7月东亚高空西风急流变化对我国雨带的影响

Impacts of the Variation of Westerly Jets over East Asian in July on the Precipitation of East China

分析了7月东亚高空西风急流北跳和急流中心西移时我国雨带的变化特征,发现急流北跳与长江中下游梅雨结束有很好的对应关系;急流中心西移则与长江中下游梅雨结束无对应关系,但急流中心西移相对于急流北跳发生的早晚对雨带北移过程有重要影响:在急流中心西移晚于急流北跳发生年份,雨带北移依次为长江中下游地区—淮河流域—黄淮地区逐渐北推,其他年份雨带则从长江流域直接北跳至黄淮地区。进一步分析表明:(1)急流北跳和急流中心西移引起中纬度大气环流发生显著变化,从而引起西太平洋水汽输送发生显著变化,孟加拉湾水汽输送无变化。(2)急流北跳和急流中心西移时大气环流调整不同,导致来自西太平洋的水汽输送变化不同,进而对雨带北移产生不同的影响。急流中心西移相对于急流北跳发生时间早晚不同,大气环流调整过程和水汽输送调整过程也不同,使得雨带北推进程不同。

The impacts of the northward jump of jets and the westward movement of East Asian westerly jet center from the West Pacific to the Qinghai-Tibet Plateau on the rainfall distribution of East China are studied,it is found that there is well corresponding ralation between the northward jump and of Mei-yu withdraw from the mid-lower reaches of the Yangtze River Area,the westward movement of jet center have no corresponding relation of the withdraw of Meiyu season,whereas the earlier or later occurrence of the westward movement of jet center than the northward jump of jet effects the process of the rain belt moving northward which is that the rain belt move northward from mid-lower reaches of yangtze River area to Huaihe River and then to area between Yellow River and Huaihe River for the years that the time of the westward movement of jet center is later than one of the northward jump of jets and from mid-lower reaches of yangtze River area to area between Yellow River and Huaihe River in other years.Further analysis are as follows：（1） the variations of the circulation are happened in middle latitude with water vapor from the Western Pacific changeing and from the Bay of Bengal no changing when the northward jump of jets and the westward movement of East Asian westerly jet center are happened.（2） the impacts of the northward jump of jets and the westward movement of East Asian westerly jet center on the circulation are different,which cause different water vapor variations from the Western Pacific and so their impacts on rain belt are different.The earlier or later occurrence of the westward movement of jet center than the northward jump of jets cause the process of circulation and water vapor variations which make the different processes of the rain belt moving northward.