Relation of Snow to Meteorology

(1)

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Technical Note (National Research Council of Canada. Division of Building Research), 1953-03-20

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(2)

DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

'fEClHIN ][CAlL

NOT FOR PUBLICATION

No.

149 NOTlE '

FOR INTERNAL USE

,PREPARED BY

L..W. Gold CHECKED BY APPROVED BY R.F'.L'.\

PREPARED FOR

Discussions on Future Snow Ref:earch Work March ＲｾＬ 1953.

SUBJECT _{Relat.,ion of Snow to Meteor.ology}

In 1942, Nakaya and his associates culminated their many observations

oq natural and artificial snow by showin the dependence of the various crystal

tyPes on temperature and water density (1). During some of their observations on

ｮｾｴｵｲ｡ｬ snow they had tl'led to relate the crystal type to the existing'

metebrIJlo-ｧｾ｣｡ｬ conditions but with little success (2). Schaefer (J)shows that re1ation-,

snips do exist ｢ｾｴｷ･･ｮ clouds of a specifiec character and the snow crystals that

they produce. Aufm Kanpe, Weickmann, and Kelly

(4)

discuss and make reference to

further observations m!}'de on the relation' or' natural snow crystals to their ｣ｯｮ､ｩｾ

ｴｾｯｮｳ of growth ｾｮ､Ｎｾｬｳｯ show a dependence of artificial snow crystals on ｴ･ｭｰ･ｲ｡ｾ

ture which is in agreement with Nakaya., uring the winter of 1951-52 observations

were made at McGill University on snow arrivirrg-ntJ:.he ground and these observations

were related to the meteorological conditions existing-aloft as estimated from '

ｾ｡､ｩｯｳｯｮ､･ observations

(5).

A dependence of crystal type on temperature in

agree-ment with Nakaya was found. It was ｾｬｳｯＭｦｯｵｮ､ that the observations made on the

ground could be readily re lated to the conditions existing aloft.

A weakness connnon to all of the observations on natural snow is the

lack of sufficient and accure,te ｭｾｴ･ｯｲｯｬｯｧｩ｣｡ｬ data., lI'o obtain information aloftt

one must· rely on observations made from aircraft or upon radiosonde data. In

some case:: neither are £.vail9-ble and one must rely upon the extrapolation of

radio-sonde observations ｭ｡､ｾ at the nearest radiosonde station. This was the method'

used in the observations made at McGill ｕｮｩｶ･ｲｳｩｴｹｾｔｨ･ results achieved indicate

that much information can be obtained even by this approximate method.

Many general relationships appeared in the observations made at McGill

and many intoresting problems came to notice., A few uf the pr.oblems will- be, enu-,

merated in the following:

(1) The observations clee,rly showed the existence of two general air

flows. In the lower 10,000 feet the general c:ir flow was southward, and above

10,000 feet, ｮｯｲｴｨｷ｡ｲ､ｾ Near 10>000 feet there was a decided minimum of

observa-tions. That is, in the neighbourhood of this height the tephigrams rarely

indicat-ed unstable regions which would initiate snowfall. This minimum may be due to ,the

(3)

.ｾ : -: J ••f • ....ｾｾ ( ..• :.1' ..ｾｾ . ; . "ｾＬ "! .. -..,:.' IJ ".' ;..,-." j,ｾ.. , ':. . ' .. '" ... , ,"' ｾ J .':' ｾ... '.ｾＮ " ·..t ...I! .-ｾＮ I . "'. \ Ｎ｟ｾＢｾ : ' ! t '.ｾ : _ . 't" :.',', ';.' I . . . . ·' ::.::.:'"1!.;..:....').;0; c..:. .. " :;:.·.:.rｾ ＮＺＮｾＧ ,. . ［ｾ . 'r" . ' : •.:. . . .I :ｾ : n. ':.1. - ;--.. '....,. ,\ . ｾ :":' : .ｾ t·::.· ":.;0 ".'L , . , ..ｾ .

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(4)

- 2

-(2) The crystal tYl=>e occurring l'IloOGi:. ｦｾｴＮｬＮｹ was the dendrite._OJ yet

it produces less in terms of inches of new snow than a ｣ｲ［ｹｳｴ｡ｬﾷｾ ±.bat is

classi-fied as an irregular assemblage of plates. The dendrites, which form over a ｮ｡ｾ

temperature range only (-140C. to -170_{C.), were usually associated with flurries}

whereas the irregulQr assenblage of pLt:es, which fornr18t temperatures above and

below dendrite region

(-9

0_{C. to -14}0_{C. and -17}0_{C. to -20°C.), were associated with}

frontal snows. The irrogulnr assemblage of plates was often a crystal which had a

column for a nucleus and p13tes growing randomly over the surface of the column.

The problem here is: ｾｾｹ are the dendrites usually associated with flurries and

the irregular ｣ｾｳｴ｡ｬｳ with the larger snowfalls that occur under frontal conditions?

(3) Another problem closely associated with the above is: What is the

actual mechanism of nucleation of the irregular crystals? This is important as

these crystals are usually associated with the major snowfalls and appear to be a

modified ｾｹｰ･ (i.e. clouds at one height release crystals which grow further when

they fall into clcuds at lower levels).

(4) In many cases ｲｾｮｧ occurred. The problem indicated here is:

Under what conditions does riming occur and could observations on crystal type and degree of riming be a useful indication of the total water density in the regions of formation aloft?

These are some of the questions that arose but there were others, particularly with respect to nucleation.

The field of relating snow to meteorology is just beginning to develop. Nakaya's experiments indicate that the crystal type is very sensitive to small

changes in temperature or wat6r density. Therefore, his work should be carefully

repeated with the greatest accuracy possible. In the field, observations on snow

crystal type should be initiated in many centres across Canada and related to the

most accUrate and complete meteorological data valid for the region. At least one

centre should be located in the immediate vicinity of a radiosonde station. The Snow and Ice Section of D.B.R., N.R.C., is fast arriving at the position where it can make a positive contribution to this newly developed field. With the laboratory facilities soon to be completed, the work of Nakaya can readily

be repeated and further advanced. In the Fall of 1953, the Meteorological Service

are to begin radiosonde observations from their station at Maniwaki, ｑｵ･｢･ｾＮ This

is in the immediate vicinity of ottawa and should offer a source of reliable

meteorological data for the region. At Dorval Airport, Montreal, a Central Analysis

Office has been set up whose records will be available. This will offer a source

of data for all regions in Canada. From the observations made at various centres

(universities if possible ), any pattern in both local and regional variations in

(5)

•

3

-To be able to evaluate the meteorological situation at any centre of

observation and relate the situation to the ｾｲｹｳｴ｡ｬ types observed will require a

man with a good backgrotUld in meteorology. Also, because of the statistical nature

of. the observations, temporary assistance of a meteorologist would not be satisfactory./ The obserT-ations should be sterted now and continually digested until sufficient

information for a valid statistic&l analysis is obtained. The field observations

should also be continually augmented by laboratory studies. With a ｭ･ｴ･ｯｲｯｬｯｧｩｳｾ

working en these problems ｲＺＮｯｮｴＺｩｮＧｾ｟ＧＱＱ［ｹｲ it IIlC'-y be possible to illuminate further' the

reasons i'or ｡ｭｔＢＧｗＮｾ variatjJ:;ns in snowfall as exemplified by the winter of 1951-52

and the winter of 1952-53.

By the Fall of 1953, the Snow and Ice Section of the Division of

Build-ing Research will be housed 'in n'3W laboratories and restrictions to expansion

removed. The foregoing ｰ｡ｲ｡ｧｲｾｰｮｇ SGrve to show how the science of meteorology can

assist in this expansion, A more general ergument for this essential co-operation

is as follo\'!s:

The p:o:-actical probj.ems encountered in tije field of snow and ice are too often challeng3d w:i.thouL 9uff5_cient thought being given to the meteorological

factors involved. Snow is for-med in the upper atmosphere due to a series of

meteorological event:::. Its suhsequent modification when falling and when lying on

the ground is governed to a great extent by meteorological conditions. The formation

of ice, its resulting physical characteristics, the degree to which it is involved in a problem under consideration, is again larpely a function of meteorological

conditions. ｓｩｮｾ･ｳｾｯｷ and ice owe their orifin to variations in climate, it is

only logical that no problem in this field should be undertaken without considering carefully the meteol'olc'G:LcDl factors involved.

As an example of this, consider the snow survey. Here, a statistical

study of the average ｾｾ｣ｵｭｵＱ｡ｴｩｯｮ and ageing of snow-cover for all areas in Canada

is being ma.de. The meteorological factors B.t the ground have been included with the

observations made on the snow-cover hut the factors which occurred in the upper

atmosphere to gi7e rise tel the sneilil ｩｾ｡Ｍｪｴ［［ been unavoidably ignored. For a complete

understandin,z of the ｶＳＮＺｾ［｟｡ｴＮｩｯｮ in ｦｬｲＺｾＨＩｾﾷＺＧｾＨＩｖ･ｬＧ it seems logical that these factors

should be ｩｾ｣ｬｵ､Ｖｑ and studied.

ｾｬｾｴ is w.ith these t11onght..s ｾｮ !T'i:ld 'c,hat e'J-:;ry effort should be made to

develop as ｾ｣ｭｰｽ･ｴ･ｬｹ as possible ｴｾＱ･ J'Tl'3teol'J1og:iJ::"t1 as?ect of each problem and

integrnts .i:. into the f.LlB.:l. sol'.llion. &nov. ｩｾｾＧ･Ｎｌ｡ｴｅｯｊ to meteorology and therefor-A

one of the prime considerations in the r:eld of snow research should be the ､･ｴ･ｾﾷ •

(6)

- 4 ...

RFERENCES:

(1) Nakaya, D., "The Formation of Ie') Crystals"

Compendium of Meteorology, Am. ｍ･ﾷＺｾｅＺｯｲＮ Soc., pp. 207-220, Boston, 1951.

Nakaya} D•., and Y. Sekido, "Gen,:;ral Claflsificntion of Snow Crystals and their

Frequen(:,f of Occu:crence"

J. Fac. ｓｾｩＮｈｯ｢ｾＮｴ､ｯ Dniv., S8r. II, 1,9:243-264 (1936).

Schaefer, V.J., "Snow and Its Relationship to Experimental Meteorologyfl

Compendi1.nll of l-1eteorology, kn, ｍＺｾＩｴ･ｯｲＮ Soc., pp. 221-234, Boston, 1951.

(4)

i Aufm Kampe, J.H" H.ie Weickmarm, and J.,J. Kelly, "The Influence of Temperature

on the Shape of Ice Cryst.als Growing at Water Saturation"

Jour., ｍＳＱＺＬｐＩｾ ..ｾ 8;.3ＺＺｬＮＶｂＮｾＱＷＮＱＬＮＬ

(7)

.' Ii--,_

No.

149

FOR INTERNAL USE

APPROVED B

NOTE

ｾＮＮＮＮＮＮ

R,.-<

ｾ＼ｴｴＮＢＢＧＢ

l../lil'rk Meteorology CHECKED BY

DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

SUBJECTI'Relation of Snow to

'f

E C1HI N II CAlL

NOT FOR PUBLlCAnON

I

PREPARED BY L...VL

ｑｏＭｦＭ､ｾ

__-PREPARED FOR ｏＧﾷｓ･ＭＭｾｾＯｾＧＮＱ 0 _ ｲｾｬＭ｟ｲ＼

I

•

In

1942,

Nakaya and his associates culminated their many

Qbservations ｾｮ｡ｴｵｲ｡ｬ and artificial snow by showing the dependence

of the various crystal types on ｴｾｭｰ･ｲ｡ｴｵｲ･ and water density (1).

During some of their observations on natural snow they had tried to relate the crystal type to the existing meteorological conditions

ＹＮｾｴ with little success (2). Sehaefer (3) shows that relationships

do exist between clouds of a specified character and the snow crystals

that they produce. Aufm. Kampe, Weickmann,and Kelly ｾＴＩ discuss and

make reference to ur e ｾ･ｲｶ｡ｴｩｯｮｳ made on the relation of natural

snow crystals to the r conaftions of growth and also show a dependence of artificial snow crystals on temperature which is in agreement with

Nakaya. During the winter of

1951-52

observations were made at

McGill University on snow arriving at the ground and these observations were related to the meteorological conditions existing aloft as

estimat_ed from radiosonde observations

(5).

A ､･ｰ･ｮ､･ｮ｣･ｾｾｾｴｾｬ

type on temperature in agreement with Nakaya was found. ｾ

found that the observations made on the ground could be readily related to. the conditions existing aloft.

(

A weakness common to all of the observations on natural snow

is the lack of sufficient and accurate meteorological data. To obtain

information aloft, one must rely on observations made from aircraft or

upon radiosonde data. In some cases neither are available and one must

ｲ･ｾｹ｟ｵｰｯｮ the extrapolation of radiosonde observations made at the

nearest radiosonde station. This was the method used in the observatio

made at McGill University. The results achieved indicate that much

information can be obtained even by this approximate method.

Many general relationships appeared in the observations made

at McGill and many interesting problems came to notice. A few of the

problems will be enumerated in the following:

(1) The observations clearly showed the existence of two

general air flows. In the lower 10,000 feet the general air flow

was southward, and above 10,000 feet, northward. Near 10,000 feet

there was a decided minimum of observations. That is, in the

neighbourhood of this height the tephigrams rarely indicated unstable

./

(8)

r

•

r 'f'

•

(

.

.'

(9)

. 0.. "

•

- 2

regions which would initiate snowfall. This minimum may be due to

the method of observation or to some natural cause.

(2) The crystal type occurring most frequently was

the dendrite, yet it produces less in terms of inches of new snow than a crystal type that is classified as an irregular assemblage

of plates. The dendrites which form over a narrow temperature

range only

ＨＭＱＴｾｃＮ

to

-11P.),

were usually associated with flurries

whereas the irregular assemblage of plates, whioh form at .

temperatures above and below dendrite region

(-9°C.

to -14C. and

Ｍｬｾ to

-2ob.),

were assooiated with frontal snows. The irregular

assemblage of plates ｾｲ･ often a orystal which had a oolumn for a

nucleus and plates growing randomly over the surface of the column.

The problem here is: Why are the dendrites usually associated with

flurries and the irregular crystals with the larger snowfalls that occur under frontal conditions?

(3) Another problem closely associated with the above

is: What is the actual mechanism of nucleation of the irregular

orystals? This is important as these crystals are usually associated

with the major snowfalls and appear to be a modified type (i.e. clouds at one height release crystals which grow further when they fall into clouds at lower levels).

(4) In many cases riming occurred. The problem

indicated here is: Under what conditions does riming occur and

could observations on crystal type and degree of riming be a useful indication of the total water density in the regions of formation aloft?

These are some of the questions that arose but there were others, particularly with respect to nucleation.

The field of relating snow to meteorology is just

beginning to develop. Nakaya's experiments indicate that the crystal

type is very sensitive to small changes in temperature ｾｲ water

density. Therefore, his work should be carefully repeated with the

greatest accuracy possible. In the field, observations on snow

crystal type should be initiated in many centres across Canada and related to the most accurate and complete meteorological data valid

for the region. At least one centre should be located in the

immediate vicinity of a radiosonde station.

l>f D.6,liZ., ｴｶＬ･Ｎ･ｾ

The Snow and Ice Sectionlis fast arriving at the position where it can make a positive contribution to this newly

developed field. With the laboratory facilities soon to be completed,

the work of Nakaya can readily be repeated and further advanced. In

the Fall of

1953,

the Meteorological Service are to begin radiosonde

observations from their station at ManiWalki, Quebec. This is in

the immediate Vicinity of Ottawa and should offer a source of reliable

meteorological data for the region. At Dorval Airport, Montreal, a

Central Analysis Office has been set up whose records will be

(10)

• ,-•

" , r :, l ,,' .ｾ

•

(11)

ｾＬ . 4

- 3

-•

Canada. From the observations made at various centres Ｈｵｮｩｶｾｲｳｩｴｩ･ｳ

if possible), any pattern in both local and regional variations in the characteristics of the snowfalls can be studied.

To be able to evaluate the meteorological situation at any centre of observation and relate the situation to the crystal types observed will require a man with a good background

in meteorology. Also, because of the statistical nature of the

observations, temporary assistance of meteorologist would not

be satisfactory. The observations should be started now and

continually digested until ｳｵｦｦｩｾｩ･ｮｴ information for a valid

statistical analysis is obtained. The field observations should

also be continually augmented by laboratory studies. With a

meteorologist working on these problems continually it may b. possible to illuminate further the reasons for annual variations in snowfall as exemplified by the winter of 1951-52 and the

winter of 1952-53.

. By the Fall of 1953, the Snow' and Ice Section of the Division of Building Research will be housed in new laboratories

ｾ wand the restrictions to expansion removed. The foregoing

e

# ｾｾｗｾ paragraphs ｳ･ｲｶ･ｾＸ a speeirle example of ｷｾ the science of

meteorologyLsQould be lR-Vlted to assist in this expansion. A

l

ｾｾ more general argument for ｴｾｬｰ paptieipetieB eeu;d ae put ferward

｜ｬｭＸｾＺ H4.-,; ｾＧＱｦ･ＮｬｉｉｬＱ＼ﾥｬ c.,.-0r.e-r-J:-.. "l Ｔｾ f.,ii<.r""s,

The practical problems encountered in. the ｦｩ･ｾ､ of snow

and ice are too often challenged without sufficient thought being

given to the meteorological factors involved. Snow is formed in

the upper atmosphere due to a series of meteorological events.

Its subsequent modification when falling ｡ｮ､ｾＬｮＺｷｨ･ｮ lying on

the ground is governed to a great extent by meteorological

conditions. The formation of ice, its resulting physical

characteristics, the degree 'to which it is involved in a problem

under ｣ｯｮｳｩ､･ｲ｡ｴｩｯｮｾｩｳ again largely a function of meteorological

conditions. Since snow and ice owe their origin to variations in

climate, it is only logical that no problem in this field should be undertaken without considering carefully the,meteorological factors involved.!t As an example of this, consider the snow

survey. Here, a statistical study of ,the average accumulation

and ageing of snow-cover for all areas in Canada is being made. The meteorological factors at the ground have been included with the observations made on the snow_cover but the factors which occurred in the upper atmosphere tb give rise to the snow have

been unavoidably ignored. For a complete understanding of the

variation in snow-cover it seems logical that these factors

should be includ'ed'and studied.

\f

It is with these thoughts in

mind that every effort should bemade to develop as completely as possible the meteorological aspect of each problem and integrate

it into the final solution. Snow is related to meteorology and

therefore one of the prime considerations in the field of snow research should be the determination of this relationship.

(12)

•

REFERENCES:

4

-(3) (1)

(4)

(2)

Nakaya, U., "The Formation of Ice Crystals"

Compendium of Meteorology, Am. Meteor. Soc., pp.

207-220,

Boston,

1951.

Nakaya, U., and Y. Sekido, "General Classification of Snow Crystals and their Frequency of Occurrence"

J. Fac. Sci. Hokkaido Univ., Sere II,

1,9:243-264 (1936).

Schaefer, V.J., "Snow and Its Relationship to Experimental Meteorology"

Compendium of Meteorology, Am. Meteor. Soc., pp.

221-234,

Boston,

1951.

Aui'm Kampe, J.H., H.K. Weickmann, and J.J. Kelly, "The Influence of Temperature on the Shape of Ice Crystals Growing at Water Saturation"

Jour. Meteor.,

8,3:168-174, 1951.

(5) Gold, L.W. and B.A. Power. To be published•