江淮地区弓状回波的分布和环境特征分析

Distribution and Environmental Characteristics of Bow Echoes over Jianghuai Region

本文结合探空、地面、再分析资料和强对流重要天气报文资料,分析江淮地区(30°~36°N、115°~122°E)弓状回波发生的主要环境条件和灾害性雷暴大风特征,重点利用我国2009—2012年新一代多普勒天气雷达资料,分析弓状回波时空分布和三维结构及其成灾机制。统计结果表明:弓状回波常发生在傍晚(17—20时),分布在安徽西北部到江苏东南部、山东东南部到江苏的西南部,以及安徽南部的两山地间的平原地区。其产生的极端大风(≥10级)占该地区极端大风的30%。产生弓状回波的天气背景主要是东北冷涡和高空槽,中等的对流不稳定度[平均对流有效位能(CAPE)为1780 J·kg^(-1)]和垂直风切变(平均1000~700 hPa风切变为11.6 m·s^(-1)),中层存在明显的干层。东北冷涡环境下的弓状回波系统具有较大的下沉对流有效位能(DCAPE)和地面的强冷池。根据雷达观测的结构,江淮地区弓状回波可分为三类:典型弓状回波(BE)类型、弓状回波复合体(BEC)类型和飑线型弓状回波(SLBE)类型,所占比例分别为28.6%、14.3%和57.1%。

This study examines the environmental conditions of bow echoes and the related damaging thunderstorm characteristics in Jianghuai Region(30°- 36°N,115°-122'°E) by using the sounding data,surface observations,reanalysis data as well as the severe weather reports in 2009- 2012.The Doppler weather radar data are also used to investigate the spatial and temporal distribution of bow echoes,as well as their three-dimensional structures and possible mechanisms in causing damaging gales.Statistical results show that bow echoes in Jianghuai Region preferentially occur in northwestern Anhui,southeastern Jiangsu,southeastern Shandong to southwestern Jiangsu,and the plain between two mountains in southern Anhui with the frequency maximum in the late afternoon.The extreme damaging gales(>24.5 m · s^(-1)) induced by bow echoes account for 30%of all the extreme damaging wind events.The typical synoptic systems associated with the bow echo are the northeast cold vortex CNECV) and upper-level trough,the moderate convective available potential energy(CAPE,1780 J · kg^(-1)) and vertical wind shear(11.6 m · s^(-1)between 1000 and 700 hPa),as well as a remarkable dry layer in the middle level.Compared with the environmental conditions affected by the upper-level trough systems,NECV is usually accompanied with a larger DCAPE and stronger cold pool on the surface.According to the structure of radar observations,bow echoes in Jianghuai Region are divided into three categories,including classic bow echo(BE),bow echo complex(BEC),and squall line bow echo(SLBE),which account for 28.6%,14.3%,and 57.1%,respectively.