吉安一次雷暴大风的中小尺度特征

Small and Medium-Scale Characteristics of a Thunderstorm in Ji'an

利用常规气象观测资料、地面自动加密站资料、探空资料、雷达资料及闪电定位资料等对2020年3月22日吉安雷暴大风天气的中小尺度系统演变特征进行分析。结果表明:1)强的位势不稳定层结,中低层(0~6 km、0~3 km)强的环境风垂直切变(≥20 m/s)以及中层干冷、低层暖湿的环境场特性有利于强风暴发生发展;2)边界层、地面中尺度辐合线和弱冷锋是此次强风暴天气的主要触发机制;3)较强的下沉对流有效位能(DCAPE)对强风暴出现的预测具有较强指示意义,短时阵性大风发生前后20 min内地面气象要素场变化具有明显的中小尺度系统特征;4)飑线回波整体移动迅速,强风暴天气发生于飑线前部中尺度对流系统中,大风发生在“弓形”回波前部凸起对流不稳定区;5)此次雷暴大风过程以负地闪为主,正地闪不明显,且负地闪频数在阵性大风出现前呈爆发性增长,大风则出现在负地闪频数最大时刻,该时刻较地面阵性大风出现提前20 min左右,负地闪开始下降时刻与地面强降水开始时刻对应。

Based on conventional meteorological observation data,ground automatic encryption station data,radiosonde data,radar data and lightning location data,the evolution characteristics of medium and small scale system of thunderstorm and gale weather in Ji'an on March 22,2020 are analyzed.The results show that:1)strong potential instability stratification,strong vertical wind shear(≥20 m/s)in the middle and low levels(0~6 km,0~3 km),dry and cold in the middle level and warm and wet in the low level are conducive to the occurrence and development of severe storms;2)Boundary layer,the surface mesoscale convergence line and the weak cold front are the main trigger mechanisms of the severe storm;3)The strong downwelling convective effective potential energy(dcape)has a strong indicative significance for the prediction of severe storms.The changes of surface meteorological elements within 20 minutes before and after the occurrence of short-term gusts have obvious characteristics of medium and small-scale system;4)The strong storm occurred in the mesoscale convective system in front of the squall line,and the strong wind occurred in the convective instability area of the bow echo;5)The thunderstorm gale process is mainly negative to ground lightning,positive to ground lightning is not obvious,and the negative to ground lightning frequency increases explosively before the occurrence of paroxysmal gale,while the gale occurs at the moment of maximum negative to ground lightning frequency,which is about 20 minutes earlier than the occurrence of paroxysmal gale on the ground,and the time when the negative to ground lightning begins to decline corresponds to the beginning of heavy rainfall on the ground.