重庆永川2018年5月21日强对流天气过程分析

Analysis of the severe convective weather process in Yongchuan Chongqing on 21 May 2018

2018年5月21日夜间至22日白天,重庆市永川地区出现了一次强对流天气过程。为了更深入地认识强对流天气过程中大尺度系统与中小尺度系统的作用机制,提高永川地区强对流天气预报能力,该文利用常规地面观测资料、探空资料、多普勒天气雷达CINRAD/SA探测资料及FY4A卫星红外C011资料,采用天气动力学诊断方法,分析此次强对流天气过程。结果表明:①21日夜间至22日白天,中高纬度的低槽东移,副热带高压略有南移,中低层系统对峙,形成低涡切变线稳定少动,不断激发中小尺度扰动,使对流云团发展。②对流云团在低涡的辐合动力作用和暖湿条件下发展为MCC,孤立的对流单体发展成为飑线,东移过程中演变为弓形,大风出现在飑线强回波带、回波前沿,强降水主要发生在强回波区及回波后侧。③大气处于上干下湿的不稳定状态,强的CAPE指数、SI指数、K指数、LI指数显示热力、动力条件较好,同时垂直风切变较强,有利于飑线中的上升、下沉气流共存以及暖湿气流输送到发展的上升气流中,以致出现大风、短时强降水。中高纬度的低槽、副热带高压、低涡切变线等天气尺度系统与MCC、飑线等中小尺度系统共同作用,配合较好的热力、动力条件,以及较强的垂直风切变与水汽辐合中心,形成了此次强对流天气过程。

There was a severe convective weather process happened in Yongchuan,Chongqing from the night of May 21,2018 to the day time of May 22,2018.In order to understand the mechanism of the large-medium scale and the medium-small scale better in the process of severe convective weather,so as to improve the forecasting ability in Yongchuan area,the dynamic diagnosis method was adopted in this paper with the routine surface observation data,sounding data,Doppler radar CINRAD/SA data and FY4A satellite infrared C011 data,which could analyze the severe convective weather characteristics.The results show that:①From the night of May 21 to the day time of May 22,both of the low troughs in the middle and the high latitudes moved eastward,the subtropical anticyclone moved southward slightly,and the middle and low levels stood opposite each other systematically,forming a stable low vortex with shear line,which constantly stimulated medium-small scale system disturbing,thus generated the convective clouds.②And the convective clouds developed into MCC under the convergence dynamics of low vortex and sufficient warm and humid conditions.The isolated convection part became a squall line,and then a bow when moving eastward.The strong winds appeared in the strong echo zone and the front echo of the squall line,and the heavy rain mainly occurred in the strong echo area and the back of the echo.③The atmosphere was unstable because its upper part was dry,while the lower was wet.And it showed there were better thermal and dynamic conditions from the high CAPE index,SI index,K index and LI index.Meanwhile the vertical wind became stronger,which is helpful for the coexistence of upward and downward current of the squall line,and the warm moist airflow transferred to the upward current,then the strong wind and short-term heavy rain started.This severe convective weather only generated under the jointly affection of the low troughs in the middle and high latitudes,subtropical anticyclone,low vortex with shear line and the MCC and the squall line,together with fine thermal and dynamic conditions,strong vertical wind shear and water vapor convergence.