2013年4月29日皖西南强风暴天气雷达资料分析

Analysis of a severe storm in southwest Anhui on 29 April 2013 based on radar data

2013年4月29日下午皖西南的安庆市和东至县发生了一次冰雹、雷雨大风强天气过程。本文以九江雷达资料为主,辅以GFS预报场和地面资料,重点对风暴单体雷达特征、雷达物理量参数演变规律进行了分析。结果表明:(1)雷达反射率因子图上,强风暴单体为涡旋状回波,回波前沿存在反射率因子高梯度区;速度图上涡旋状回波区对应着连续出现中气旋的现象,说明强风暴单体为具有涡旋形态的超级单体;强风暴顶高于11 km,大于50 dBz的强反射率因子高度超过-20 C层的高度等特征是产生大冰雹的重要指标。(2)风暴和中气旋参数分析表明,冰雹发生在最大反射率因子高度(HT)和风暴顶高(TOP)出现最强值的上升阶段中,最大垂直液态水含量(VIL)为58 kg·m-2,最大反射率因子(DBZM)极值为77 dBz;VIL密度(DVIL)≥4.0 g·m-3的持续时间达1 h以上,其最大值超过6.0 g·m-3。(3)该过程大冰雹产生在最大DVIL值出现后半小时,在DVIL为5.0 g·m-3时且在高梯度区附近出现;大风出现在中气旋持续时间较长和中气旋位置较高的时候。

A severe storm occurred at Anqing City and Dongzhi County on 29 April 2013. The radar echo characteristics and the evolution of physical parameters of the storm cell were analysed based on Jiujiang radar data and ancillary data from GFS forecast fields and surface con-ventional observations the results are as follows.⑴Radar reflectivity indicates that the severe storm has a vortex-shaped echo. High reflectiv-ity gradient area was observed in front of the vortex-shaped echo. The fact that the vortex-shaped area in the velocity map had a continuous mesoscale cyclonic flow indicates that the severe storm was a supercell storm. The top of the severe storm was taller than 11 km, above the-20℃level height, which is considered to be an important indicator for the storm to produce large hails.⑵Based on storm and meso-cy-clone parameters, hails occurred when the height of the maximum reflectivity （HT） and the storm top height （TOP） were increased to their peak values. The maximum vertically integrated liquid water （VIL） was 58 kg＆#183;m-2, and the maximum reflectivity （DBZM） was 77 dBz. The VIL den-sity （DVIL） with value greater than 4.0 g＆#183;m-3 lasted for more than 1 hour, and its maximum reached over 6.0 g＆#183;m-3.⑶In this severe storm case, large hails occurred half hour after the maximum DVIL was observed, where DVIL had the largest gradient with a value of 5.0 g＆#183;m-3. Strong wind was found when the meso-cyclone persisted relatively long in duration and high in altitude.