東亞與西北太平洋地區夏季氣候，主要受季風環流與颱風所主宰。關於季風系統的運作，我們已有所瞭解，然而在全球溫度不斷升高的同時，季風環流系統是否還可以維持相同的運作模式？還是會產生增強或減弱的不同演變趨勢？季風環流的改變對區域氣候影響又如何？是值得我們進一步探討的問題。從IPCC 的報告我們知道了，全球暖化下的熱帶地區，水氣蒸發量勢必因溫度升高而增加，結果將使原本的對流上升區因有更多的水氣進入到大氣中，產生降雨量增加的現象。若以全球大氣環流的觀點來看，Held and Soden（2006）認為，大氣環流的強度勢必將減弱，Tanaka 等（2004）也從觀測資料裡分析出，熱帶地區的沃克環流（Walker circulation）強度有逐漸減弱的趨勢，至於南北向的哈德里環流胞（Hadley cell）強度，於冬季有增強的趨勢，但是夏季變化則較不明顯。未來呢？季風環流的強度是否真會產生改變？原本的對流上升區又是否會被抑制，進而影響季風區降雨量的多寡？這些問題對生活於亞洲季風子系統區域的人民來說至關重要，也將會產生重大的影響。本研究即以此為出發點，希望藉由IPCC 第四次評估報告中的全球海氣偶合模式輸出結果為研究基礎，瞭解在全球暖化下，季風環流的結構與強度是否會被改變？若被改變了，那又是什麼樣的物理機制和過程造就了這樣的結果。最後，我們也將會進一步了解未來環境狀態下，颱風移動路徑與活躍度是否也有所改變。
The monsoon circulation and typhoon are the major system to dominate the regional climate of East Asia , South Asia and western North Pacific. Taiwan is also located in this monsoon area, so it is very important to understand the variation of the Asian monsoon system. From the IPCC report（2001）, we know that because of the increase of greenhouse gases in the troposphere, the atmosphere becomes warmer and moister, especially in tropical area. In the convective ascending region, more moisture will be brought into the troposphere via the upward motion and induce more precipitation. On the other hand, negative precipitation anomalies are found over the descending area. The precipitation anomalies also show a notable meridional movement which varies with the seasonal variation of the tropical convection zone. From a global circulation point of view, Held and Soden（2006） suggested that the global circulation associated with convection will be reduced under global warming, Tanaka et al.（2004）also found that the intensity of Walker circulation has weakened in recent decades, and the Hadley circulation indicates intensifying trend in boreal winter. If the hypothesis occure, how will the Asian monsoon circulation be changed? Will it be enhanced or reduced? Will the precipitation over Asia be increased or decreased ? This is an interesting and important question for us. In this project, I will use the Fouth Assessment Report（AR4） of the Intergovernmental Panel of Climate Change（IPCC） model outputs to examine how the East Asian and western North Pacific summer monsoon circulation are changed under future climate projection. Further, I will also analyze possible mechanisms of monsoon circulation changes, and finally analyses the shift of the typhoon track and activity over the WNP‐EA region in the future climate.
