東亞夏季季風期間季內振盪的年際變化

Interannual Variability of Interaseasonal Oscillation during the East Asian Summer Monsoon Period

鄒治華(Chih-Hua Tsou) ； 柯文雄(Wen-Shung Kau) ； 徐邦琪(Pang-Chi Hsu) ； 潘淑鈴(Shu-Ling Pan)

《大氣科學》 31卷3期 (2003/09) Pp. 239-259

摘要

本研究的相的在探討東亞夏季季風期間，季內振盪的年陳變化。我們透過小波轉換，將LOR過濾出30~60天與10~20天季內尺度的波動，分析季內振盪的年際變化。研究結果顯示出亞洲季風區，LOR的變化以30~60天波動的貢獻較。南海/西太平洋地區為亞地區之季內對流振盪變異量最大的地區，其季內對流變化主要由30~60天振盪的貢獻而來。
本文續以南海地區300天對流波動的強度作依據，進一步探討30~60天對流振盪的年際變化。木現30~60天振盪活躍年，季內對流振盪(包含30~60天與10~20天)LOR波動與LOR原始值相位一致，其中又以30~60天LOR波動與LOR原始值之相位關係較為一致;而30~60天振盪不活躍年，30~60天與10~20天LOR波動的變化，對LOR原始值的變化都很重要。活躍、不活躍年之波動來源不完全相同，活躍年南海地區主要的波動來源為赤道印度洋向東傳的波動，此向東傳的訊號可從赤道附近往北擴展到北邊(10~15°N);而不活躍年時南海地區主要的波動來源則為赤道中太平洋向西北傳的波動。活躍年(不活躍)時印度洋、孟日拉灣及南海地區SST均為正距平(負距平)。印度洋、孟加拉灣及南海地SST正距平有利於30~60天東移波動之發展，而垂直東風風切並非影響30~60天季內對流東移之主要原因。

關鍵字

東亞夏季季風 ； 季內振盪 ； 年際變化

並列摘要

The purpose of this study is to diagnose the interannual variability of ISO (Interaseasonal Oscillation) during the EASM (East Asian Summer Monsoon). Wavelet analysis was utilized to filter the 30-60 day and 10-20 day oscillation. The result show that ISO is dominated by 30-60 day oscillation in EASM region. In addition, the ISO in South China Sea/ Western Pacific where the climatological maximum variance of ISO in EASM region occurs is also dominated by 30-60 day oscillation.
We further investigate the interannual variability of the 30-60 day oscillation, based on the intensity of 30-60 day oscillation over the South China Sea. The result show that during the 30-60 day active year, the interannual variability of ISO is highly correlated with the interannual variability of original OLR over the South China. The interannual variability of ISO in South China Sea is also dominated by 30-60 day oscillation. However, during the 3
0-60 day inactive year, the 30-60day and 10-20 day oscillation are equally important to the interannual variability of the precipitation over the South China Sea. The originationj and propagation of 30-60 day oscillation was significantly different between the active and inactive years. The former was primarily contributed by the eastward propagation mode originated for equatorial Indian Ocean. This eastward propagation mode not only propagated eastward but also extended northward to 10-15°N. The latter resulted from the westward propagation mode from equatorial Central Pacific. During active (inactive)year, warm (cold) SST anomalies appeared over the Indian Ocean and Bay of Bengal. This implies that SST anomalies over the Bay of Bengal and South China Sea may have strong influence on the interannual variability of eastward propagation mode. On the other hand, the vertical wind shear has little impact on the interannual variability of the eastward propagation mode .

並列關鍵字

East Asian Summer Monsoon ； Interaseasonal oscillation ； Interannual variability