一次西南涡东移诱发的川渝暴雨诊断分析

Diagnostic Analysis of the Heavy Precipitation in Sichuan and Chongqing Caused by Eastward Shift of Southwest Vortex

摘要: 利用NCEP-FNL 1˚ × 1˚格点再分析资料和中国自动站与CMORPH小时降水融合产品降水资料，通过对大气环流背景、动力和热力作用以及水汽输送分析，对2017年7月5~6日在川渝地区一次西南涡东移诱发的强降水过程进行了诊断分析。结果表明：西南涡结构随其自身的移动而变化，雨带主要分布在低涡中心区和低涡移动方向的右前方，并且当西南涡中心移动时，雨带也随之移动，降水强度则随着西南涡强度增强而增加。强降水区域上空低层辐合，高层辐散明显，上升运动强烈，为暴雨的发展和维持提供了动力条件。暴雨发生前储存了大量的不稳定能量，来自孟加拉湾和南海的暖湿空气为此次暴雨提供了充足的水汽。湿Q矢量诊断分析表明，散度辐合区与降水区相吻合，且低涡中心强度、降水量大小与其辐合强度呈正相关，能较好诊断暴雨区域和强度。

Abstract: By using the NCEP-FNL 1˚ × 1˚ reanalysis data and China automated station and CMORPH kour pre-cipitation fusion products precipitation data, the circulation background, atmospheric dynamics, water vapor, thermal effects, and the non-geostrophic wet-Q vector were analyzed. The results show that the structure of the southwest vortex changes with its movement, and the rain belt is mainly distributed in the center of the low vortex and the right front of the low vortex. Precipitation intensity increases with southwest vortex intensity. Low-level convergence, high-level divergence and strong upward movement are found above precipitation center which provide the dynamic conditions for the development and maintenance of heavy rain. The lower tropospheric temperature in the lower troposphere decreases with height, indicating that a large amount of unstable energy is stored in the event of heavy rain. Warm and humid air from the Bay of Bengal and South China Sea provided sufficient water vapor for the storm. The convergence of wet-Q vector divergence coincides with the precipitation area during this precipitation, and the vortex center intensity and precipitation are positively correlated with their convergence strength, so they can be used to diagnose the torrential rain area and intensity.