夏季热带印度洋大气热源主模态与中国东部降水的关系

RELATIONSHIP BETWEEN LEADING MODE OF ATMOSPHERIC HEAT SOURCES OVER TROPICAL INDIAN OCEAN AND PRECIPITATION IN EASTERN CHINA DURING SUMMER

利用1979—2008年NCEP/NCAR再分析资料和中国区域160站降水资料,分析了热带印度洋及南亚地区夏季大气热源的气候特征,探讨了热带印度洋夏季大气热源主模态与中国东部降水的关系。结果表明:与春、秋、冬季相比,夏季大气热源强度强、范围广,热源最强中心在孟加拉湾北部大陆边缘;当孟加拉湾、苏门答腊岛西部海域、阿拉伯海的中东部以及恒河平原等地的夏季大气热源增加(减少),而赤道印度洋的中西部地区、阿拉伯海北部边缘等地的夏季热源减少(增加)时,有利于长江中下游地区、华北北部、东北以及西南大部分地区夏季降水的增加(减少),不利于华北南部以及江南地区尤其华南地区的夏季降水的增加(减少);热带印度洋夏季大气热源的主模态主要通过影响对流层高、低层的环流来影响中国东部降水。值得注意的是,与热带印度洋夏季大气热源的主模态时间系数的年际变化相比,其年代际变化对中国东部降水影响更显著。

The climatic features of atmospheric heat sources over the Tropical Indian Ocean（TIO） and South Asia in summer are analyzed and the relationship between the first EOF（Empirical Orthogonal Function）mode of atmospheric heat sources and precipitation in eastern China in summer is discussed utilizing NCEP/NCAR reanalysis data and precipitation data of 160 stations in China from 1979 to 2008.The results show that compared with other seasons,summer has wider and stronger atmospheric heat sources and the northern continental margin of the Bay of Bengal has the strongest atmospheric heat sources.When atmospheric heat sources over the Bay of Bengal,western Sumatra,the mid-east Arabian Sea and the Gangetic Plain are rising（reducing）,and when they are reducing（rising） over the mid-west Equatorial Indian Ocean and the northern edge of Arabian Sea,it is beneficial to the increase（decrease） of precipitation in the mid-Lower reaches of Yangtze River,the northern North China,Northeast China and most parts of the Southwest China but has adverse effects on the increase（decrease） of precipitation in the southern North China and the mid-Lower reaches of Yangtze River,especially South China.It can be concluded that the first EOF mode of atmospheric heat sources over the TIO affects precipitation of eastern China mainly by impacting the circulation of high and low troposphere.It is noted that compared with interannual variation of time coefficient of the first EOF mode over TIO,its interdecadal variation influences precipitation in eastem China more significantly in summer.