2013年3月20日广东东莞罕见龙卷冰雹特征及成因分析

利用常规观测、NCEP/NCAR再分析、多普勒天气雷达及自动气象站资料等，对2013年3月20日发生在东莞的一次罕见龙卷、冰雹等致灾性强对流天气过程进行分析。结果表明：1）龙卷过境时的单站气压、温度、风向风速与雷雨大风过境时明显不同，前者具有较典型的龙卷特征。2）华南地区高低空强的风随高度增大的垂直变化、上干下湿的位势不稳定层结以及低层高湿、增温为对流天气发展提供了有利的环境条件，冷空气南压和近地面边界层中小尺度辐合系统为其提供了触发机制。3）中等强度的对流有效位能（CAPE）、强的0-6 km深层垂直风切变以及较强的0-1 km低层垂直风切变为龙卷产生提供了可能性。4）龙卷、冰雹强对流风暴的发展加强与近地面边界层中小尺度辐合系统加强有密切关系。5）同时出现冰雹、大风、龙卷时，最强回波为72 dBz；龙卷出现在超级单体的钩状回波附近，更靠近后侧V形缺口；多时次观测到三体散射（TBSS）回波，与降雹对应；反射率垂直剖面图上可见明显的低层弱回波区、中高层回波悬垂，有界弱回波区（BWER）先于龙卷20多分钟出现。径向速度图上，龙卷出现时超级单体风暴同时具有龙卷涡旋特征（TVS）和中气旋特征。

Analysis of a rare hail-producing tornado event on 20 March 2013in Dongguan,Guangdong Province

Based on conventional surface and upper-air data, reanalysis data from NCEP/NCAR, and nonconventional data from Doppler weather radar and surface automatic weather station （AWS）, we analyzed a disastrous severe convective weather event with rare tornado and hail on 20 March 2013 in Dongguan, Guangdong Province. The results are summarized as follows. 1） The pressure, temperature, wind direc-tion, and wind speed observed at the station passed over by the tornado clearly have different characteristics from those caused by thunder-storm gales. 2） The following factors provided a favorable atmospheric condition for the development of convections：the increasing strong wind with altitude in Southern China, the unstable potential stratification with the dry air above and humid air below, and the high humidity and temperature in the low-levels. Additionally, cold air moving southwards, and meso-and micro-scale convergence systems near the ground served as a trigger mechanism for the tornado event. 3） The genesis of the tornado is possibly resulted from the moderate convective available potential energy （CAPE）, deep and strong vertical wind shear between 0 and 6 km, and 0-1 km low level wind shear. 4） The strengthening of convective storms associated with the hail-producing tornado is closely related to the intensifying of the meso-and micro-scale convergence systems near the ground. 5） The strongest radar echo is 72 dBz, observed when hail, gale and tornado occurred simultaneously. The tornado occurred near the hook-shaped echo embedded in a supercell close to the rear V-shaped gap. Three body scattering （TBSS） echoes were ob-served multiple times, which corresponds to hails. The low-level weak echo region, and mid-and high-level echo pendency can be found in radar reflectivity vertical profiles, and the bounded weak echo region （BWER） emerges 20 minutes earlier than tornado. When tornado emerg-es, tornado vortex （TVS） and mesocyclone in the supercell storm can be found in the radial velocity chart.