2021年6月末至7月初贵州持续暴雨维持机制分析

Analysis on the Maintenance Mechanism of Continuous Rainstorm in Guizhou from the End of June to the Beginning of July 2021

本文利用MICAPS平台提供的常规观测资料、区域自动站降水资料和NCEP1˚ ×1˚ 6 h再分析资料计算的相关物理量资料,对2021年6月28日~7月4日贵州持续暴雨天气过程进行分析总结。得出:① 此次持续暴雨天气过程是在亚洲中高纬度地区维持稳定双阻形势,西伯利亚地区冷涡低槽发展东移,槽底不断分裂短波槽从河套地区东移引导弱冷空气南下以及副高先东退后西伸北抬,云南和四川不断有短波槽东移影响贵州,中低层切变线长时间维持,为持续暴雨的发生发展提供了大尺度背景和动力抬升条件。② 中低层西南低空急流加强北抬并长时间维持,贵州长时间处于急流左侧高能高湿不稳定区,为暴雨的维持和发展提供了充足的水汽和能量条件。③ 涡度“低层辐合、高层辐散”的有利配置结构,使中低层系统得以发展和维持,为暴雨的发生提供了持续的动力条件;④ 地面弱冷空气夜间从河套或华北地区南下,使梅雨锋夜间增强活跃,其西段长时间在贵州境内维持摆动,触发持续暴雨天气,暴雨主要出现在夜间到早晨。

This paper uses the conventional observation data provided by MICAPS platform, the precipitation data of regional automatic stations and NCEP1˚ ×1˚ 6 h relevant physical quantity data calculated by reanalysis data to analyze and summarize the continuous rainstorm weather process in Guizhou from June 28 to July 4, 2021. It is concluded that ① The continuous rainstorm weather process is to maintain a stable double resistance situation in the middle and high latitudes of Asia. The cold vor-tex trough in Siberia develops and moves eastward, the trough bottom continues to split, and the short wave trough moves eastward from the Hetao area, guiding the weak cold air southward and the subtropical high retreats first eastward and then extends westward and northward. The short wave trough in Yunnan and Sichuan continues to move eastward to affect Guizhou, and the shear line in the middle and low layers is maintained for a long time, it provides a large-scale background and dynamic uplift conditions for the occurrence and development of continuous rainstorms. ② The southwest low-level jet in the middle and low levels strengthened its northward lift and maintained for a long time. Guizhou has been in the high-energy and high humidity unstable area on the left side of the jet for a long time, providing sufficient water vapor and energy conditions for the maintenance and development of rainstorms. ③ The favorable configuration structure of vorticity “low-level convergence and high-level divergence” enables the development and maintenance of the middle and low-level system, and provides continuous dynamic conditions for the occurrence of rainstorms;④ The weak cold air on the ground descends southward from Hetao or North China at night, making the Meiyu front more active at night. Its western segment has been swinging in Gui-zhou for a long time, triggering continuous rainstorm, which mainly occurs from night to morning.