weather typing with regard to dynamic climatology

W E A T H E R T Y P I N G W I T H R E G A R D TO D Y N A M I C C L I M A T O L O G Y

FI~AI~-TI~EK R~.XN

Geophysical Institute, Czechosl.. Acad. Sci., Prague*)

INTRODUCTION

Dynamic climatology in the meaning of Bergeron's well-known pape r [l] is undoubtedly one of the modern branches of climatology which, tog@ther

w i t h classical climatology, can be of use to the climatologist in perfecting his knowledge of the climate. Moreover, dynamic climatology enables the recovery of data typical of climatic elements during various synoptic situations and thus by means of statistical methods facilitates synoptic weather-forecasting for small and special regions (e. g. for mountainous districts, for regions wind- wards and leewards .of the mountains at certain prevailing currents etc.). Dynamic climatology can also be used in evaluating approximative climatic means for localities with a short observation series by considering anomalies in the atmospheric circulation during the observation period and by correcting the data measured with regard to the climatic state of the circulation (for instance by correcting the measured precipitation amounts).

The basis of the climatological t reatment of time series of the meteorological elements observed are certain time periods, a certain calendar [2]. The calendar for dynamic-climatological treatment must be chosen so that the day with very similar synoptic situation are joined together into groups, each having a certain important synoptic characteristic (e. g. groups with the same distribution of the pressure patterns, of the direction of the front-movement etc.).

In order to arrange the various synoptic situations into groups according to the characteristics of the pressure pattern, fronts (their position and direction of movement) and the prevailing air currents, it is necessary to find the correct principles for abstracting the basic common features from the individual situations. We assume that for the purpose of climatological t reatment it is best to consider the position of the outstanding sea-level cyclones and anticyclones together with the prevailing direction of their movement, which is regularly identical with the direction of the stearing flow (or the jet stream) in the upper troposphere, as the general criterion. Then the cyclonic or anticyclonic charakter of the sea-level current is the second criterion used. This last criterion, known from pure synoptic treatments, cannot be the chief one, bu t it is of great importance in climatological evaluation due to its influence on the weather character in the region studied.

Hence we use the common features known from synoptic situations and arrange them into groups, called "the elementary synoptic types".

Finally, the following should be noted. First -- for each day of the period treated one single synoptic type has been fixed or the day has been omitted from the treatment (in eases of a very complicated and therefore untypical synoptic situation). Secondly, the typing has been done for the territory of Czechoslovakia; in doubtful cases, for its western part with a note that in the region of Slovakia there exists a distinct type.

*) Address: Bo~nl II , Praha 13-Spo~ilov.

Studia geoph, et geod. 3 (1959) 177

F. R e i n

M E T H O D O F T R E A T M E N T

The method of synoptic typing elaborated and used by J. Brs Z. Gregor and the staff members of the I-Iydrometeorological Inst i tute in Prague was chosen as a work-basis. For greater clarity of the classification some changes have been made. The result is the classification of the synoptic situations into nineteen synoptic types, nine of them having an anticyclonic, ten a cyclonic character. This number of types is large, but it is not possible to use fewer types without destroying the design of the treatment, i. e. getting those types, which could be characterised by a certain different weather in the individual districts of the territory.

o

! l

Fig. 1. The symbols used on the k inemat ic ch a r t s of the fo]lo- ) b wing figure: a - - boun d a ry b e t w een the cyclonic and an t icy-

C clonic act ivi t ies , b -- prevai l ing m o v e m e n t of t h e f ron ts and sea-level cyclones, c - - prevai l ing posi t ion of t h e ant icyclonic

d centers , d - - prevai l ing posi t ion of the cyclonic centers , e - - e prevai l ing m o v e m e n t of the ant icyclonic centers .

A survey of the types is given in Tab. I, their synoptic schemes in Fig. 2. Fig. 1 explains the symbols used in the schematic charts of Fig. 2. The nine- teenth type has no scheme, because it is characterised by the absence of a pres- sflre gradient in central Europe, usually in a large region of low pressure over half of the European continent (this situation is called in German "verwasche- nes Druckfeld").

In the group of anticyclonic types no northern type is considered. This is because of the pure nothern situation which occurs very rarely and therefore such quasi-northern anticyclonic situations can easily be joined to the north- west or north-east type. Among the cyclonic types two western types (Wc and Wcz) are arranged, the latter having the southern track of the frontal systems (centers of the cyclones at about 50 ~ N lat.). In these above-mentioned cases the territory of Czechoslovakia nearly always lies in the cold air, the warm sector of the cyclones being over Bayern, the Alps and northern Italy. Similarly the southwestern cyclonic situations are divided into two types (SWc 1 and SWc 2). The first (SWc 1) is characterised by a cyclone or a trough over southern England, the Channel, Biscay or France, around which the warmer moist air flows into central Europe with the fronts often without a continuous frontal zone. The other type on the other hand regularly has a continuous frontal zone in the S W - - N E direction over central Europe. Czechoslovak territory often lies in the warm sectors. This type is very similar to the zonal western type because of the character of its pressure pattern and temperature distribution in the lower troposphere.

Likewise the northern type does not occur among the anticyclonic types and the southern and southeastern types have not been arranged among the cyclonic types. This might be regarded as a drawback in the classification system. But this is not true, because the southern cyclones, abundant in precipitation in central Europe, are regulary joined together with the cyclonic trough, with the cyclone ove r central Europe or with the eastern cyclonic type. All the mentioned types have been arranged in the present classification and hence the arranging of an individual southern and southeastern cyclonic type has obviously not been necessary.

178 Studia geoph, et geod. 3 (1959)

Weather Typing wit h Regard. to Dynamic Climatology

~

0 e ~

0

r~

f2~ ~

o . r o o o o o o

o o o o

o o o

o o

~ ~ . ~

o o

o 0

o 0

0 o

�9 �9

o o

~ . ~

o o 0 o

- ~ . ' ~ o~ ~" ~ ~ o ~ ~

"~ ~ o o _ o ~ o

o ~ ~ ~ o~

S t u d i a g e o p h , e t g e o d . 3 (1959) 179

.F. Rein

\ kS!. . ~ ~--~

�9 : ,. ~ ( ]

Fig. 2. Kinematic charts of single synoptic types.

],~0 Studia geoph, et geod. 3 (1959)

Weather Typing with Regard to Dynamic Climatology

:,. �9 ".

, / - � 9 ~ t ~ Bc

i i ~

Fig. 2. (Gont, inuation.)

Studia geoph, et geod, 3 (1959) ] 81

F. Rein

Fig. 2. (Continuation.)

THE PERIOD TREATED

For this treatment a short period of seven years (1950-:-1956) was chosen. We did this, because it seemed that for the dynamic-climatological method i t is not necessary to use long periods as in classical climatology. Another reason for such a choice was that both the climatological network in Czecho- slovaki~ as well as the available synoptic charts, especially the topographies of the higher isobaric levels up to the year 1949, did not satisfy our demands on the density of the climatological network and the accuracy of the synoptical analysis due to a very small number of synoptic and aerological s t a t ions especially in southeastern Europe.

In classifying the synoptic situations we have carefully reanalysed the doubtful cases so that we assume the arrangement into the types chosen is correct. We used the synoptic charts from 06 GMT for each day, published by the synoptic service of the Hydrometeorological Inst i tute in Prague. In some cases it seemed to be necessary to take another analysis; the synoptic charts of the isobaric level 700 mb or the charts published by the German meteorological service were then used.

The days , the synoptic situations of which could not be arranged in any type-group, were omitted. There were 205 such days during the whole period treated i. e. cca 80/o of the whole time-interval. We assume tha t this is not caused by errors in our typing because the cases omitted are not typical either for their synoptic situations or for the weather. By omitting these cases better survey has been gained.

T H E R E S U L T S O F T H E T R E A T M E N T

A calendar of the synoptic types for the period mentioned has been constructed [3]. In this paper the frequencies of individual types, the frequencies of various time-intervals of individual types and finally the frequencies of the changes from one type to another are given.

Tab. I I contains the absolute frequencies of synoptic types. The most frequent types are Wc (west-cyclonic), then the middle-European anticyclone, one of the southwestern cyclonic types, the middle-Europeazl trough (BC), the northwestern cyclonic type and western anticyclonic type. Other types do not have such great frequencies during the period treated.

182 Studla geoph, et geod. 3 (1959)


I

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~ v

0

e ~

0

~ ~ ~ ~ ~ ~ ~ ~ ~ 2 ~ ~ ~ ~ ~ ~

O ~

~C3

I

0 1

, . - t

,...i O I ,- . i , - . i

�9 .~ ~ ~ ~-

U'2 0~.

S t u d i a g e o p h , e t g e o d . 3 (1959) 183

F. Rein

Some types show scarcely any seasonal changes of their frequencies. Among such -persistent types are the SWa, SWc 1, BC, Cc, and 1VWc types. On the contrary, some of the other types exhibit important seasional changes during the year. Of these the H, Wa, Sa, Sea, Wc~, Nc and 0 types are the most significant. Especially in the case of the Wa type, the summer maximum of occurrence, the summer minimum of the Sa and SEa types and the summer maximum of the type are remarkable. In this table the frequencies of the cases omitted are also included sub "19".

Tab. I I shows that 8 of the 20 types used in the given classification are important dueto their frequent occurrence, the other 12 being comparativelyrare.

Adding the separate type-frequencies into groups according to their characteristic dieretion of prevailing flow, we conclude that the zonal currents ' occur in about ~ of the whole period, the meridional current of northern direction in about ~ and those from the south in about ~ of the cases of the whole time interval considered (i. e. 1950--1956).

The other table, I I I , shows the frequencies of certain duration (in days) of separate synoptic types. From this table it follows that the most frequent types usually arranged in shorter periods, i. e. of 1--4 days in duration, bu t with some of the non-frequent types, e. g. the Wcs, SWc 2, Ec and other types, longer periods of 3 and more days prevail. This fact is shown more clearly in Fig. 3, where the histograms of the relative frequencies of the por- tions of period duration in the total type-frequencies are shown. The maximum frequency of the majority of types is a period of one-day; only some non- frequent types push their maximum to longer periods. From this it follows that the "common" elementary types have small persistence, whereas certain rare synoptic types, commonly bounded by blocking situations, show greater persistence throughout year than the westerlies or similar situations.

The last Tab. IV shows frequencies of transition one synoptic type to another. This characteric has been computed for five important types, namely for central anticyclonic, western cyclonic, northwestern cyclnic, southwestern cyclonic of the first order and middle-European trough types. For each type the frequencies, both of the precedent as well as of the consequent types, are given.

The first part of Tab. IV contains the.relations of other types to the central anticyclone. From the data it follows that the typical types precendent to H are Wc and Wa, further BC in summer and NWc in autumn. The frequent alternation of the western types with the anticyclones (mostly with the moving anticyclones) is a feature of the prevailing position of the polar frontal zone over Europa in the vicinity of 50 ~ N. This follows from the transition-frequencies of the Wc type too. This means that the features of the zonal circulation can be investigated throughout the year, while those of the important meridional circulation (BC type preceding H) only during the summer period.

The next part of Tab. IV contains the types preceding and consequent t o the western cyclonic type (Wc). Here also the alternation of zonal circulation types, i. e. of Wc with Wa and H can be seen. Besides the types mentioned, the SWc 1 type often precedes Wc, which signifies the frequent shifting of the central cyclone from the Channel to Scandinavia during the whole year. From the table of the types consequent to Wc it also follows tha t this central cyclone is usually relieved over Great Britain after one or several days by an anticyclone, which causes the change of the Wc into the N Wc type in central Europe.

] 8 ~ Studia geoph, et geod. 3 (1959)

Weather Typ ing with Regard to Dynamic Climatology

Tab . I I I

F requenc i e s of du ra t i on of t he synop t i c t ypes (in days)

V I I I Yea r T y p e D a y s I I I I I I IV V VI V I I I X ( n u m b e r , of days )

H 1 6 : 5 4 8 5 3 2 2

1

9 4 2

2

9 7 5 8 2 1 2 2

1 1

X X I IXI I

3 3 6 . 5 3 2 4 1 1 1 1 1

63 76 45 24 15 18 14

8 18

Wa 1 2 3 4 5 6 7 8 9

10

5 39 44

1 24 8

15 12

7 0 9

10

N W a

SWa 3 2

2

2 1 2

24 20

3 8 0 6

11 14 21 12

Sa 1

1 1 1

1 4 8 9

16 5

SEa

I

2 1

[ 1 i

J I

1 11 8 6 8

20 18

0 8

Studla geoph, et geod. 3 (1959) 185

F. R e i n

Con t inua t i on of Tab. I I I

V I I V I I I t Y e a r IV V VI I X X X I X I I (number T y p e D a y s I II i I ~ of days)

2~Ea

Ea

Wc 1 2 3 4 5 6 7 8 9

10

. 1

2 1 1

1 3 1 1 1

1 1 1 1

1 5 3 4 2 4 1 2 1 1 1

1

1 2 1 3 1 1 1 I 1 1 1

1

1 2 3 1 1 .1 1 1 1

3 4 1 5 3 2 3 2 5 3 2 3 1 1 2 1

2 3 1

1 1

1

1 2 1

1

1

1

7 3 4 2

1

14 12 12

4 10

0 7

11 12 18 16 10 12

5 42 1 70 2 57 1 44 1 40 2 24 1 21

8 0

1 20

Wc~ 1 1 1

1

1

1

1 1

1 2

1

1

1 I 1 1

1

1

7 10 15

8 10

6 14

S W c 1

S W c z

1 2 3 4 5 6 7 8 9

10

1 1

1

1

2 1 4 3

1 2

1

3

1 4 5

1

1

1 1 1

1

1 2 1 .

24 64 21 32 20 18

7 8 9

20

7 18

9 0

15 6 7 8 9

1 8 6 Studia geoph, et geod. 3 (1959)

W e a t h e r T y p i n g w i t h R e g a r d to D y n a m i c C l ima to logy

C o n t i n u a t i o n of Tab. I I I

Type D a y s V V I V I I V I I I I X

B C

I I I I I I IV

3 1 I 1 1 2 3

1 2

1

1 1

4 .4 2 4 3

1 1 1

1

X I I Y e a r X X I ' (number

of days )

3 51 2 5 2

' 2 4

24 1 20 1 24

0 8

27

Ec

I 3 3 1 1 1

1

1 1 1 1

1

1

4 2 1

1

2

2 1

1 2 1

2

2

4 2 1 2

1 1

1

17 34 24 20 20

6 7 0 9

22 28

9 24

0 18

7 0 9

iVEc

N c

l ~ W c

1 2 2

1

2 5 2 1 2

1

1 .

1 1

2 3 1 1 I

3 1

2 2 1

4 1 2 2 1 2

1 1

1

1

3 2 2 1 1 1 1

17 12 15 12 10

22 12 21 12

26 44 42 40 40

6 0 8


F. R e i n

4O

lO

50

~ 3 4 5 & 1 8 ~

10 t0

I I ~ S & t 8 9 1 0 ~ 3 % 5 6 t 8 9 t 0

10

4 2 5 % 5 6 1 1 9 ~

4 0 5 a ~ ~ G I o S O

'~ N " M I lSbSs |9M t ~3~$&1871 f &5% S &~ 89'[0

i t ~c 'IZ~,h. Sf, 11?'m

40 1

3~ 3O

I Z~,bS& t 8 9t0 1 2 ~ S & ~ I9 'A

~ ~c, -

l~3~s&~89,m

4 2 3b 5&~I19411 i Z 511. SG ~ I19~ 'I Z l u , , , , .

i Z3 k. 5 G lo l l91

t 2 3 % $ & ~ 8 9 e ~ Z 3 % $ & ~ S q ~ t 2 3 % 5 & u

Fig. 3. The relative frequencies of the periods of duration of the synoptic types. (Absc.: days of duration, ordin.: frequencies in per cent.)

188 Studla geoph, e~ geod. 3 (1959)


i ~.~ ~.

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r~

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m m ~

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at

r~

r~

r~

. ~ m m

S t u d l a g e o p h , e t g e o d . 3 (1959) 189

2". R e i n

P-I

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0

m

o

r~

o

o

0

0

n

n

eO ~4

o r J

o

i ,.-i ,.-i

f I

190 S t u d i a g e o p h , e t g e o d . 3 (1959)


0

0

Ce~

r r

I

,--~b"q r

I

a'q

Studia geoph, et geod. 3 (1959) 191

N

,d

o

o

o

P. Rein

I t is also interesting tha t throughout the year the Wc type has no connection with the Sa, SEa, Ea and NEa types. This means tha t in no case do the changes of the zonal circulation to a blocking with the anticyclone over northern, eastern or southern parts of the European continent take place.

The third part of Tab. IV. shows the distribution of frequencies of precedent and consequent situations to the S Wc 1 type. In both cases sharp maxima are seen. The outstanding situation precedent to SWc 1 is the central middle- European anticylcone; among t he consequent situations two are remarkable, namely the trough over central Europe and the western cyclonic type. The trough in connection with the central cyclone prevails. This form of transition of the SWc 1 type occurs in 41% of all the cases studied, that of transforming SWc 1 to Wc (or Wcs, Wa, SWc 2) in 31%, while the SWc 1 preceding H has been found in only 25% of the cases.

The type SWc 1 belongs to those types which are preceded by various synoptic types but are usually followed by only two groups of types. This was not the case for example with the northwestern cyclonic type. The statistical results of studying such type as SWc 1 can be useful in some prognostic considerations.

The last synoptic type (the last according to our list) is that characterised by a trough over central ~Europe. Its features of transition are nearly the opposite of those of the S Wc 1 type. The total of frequencies of the two groups of the most frequent precedent types (the first group formed by the S Wc 1, S Wc 2, S Wa and Sa types, the second by Wc, Wcs and Wa types), is 60%, 40% due to the first and 20% due to the second group mentioned. On the other hand, the consequent types show the following frequencies: the group consisting of anticyclonic types with an anticyclone over western or central Europe (H, Wa and 1VWa) thus shifting the blocking anticyclone from the west European coast to the continent has only 25% frequency. The second outstanding group of types signifying the change of the meridional BC type by a zonal circulation (types Wc, Wc~, SWc 2 and NWc) also has a 25% frequency.

192 Studla geoph, et geod. 3 (1959>


In the case of the BC type a more frequent occurrence of certain preceding types rather than an outstanding total of occurrence of a well expressed consequent group of synoptic types, can be seen.

Both with the S Wc 1 type as well as in the case of the last type studied none of the transitions are especially limited to a certain season bu t they occur with a small variability throughout the year. The only exception is the transition of BC to the anticyclonic types, which, however, does not take place regularly during the winter and spring seasons.

CONCLUSIONS

The typing of the synoptic situations over central Europe, realised by members of the Czechoslovak gydrometeorological Insti tute has been changed in some inessential features and i sappl ied to the whole climatological network of Czechoslovakia for the purpose of obtaining dynamic-climatological characteristics of the Czechoslovak climate. As the first epoch" of this project 19 synoptic t y p e s have been chosen (Tab. I), a calendar for the time-period 1950--1956 has been constructed for them and some of its statistical features (forming the main contents of this paper) have been analysed.

In studying the characteristics mentioned some results were as follows: 1. The relation of the anticyclonic to the cyclonic types over the region

studied is cca 1 : 2. 2. The most frequent types are Wc (326 cases out of a total of 2557), H (281

c.), SWc 1 (223 c.), BC (210 c.) and NWc (206 c.). 3. The rarest types are 0 (24 cases) and Sa (42 c.). 4. Some types are persistent throughout the year. They are e. g. SWa,

Wc, S Wc 1, BC, N Wc. Other types show a remarkable seasonal variability (e. g. H, Wa, Sa, SEa, Wcs and Nc).

5. Of the 19 synoptic types eight are important due to their frequency. They contain 650/o of the whole period treated.

6. The distribution of the duration of synoptic periods shows that the most frequent types gain their maximum frequencies because of one- or two-day periods, while the usually maximum frequency of duration of the rare types is the period of three -- or more days.

7. Interesting results have been gained by studying the frequencies of transition of the five meteorologically most important types. I t has been shown that some types never change into certain other types (e. g. Wc has no transi- t ion into Sa, SEa, Ea and •Ea etc). On the other hand the almost regular alternation of the types Wc and H (resp. Wa) has been shown very well.

The typing of the synoptic situations presented in this paper will be used in climatological treatment. The great number of types may cause some difficulty in the study due to a great dispersion of the climatological data into large and relatively small groups, which with rare types can give rise to re- suits which are little t rustworthy statistically. But typing into a small number of types could cause unreal results due to a great variability and variety of weather during the different synoptic types in the mountainous-country of Czechoslovakia. That is why this method of treatment has been chosen.

R e c e i v e d 5. 5. 1958. Reviewer: M. Kon6ek


F. Rein, Weather Typing with Regard to Dynamic Clinmtology

Re]emnces

[I] T. B e r g e r o n : Richtlinien einer dynamischen Klimatologie. Meteorolog. Zsehr., 1930, pp. 246--262.

[2] F. R e i n : Pom~r mezi metodazni klasick6, komplexni a dynamick6 klimatologie. Meteorologiek6 zpr~ivy, VII (1954), pp. 1 - 3.

[3] M. K o n ~ e k , F. 1%ein: Kalende%~ synoptick:~ch typf* za obdobi 1950-- 1957 (Calendar of synoptic types for the period 1950-- 1957). Not yet published.

Pe3mMe

T H H H 3 A I / H H C H H O H T H q E C H H X HOJIOH~.EHHI~ C V*-IETOM EE HCYIO.IIt: ,3OBAHHH B. ,~HHAMHHECHOFI H J I H M A T O J I O F H H

FRANTI~EK REI~

Feo~u~u,~ec~uf~ uucmumym qCAH, llpaza

On~caHRe cnoco6a pacnpe~Ienemm cn~onT~qeci<nx nonomeH~fi Ha~ Cpe~I~efi EBponofi sa nepHo;~ 1950--1956 rr. no ~ne.~teHwap~M C~mOnTnqeCK~M THIIaM. B HaqecTne rnanHoro ~)nwepna ;Inn ~aacc~1q~m~ai~m~ 61,me npmmTO npco6na~ammec weqeHne B c p e ~ e ~ Tpono- ccpepe Ha~ paccMaTpHBae.~mfi 06:IacwhIO. BT0pn~H~.~t KpnTepneM 6~mO Jm~aoHanLHoe

aHTHJ/~IRnoHan~Hoe 3a~piIB.~leHHe ~3o6ap npHseMHo~ CIIlIOnTIIqeCl~O~ ~apT~]. Wa~m~ 06pa30M 61an0 noayqeHO Ile.rIHKOM 19 DnO31OHTLIpHLIX CHHOHTIIqOCI(IIX THn0B (9 8HTHI~HK.'IO- HflnbHOrO H 10/In~.'lOHanhHOr0 xapaETepa). }~paTHoe onncaHHe TI4nOB npHBe/leno B TaSfl. I, C00TBOTCTByIoIIIHO ;H0 l(HneMaTifqegi(iie EapTM -- Ha pgc. 2. PHc. 1 no~ICH~leT CHMSO/II4qee- KHe o6ozHaqeH,~n, HpHBe,~OHII]hIO ila p)tc. 2.

fl~a,mbm o6pa6orm~ Tnnos mcnmqa~OT l!pn~mpHo 92% o6mefi npo~on~ITenSHOCTH o6- pa6oTamtoro nepnoRa; OCTaTOK i[33a C.'IOH{IIOCTII H CHHOHTIIqecIgOFO noJ]o~eH);n, a s c~iny 3TOFO H OTCyTCTBH;I THHHqHOCTH, npnmnoc~, HC~qIOqHTB H3 06pa6oTI~n. B Ta6n. II npI~BO- ,~ITCH HaCTOTI,I ~HOH C OT,~C$1BIIS[3!II aneMenTapHstM~4 THnaMH, B Ta6n. III -- nx ~nnTenh- HOCTI, I4, HaHoHeI~, B Ta6:L IV -- qaCTOThI nepexo~a ~n~ 5-TH }~an6onee Ba)'~HMX TnHOB. B Ta6n. IV npnsO~aTCn HOH3MCHIIO qaCTOTLI npe~IM~lyn1Hx n noene~ymunlx TI4HOB.

Ha oeHosa~imt npmu~;mos, rtp~se;lem!btx B HaCTOHU~efl pa6oTe, 6Bin COCTaBneH Ka/len- ~aps CHHOnTIIqCCEIIX TIIHOB, t(OTOp[4~ 3~ecl, lle npHBO~HTC;I. -~TOT ]<aneH~aps nocaymnT OCHOBaHIIeM ,qdIH pa60T ~IIHdM!IHOCI{0-EJIILMaTO,qOFHtleCI~OFO xapaKTepa.

IIoeTynHno 5. 5. 1958.

[94 Studia geoph, et geod. 3 (1959)

weather typing with regard to dynamic climatology

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