ENSO年後春季東亞大氣特性之分析第二部份：高低層環流之特性及推論

Spring Time East Asia Large Scale Characteristics Post ENSO Part II: The Circulation Pattern of Different Levels

胡志文(Jyh-Wen Hwu) ； 王作臺(Jough-Tai Wang)

《大氣科學》 22卷3期 (1994/09) Pp. 361-385

摘要

本研究是本序列研究之第二部份，第一部份著重於瞭解ENSO成熟期後春季東亞及西太平洋地區OLR及SST之特徵空間結構，本部份的重點，則在於探討ENSO成熟期後春季環流場之擾動，同時提出一推論來總結ENSO年後春季東亞／西太平洋地區的SST、OLR及各層環流之空間特徵。此部份所用的方法和資料與第一部份相同，只增加了環流資料及其與SST的奇異值（SVD）分析，分析的結果顯示，在ENSO成熟期後之春季，200 hPa面上，在赤道區155°E以西（東）有西風（東風）之距平，中及東太平洋赤道兩側有反氣旋式及正高度距平，青藏高原有氣旋式及負高度距平，其南側西風噴流增強。500 hPa面上，孟加拉灣到南中國海有西風距平，中國東部有南風距平，日本附近有氣旋式距平。850 hPa面上則顯現了中國東南沿海有西南風距平。由SST、OLR及環流共同分析所得之結果，並參考本地區有關乾濕梅大尺度條件之研究，吾人推論本研究所顯現的現象，傾向於說明ENSO成熟期後之春季較易有濕梅狀況之條件，文中用測站之觀測雨量及OLR反求之雨量驗證此推論，並討論了低頻擾動之可能影響。

關鍵字

梅雨 ； ENSO後 ； 東亞環流

並列摘要

This study attempts to identify the effect of the tropical forcing on the weather and climate in the East Asia region. There contains two parts in this work. Part II results of this study are presented in this paper. And it emphasizes in understanding the circulation characteristics, also during the Spring period. The Singular Value Decomposition (SVD) method are adopted to investigate the spatial pattern of the eigen vectors of the sea surface temperature (SST) and the circulation field of different levels.The results indicate, during the Spring time after the mature phase of ENSO, in equatorial region at 200 hPa level, there tends to have westerly (easterly) anomaly west (east) of 155°E. Anticyclonic circulation and positive height anomaly are found in the equatorial central and eastern Pacific. In the Tibetan Plateau area, it is characterized with the cyclonic structure and negative height anomaly, and the intensity of southern branch westerly jet are intensified. In the 850 hPa level, in the South China Sea and the southeast coast of Mainland China possess a southwesterly anomaly.From the SST, OLR and circulation results, along with the schematic model about the large scale characteristics for the dry and wet Mei-Yu seasons, a conjecture is proposed to summarize the essential anomaly patterns. It is postulated that the large scale characteristics during the Spring period after the mature phase of ENSO event favors the occurrence of a moist (wetter) Mei-Yu season. Preliminary analysis of OLR rainfall data supports this hypothesis. The possible modification of the low frequency variation to this hypothesis is also discussed.

並列關鍵字

Mei-Yu ； Post-ENSO ； Circulation ； SST ； EOF ； SVD