鄂西南一次早春强对流过程的多源资料分析

Analysis of an early spring convective weather event in southwest of Hubei province based on multi-source data

综合利用多普勒天气雷达、风廓线雷达、微雨雷达、二维视频雨滴谱仪、三维闪电监测网等多源探测资料对2020年2月14日发生在鄂西南一次伴有局地冰雹和雷雨大风的强对流过程进行了中小尺度特征分析,并探讨了分类强对流识别预警算法在强对流短临识别预警中的应用。结果表明:(1)由于鄂西南山地的阻挡作用,冷锋在宜昌北部南下缓慢,华北低槽、850 hPa低涡北部的暖式切变线和冷锋前侧不断渗入的冷空气在鄂西南交汇形成上干下湿的不稳定层结;中低层西南暖湿气流沿着低层锋区向鄂西南输送并发展,850 hPa切变线、地面冷锋和暖倒槽配合触发强对流发展加强,强冰雹发生在冷锋和暖倒槽交汇处。(2)风廓线雷达资料显示鄂西南处在地面冷锋前部暖倒槽中,持续增强的中高层西南急流和冷锋前侧不断渗入的冷空气有利于强对流的发生发展。(3)二维雨滴谱仪完整记录了降水过程的雨滴谱分布特征,粒子直径大多在1 mm以内,最大直径接近6 mm。(4)由微雨雷达探测的雨滴谱垂直分布特征可知,降水前期环境湿度低,蒸发作用明显;而在强降水时段,近地面雨滴碰并增长作用明显。(5)三维闪电观测网获得的闪电频次与雹暴单体的强度变化呈正相关,且两个雹暴单体的初次地闪分别提前于降雹30 min和33 min。(6)多普勒天气雷达探测到有界弱回波区、钩状回波等典型冰雹回波特征,而中气旋、中层径向辐合及高空辐散区的存在表明对流云内维持了较强的上升气流,有利于冰雹的生成生长。

The meso-and micro-scale characteristics of an early spring convective weather event in southwest of Hubei on February 14,2020 is analyzed comprehensively by using multi-source detection data such as Doppler weather radar,wind profile radar,micro rain radar,two-dimensional video disdrometer and three-dimensional lightning monitoring network,and then the application of the classified severe convective weather identification and warning algorithm is discussed.The results show that:(1)Because of the blocking effect of the moun⁃tains in southwest of Hubei,the cold front moves southward slowly in the north of Yichang,and an unstable stratification of upper dry and lower wet,induced by the intersection of the low trough of North China,the warm shear line in the north of the 850 hPa vortex and the cold air infiltrating in front of the cold front,forms in southwest of Hubei.Due to the combination of the warm and humid air of the mid-and low-level southwesterly flow transported along the lower frontal zone,the 850 hPa low level shear line,the surface cold front and the warm in⁃verted trough,the convection is triggered and intensified,and the strong hail occurs at the intersection of the cold front and the warm inverted trough.(2)The wind profile radar data indicate that the southwest of Hubei is located in the warm inverted trough in front of the surface cold front.The continuous enhancement of the middle-upper level southwesterly jet and the incessant infiltration of cold air in front of the cold front jointly stimulate the occurrence and development of strong convection.(3)Disdrometer results illustrate that the raindrop pattern cap⁃tured the accompanying precipitation process,with the particle diameter mostly within 1 mm and the maximum diameter close to 6 mm.(4)According to the characteristics of raindrop vertical distribution detected by the micro rain radar,due to the low environmental humidity in the early stage of precipitation,remarkable evaporation is existing;but in heavy precipitation period,the effect of coalescence and growth of raindrops near the ground is obvious.(5)The lightning frequency obtained by three-dimensional lightning monitoring network is positively correlated with the intensity variation of hailstorms,and the initial ground flash of two hailstorms is about 30 min and 33 min in advance of hailstone falling,respectively.(6)Doppler radar detected typical hail echo characteristics such as bounded weak echo area and hook-like echo,while the existence of mesocyclone,middle radial convergence and upper divergence area indicates that strong updraft is maintained in convective clouds,which is conducive to the generation and growth of hailstones.