安顺一次罕见秋季特大暴雨天气分析

Analysis of a Rare Autumn Rainstorm in Anshun

利用FNL 1°×1°再分析资料、FY-2F卫星TBB资料及常规气象观测资料,对2020年9月14日发生在贵州安顺的1次罕见秋季暴雨天气过程进行分析。结果表明:副热带高压东退,引导短波槽东移和低涡切变线南压,为暴雨的发生提供了有利的天气尺度背景条件;强水汽辐合中心稳定维持在安顺,暴雨中心与水汽辐合中心相对应;暴雨区上空低层暖平流和中层冷平流的叠加,利于上升运动的发展,为能量和潜热的释放提供有利条件;中尺度对流云团在生成阶段发展迅速,成熟以后减弱缓慢,并在安顺上空稳定少动,是导致全市范围出现暴雨到特大暴雨的主要原因,且暴雨区与TBB≤55℃的区域对应较好;在对流云团生成的区域,其水汽、能量和抬升条件均较好,在对流云团东移影响的区域,大气层结不稳定,湿层深厚,但能量条件较差,导致此次暴雨过程的对流性不是很强,在降水最强时段,小时雨强大多在20~40 mm·h^(-1)之间。

Using FNL 1°×1°reanalysis data,FY-2F satellite TBB data and conventional meteorological observation data,the process of a rare autumn rainstorm that occurred in Anshun,Guizhou from September 13 to 14,2020 was analyzed.The results show that the eastward retreat of subtropical high leads the eastward movement of short-wave trough and the southward pressure of low vortex with shear line,which provides favorable synoptic scale background conditions for the occurrence of heavy rain.The strong water vapor convergence center remained stable in Anshun,and the rainstorm center corresponded to the water vapor convergence center.The superposition of warm advection in the lower layer and cold advection in the middle layer in the rainstorm area is beneficial to the development of ascending motion and provides favorable conditions for the release of energy and latent heat.The mesoscale convective cloud developed rapidly in the generation stage,weakened in intensity and moved slowly after maturity,and moved steadily and rarely over Anshun,which was the main reason for the occurrence of rainstorm to extremely heavy rainstorm in the whole city,and the rainstorm area corresponded well to the area with TBB≤55℃.On the one hand,the atmospheric water vapor,energy and uplift conditions are good where the convective cloud cluster is generated.On the other hand,in the area affected by the eastward movement of the convective cloud cluster,the atmospheric stratification is unstable and the wet layer is deep,but the energy conditions are poor.Therefore,the convective property of the rainstorm process is not very strong,and the hourly rainfall intensity is mostly between 20 and 40 mm per hour during the period of strongest rainfall.