面積を指標としたシベリア高気圧の年々変化と東西差 Interannual Variation and East-west Expansion of the Siberian High Based on an Areal Index

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シベリア高気圧全体の年々変化を客観的に解明する目的で, 1月の月平均SLPを使用し, 1951~1990年におけるシベリア高気圧の拡大を表す指標として,1,030hPaの閉曲線内部の面積を求めて解析を行った.<br> その結果,シベリア高気圧全体の面積の年々変化としては,7~10年程度の周期的な変動がみられた.<br> 次に,シベリア高気圧を経緯度で分けることにより東西への「広がりの指数」を定義し,それぞれの変動を明らかにした.その結果,東への広がりは安定して面積が大きいのに対し,西への広がりは変動が非常に激しいことがわかった.~次に,シベリア高気圧の東西への拡大と上層の循環場との関連を求めた. 500h Pa面高度のEOF解析を行い,それぞれのパターンを,従来提唱されている上層高度場のテレコネクションパターンと比較した.その結果,第1モードは西大西洋 (WA) ないしは北大西洋振動 (NAO) パタージと対比することができ,シベリア高気圧の西への広がりと有意な相関があることがわかった.第2モードは西太平洋(WP)ないしは西太平洋振動(WPO)パターンと対比することができ,シベリア高気圧の東への広がりと有意な相関があることがわかつた また,第3モードは太平洋一北米(PNA)+ユーラシア(EU)パターンと対比することができるが,地上でのシベリア高気圧の東西方向への拡大とは有意な相関がみられない.しかし,シベリア高気圧の東西への拡大の影響を除去すると, PNA+EUパターンとシベリア高気圧の中心強度とは有意な相関があることがわかった,このように,上層の高度場で示された循環場とシベリア高気圧の東西への拡大,および一定の条件の下での中心強度と有意な相関があることは,シベリア高気圧の形成・発達のメカニズムに,これらのテレコネクションが関係していることを示唆している.

The Siberian high forms every winter with some degree of interannual variation in its location, . extent of area covered, , and intensity. The climate around Siberia is significantly affected by the expansion of the Siberian high during its mature period. An attempt was made to clarify the interannual variation of the Siberian high using monthly SLP data from the month of January from 1951 to 1990. The area over which pressure exceeded 1, 030 hPa was taken as the index of expansion of the Siberian high.<br> By analyzing the interannual variation of the Siberian high, a periodicity of 7 to 10 years was detected. It was also found that the eastward expansion of the Siberian high remained large while the extent of its westward expansion varied greatly.<br> The relationship between the east-west expansion of the Siberian high and the upper air circulation was examined. The distribution of eigenvectors 500 hPa in height with varimax-rotated EOF analysis was compared with teleconnection patterns. The first component was similar to the West Atlantic (WA) or North Atlantic oscillation (NAO) pattern and it had a high correlation with the westward expansion of the Siberian high. The second component was similar to the West Pacific (WP) or West Pacific oscillation (WPO) pattern and it was highly correlated with the eastward expansion of the Siberian high. The third component was similar to the Pacific/North American oscillation (PNA) and Eurasian (EU) patterns and it showed no correlation with the east-west expansion of the Siberian high. However, if the years of extreme east-west expansion of the Siberian high were excluded, the others correlated with the third component of EOF analysis and with the strength of the central pressure of the Siberian high. These results therefore indicate that the mechanism by which the Siberian high forms and develops is related to the teleconnection patterns of the upper air circulation.<br> In previous studies on the interannual variation of the Siberian high, the variations in intensity and position were often analyzed based on the strength of pressure at a single point. However, in this study the Siberian high was analyzed using an areal index, specifically the area in which the pressure exceeded a specific SLP value, and therefore it was possible to clarify the east-west differences in the structure of the Siberian high with respect to the upper air circulation patterns.

収録刊行物

  • 地理学評論. Ser. A  

    地理学評論. Ser. A 73(2), 81-94, 2000-02-01 

    The Association of Japanese Geographers

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各種コード

  • NII論文ID(NAID)
    10004957702
  • NII書誌ID(NCID)
    AN1016484X
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    00167444
  • NDL 記事登録ID
    4976093
  • NDL 雑誌分類
    ZG1(歴史・地理)
  • NDL 請求記号
    Z8-571
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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