中文摘要：

采用NCEP再分析资料、常规观测资料、卫星云图资料及地面降水资料，对2004年9月2日～8日发生在川东和重庆的大暴雨的影响系统及其环境场作了分析研究。结果表明，此次暴雨分为三个阶段，降水系统主要有两个：第一、三阶段的主要降水系统是低空切变线；第二阶段的主要降水系统是西南低涡，而西南低涡影响期内的雨量最强、范围最大。西南低涡开始时为一口中尺度系统，最后发展达α中尺度系统。其影响时间从4日00时到6日06时（国际协调时），持续了54小时。本文对此次暴雨过程所做的研究表明，川东地区的特殊地形，500hPa高空小槽以及700hPa、850hPa低层鞍型流场均是西南低涡产生和维持的重要条件；西南低涡上层为暖性结构；在暴雨过程中有20个雨团接连发生，中尺度系统是这次暴雨的直接影响系统；对水汽收支的计算表明，水汽可能来自于低纬度热带地区。本文还对西南低涡与东北低涡的异同作了比较。

英文摘要：

Based on the 6-hour-interval reanalysis data with 1.0^9 × 1.0^9 resolution from NCEP/NCAR, station observational data and so on, the environment fields and the influencing systems of the heavy rainfall during 2 - 8 September 2004 are analyzed. The results show that there are 3 stages during the heavy rainfall, and there exist two main rainy influencing systems in the first and third stages, the main rainy influencing system is the low level shear lines; in the second stage, the southwest vortex, which is the low pressure or vortex to the east of the Tibetan Plateau in the lower troposphere, is the main rainy influencing system, and in the second stage, both the precipitation and the range of rainfall reach the maxima. In earlier stage, the southwest vortex is a meso-β-scale system, then it develops, and its diameter reaches 200 - 500 km, which belongs to the meso-α-scale system. It appears at 0000 UTC 4 September and disappears at 0600 UTC 6 September. It lasts 54 hours. In this paper, the heavy rainfall related to the southwest vortex is studied, and results indicate that the special terrain of eastern Sichuan, the trough at 500 hPa and the vortex at 700 hPa in the lower troposphere could be all favorable conditions contributing to the formation and maintenance of the southwest vortex; there are twenty rainy clusters during the heavy rainfall; it implies that mesoscale system is the direct influencing system; the result of the moisture budget computation shows that the water vapor could come from the low-latitude tropical region.