2023年宜宾市“5.31”区域性暴雨特征及其成因

Characteristics and Causes of "5.31" Regional Rainstorm in Yibin

利用常规气象观测资料、FY4卫星资料、多普勒雷达资料和ERA5再分析资料,对2023年5月31日发生在宜宾市的区域性暴雨进行诊断分析。结果表明:(1)在副热带高压南落、高空低槽东移的大尺度背景下,回流冷空气与来自南海、孟加拉湾的暖湿气流在四川盆地南部交汇,配合高层辐散抽吸作用,造成了此次暴雨天气过程。(2)冷空气到来前,由地面辐合线触发热对流产生暖区降雨,热对流发生在温度梯度密集区偏暖一侧;随着冷空气南下,由冷空气、地形抬升触发强降雨,强降雨区随冷空气由北向南推进。(3)低层水汽通量辐合区与强降雨区吻合较好,对短临预报具有重要的参考意义。

The regional rainstorm occurring in Yibin on May 31,2023 was diagnosed and analyzed by using the conventional meteor-ological observation data,FY4 satellite data,Doppler weather radar and reanalysis data of ERA5.The results showed that:(1)Under the large-scale circulation situation of the subtropical high-pressure southward descent and the eastward movement of the upper trough,the cold air countered the warm and humid air from the South China Sea and the Bay of Bengal in the southern part of the basin,cooperated with the high-level divergence suction,resulting in regional rainstorm.(2)Before the arrival of cold air,the thermal convection was triggered by the ground convergence line to produce warm area rainfall,and the thermal convection occurred on the warm side of the temperature gradient intensive area.As the cold air moved southward,the heavy rainfall was triggered by the cold air and terrain uplift,and the heavy rainfall area advanced from north to south with the cold air.(3)The convergence area of the water vapor flux in the low layer was in good agreement with the heavy rainfall region,which was of great reference significance for the short-term weather forecast.