摘要
2020年 5月 19日贵州在西北气流影响下发生了一次混合性强对流(冰雹、大风、强降水)天气过程,各家数值模式均漏报了此次过程.本文利用地面和高空观测资料、多普勒雷达资料、NCEP 1°×1°和ERA5 0.25°×0.25°再分析资料对该过程的强对流天气特征、中尺度环境条件、中小尺度对流系统演变和结构、触发和维持机制等进行分析.结果表明:(1)本次过程是在 500 hPa西北气流背景下发生在低层南风气流里的一次暖区强对流天气过程,由从孟加拉湾途经云南和从北部湾途经广西的两支暖湿气流交汇于贵州西北部触发形成,过程风雹特征显著,局地性强;(2)环境场特征表现为大气层结上干下湿、不稳定度大、对流有效位能(Convective Available Potential Energy,CAPE)较高、对流抑制(Convective Inhibition,CIN)能量较低以及垂直风切变较强;(3)雷达回波上表现为一个超级单体自西北向东南移动,出现了钩状回波、低层弱回波区、中高层回波悬垂、中气旋、垂直累计液态水含量高等典型特征;(4)边界层的中β尺度气旋性涡旋叠加地形影响造成的动力强迫抬升利于对流触发,用气块理论分析发现边界层动力强迫造成的气块抬升高度与水平辐合强度、垂直方向辐合高度、辐合持续时间密切相关,本次过程通过定量取值计算出的边界层动力强迫气块上升高度远大于大气自由对流高度,大气动力强迫转化为热力强迫,上升运动发展,对流风暴触发;(5)各家数值模式漏报主要原因为大气热力物理量,特别是CAPE值预报存在较大偏差.
Abstract
On 19 May 2020,a mixed strong convective weather process(hail,strong wind,and heavy precipitation)occurred under the influence of northwest airflow in Guizhou,and various numerical models omitted this process.Using ground and high-altitude observa-tion data,Doppler radar data,NCEP 1°×1° reanalysis data and ERA5 0.25°×0.25° reanalysis data,the weather characteristics,mesoscale environmental conditions,evolution and structure of medium-scale convective systems,trigger and maintenance mechanism of this con-vection were analyzed.The results show that:(1)This convection occurred in warm sector of the low-level southerly wind under the influ-ence of 500 hPa northwest airflow and was triggered by the intersection of two warm-humid air streams from the Bay of Bengal through Yunnan and from the Beibu Gulf through Guangxi in the northwest of Guizhou.The wind and hail characteristics were significant and the locality was strong in this process.(2)The characteristics of the environmental field were as follows:the upper layer of the atmosphere was dry and the lower layer was wet,the instability was large,the Convective Available Potential Energy(CAPE)was high,the Convect-ive Inhibition(CIN)energy was low,and the vertical wind shear was strong.(3)On the radar echo,a supercell moved from northwest to southeast with typical features such as hook shaped echo,low-level weak echo area,mid to high-level echo overhang,mesocyclone,high vertical cumulative liquid water content.(4)Dynamic forced uplift was beneficial for convective triggering under the influence of meso-scale-βcyclonic vortex and complex terrain.Using the gas block theory,the lifting height of the gas block caused by dynamic forcing was closely related to the strength of horizontal convergence,vertical convergence height,and convergence duration.In this process,the rising height(H)of the gas block calculated by quantitative values was much greater than the height of the free convection height(LFC),and the dynamic forcing was transformed into thermal forcing,leading to the development of rising movement,triggering a convective storm.(5)The main reason for numerical model omissions was a large deviation between the atmospheric CAPE forecast and the situation of the weather.
基金项目
贵州气象省市联合基金项目(QHLSSLJ[2022-04])
六盘水雷暴大风预报预警团队(GGTD-202204)
NETL
NSTL
万方数据