Spatial-temporal properties of moisture budget and associated large-scale circulation in the Yangtze River Basin

Abstract

通过分析1961-2005年长江流域水汽收支的时空变化及环流特征,发现:1)长江流域春季、秋季、冬季和年均水汽收支下降,而夏季增加;长江上游除夏季外均变化显著,中下游则只有春季、夏季和秋季变化显著;2)长江中下游各季节及年水汽收支与降水的关系都通过了显著性检验,其中夏季关系最好,而长江上游只有春季和秋季通过显著性检验;3)夏季长江流域水汽输送下降,但水汽收支却增加,可能与东亚夏季风减弱有关,而东亚夏季风的减弱可能与东亚大陆上空低层大气位势高度显著增强有关.;Trends of moisture budget were explored during 1961 to 2005, using simple linear regression method, in the Yangtze River basin, China. The results indicated that: 1) the moisture budget decreased in winter, spring and fall, but increased in summer. The trend of moisture budget was significant except for summer in the upper Yangtze River basin. While significant trends could be identified in moisture budget in spring, summer and autumn in the middle and lower Yangtze River basin;2) the correlation between moisture budget and precipitation was significant related at all of the seasons in the middle and lower Yangtze River basin, and was significant related in spring and autumn in the upper Yangtze River basin;3) the summer moisture transport was in significant decreasing trend in the Yangtze River basin, which might be closely associated with lower layer geopotential height. The summer circulation showed increasing continental high over north China, which weakened the southwesterly summer monsoon and limits propagation of the summer monsoon to north China, resulting in more water vapor budget in the Yangtze River basin and less in north China.