2020年8月10~14日四川盆地一次持续性暴雨过程特征及成因分析

Characteristics and Cause Analysis on a Continuous Severe Rainstorm Process in Sichuan Basin from August 10 to 14,2020

利用ERA-interim再分析资料和国家自动站观测资料,分析了四川盆地2020年8月10日~14日一次持续性强降水过程的特征及成因。结果表明:天气尺度系统的有效配合给此次暴雨过程提供了有利的环流背景,在冷空气及西南水汽的汇聚下,触发此次持续性强降水,整个过程可分为4个阶段,降水带自盆地西部向东移动;各暴雨区在强降水时刻,低层正涡度、负散度的强辐合,高层负涡度、正散度的强辐散抽吸作用均利于大气的上升运动,给持续强降水提供动力条件;相较于第二、三阶段,第一、四阶段的涡度、散度及垂直速度数值明显偏小,使得累计降水量偏少;各阶段降水过程的强降水中心、水汽辐合、上升运动区均位于中、低层低值系统(高原低涡、西南低涡、切变线)的东南侧;第二阶段降水过程中较强的水汽辐合及整层大气一致且极强的上升运动将水汽抬升输送至对流层中高层,导致该阶段累计降水量最大。

The ERA-interim final-analysis data,precipitation data of national automatic stations are used to analyze the characteristics and causes of a continuous server rainstorm in Sichuan Basin from August 10 to 14,2020.The results show that the precipitation process was divided into four stages,and the precipitation zone moved from southwest to northeast of the basin.The effective coordination of synoptic scale system provided favorable circulation background,with the cooperation of cold air and the warm moist flow,the continuous severe rainstorm occurred.At the time of heavy precipitation in each rainstorm area,the strong convergence of positive vorticity and negative divergence in the lower layer and the strong divergence of negative vorticity and positive divergence in the upper layer were conducive to the upward movement of the atmosphere,providing dynamic conditions for the continuous server rainstorm.Compared with the second and third stages,the vorticity,divergence and vertical velocity in the first and fourth stages were obviously smaller,which made the less accumulated precipitation.The rain storm center,the water vapor convergence center and ascending region in each stage were all located in the southeast of the low-value system in the middle and low level.In the second stage,the strong water vapor convergence and the consistent and strong upward movement of the atmosphere uplifted and transported the water vapor to the middle and upper troposphere.Therefore,the accumulated precipitation in the second stage was the largest.