Fig. 351, p. 623, and lower figure same as Fig. 357, p. 625 in Meddelelser om Gronland, Bd. 75, 1930.
Fig. 14	Supplied.
Fig. 15	Same as Tafel X at p. 252 in “Danmark Expeditionen til Gronlands Nordostkyst 1906-1908.
Figs. 16-17	To be found in Scoresby, Wm., Transactions of the Royal Soc. of Edinburgh. Vol. 9. pp. 299-305.
Fig. 18	Same as Fig. 89 (p. 160) in S. Petterssen: Weather Analysis and Forecasting, Copyright by McGraw-Hill, New York.

303      |      Vol_VII-0309                                                                                                                  

Fig. 19	Same as Fig. 90 in book referred to under Fig. 18.
Fig. 20	Same as Fig. 124 (p. 269) in book referred to under Fig. 18.
Fig. 21	Same as Fig. 126 (p. 271) in book referred to under Fig. 18.
Fig. 22	Same as Fig. 128 (p. 273) in book referred to under Fig. 18.
Figs. 23-28	Supplied.

Unpaginated      |      Vol_VII-0310                                                                                                                  

---

REFERENCE TO LITERATURE

1. Baur, F. “Das Klima der bisher erforschten Teile der Arktis.”

Arktis, No. 2, Gotha, 1929.

2. Bedient, H. A. Unpublished Report. Air Weather Service,

Washington, D. C., 1950.

3. Bergeron, T., Geofys. Pub., Vol. 5, No. 6, Oslo, 1928.

4. Bogolepow, M. Met Zeitschr. Vol. 49, No. 7, p. 258-261. 1932.

5. Brontman, L. “On the Top of the World.” Victor Gollancz Ltd.

London, 1938.

6. Canadian Dept. of Marine and Fisheries. “Report of the Meteoro–

logical Services of Canada for the Year Ending December 31, 1908.”

Ottoawa, 1912.

7. Canadian Dept. of Transport. “Canadian Polar Year Expedition,

1932-1933. Meteorology.” Vol. I. Ott oawa, 1940.

8. Carmichael, H. and Dymond, E. G. Proc. Roy. Soc. Ser. A. Math.

and Phys. Sci., Vol. 171, pp. 345-359. London, 1939.

9. Collinson, Sir Richard. “Journal of the Enterprise,” p. 176.

10. Craig, R. A. Am. Met. Soc. Monographs, Vol. 1, No. 2. Boston,

Mass., 1950.

11. Dobson, G.M.D., Proc. Roy. Soc. London, A, 129, 1930; A, 185,

1946; A, 110, 1926; A, 114, 1929.

12. Dorsey, N. G. “Meteorological Characteristics of Northern Arctic

America.” (unpublished). Mass. Inst. of Tech., 1949.

13. Dzerdzerjevski, B. L. “Circulation Schemes in the Troposphere

over the Central Arctic.” Inst. of Theoretical Geoph. Moscow

and Leningrad. 1945.

304      |      Vol_VII-0311                                                                                                                  

14. Flohn, H. Polarforschung, Ser. II, 17(1-2): pp. 143-149.

Kiel, 1947.

15. Gutenberg, B. Bul. Am. Met. Soc., Vol. 20, pp. 192-201.

16. Hann, J. and Suring, R., “Lehrbuch der Meteorologie,” p. 180,

Leipzig, 1937.

17. Haurwitz, B. and Austin, J. M., “Climatology,” McGraw-Hill,

New York, 1944.

18. Helmholtz, H. von. Met. Zeitschr. Bd. 5, pp. 329-340. 1888.

19. Holz, R. S. “Pole Vaulting for Weather.” Unpublished. Air

Weather Service, Washington, D. C., 1950.

20. Hovm o ö ller, E. Meddelelser om Gr o ö nland, Bd. 144, No. 1,

Appendix 1. 1947.

21. International Meteorological Organization, Publication No. 62,

Lausanne, 1948.

22. Kaye, G.W.C. and Evans, E.J., Nature, Jan. 1939.

23. Koch, J. P. and Wegener, A., Meddelelser om Gr o ö nland, Vol. 75,

pp. 405-676.

24. K o ö ppen, W., “Die Klimate der Erde”, Berlin, 1923.

25. K o ö ppen, W. “Klimakunde von Russland.” Handbuch der Klimatologie,

Band III, Teil N. Berlin, 1939.

26. Malmgren, F. Geofys. Pub., Vol. 4, No. 6. Oslo, 1926.

27. Meteorological Division, Dep. of Transport, “Meteorology of the

Canadian Arctic”, Toronto, 1944.

28. Mohn, H. “Meteorology.” The Norwegian North Polar Exp. 1893-1896.

Vol. VI. Christiania, 1905.

305      |      Vol_VII-0312                                                                                                                  

29. Mohn, H. “Report on the Scientific Results of the Second Nor–

wegian Arctic Expedition in the Fram. 1898-1902.” Christiania,

1907.

30. Namias, J. and Smith, K. “Normal Distribution of Pressure at

10,000 feet over the Northern Hemisphere.” U. S. Weather Bureau,

Washington, D. C., 1944.

31. Petterssen, S., “Weather Analysis and Forecasting,” McGraw-Hill,

New York, 1940.

32. Petterssen, S. Proceedings of the Centenary Celebrations, Roy.

Met. Soc., London, 1950.

33. Phillips, W., Unpublished report on flying hazards at Alaskan air–

fields. Air Weather Service, Washington, D. C., 1951.

34. Rigby, M. “Climatology of the Arctic Regions.” Parts I-III.

Air Weather Service, Washington, D. C., 1946.

35. Roberts, B., The Polar Record, Vol. 4, No. 27.

36. Rothwell, P., J. of Acoust. Soc. of Am., Vol. 19, pp. 205-221.

37. Saby, S. and Nyborg, W. L., J. of Acoust. Soc. of Am., Vol. 18,

pp. 316-322.

38. Scoresby, W., Trans. Roy. Soc. of Edinburgh, Vol. 9, pp. 299-305.

1821.

39. Simpson, G. C. “Meteorology.” British Antarctic Exp., 1910-1913.

Vol. I. Discussion. Calcutta, 1919.

40. Sorge, E., Geog. Journ. Roy. Geog. Soc., Vol. 81; 333-352. 1933.

41. Stefansson, V. “The Friendly Arctic.” New York, 1943.

42. Sverdrup, H. U., Petersen, H. and Loewe, F., “Klima des

Kanadischen Arkipels und Gr o ö nlands.” Handbuck h der Klimatologie,

edited by K o ö ppen and Geiger. Vol. II, Part K. 1935.

306      |      Vol_VII-0313                                                                                                                  

43. Sverdrup, H. U. “Meteorology, Part I, Discussion.” The

Norwegian North Polar Expedition with the Maud. Scientific

Results, Vol. II. Bergen, 1933.

44. Sverdrup, H. U. “Meteorology, Part II, Tables.” The Norwegian

North Polar Expedition with the Maud. Scientific Results, Vol. II.

Bergen, 1933.

45. Tikhomirova, E. I. “Klimaticheskii Ocherk Karskogo Maria” (Climatic

Outline of the Kara Sea). Trans. Arctic Sci. Res. Inst. U. S. S. R.

Vol. 187. Moscow, Leningrad, 1946.

46. T o ö nsberg, E. and Langlo Olsen, K. L., Geofys. Pub., Vol. 13,

No. 12, Oslo, 1944.

47. U. S. Weather Bureau, “Normal Weather Maps,” Washington, 1944.

48. U. S. Weather Bureau and Air Weather Service. “Upper Air Wind

Normals for the Northern Hemisphere.” Washington, D. C., 1945,

(Unpublished).

49. Vederman, J. and Smith, C. D., Bul. Amer. Met. Soc., Vol. 31,

No. 6: 197-205. 1950.

50. Waelchen, K., Zeitschr. f. Geophys., Vol. 10, p. 322.

51. Wegener, A., “Danmark Expeditionen til Gr o ö nlands, Nordostkyst

1906-08,” pp. 127-355.

52. Wegener, A., Medelelser om Gr o ö nland, Vol. 42, p. 561.

53. Wexler, H., Monthly Weather Review, Vol. 64, No. 4, Washington,

1936.

54. Wexler, H., Bul. Amer. Met Soc., Vol. 29. No. 10; 547-550. 1948.

55. Whipple, F. W. Proc e é s Verbaux, Intern. Met. Assoc., Edinborough,

1936.

307      |      Vol_VII-0314                                                                                                                  

56. Wiese, W. “Scientific Results of the Arctic Expedition on the

Sedov.” Trans. of the Arctic Inst., Vol. 1, 1936.

308      |      Vol_VII-0315                                                                                                                  

       

LEGEND TO DIAGRAMS

Fig. 1.	The principal climatic zones of the northern hemisphere. Ref. Kőppen [ 24 ] .
Fig. 2.	Mean meridional distribution of temperature. Ref. Hann and Sűring [ 16 ] .
Fig. 3.	Mean meridional distribution of ozone. Ref. Craig [ 10 ] . the unit of ozone amount is the equivalent height of a column of ozone at standard pressure and temperature.
Fig. 4.	Mean meridional distribution of relative humidity. Ref. Haurwitz and Austin [ 17 ] .
Fig. 5.	Some typical examples of temperature soundings. Upper diagram: July. Lower diagram: January. Ref. Canadian Meteorological Service [ 27 ] .
Fig. 6.	Mean meridional cross-section of temperature (°C) in January. Ref. Petterssen [ 32 ] .
Fig. 7.	Mean meridional cross-section of temperature (°C) in July. Ref. Petterssen [ 32 ] .

309      |      Vol_VII-0316                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Fig. 8.	Mean meridional cross-section of annual variation of temperature (°C.)
Fig. 9.	Some examples of temperature inversions in the Arctic.
Fig. 10.	Annual variation of temperature inversions. Ref. Sverdrup [ 43 ] .
Fig. 11.	Relation between inversion conditions and wind speed and cloudiness. Ref. Canadian Meteorological Service [ 27 ] .
Fig. 12.	Diagrammatic representation of sound beams. A: Uniform temperature; B: Normal lapse rate; C: Inversion with sound source below the inversion; D: Inversion with sound source above inversion layer; E: Multiple inversion; F: Influence of wind.
Fig. 13.	Superior mirage. Upper picture Gundahl’s Knold (76°43′ N., 32°01′ W.) without optical distortion. Lower picture strong vertical distortion due to inversion layer. Ref. [ 23 ] .

310      |      Vol_VII-0317                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Fig. 14.	Diagramatic representation of looming. Hatched areas indicate twilight or darkness.
Fig. 15.	Inferior mirage near Cape Bismark, 1st Oct. 1907. Ref. Wegener [ 51 ] .
Fig. 16.	Telescopic appearance of ships, as observed in the Greenland Sea, June 28th, 1820, 73°30′N., 11°10′W. Ref. [ 38 ] .
Fig. 17.	Telescopic appearance of east coast of Greenland, at a distance of 35 miles, July 18th, 1820, 71°20′N., 17°30′W. Ref. [ 38 ] .
Fig. 18.	Source region of principal air masses in winter. Ref. Patterssen [ 31 ] .
Fig. 19.	Source region of principal air masses in summer. Ref. Petterssen [ 31 ] .
Fig. 20.	Mean position of main frontal zones in winter. Ref. Petterssen [ 31 ] .

311      |      Vol_VII-0318                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Fig. 21.	Mean position of main frontal zones in summer. Ref. Petterssen [ 31 ] .
Fig. 22.	Cross-section through principal frontal zones. Ref. Petterssen [ 31 ] .
Fig. 23.	Example of synoptic situation, showing traveling cyclones and anticyclones.
Fig. 24.	Mean meridional distribution of percentage frequencies of cyclogenesis (CG), cyclone centers (C), anticyclo– genesis (AG), and anticyclones (A) in squares of 100,000 sq. kilometers. Ref. Petterssen [ 32 ] .
Fig. 25.	Geographical distribution of percentage frequency of cyclones in winter. Ref. Petterssen [ 32 ] .
Fig. 26.	Geographical distribution of percentage frequency of cyclones in summer. Ref. Petterssen [ 32 ] .
Fig. 27.	Geographical distribution of percentage frequency of anticyclones in winter. Ref. Petterssen [ 32 ] .

312      |      Vol_VII-0319                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Fig. 28.	Geographical distribution of percentage frequency of anticyclones in summer. Ref. Petterssen [ 32 ] .
Fig. 29.	Mean surface pressure for January (in mbs.) Ref. Dorsey [ 12 ] .
Fig. 30.	Mean surface pressure for April (in mbs.) Ref. Dorsey [ 12 ] .
Fig. 31.	Mean surface pressure for July (in mbs.) Ref. Dorsey [ 12 ] .
Fig. 32.	Mean surface pressure for October (in mbs.) Ref. Dorsey [ 12 ] .
Fig. 33.	Mean altitude of the 700-mb. pressure surface for January (in feet). Revised from Namias and Smith [ 30 ] .
Fig. 34.	Mean altitude of the 700-mb. pressure surface for July (in feet). Revised from Namias and Smith [ 30 ] .
Fig. 35.	Surface wind roses-Mean distribution of the surface wind by both speed (mph) and direction. Winter.

313      |      Vol_VII-0320                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Fig. 36.	Surface wind roses-Mean distribution of the surface wind by both speed (mph) and direction. Summer.
Fig. 37.	Example of diurnal variation of wind speed over the pack-ice and at the coast. Ref. Sverdrup [ 43 ] .
Fig. 38.	Mean air flow and upper wind distribution at 3 Km. (10,000 feet) during winter. Long arrows give mean flow pattern. Wind roses showing frequency distribution of various wind directions and speeds have been entered for certain stations, and sector mean winds are given for certain locations.
Fig. 39.	Mean air flow and upper wind distribution at 3 Km. (10,000 feet) during summer. Long arrows give mean flow pattern. Wind roses showing frequency distribution of various wind directions and speeds have been entered for certain stations, and vector mean winds are given for certain locations.

314      |      Vol_VII-0321                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Figure 40.	Mean air flow and upper wind distribution at 6 Km. (20,000 feet) during winter. Long arrows give mean flow pattern according to (ref. 48). Wind roses showing frequency distribution of various wind directions and speeds have been entered for certain stations, and vector mean winds are given for certain locations (ref. 48). Wind roses near the 40,000-foot level are shown in the inset.
Figure 41.	Mean air flow and upper wind distribution at 6 Km. (20,000 feet) during winter. Long arrows give mean flow pattern according to (ref. 48). Wind roses showing frequency distribution of various wind directions and velocities have been entered for certain stations, and vector mean winds are given for certain locations (ref. 48). Wind roses near the 40,000-foot level are shown in the inset.

315      |      Vol_VII-0322                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Figure 42.	Frequency distribution of wind according to direction, 3 Km. (10,000 feet) during winter.
Figure 43.	Frequency distribution of wind according to direction, 3 Km. (10,000 feet) during summer.
Figure. 44.	Mean surface temperature (°F) during January.
Figure. 45.	Mean surface temperature (°F) during July.
Figure 46.	Mean surface temperature profile along 140 E. meridian (approximately).
Figure 47.	Examples of the diurnal variation of temperature at Arctic stations with continental and maritime climate. Ref. Sverdrup [ 43 ] .
Figure 48.	Mean precipitation amounts (inches).
Figure 49.	Mean snow depth on ground (inches).
Figure 50.	Diurnal variation of relative humidity and vapor pressure over the pack-ice. Ref. Sverdrup [ 43 ] .
Figure 51.	Mean cloudiness during February (percentage of total cover).

316      |      Vol_VII-0323                                                                                                                  

       

LEGEND TO DIAGRAMS (cont.)

Figure 52.	Mean cloudiness during August (percentage of total cover).
Figure 53.	Station locator map.