浙中一次多风暴类型强对流天气成因及多普勒雷达特征

Doppler Radar Characteristics of a Multi-storm Severe Convective Weather Event in Middle Zhejiang Province

利用常规资料、区域自动站加密资料、探空资料、GFS 0.25°×0.25°逐6h的分析场数据和SB多普勒天气雷达资料对2018年5月18日发生在浙中地区的一次强对流天气过程进行分析。结果表明:此次过程产生了脉冲风暴、中等到强多单体风暴和飑线这3种风暴类型,分别出现冰雹、大范围强降水和雷雨大风等强天气。3种风暴的雷达回波在回波形态、强度、垂直结构、平均径向速度、垂直累积液态水含量VIL等特征如下:①脉冲风暴呈块状,初始回波高度在6~9km,强回波所在高度在-10℃等温线附近,强回波值达60dBz以上,VIL值出现跃升且最大值在50kg·m^-2以上,冰雹出现在反射率因子核和VIL值迅速下降之后;②中等到强多单体风暴呈带状,大降水效率和“列车效应”是发生大范围强降水的主要原因,雷雨大风天气则与反射率因子核迅速下降、MARC、低层强辐散区有关;③飑线呈弓形回波形态,移速快,引起了大范围的雷雨大风天气。此次过程影响系统多,天气复杂,存在较大预报难点,在短时临近预报技术研究上有重要借鉴意义。

A severe convection process on 18 May 2018 is studied by the conventional observation data,GFS analysis field data with the spatial resolution of 0.25°×0.25°and temporal resolution of 6 hours,automatic weather station data,and SB Doppler radar data in the middle part of Zhejiang Province.It is demonstrated that this process triggered three types of storms:pulse storm,multi-cell storms and squall line.These storms were accompanied by the hail short-term heavy rain,thunderstorm and gale,respectively.The corresponding characteristics of the radar echoes of three storms are as follows:(1)The radar echoes of the pulse storm were in lumpy pieces.The initial height was 6 to 9 km and the heights of strong echoes were around the isotherm of-10℃.The strong intensity was up to 60 dBz.The VIL value increased rapidly and the maximum value was 50 kg·m^-2.The small hail and gale appeared after the rapid decrease of reflectivity and VIL.(2)The medium-to-strong multi-cell storms were in a belt-like distribution.The train effect and high precipitation efficiency were responsible for the wide range heavy precipitation.The gale was in relation to MARC(Mid-Altitude Radial Convergence)of the velocity product and strong convergence.(3)The squall line appeared to be a bow echo.It moved with high speed and caused the extreme gale and thunderstorm.This multi-storm severe convective process is of important significance for short-term weather forecasting in the future.