く灘鋳難

(1)

ON THE RELATIONSHIPS BETWEEN THE HARMONICS OVER THE 500MB SURFIACE AND THE DISTRIBUTION

PATTERNS OF THE CHMATIC ELE］MENTS

OVER THE NORTHERN HEMISPHERE

Takayoshi AOYAMA

INTRODUCTION

The climate can be considered as a system which is composed of a unity embracing at least one hemisphere． Therefore， the global study may be one of the important approaches to clarify the fluctuation of climate and general circulation of the atmosphere on the stand−

point of synoptic climatology． In the context of these global studies it would be also central problem to obtahl the relationships between circulation pattern and weather elements． At this pohlt much attention has been given to the classification of the circulation． For in・

stance， Dzerdzeevskii（1962，1966）and Girs（1966）classified the circulation patterns over the Northern Hemisphere． In view of the problems of defining characteristic circulation patterns subjectively， however， much thought has been given in recent years to objective classification techniques， like that of eigenvector and harmonic analysis．

For global studies of pressure field eigenvector analysis can be used． Kutzbach（1970）

tried to use this method of sea−level pressure field over the Northern Hemisphere and demonstrated the variation of each component pattern for recent 70 years． Kalnicky（1974）

sψsequently applied this to catalogue of Dzerdzeevskii s circulation types and showed ob・

jectively the variations of circulation patterns since the year of 1950． Temperature anomaly patterns over Japan and their changes during the past 74 years were examined using eigen−

vector analysis of mean July and August temperature fields by Mikami（1975）． He also clarified the relationship between the component patterns of temperature and the 500 mb surface patterns on the standpoint of the dynamic climatology． These studies may make possible to develop further the studies by Dzerdzeevskii．

The techniques of harmonic analysis can describe o切ectively wave pattern aloft by．

several sine or cosine terms． Graham（1955）and Fujita（1956）demonstrated that the ob・

served flow pattern of the upper・level westerlies was separated to basic and perturbation flow by harmonic analysis and the observed f【ow and the basic flow showed a striking similarity． Arai（1958，1965，1970）investigat硝d the circulation pattern aloft by harmonic analysis and pointed out the statistical properties of harmonic waves． Also， he considered the annual and inter−annual changes of the harmonic waves． Aoyama（1976）demonstrated the circulation patterns over the Northern Hemisphere associated with the first three har−

monics． These works referred above indicate that the harmonics can describe objectively the character of the general circulation． This may make possible to develop the classification of circumpolar current based on the concept by Girs（1966）．

Ascheme relating to the surface and upper・level patterns becomes significant problem in this context． The studies of Dzerdzeevskii（1962，1966）and Girs（1966）are also concerned

(2)

with this theme． They pointed out that the each circulation type gave the different effects on different regions． Arai（1964）distinguished the 500 mb surface patterns based on the harmonic waves and demonstrated that these circulation types related to the weather in Japan and Europe． The study of Seur（1954）showed particularly interesting result． He demonstrated that the degree of the asymmetry or eccentricity of the circumpolar westerlies affected significantly the 4istribution of the weather on、 a hemispheric scale． It was also in・

dicated that the amplitude of the first harmonic is a measure of the asymmetry or eccen・

tricity of the circumpolar f【ow． Thse investigations suggested that the distribution of the weather can be related with the circumpolar flow based on the harmonics．

In addition to Seur s work， the study of Aoyama（1976）suggested that there were the weather patterns corresponding with harmonics respectively． That is to say， these are ca皿ed as component weather patterns． This also indicates that the observed weather pattems can be described by these component weather patterns． In this article the distribution patterns of c血mate associated with the circumpolar westerlies will be treated objectively．

DATA AND METHODS

The data for the analysis of the circumpolar westerlies are obtained from the monthly mean 500 mb weather charts for the Northern Hemisphere（Japan Meteor． Agenc．，1961，

1961−1970）for 1946−1970． When the upper−level circulation was analysed by harmonic analysis， it was pointed out by Arai（1965）that the harmonics should be computed along the several latitude circles， for examples 30°N，50°N and 70°N． However， the latitude circle of 50°N is chosen fbr this study， since the heat transport in the layer 850−500 mb is the greatest at 40°N−50°N（Kreuger et aL，1965）and since the amplitude of harmonics are l・・g・・t・t50°N（A・ai，1970）． The 500 mb h・ight・f・v・・y 10°1・ngitude al・ng 50°N・・e u・ed for 36 coefficient harmonic analysis． Then longitude is counted as zero at Greenwich and in−

creasing toward the east through 360 degrees．

In order to make a search of the circulation types relating to the harmonics along 50°N，

the simultaneous correlation maps between them are obtained using the 500 mb height of

・v・ry 10°1・ngitud・fr・m 30°N t・60°N・nd・f・v・・y 20°1・ngitud・al・ng 70°N・nd 80°N latitude circles． These maps show the distribution of the correlation coefficients between the amplitude or phase angle of the harmonics and 500 mb height at each intersection of latitude and longitude．

In the analysis of the distribution patterns of surface climatic elements the monthly mean sea・level pressure and temperature in three months， December， January and February， are used（U． S． Depart． Com．，1959，1967，1961−1970）． Figure l indicates the geographical locations of all stations that contribute for 25 years of data to this study．

In order to reveal the distribution pattems of climatic elements related to the harmonics，

the multiple regression analysis is applied． In the case of six hldependent variables， namely amplitude and phase angle of the first three harmonics， we have a equation

Yi，j＝a1，iAl，j＋a2，iA2，j＋a3，iA3，j＋b1，ip1，j＋b2，ip2，j＋b3，ip3，j

where

Yi，」：Monthly mean sea−level pressure or monthly mean temperature at station i，

An．j：The harmonic amplitude with the wave number n，

Pn．j ：The harmonic phase angle with the wave number n，

an．i，bn．i：Partial regression coefficient，

i ：Station number，

(3)

5

o α ㏄ α

2 1

㌔ρ@●

G

滝 o

一、＼

ｳ＼

縛 ^合距う

δ《試 ^A

伍｝

σ9 ／

・・＼

ず ^〆

ψ ひ

oム ●

o罵

嘩殖＼・＼

為

唱

φ ＼

8 ^鞘

、ぺ

一

どつ窪イ、昏

室

轡

5N

セレ

勤 o

＼

凄講 ^％

麗

轤V

き

@諭

uf出階

、口

≧ 蕊馬

@ ・

@窺 ^謙 ●

@も

@命

o

、も 1

町

0η

／

〇一 bo

Q臣 4 z騨

，茅》

@ 6 、

@ ● 」，

@ ，甚毫一

蒼 ρ

@一 i L

皇」凶う

G、

ﾃ篭喚銅暑舅

6

鴨

【

メQ

1費霊

爲釜

、

《ざ一お

ρ ． I I 一

1 一

三 ◎ 、

〆〜

8^騨

→ 夢

ψ 女 ^＼ ^讐

ぎ

室

お

〆 2 〜 ● ● 弔

ち7 φ噸

な

傷 Y置

o

／、

ト

、

一

な与

9

も

名

怨 Cゐ

「

M＿蒋，

・／

秩f

ρ 遭

婁

＼

7●

o ・》 ^！

−A

＼傷酪

ε

輪＼禰 ^／ ^〆

8 ^尺

L40 〆

、

ド〆

星

／

◎ o

湘a● ●Ch

／

尋馳馳

A

晶

、、、

̲馳

＼妬 1

〜、

一 ^一／／

、、馳 ^

k1y ＼ ^．一 ^／

§

o@ ●

f

、、

E：、、i

適

、、

Gu

ゴr

M㌔㍉

「rr「

Y ／ ^§

〆・ −Pi．一

璽Ya ．鼈」r一＿．〆，

Y ／_@匪

^ゴ

＼ ^{● ・}

、1 、、、、 1、

ko● 1

一／

ダ

lP ¹¹⁰ ^1節 ¹⁴⁰ ^L船 ¹⁶⁰ ¹⁷⁰

Fig．1 Distribution of stations・

」：The order of years 1946−1970．

For each month of December， January and February the multiple regression analysis is apPlied to the data for each station of 81 and the partial regression coefficients are obtained・

The partial regression coefficients express the rate of change of Yi，j，being the monthly mean sea−level pressure or the monthly mean temperature， for unit change in their respective in・

dependellt variable with the e脆ct of the other independent variables held constant． There・

fbre， the spatial distributiolls of regression coefficients demonstrate the component patterns of the pressure or temperature variations associated with harmonics． Moreover， the long・term variations of each component pattern of the climatic elements are represented by the t㎞e series of their respective parameter of harmonics．

(4)

SEASONAL CHANGE AND STATISTICAL PROPERTIES

OF THE HARMONICS

Seasonal change of the ha㎜onics

The standard deviations of 500 mb heights along 50°N represent the magnitude of trou帥s and ridges over 500 mb surface． Thatis to say， this is one of the indices for large−

scale circulation patterns． The value reaches a maximum in January（126 m）and a minimum in August（37 m）． This suggests that the circumpolar vortex is markedly asymmetric with the most intensified troughs and ridges in January and is centered closely to the pole with the most weakened one in August． Although the standard deviation increases threefold from summer to winter， the month・to・month variation reaches the minimum in December−

Febmary and July−August． It is expected that the homogeneous circulations persists in these two periods respectively．

Harmonic analysis provides objective evidence of the dominant wave pattern． The circum・

polar current was analysed by this method based oll the contour of 17，800 ft in daily 500mb chart（Graham，1955）and the 500 mb height along fixed latitude circle（F唾ta，

1956）．These investigations demonstrated that the observed f【ow pattern of the upper・1evel westerlies was separated to basic and perturbation flow by this technique and the observed flow and the basic one showed a striking similarity each other． This basic flow is also quite stationary through the season． Therefbre， the observed circumpolar f［ow can be represented sufficiently by the monthly mean basic flow composed of the first three harmonics．

Table l The monthly mean amplitude（m）of the harmonic waves， wave number 1−6．

sD

6

M

sD

5

M

4

M 阻

3

M 鋤

2

m

M

1

M sD

藤瓶繋

M：monthly mean for the period of l 946−1970．

SD：standard deviation of the monthly mean amplitude

Table l shows the amplitude and its standard deviations of the harmonics based on the monthly mean 500 mb heights at every 10°10ngitude along 50°N． The first four harmonic amplitude show the distinct seasonal trends and reach a maximum in winter and a minimum in summer． However， in the cases of wave number 5 and 6 the seasonal change of the har・

monic amplitude are not recognized． Moreover， the amplitude of the first three harmonics

(5)

are conspicuously larger than that over the fourth harmortic in the period from November to March． It is poillted out by many workers（Kubota and Iida，1954， Saltzman et al．，1962，

Shapiro et al．，1963）that the properties of the harmonics are different between the first three harmonics and the others with the critical wave number 4。 As indicated in Table 2，

about 70％or 80％of the monthly mean total amplitude is occupied by the resultant wave f（）rthe first three harmonics except in July and August． Especially， from November to March the resultant wave for the first three harmonics can represent about 90％of the total amplitude．

Table 2 Amplitude ratio（％）

WAVE NUMBER

1 2 3

M ^SD M ^SD M ^SD T JAN ³¹ ¹⁸ ³⁴ ¹⁷ ²⁵ ¹³ ⁹⁰ FEB 29 ¹⁸ 32 20 28 14 89

MAR ³³ ¹⁹ ³² ¹⁸ ²⁴ ⁹ ⁸⁹

APR ⁴⁰ ¹⁸ ²⁸ ¹⁶ ¹³ ¹⁰ ⁸¹

MAY ⁴⁶ ¹⁶ ²⁹ ¹² ⁷ ⁷ ⁸² JUN ^42『 ²⁰ ²⁴ ¹⁵ ¹⁴ ¹⁰ ⁸⁰ JUL 20 19 14 9 21 15 55

AUG ¹⁹ ¹³ ²³ ¹³ ¹⁴ ¹² ⁵⁶

SEP 32 16 25 15 16 lI 73

OCT ⁵¹ ²⁰ ¹³ ^ll ¹⁵ ¹⁴ ⁷⁹ NOV ⁴⁷ ¹⁷ ²² ¹² ¹⁷ ¹³ ⁸⁶ DEC ³⁷ ¹⁹ ³³ ¹⁷ ²⁰ ¹¹ ⁹⁰

M：Monthly mean for the period of 1946−1970．

SD：Standard deviation ofamplitude ratio．

On the phase angle of the harmonics the calculation does not give frequently accurate value as the amplitude being smaU． The critical amplitude of this tendency is about 20 m in

mid・1atitude and about 30 m in high−latitude for the super・long waves at 500 mb surface

（Arai，1970）． Therefore， the frequency of inaccurate phase angle is large in the warm season，

especially in JUly and August． From December to February， however， the phase angle of the first three harmonics are considered reliable except that of the first harmonic in January of 1947．Through this period the mode of the frequencies for these phase angle are almost con−

stant．

As described above， the basic f［ow composed of the first three harmonics represents sufficiently the observed circumpolar f【ow and is quite stationary through cold season． The forms of the first three harmonics for January are demonstrated ill Figure 2． These forms represent the dominant wave pattern in winter． Wave number l has one trough， situated over the central North Pacific Ocean， and one ridge， situated over the Atlantic coast of Europe．

Wave number 2 has two troughs， situated over the eastern coast of Asia and the central portion of the North Atlantic Ocean， and two ridges， situated over the eastern Europe and the eastern part of the Pacific． Wave number 3 has three troughs， over the eastern Europe，

the western part of the Pacific and the North America， and three ridges， situated over the eastern part of Asia， the eastem part of the Pacific and the eastern part of the Atlantic． The illcreasing amplitude of these harmonics represent the intensified troughs and ridges． The in−

creasing phase angle indicates a westward retrogression of the troughs and ridges and de・

creasing one a eastward progression．

(6)

30 PW

1

30eE−．

60e『 Fig．2

The hemispheric form of the harmonic waves（m）． Heavy solid line＝first harmonic，

thil solid lne＝second harmonic， dottβd line＝third harmonic．

StatiStical properties of the hanmonics

Multiple regression analysis must be evaluated on the some assumptions． Some of these are that the variables are normally distributed and mutually independent．The frequency dis・

tributions of the parameters of the first three harmonics are not always normal． Especially，

that of the third harmonic amplitude is markedly different． Since the assumption of nor・

mality can be applied to these data based on the empirical consideration， however， the transfbrmation of these data are not made．

In order to examine the assumption of mutual independence， a square matrix of correla・

tion c㏄mcients between each of the variables， the amplitude and the phase angle， is shown in Table 3． Negative significant correlations between the first and the second harmonic am・

plitude and between the amplitude of the first harmonic and the phase angle of the second one are recognized． And the positive correlation coefficient between the phase angle of the first and second harmonics is also significant． Therefore， the first and second harmonics apPear to correlate each other．

TaUe 3 The correlation matrixl for the amplitude and the phase angles of the first three harmonics．

WAVE NUMBER

Amplitude Phase Angle

1 2 3 1 2 3

Amplitude

123

WAVEmUMBER _Phase

̀ngle

123

1

￨0．47 1

￨0」5 −0．05 1

￨0．24 −0．ll −0」7 1

￨0．40 −0．15 0．30 034 1

O．06 −0．28 −0．19 0．25 0．21 1

As considered above， some problems in this statistical procedure arise， when the am−

plitude and the phase angle are used as independent variables． Therefore， careful thought should be given to the interpretation of the distribution of regression coefficient・Based on the component pattems of sea−level pressure and temperature， for example， the probable

(7)

synoptic processes are examined． Moreover， account is taken of the relationships between these component patterns and circulation patterns aloft associated with the harmonics．

THE RELATIONSHIPS BETWEEN THE VARIATIONS OF THE CIRCULATION PATTERNS AND SUNSPOT。NUMBERS

Time series of the mean amplitude and phase angle for three months， December， January and February， and of its five year running means are demonstrated in Figure 3．These show the remarkable inter・annual variations． In regard to the amplitude， it is apparent that the first harmonic increases in the first half of 1950 s and the third harmonic in the first half of 1960 s．The variations of the phase angles show also distinct tendencies． In the periods of the first half of 1950 s and of the second half of 1960 s the phase angles tend to increase and the harmonics， therefore， progress westward． On the contrary， the eastward progression is re−

cognized in the period from about 1955 to about 1965．

M

160・

140・

120・

100・

80・

60・

40・

20・

M

・140

・120

・100

Deg，

120・

100・

80・

v！ ^、

N−一，，一！

、

Deg．

40

20

0

M

100・

80・

60

40・

、 N −＿＿！

一

N＝3

、、

、、、、一一

、、、

r9 514 51g r・ r・ 50 55 塵60 65 70

OOO Deg・

200・

180・

160・

140・

γ V v

N＝3

戸＼、

一一、

@ 、

fC ^{、層「}@、 _＼ ^1／

，一、ノノ

49 L 50

54 t 55

59

60

6645 ゜69 5 70

・340

Fig．3（1））Time series of the three month（December，

Fig・3（a）Time series of the three month（December， January・and Fel）ruary）mean phase angles January and February）mean amplitude of of the first three harmonics for 1946＿

the first three harmonics for 1946＿1970． 1970．

Th・b・・ken line・ep・esent・5−yea…unning Th・b・・ken・lin・・ep・esents 5−yea・・unning mean。 mean．

The variations of the amplitude and phase angles seem to be cyclic on these time series，

especiaUy being clear in the five year nmning mean． Although the accurate thne period can not be evaluated owing to the inadequate data， it is possible that the periods are about 10−

15years． Especially， about 10・year periodicity of the amplitude of the third harmonic suggests the effect of the sunspot activities． The relationship between sunspot−numbers and

(8)

8

7

6・

2・

1・

0

：：：：：

iiiii…・

……iii

；；：：

iiiiiiiiiiii

Fig．4

堰Fi：i

：i：i：；

iiiii：

奄奄奄奄堰F

｡，●

…：…：……薫繕i：i：i：

：：：i：

；iiii

奄奄奄堰F

奄奄奄奄 iiiiii…i…i…

ii：ii

奄奄奄奄 iii：ii

奄奄奄奄奄

20 40 60 80 100 120 140160 SUNSPOT NUMBERS

180 200 220 240

Frequency distribution of the sunspot−numbers for December， January and February 1946−

1970．

10ng waves were investigated based on the data for the period from 1946 to 1956 by Arai

（1958）．He demonstrated the high negative correlation between them． In order to investigate this point， the frequency distribution is made based onヰhe monthly mean sunspot−numbers for three months， December， January and February， between 1946 and 1970（Figure 4）．

This figure shows the bimodal distribution with two modes of the class intervals of sunspot・

numbers between 10 and 30 and between 110 and 130． According to this histogram， the harmonics are fallen into two groupes， which correspond to the sunspot−numbers of O−70 and 70−150 respectively． The statistical significance of the difference between the average of two groups are examined by the method of t−test（Table 4）． Since伽s relationship fbr the first and second harmonics seems to reverse between before and after the year of about 1960，t−test is applied to each period of 1946−1960 and 1961−1970 respectively． Next，

the correlation coefficients between the sunspot・numbers and the harmonics are obtained for each group in every period． However， the changes of the harmonics appear to have a predominant period of two to three years． The period like this is recognized in the change of the intensity of the center of action， jet stream and the severity of sea ice． Although， the reason of the periodicity in this time range is not made sufficiently clear， the effects of inf【uences of such as auto−oscillations of the atmosphere and of the earth s rotation are believed as the causes（Maksimov，1970）． At least these changes do not appear to have the simple relation with the sunspot−numbers． Therefbre， the calculation of the correlation co−

efficients are based on three year nmning mean of the harmonic．

In regard to the phase angle，the difference between the average of the two groupes is not significant． On the other hand， the significant1）differences are recognized in respect of the amplitude of the first and second harmonics as shown in Table 4． These relations are reverse between the periods of the before and after the year of 1960． In the period from 1946 to

1960 the correlation coefficient is negative in the case of the first harmonic and the positive in the case of the second harmonic and in the period from 1961 to 1970 it is the positive for the first harmonic and the negative for the second one． It is very interesting because of the results which suggest the double sunspot cycle． Although the amplitude of the third har−

monic in the group with low sunspot・numbers tends to be larger than that with high sunspot・

numbers， the significant difference is not recognized． However， the correlation coef行cients are significant with the significant level of 99％．

Although the period of the data used are inadequate， being only 25 years fbr this problem， it is indicated that the statistical relationships between the sunspot−numbers and the amplitud壁of the harmonics are significant with the significant level over 90％． This also

(9)

Table 4 Relationship between the amplitude of the first three harmonics and sunspot−numbers in winter（Dec．， Jan．， Fe1）．）．

Mean amplitude of harmonics Wave

獅浮高b? Period Monthly mean

唐浮獅唐垂盾煤@number

@ O−70

Monthly mean

唐浮獅唐垂盾煤@number

@ 70−150

t−value Correlation

モ盾???奄モ奄?獅煤@1）

123 1946−60 P961−70 P946−60 P961−70 P946−70

119．9（16）

W5．8（17）

V8．9（16）

P02．3（17）

W8．4（33）

73．8（21）

P09．3（13）

P03。2（21）

W2．1（13）

V5．8（34）

4．03＊＊＊

Q．11＊

Q．96＊＊

Q．17＊

k29

一〇．28

O50＊＊

O54＊＊＊

￨0．47＊

￨0．46＊＊

1）Correlation coefficients are calculated between the sunspot−numbers and the 5−year running mean amplitude．

Frequencies in brackets（）．

Significant level：＊〈x 5％，＊＊〈x l％，＊＊＊〈x O．1％

suggests the existence of the distribution patterns of the pressure and temperature associated with sunspot・numbers．

THE COMPONENT PATTERNS OF THE SEA−LEVEL PRESSURE AND THE TEMPERATURE DISTRIBUTION RELATED TO THE HARMONICS

In order to clarify the relationships between the upper・level circumpolar westerlies and the distribution pattern of the pressure or temperature， multiple regression analysis was applied and the diStribution maps of the partial regression coefficients are constructed．

In these maps， as already discussed before， the values express the magnitude of change of the pressure or the temperature fbr unit change in their respective illdependent variable，

being one of the amplitude or the phase angles of the first three harmonics， with the effect of the other independent variables held constant． Therefbre， these maps represent the com−

ponent patterns associated with wave patterns aloft． In the area with positive regression co−

efficient on these maps the pressure or the temperature increases with the positive d6viation of the amplitude or the phase angle． In the case of the negative deviation of amplitude or the phase angle， meaning progressive wave， the reversed processes are true． Thus， each map can give two considerable reversed synoptic processes． Namely， one is the pattern in the case of the positive deviation of the amphtude or phase angle from their respective means and the other is the pattern in that of the negative one． In these respect， however， only the cases of the positive one are ilustrated hereafter．

Component patterns of the pressure and the tempera加re related to the harmonic amplitude．

77ze first harmonic．

Figure 5 shows the distribution of the partial regression coefficients f6r the pressure and the amplitude of the first harmonic． This pattern is in agreement with that of the s㎞u1−

taneous correlation map between the amplitude of the first harmonic and 500 mb heights．

Moreover， the Aleutian Low coincides with the trough of the first harmonic and intensifies with its amplitude over the northem part of the North Pacific． Over Europe and the Atlantic， where the normal ridge of the first harmonic is located， the high pressure belt in・

tensifies and shifts toward high latitudes． On the other hand， La Seur（1954）has demon一

(10)

strated the pressure pattern of the Northern Hemisphere associated with extreme asymmetry of the circumpolar f［ow． The component pattern obtained here is in essential agreement with this Seur s pressure pattern．

The distribution of the partial regression coefficients fbr the temperature and the am・

plitude of the first harmonic is shown in Figure 6． This component pattern demonstrates that the distribution of the temperature change associated with the amplitude of the first harmonic is reversed between the eastem and western sides of the Continent． That is to say，

the area with the positive values extends over Europe north of about 40°N and on the con・

trary over the east coast of Asia south of about 40°N． Moreover， it is an interesting fact that the higher latitudes in Europe and the eastern part of North America become the region with positive values and that in the east coast of Asia and the western part of North America is the region with negative values． This component pattern presented here is in agreement with the temperature distribution in the United States associated with extreme asymmetry of the circumpolar westerlies presented by Seur（1954）as well as his pressure pattern， as pointed out previously．

From the foregoing remarks， the following synoptic processes associated with the Iarge amplitude of the first harmonic can be thought． Since the 500 mb height increases in the belt between 45°N and 55°N over the western Hemisphere， from Europe to North America across the Atlantic Ocean， the circulation in the higher latitudes becomes hi帥index type and that in the lower latitudes is low index type with large amplitude（Aoyama，1976）．

Corresponding to these circulation type， meridional temperature gradient increases in higher latitudes and decreases in lower latitudes． Moreover， the sea−level high pressure regions are intensified in this sector， especially over Europe and the northern part of North America，

associated with the 500 mb surface pattern． Over Europe the center of the high pressure located at about 50°N． Therefore， it is the probable processes that the westerlies are inten−

sified north of this high pressure center and have an effect of the warm Atlantic on the region from the coast of Europe to the Ural Mountains， as indicated by the above normal temperature． On the other hand， along the southern margin of this high pressure area the effect of the cold air from Siberia is indicated by the region with the below normal tem・

perature． Over North America the center of the high pressure is located in the region of the northern Hudson Bay． Because of this pressure pattern， the westerlies weaken in the eastern part of North America and the effect of the Atlantic Ocean seems to be intensified as in・

dicated by the above normal temperature．

Over the Pacific and the east coast of Asia the low pressure area is intensified in the zone between 50°N and 55°N over the 500 mb surface． Therefore， the circulation corresponds to high index type south of about 55°N and low index type north of that respectively． Cor−

responding to these circulations， the meridional gradient of the temperature intensifies southward of about 50°N and weaken northward of this latitude． Because of the lack of the observation station over the Northern Pacific， the relationship between 500 mb and sea・1evel pressure pattern can not be demonstrated clearly in this study． However， over the region of the eastern coast of Asia and the western part of North America at least， the sea・level pres・

sure pattern almost corresponds to the 500 mb one． Over the east coast of Asia it appears reasonable to attribute the below normal temperature in the vicinity of the Sea of Okhotzk to the cold air from Siberia which is indicated by the increased pressure gradient between the north Japan and the Kamchatka Peninsula． Over the northwestern part of North America the flow with strong south component is represented by the both pattems of the sea・1evel and the 500 mb surface． However， the temperature is below normal in this region and the reasonable explanation can not be given to these facts．

(11)

O．。。蛋

り．bo匡

＼

㌧

、

♂

＼／／／ξ

「

r

r ぺ

！−t

｝

t

ぐ

（ OO・

噸．．

／

ノr C

tJ●

＿＿@一rU ＝

」二專凶一凸＿＿

cじ

くむ

距邑 L

7 一＿

薩…罫犠＿＿

P鮭＿

盲 ■・＼＿

、く 1 − −

亀、｛ v 、

、 M

I F．煤F

饗 s 1〜

・継漿昏

P l

°S@曳 ^R

ふ『

｝〒

藁

／ NL@＼

♂ ！・ N

嚇

雪占

、

識欝／灘

，）ざ

ノ

、 N．嬉

㌧

、

）乃「

ぬに

《°・1

L Ml P bC．， J NNIt 誤．

7

、℃

／

翫

嚇

漂〜．

覇／ v K

平タ

喚◎㌻・

（）b 詑ノ〆 tet ，〜誠

4輪一

ヌ

∠ t

タ穐騨

耐鱒A 、tv i

し、」

tV2．i

潔

、、慣鱒．鷲ゆ 2

聖。【・わげぺψ冤＼、

・螺

ら

5

3

一＃＋．◎職

一ら一〒一一＋一一一一一「一丁く5 隣＿一一＝i＿・《ケ，ずrレ

＿＿、♂ V

s 一し劉〆窃㌧

ヒ 1 ， ⁰ ギ〆 ^斗／／；1を y

°￡ズノo．；：／で

ノ ^リ

〆 ^潤@ ^v．・ ^v ^％〆

ケ1 ， Q 7

脇

^{ピ／fft（、}

風 4 十山 tx）t−

一→ ン＿L ，一

＿f ∫ r ゲ oずプ r♂Lろ戸

鴛z．｛・tt ゴ tイ．

♂￠

信Eこ

蕪窄りげ■

魑

oT

一b

も Ltln N 豊

〆＾

@尺

〒

s，試

マ

、ド軸 sτ

o 「珊 a

卜欧

Bah 一g

り

〜㌧〉「

礼

％

㌧鶴・

〃㌃

砺●

呂

＝

詔

＼も

＾、

／卜暢・

，

／＼

1 写

へ

、

ド 3

岩

・N @fP で V u／ ° 、、・マヒ ^x e・緊＆．・叫．・・、 t 晦・入 h

＾＋・P 鋼

塾

壌1

〆

｛

邑lt r

喋叱

ヤ

v ^曜 ^十1

＿一一掴看一〇

、

Q灘

態猿賦』 ^も

＼［t風

人｛ P ぐび監＼之ズ^，、

へ、、、鴨鯉 eX

ヒ、レ

㌧L直、、o ／

町 ●F

ヤ 4π一凸 1t

yρ一イ @ い●

卵キ↓

「uLs ！z「

三苫・．

．記きヤ．

● ぺ＼㌧F pt ／＼

，／、t

♂・

ぐ

囎潜ヒ．

繋滋vt／

6噛一昏旨L−−b−一＿一一一一

嵩。一鐸・」．←＿〜「層 L 、一一〜福＿＿＿1 ざ一「一一一一L＿＿

艦た t ⁹

購鶏蘇一ミ

く灘鋳難

P ＼＼

ノヤ

ア ^、

＼

ぺ ^、＼汐、ヤヤ． ^㍉㌧じ＼べ．＼

、恥覧＼♂°

● ＼、δ N、、

イ

試

墨

，・昏o 弼

羅^F ^軽苓

卜隼 1嚢一尊幾

顎漫鍛携／覆

電加∵ @b爆

yi，ご．

儀う「^や♂

助㌔ ρ灘

妬 t−○しz

P 十

、A「p r L トレ k ，砲

㌔卜、「 i

運．

＼σザ鱈・鵡i

f霧嫉

バ凶、

か》

《

言

％・㌔、をワ

(12)

17〜θ3θCO126『harmonic．

The distribution pattern of the partial regression coefficients for the pressure and the am−

plitude of the second harmonic is shown in Figure 7． The pattem obtained here is also s㎞ilar to the 500 mb surface pattern correlated with the amplitude of the second harmonic．

The low pressure areas are intensified with the amplitude of the second harmonic over the eastern part of Siberia and the Atlantic Ocean， where its normal troughs are located respec・

tively・On the other hand， the high pressure areas are intensified over the eastern Europe and in the vicinity of Alaska， where the normal ridges of the second harmonic can be found respectively． This component pattern is in agreement with one ofthe zonal circulation shemes over the Northern Hemisphere presented by Dzerdzeevskii（1966）．

The distribution pattern of the partial regression coefi icients for the temperature and the amplitude of the second harmonic is presented in Figure 8． This pattern indicates that the distribution of the temperature associated with the amplitude of the second harmonic is the quite reverse between the eastern and western part of the Eurasian continent． Namely， over Europe west of the Ural Mountains the temperature tendencies are rising in the area north of 40°Nand falling south of 40°N． In contrast with this， the reverse is almost true over the eastern coast of Asia． Dzerdzeevskii（1962）pointed out the difference of the temperature variation associated with the change of zonal circulation between the eastern and western part of the Eurasian Continent．

Accord㎞g to the result presented here， the following synoptic processes associated with the large amplitude of the second harmonic can be thought． One of the upper・1evel troughs intensified over the Atlantic and one of the ridges over the eastern part of Europe． Corre・

sponding with this， the sea−level pressure tendencies are rising over East Europe and falling over the central Atlantic． These sea・level pressure distribution and upper−level pattern suggest the intensified southerly flow in the region between these trough and ridge． More・

over， strong advection of warm air from the south is indicated by the positive deviation of temperature． Along the eastern and southern margin of the high pressure area over East Europe the cold air advection is suggested by the negative deviation of temperature from Siberia to the eastern portion of the Mediterranean Sea across the Caspian Sea． On the other hand， the similar relation between the upper−level and the sea−level patterns is also true over the eastern portion of Siberia and Alaska． The strong southerly flow suggested by the isobars and the positive deviation of the temperature indicate the intensified influence of the warm Pacific Ocean in this region． The low pressure area， corresponding with the upper・level trough， extends over the belt from the central part of Siberia eastward to the vicinity of the Kamchatka Peninsula． Along the southern part of this low pressure belt the intensified influence of the cold continent can be expected by the strong westerlies， suggested by the pressure gradient， and the low temperature． The similar processes are also true over North America． Namely， the upper−level ridge is located on the eastern part of the Pacific and the sea−1evel high pressure area associated with this ridge extends from the southern portion of Alaska southeastward to the eastern United States． These circulation patterns and the low temperature over North America suggest the strong cold air advection from the north．

77ze third hanuonic．

The pressure pattern associated with the amplitude of the third harmonic is demonstrated in Figure 9． The region with the positive coe fficients spreads over the low latitude side and is especially pronounced over British Isles and the southern part of Alaska． Also， over the central part of Siberia the positive region seems to reach relatively higher latitudes． The area with the negative coe伍cients extends over the high latitude side and indicates the distinct

(13)

゜。

卜．bo刷』

Q

℃巴

ノ．

菱

駕島￡墜

3

／

一−e−一一?･−

3

野．

頼l．、．灘

〆

イィ泥イ》

rL

離

@

@．鎗

〉螺薦．

〉

々ゐ．

㍗

ρσ、 00

0て

σ

頻￡

武、、

冠演・

譲粉於

ノ響

〉

．r

砺・