黔西南一次中β尺度强对流天气分析

Analysis of a Meso-βScale Severe Convective Weather in Southwest Guizhou

2020年5月2日,黔西南出现中β尺度的强对流天气,安龙钱相出现42 m•s^(-1)灾害性大风,最大冰雹直径普安罗汉25 mm,最大小时雨强册亨站66 mm•h^(-1)。对常规地面观测资料、高空观测资料、多普勒天气雷达资料以及NOAA的HYSPLIT模式同期驱动资料等分析,结果表明:①本次过程主要受高空槽、中低层切变线、地面辐合线、云南热低压等系统共同影响;②大气不稳定层结明显,抬升凝结高度较低,20时百色探空呈“沙漏”结构,0~6 km强垂直风切变、高干暖盖指数、对流层中层为明显干层、高层动量下传均利于雷暴大风的形成;湿球温度0℃层高度和-20℃层高度利于大冰雹生长;水汽充沛有利于短时强降水,后向轨迹模式HYSPLIT模拟出4条兴仁站水汽输送路径:本地、西、西南、东北路径;③过程中卫星红外云图上为椭圆形雹暴云团发展移动,TBB中心低于-60℃,对流云顶伸展较高;④3条回波路径均为西北—东南方向;大冰雹发生时,雷达回波呈现“钩状”、三体散射长钉、回波悬垂、风暴顶强辐散、垂直液态含水量跃增、高回波顶高等特征;短时强降水发生时,存在回波质心低、低层强烈径向辐合、雷达产品雨强大等特点;⑤安龙钱相发生灾害性大风时,65 dBz反射率因子核位于6 km,回波梯度大,反射率因子核迅速下降,存在侧向入流槽口、径向正负速度对、深厚中层径向辐合、风暴顶强烈辐散、明显旋转等特征,正速度模糊达35 m•s^(-1);特殊地形的“狭管效应”对产生本次灾害性大风有增幅作用。

A meso-βscale severe convective weather occurred in Southwest Guizhou on May 2,2020.A disastrous gale of 42 m•s^(-1) occurred in Anlong,Qianxiang,and the maximum hail diameter was 25 mm in Luohan in Pu'an and the maximum hourly rainfall was 66 mm/h at Ceheng station.The conventional ground observation data,high altitude observation data,Doppler weather radar data and NOAA HYSPLIT model synchronous driving data are used to analyze the weather process.The results are as follows:①This process is mainly affected by the high altitude trough,the shear line of the middle and low levels,the surface convergence line and the Yunnan thermal low pressure.②The atmospheric unstable stratification is obvious.The elevation and condensation height is low and the sounding of Baise presents"hourglass"structure at 20:00.The strong vertical wind shear of 0-6 km,high dry warm cover index,obvious dry layer in the middle troposphere and momentum downward transmission in the upper troposphere are conducive to the formation of thunderstorm and gale.The height of wet bulb zero layer and-20℃layer are conducive to the growth of hail.And the good water vapor condition is conducive to short-term heavy precipitation.The backward trajectory model HYSPLIT simulates four water vapor transport paths of Xingren station:local,West,southwest and northeast;③In the process,the satellite infrared image shows that the elliptical hailstorm cloud cluster develops and moves,the TBB center is lower than-60℃,and the convective cloud top extends higher;④The three echo paths are northwest southeast;when the hail occurs,the radar echo presents the characteristics of"hook",three body scattering spike,echo hanging,strong divergence at the storm top,vertical liquid water content jump,high echo top and so on;when the short-term heavy rainfall occurs,the echo center is low,the low-level strong radial convergence,and the radar product rain is strong;⑤When the disastrous gale occurred in Anlong Qianxiang,the 65 dBz reflectivity factor core was located at 6 km,the echo gradient was large,and the reflectivity factor core decreased rapidly.There were lateral inflow slot,radial positive and negative velocity pairs,radial convergence in deep and middle layers,strong divergence at the top of the storm,obvious rotation and other characteristics,and the positive velocity ambiguity reached 35 m•s^(-1).The"narrow tube effect"of topography has an increasing effect on the occurrence of this disastrous gale.