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A Climatological Study of Typhoon Formation and Typhoon Visit to Japan

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A Climatological Study of Typhoon Formation and Typhoon Visit to Japan 気象砺究所研究報告 第36巷 第2号 61－118頁 昭和60年6月 Papers in Meteorology and Geophysics、ア01． 36，No． 2，PP，61－118．June 1985 A Climatological Study of Typhoon Formation and Typhoon Visit to Japan by Takashi Aoki＊ ハ4α¢070Jog1αzlノ～2s2α76h lnsオπ㍑彪，ITsz漉％わα，1わα7α勉，305∫‘功αη （Received Feb．28，1985；Revised March28，1985） Abstract The formation of typhoons in the westem North Pacific and typhoon visits to Japan are investigated from a climatological standpoint．The relationship between the frequency of typhoon formation or typhoon visits and the sea surface temperature in the North Pacific is also studied． First，the formation of typhoons for the30．year period from l953to1982is examined． The average number of typhoons formed is27a year． For the amual var量ation of monthly『 frequency of typhoon formation，the maximum frequency occurs in August and the minimum in February。 Typhoons are formed most frequently in the ocean east of the Philippine Islands．The latitude of typhoon formation moves northward in summer and then retreats equatorward． Secular variation in the frequency of typhoon formation is studied by trend analysis and power spectrum analysis。The frequency showed a peak in the middle of the1960ンs．The frequency of typhoon formation increased until the middle of the1960’s an（i then decreased・ There exist two periodicities of3to4years and6to7years in the secular variation of typhoon formation． In the frequent／infrequeht months of typhoon formation the following characteristics are found． The frequency shows a marked increase north of15。N in the case of frequent typhoon formation．The polar vortex is weak／strong．The zonal index is high／low，because the Aleutian low is active／inactive and the subtropical anticyclone and the intertropical con－ vergence zone exist north／80uth of their normal positions． The negative／positlve anomalies of sea surface temperature are extensive in the subtropical ocean south of Japan。 Next，typhoon visit to Japan is investigated for the perio（i of 70 years from l913to 1982．When a typhoon apProaches Japan and comes within a distance of apProximately300 km from the coast，it is（iesignated as a typhoon that visits Japan。The average amual number of typhoon visits is9． The maximum monthly frequency occurs in August and there are no typhoons from January tσMarch in Japan。 The area of the most frequent visits is the sea south of the Okinawa Islands。Typhoon visits are the least fre〔1uent in the sea northeast of the Hokkaido District。 The∫requencyr of typhoon visits is high in the open sea and straits and is relatively low near the islands an（1momtains．The typhoon season opens負rst near the Nansei Islands，and then the fre－ quency increases also in northern areas。 In the later typhoon season，typhoon visits occur frequently in the sea southeast of the Pacific coast． Secular variation of typhoon visit is examined by trend analysis and power spectrum analysis． The frequency is lower from the latter half of the1920ンs to the1930’s．There exist h三gh frequencies of visit from the latter half of the1940’s to the early1950’s and ＊Present af五liation Japan Meteorological Agency，Tokyo100，Japan。 62 T．Aoki Vo1．36， No．2 around1960。 The results also show the existence of variations of approximately2to2，5 years and 5to6 years periodicities，in addition to a perio（iicity of40 years． In years of frequent／infrequent typhoon formation，typhoons frequently／infrequently visit the coast from the Tokai District to the Kanto District。 The annual variations of regional typhoon visit to Japan are studied by principal com－ ponent analysis． The first four eigenvectors account for97．5％ of the total variance and the pro丘1e of the annual variation in frequency of regional typhoon visits is adequately describe（i by the four eigenvectors． AregionaldivisionofJapanisproposedbyusingtheamplitudecoe伍cientscorrespon（1－ ing to these four eigenvectors． Ten regions are obtained． Broadly speaking，these regions can be divided into four groups． The Pacific Ocean side and the Japan Sea side form one boundary while the Kinki and Shikoku Districts form another． Finally，the correlations between the frequency of typhoon formation or typhoon visits and sea surface temperature are analyse（L The frequency of typhoon formation shows a minimum during El Ni五〇events and maximum frequency is observed two years Iater．There is simultaneous correlation in the sense that as the sea surface temperature in the eastem Equatorial Pacific rises，the fre－ quency of typhoon formation（1ecreases，and vice versa。 There are significant correlations between the number of typhoons formed and the sea surface temperature in the preceding year and two years before． The same relationship hOlds true for typho6n visit． High positive correlations are found for the sea surface tem－ perature in the eastem Equatorial Pacific，while there are negative correlations for the northwestem part of the North Paci丘c． For typhoon visit，there are significant positive correlations with the sea surface temperature of the summer of the preceding year in the ocean south an（i southeast of Japan． To predict the frequency of typhoon formation and typhoon visit，．multiple regression equations are develope（i by hsing sea surface temperatures as independent variables．The multiple correlation coefncients for typhoon formation and typhoon visit are O．854and O．825， respectively． These equations may be useful in long－range forecasting． Contents 1 Introduction．。． 63 L L Review of Climatological Studies of Typhoon Formation and Typhoon Visit to Japan．．．．．． 63 L2．Purpose of This Study 65 1．3． Data 65 2 Climatology of Typhoon Formation 66 21。Frequency of Typhoon Formation．。．。 66 2．1。1．Distribution of Typhoon Formation 66 2．1．2。Annual Variation of Typhoon Formation．．．．． 69 2．2．Secular Variation of Typhoon Formation 75 2。2．1．Trends in Frequency of Typhoon Formation． 75 2．2．2．Power Spectrum Analysis of Typhoon Formation 76 2．3．Contrastive Study for Frequent and Infrequent Months of Typhoon Formation 77 2．3。L Typhoon Formation in Frequent and Infrequent Months 77 2．3・2・Large－Scale Circulation of the Atmosphere in Frequent and Infrequent Months 79 2．3。3．Cloudiness in Frequent and Infrequent Months．．．． 80 2．3．4。Sea Surface Temperature in Frequent and Infrequent Months 81 2．4．Summary。 83 3 Climatology of Typhoon Visit to Japan 84 3．1，Frequency of Typhoon Visit to Japan．．．．． 84 3．1。1．Distribution of Typhoon Visit to Japan 84 3．L2。Annual Variation of Typhoon Visit to Japan． 86 3．2．Secular Variation of Typhoon Visit to Japan．．．． 90 1985 AClimatologica1StudyofTyphoon 63 3．2。1。Characteristics of the Secular Variation of Typhoon Visit to Japan．．．．．．．．．． 90 3．2。2，Power Spectrum Analysis of Typhoon Visit to Japan ．．，．．．．，．．．．．．．＿．．， 91 3・2・3・Relationship between Frequency of TyphoQn Formation and Typhoon Visit toJapan＿．。99．9．．甲．．．．．．臼．．．9．．．．．噸．り9．9．－9．．．．響．－－．－．．．曾．．．．．．．．．臼．．．9991 3。3。Regional Division of Japan Based on Typhoon Visit．．。．．．．．．．．．．．．．．．．。．．．．．．．． 94 3、3。L Principal Component Analysis of Annual Variations of Regional Typhoon Visit 94 3．3。2，Method of Classi丘cation．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．。．．．．．．．．．．．．．．．．．．．．95 3．3。3．Results of Analysis．．．．．．．．．．．．。．．．．．．．．．．．。．．．．．。．．．．．．．．．．．．．．．．．．．．．．．．． 97 3・4。Summary．．9．．．．．乳．曾．．．9．9．．噸．．．．9．．．．．9．．．．．．曾．．．．．．．9．．．．．．り．．．．．．．．．．．．9．．．曾 99 4。Relationship between Typho6n and Sea Surface Temperature．．．．．．．。．．．．．．．．．．．．．．．．100 4・1・Correlation between Frequency of Typoon Formation and Sea Surface Temperature lOO 4．L l．EI Ni五〇Events and Frequency of Typhoon Formation．．．．．．。．．．．．．．．．．．．．．．100 4・L2・Seasonal Variation of Correlation Pattems for Frequency of Typhoon Formation IOl 4・1・3・Distribution of Correlation Coef五cients for Fre（1uency of Typhoon Formation．．102 4，2。Correlation between Frequency of Typhoon Visits to Japan an（l Sea Surface Temperature．ロ．．．9．．9．9．．99．．．．．D．D．．．．．．9一．曾．9．．．．．．．．．．．．．．6．｝．．．．．9．．．9．9．．！05 4・2・L Seasonal Variation of Correlation Pattems for Frequency of Typhoon Visits 105 4．2，2．Distribution of Correla亡ion Coe伍cients for Frequency『of Typhoon Visits．．．．106 4．3．Multiple Regression Analysis。．．．．．．．．．．．．．．．．．．．．．。．．．．．．．．．．．．．．．．．．．．．．．。．．．108 4．3。1。Possible Independent Variables．．．．．．．．。．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．。．109 4・3・2・Development of Multiple Regression Equations．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．U1 4。4．Summary．．．．．．．り．．．．り9．り．．9．．曾．．．．．．99．．．．9．．9．．．．9．．．．．．．り．．．．．．．．．．．．．．．．．9．ll2 5． Conclusions．．．．．．し．．．．．．．．．．．．．．．9．．．．9．．．．．．．9．．．．9．．．．．．．．．．9．．曾．．．．．．．．．．．．．．．．． 113 Acknowledgements．．．．．．．．．．。．。．．．．．．。．．．．．．．．．．．．．．．。．．．．．．．．．．．．．．．．．．．．．．．．。．．．．．．．115 References．9．．9．．．．．．◎．．．．．．．．．．．．．．．雪．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．99 115 和文概要3．D．．．．9一．．．．．．9．D．．．．．6臼．い．．9C．．9．．9．99－9．．．9．9．．．．．．．．．．．．．9．．．．．．．．9．．9一．．．118 1．Introduction Meteoro1ogical activities in Japan have developed greatly since the beginning of this 1．1Rc漉ωofα伽α孟oZo9εcαZS飢αεε80f century，and meteorological stations have been T〃P尭ooπForηεα孟εoπαπδT〃phooπ 1Vεs甜 established on various islands as far away as 加」αPαn！ Hachijojima，Chichijima，the Nansei，Islands Atyphoonisoneofthemostviolent and Formosa，as shown in Fig．1．Meteoro－ storms in the world．A number of typhoons 10gical data obtained from ships have been are formed in the westem North Paci行c every collected via marine ra（1io since l910．Con－ year，some of which strike Japan．Strong sequently，numerous observational data on winds and heavy rainfalls associated with typhoons have become available． typhoons are a major cause of natural disasters Otani （1940） investigate（l the average in Japan．The damage suffered from typhoons monthly tracks of typhoons。He found that
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