江淮流域2003年强梅雨期的水汽输送特征分析

在分析2003年6月21日到7月11日江淮流域强梅雨期间降水概况和大气环流基本特征的基础上,通过对水汽输送流函数及非辐散分量、势函数及辐散分量及江淮地区水汽收支的分析,表明江淮流域是该时期全球范围内水汽汇的一个高值中心,且水汽通量大值区和水汽辐合区与降水大值区基本一致.从水汽的输送来看,夏季印度风环流和南海夏季风是向江淮流域输送水汽的主要通道.梅雨期内,中层大气中的水汽主要是垂直上升运动对低层水汽的抬升作用,同时,低纬大洋上的水汽也可途经青藏高原后再从西边界向东输入到江淮地区,它的输送有可能增大江淮流域上空对流层中层大气中的水汽含量,从而有利于强梅雨在江淮流域的发生.计算分析还表明2003年强降水从前期的长江流域移到后期的淮河流域,是与大范围的水汽输送和辐合中心北移相联系的,较小空间范围的强暴雨洪涝的发生在有利的大尺度环境下,还与其他条件有关.

A Diagnostic Study of Water Vapor Transport and Budget during Heavy Precipitation over the Changjiang River and the Huaihe River Basins in 2003

By analyzing the features of the atmospheric circulation systems from 21 June to 11 July 2003, which corresponds to the heavy precipitation over the Changjiang River and the Huaihe River basins in 2003, the water vapor transport vector is decomposed into the sum of its nondivergent (rotational) and divergent (irrotational) components in terms of the streamfunction and potential, and the water vapor budgets are calculated in three regions of the Meiyu front system. The results indicate that the Changjiang River and the Huaihe River basins are the strongest water vapor sink over the global from 21 June to 11 July 2003. The minimum potential region (the maximum convergent region) of water vapor transport vector corresponds to strong precipitation region. The Indian monsoon circulation and the South China Sea monsoon in summer play important roles in the moisture transportation. Besides the vertical ascending motion transporting the moisture up to the middle levels, the moisture, which comes from low latitudes and turns to west when it goes through the Tibetan Plateau, can increase the humidity content in the middle levels over the Changjiang River and the Huaihe River basins and is favorable for the forming of the severe precipitation.