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前人的模式研究表明全球变暖之后亚洲夏季风降水和环流的改变存在着一种自相矛盾的现象。本文利用最新的IPCC-AR4模式模拟资料和FOAM模式来研究亚洲夏季风对全球增暖的响应机制。大多数IPCC-AR4模式以及FOAM模式重现了亚洲夏季风降雨与环流变化的自相矛盾性。利用FOAM模式,本文通过系统改变海洋增暖信号来理解海洋变暖在季风响应中的作用机理。结果表明亚洲夏季风降雨和环流对全球变暖的不同响应主要是由于印度洋的变暖加强了中上层大气的变暖(从而降低了经向的热梯度)和水汽输送。全球增暖导致海陆温差的增大使得大气对流中心北移从而减弱了北印度洋的底层大气季风风速。这些敏感性实验还表明了太平洋的变暖增强了亚洲夏季风环流但减少了降雨量,从而削弱了印度洋增暖对亚洲夏季风的颖响。模式研究还表明了海洋的增暖能够增强亚洲夏季风自身的内在变率。
Previous model studies show that there is a paradoxical phenomenon in the change of summer monsoon rainfall and circulation in Asia after global warming. In this paper, we use the latest IPCC-AR4 model data and FOAM model to study the response of Asian summer monsoon to global warming. Most of the IPCC-AR4 models and the FOAM model reproduce the paradoxical changes in the Asian summer monsoon rainfall and circulation. Using the FOAM model, we understand the mechanism of ocean warming in the monsoon response by systematically changing ocean warming signals. The results show that the different responses of Asian summer monsoon rainfall and circulation to global warming are mainly attributed to the warming of the Indian Ocean and the warming of the upper-middle atmosphere (thus reducing the meridional thermal gradient) and water vapor transport. The warming of the earth led to the increase of the temperature difference between the sea and the land, which led to the northward shift of the atmospheric convection center and the weakening of the underlying atmospheric monsoon wind in the North Indian Ocean. These sensitivity experiments also show that warming in the Pacific enhances the circulation of the Asian summer monsoon but reduces rainfall, thus weakening the warming of the Indian Ocean to the Asian summer monsoon. The model study also shows that the warming of the oceans can enhance the inherent variability of the Asian summer monsoon.