川渝盆地东部两次典型西南涡 暴雨成因的对比分析与诊断

Cause Analysis and Diagnostic Analysis of Two Typical Southwest Vortex rainstorm Occurring in Eastern Sichuan Chongqing Basin

摘要:

利用FY-4A卫星资料、ERA5再分析资料及多源观测数据，分析了2022年6月22日、26日川渝盆地东部两次西南涡暴雨过程的降雨特征及发生条件，并通过热力条件及动力作用分析，对西南涡发展和维持机制进行了诊断。结果表明：两次过程有一定的相似性，强降水落区均位于低涡东侧及西南—东北走向的低空切变线附近。从两次过程的差异来看，“6.22”过程受热力作用驱动更明显，地表感热加热、对流层中上层感热加热和凝结潜热释放增温是西南涡发展的主要原因。“6.26”过程则是动力作用主导，其环流特征相较于前者更清晰，水汽及能量条件更好，而水平风场的辐合促进了局地涡度增大，导致西南涡发展强度更强、维持时间更长，因而产生了比“6.22”稍强的暴雨天气过程。

Abstract:

Based on FY-4A satellite data, ERA5 reanalysis data and multi-source observation data, the rainfall characteristics and occurrence conditions of two southwest vortex rainstorm processes in the east of Sichuan Chongqing Basin on June 22 and 26, 2022 are analyzed,and the mechanism for the development and maintenance of the southwest vortex is diagnosed through the analysis of thermal conditions and dynamic effects. The results show that there is a certain similarity between the two processes,and the strong downfall areas are located near the low-level shear line on the east side of the low vortex and the southwest northeast direction. From the difference between the two processes, it can be seen that the "6.22" process is more driven by thermal effects, and the main reasons for the development of the southwest vortex are surface sensible heating, sensible heating in the upper and middle troposphere, and the release of latent heat from condensation. The "6.26" process is dominated by dynamic action, and its circulation characteristics are clearer than the former, with better water vapor and energy conditions. The convergence of the horizontal wind field promotes the increase of local vorticity, leading to stronger development intensity and longer maintenance time of the southwest vortex, resulting in a slightly stronger rainstorm weather process than the "6.22" process.