贵州中北部一次冰雹和雷暴大风过程综合诊断

Comprehensive Diagnosis of a Hail and Thunderstorm Gale Process Occurring in North-central Part of Guizhou Province

2021年5月15日贵州省中北部发生了一次以冰雹和雷暴大风为主的强对流过程,最大瞬时风速达到44.3 m∙s^(−1),最大冰雹直径达到40 mm。基于MICAPS常规气象观测资料、欧洲中心ERA5逐小时再分析资料和多普勒雷达资料,对本次过程的天气系统配置、物理量场和雷达回波特征等进行综合诊断。结果表明:(1)500 hPa高原槽东移,槽后冷平流推动低层切变线南压,配合地面冷锋和辐合线活动,触发了本次强对流天气。(2)过程前后,贵州省中北部呈“上干下湿”和“上冷下暖”的结构特征,中低层西南急流带来充足水汽,K指数、△T(850~500)hPa显示大气层结呈较强不稳定状态,此外还有中等偏强的垂直风切变、适宜的0℃和−20℃层高度,整体表现为有利于冰雹、雷暴大风发生发展的环境。(3)雷达回波特征显示,午后地面辐合线附近多个雷暴单体生成发展,回波由团状变为弓状,高质心、高伸展且50~60 dBZ回波接地,表现出有界弱回波区、回波悬垂和前后向的V型槽口等特征,形成大冰雹和极端雷暴大风;夜间雷暴单体先分裂再弥合,强度减弱,形成层状云和积状云的混合云团,雷暴大风和短时强降水天气发生。

A severe convective process dominated by hail and thunderstorm gale occurred in north-central part of Guizhou Province on May 15,2021.The maximum thunderstorm gale wind speed reached 44.3 m/s,and the maximum hail diameter reached 40 mm.Based on the MICAPS routine meteorological data,ERA5 hourly reanalysis data of ECMWF and Doppler radar data of Guizhou Province,the weather system configuration,physical quantity fields and radar echo characteristics of this process were comprehensively diagnosed.The results show that:(1)The 500 hPa plateau trough shifted eastward,and the cold advection behind the trough pushed the low-level shear line southward,which triggered the strong convective weather with the surface cold front and convergence line activities.(2)Before and after the process,the central and northern parts of Guizhou Province were characterized by an“upper dry and lower wet”and“upper cold and lower warm”.The southwest jet stream in the middle and low levels brought sufficient water vapor.The K index,temperature difference between 850 hPa and 500 hPa indicated the strong atmospheric instability.Additionally,there was a moderately strong vertical wind shear,suitable 0℃and−20℃layer heights.Overall,this environment was favorable for the occurrence and development of hail and thunderstorm gales.(3)The radar echo characteristics showed that multiple thunderstorm cells were generated and developed near the ground convergence line in the afternoon.The shape of echoes changed from clumpy to arched,with high centroids and high extension heights,and the 50~60 dBZ echos were closed to the ground.The echo exhibited characteristics of bounded weak echo regions,echo overhangs,and V-shaped grooves in the forward and backward,causing heavy hail and extreme thunderstorm gale.During the night,thunderstorm cells split and then coalesced,resulting in weakened intensity,and becoming a mixed cloud cluster of stratiform and cumuliform clouds,causing thunderstorm gales and short-term heavy precipitation.