中文摘要：

利用再分析资料ERA-40计算了东亚气候平均对流层水汽输送（MT）、平均气流水汽输送（MMT）、瞬变涡动水汽输送（EMT）及其散度，并同降水场进行比较分析．结果表明，季节平均水汽散度场同东亚降水分布型存在一定的配置关系，水汽辐合区对应于降水大值区，辐散区降水较少．东亚大部分地区MMT散度大于EMT，但符号相反，即MMT是MT的主要部分，决定了后者散度空间分布特征．夏季风期间，东亚MMT表示季风水汽输送，其大尺度辐合区对应于季风降水区，辐散区覆盖了西北内陆干旱区．中高纬EMT四季均为恒定向北的水汽输送，是内陆干旱区和非夏季风控制区降水水汽的主要供给者．从夏到冬EMT水汽辐合区扩大，MMT辐合区缩小，后者的散度决定了东亚干湿气候区分布．因而季风与瞬变涡动竞争形成东亚独特的降水格局．这些特征的揭示为东亚区域气候形成与变异机理研究提供了新思路．1998年夏季案例分析表明，长江、松花江和嫩江发生流域性洪涝灾害主要是大尺度夏季风水汽输送异常辐合造成，瞬变涡动贡献不大．

英文摘要：

Abstract This paper aims at investigating the climate-mean integrated moisture transport （MT） of troposphere for 1971~2000 and the relationship between moisture divergence and seasonal precipitation in East Asia. The results made from ERA-40 shows that the spatial pattern of the precipitation approximately coincides with large-scale moisture divergence. A further decomposition manifests that the monthly-wind moisture transport （MMT） plays the dominant role for seasonal divergence patterns. The MMT convergence areas approximately fit in the big precipitation areas, while the MMT divergence almost covers the arid and semi-arid zones in northern China and Mongolia. The transient eddy moisture transport （EMT） is about ten-time smaller than MMT＇s in magnitude and plays a key role in moisture transport northward for nonmonsoon period. Usually, EMT divergence is of inverse phase to MMT＇s, suppressing the MMT impact on precipitation in summer monsoon zones, and it is the major one that supplies water vapor to the precipitation in arid and semi-arid zones. However, their divergences are compatible and overlapped in phase around the phase transition belt of the MMT divergence. It turns out that large-scale precipitation characteristics greatly rely on competence of MMT and EMT, being the physical cause that lead to specific pattern of the large scale precipitation. Besides, the mechanism of regional climate formation also implies the mechanism of regional precipitation change. A case study shows that the severe floods in both Yangtz River and Songhua-Nen rivers basin in 1998 resulted from anomalous MMT convergence of monsoon moisture transport, while both MMT and EMT divergences led to anomalous dry climate in the north and the northwest of China. In addition, it is the strong EMT divergence resulting in significant rainfall reduction in the south part of North China and the southeast coast of China. One could also make a further investigation on the causes leading to the anomaly of MMT or EMT, or both. Thi