1991年江淮持续性特大暴雨的夏季风活动分析

文章分析了1991年江淮梅雨期间的东亚夏季风活动及其在梅雨期对流性暴雨形成中的作用。结果指出，第一场暴雨发生在夏季风暴发之前，它主要受副热带西风气流影响；后两场暴雨期间由于副高和东南季风稳定少动，西南季风的暴发和活动起了十分重要的作用，其进退演变导致了江淮梅雨的维持和中断。西南季风的一个重要作用是将热带地区（阿拉伯海及孟加拉湾）对流性很强的大气输送到江淮一带，由此使江淮流域在梅雨中后期形成了远强于一般年份的对流性降水，特别是第三场暴雨。文中通过定义低纬偏西风强度，讨论了强风带上强风速核的地域分布和传播特征。

Analysis of Summer Monsoon Activityduring the 1991 Excessively Torrential Rain over Changjiang-Huaihe River Valley

The features of monsoon activity and its role (Jianghuai) during the 1991 excessively torrential rain over Changjiang Huaihe River valley are analyzed. The results show that the first episodes of torrential rain occurs before the onset of summer monsoon and is mainly induced by synoptic systems in subtropical westerlies; while the activity of southwest monsoon becomes most important during the second and third episodes of torrential rain when subtropical high in West Pacific and southeast monsoon stay stably. The maintenance and break of Meiyu are as a result of the activity of southwest monsoon. A significant effect of southwest monsoon is to transport convective air from tropical area (Arabian Sea and the Bay of Bangal)to Jianghuai valley, thus the convective rain formed in the middle and late stages of the Meiyu is much stronger than that in the normal year, especially in the third episode. The distribution and propagation of strong wind core along southwest airflow are also studied.