海洋在亚洲夏季风对全球变暖响应中的作用(英文)

The Roles of Oceans in the Asian Summer Monsoon Response to Global Warming

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 modeling studies have indicated a paradox of the Asian Summer Monsoon （ASM） precipitation and circulation changes in global warming. Here, we use the most recent IPCC-AR4 model outputs and the Fast Ocean-Atmosphere Model （FOAM） to understand the mechanisms of the ASM response to global warming. Most of the IPCC-AR4 models and FOAM model reproduce the same paradox as in the previous modeling studies. A series of sensitivity experiments with FOAM are conducted, in which SST warming anomalies are varied systematically to understand roles of oceanic warming in the ASM responses to global warming. The results explicitly demonstrate that the ASM rainfall-circulation paradox in global warming is primarily associated with the Indian Ocean warming which enhances the middle to upper troposphere warming （thus reduces meridional thermal gradient） and moisture transport. The intensification of land-sea thermal con- trast in global warming tends to shift convection center to the north and slow down the low-level monsoonal winds over the northern Indian Ocean. The sensitivity experiments further demonstrate that the Pacific warming tends to intensify the winds but reduce rainfall of the ASM, therefore offset the impacts of the Indian Ocean warming on the ASM. The modeling studies also suggest that oceanic warming can enhance the ASM internal variability.