2022年河南“7·25”雷暴大风天气成因分析

Analysis of the Causes of Thunderstorm and Windy Weather in Henan on July 25,2022

利用常规观测资料、区域自动站资料、雷达数据和NCEP 1°×1°逐6 h再分析资料等,对2022年7月25日河南雷暴大风的天气学成因进行了分析。结果表明:高层冷空气叠加在低层暖区之上形成的强烈位势不稳定层结及较强的垂直风切变,为强对流天气发生发展提供了有利的环境条件。700 hPa以下持续的西南气流对水汽输送和补充起到了重要作用。强对流区不稳定指数增大,对流有效位能(CAPE)、下沉对流有效位能(DCAPE)突增,且均大于河南强对流阈值,θ_(se)垂直递减率增大,为强对流提供了不稳定能量。对流层中高层有干冷空气侵入,使下沉气流蒸发加强,导致其气温急剧下降,形成地面冷池和小高压。当1 h正变压中心≥2.6 hPa,1 h变温中心下降达6℃以上,且强对流上下游的1 h变压差值≥3.2hPa时,1 h变温≤-4℃的地面冷池附近对应着国家基本气象站和气象观测站分别出现19~30 m·s^(-1)(8~11级)和25~38 m·s^(-1)(10~13级)的大风。地面中尺度辐合线促使对流云团的生成发展,云团发展强盛阶段移动加快(50~70 km·h^(-1))。雷暴大风、强降水发生在云团前沿TBB等值线梯度大值区和TBB≤210 K的冷云区。造成雷暴大风的主要雷达特征为阵风锋、飑线、弓形回波、中气旋;飑线回波尺度大(200~300 km),中心强度强(60~70 dBZ),强回波顶高(7~8 km),移速快(55~70 km·h^(-1))。飑线的形成和发展是造成河南中东部发生大范围雷暴大风的主要原因。

Based on conventional observation data,regional automatic station data,radar data and NCEP 6 h 1°×1°reanalysis data,the synoptic causes of thunderstorm gale in Henan on July 25,2022 are analyzed.The results show that the superposition of high-level cold air on the low-level warm area formed strong potential instability stratification and strong vertical wind shear,which provided favorable environmental conditions for the occurrence and development of severe convective weather.The continuous southwest airflow below 700 hPa played a role in water vapor transport and replenishment.The instability index of strong convection area increased,the CAPE and DCAPE suddenly increased,both greater than the threshold of severe convection in Henan,and the vertical lapse rate ofθse increased,which provided unstable energy for severe convection.The invasion of dry cold air in the middle and upper troposphere intensified the evaporation in downward airflow,resulting in a sharp drop in its temperature and the formation of a ground cold pool and a small high pressure.When the 1 h positive pressure change center was≥2.6 hPa,the 1 h temperature change center dropped by≥6℃;when 1 h pressure change difference between the upwind and downwind of severe convection was≥3.2 hPa,in the cold pool with 1 h temperature change≤-4℃,there were very strong winds corresponding to the gales measured at national basic weather station with 1930 m·s^(-1)(wind force of Scale 811)and meteorological observation station with 2538 m·s^(-1)(wind force of Scale 1013).Mesoscale convergence line on the ground intensified the formation and development of convective cloud clusters,and the cloud clusters moved faster at the speed of 5070 km·h^(-1)in their strong developing stages.Thunderstorms with strong winds and heavy precipitation occurred in the TBB contour gradient area at the front of the cloud cluster and the cold cloud area with TBB≤210 K.The radar features that caused thunderstorm gale were mainly the gust front,squall line,bow echo and meso-cyclone.The scale of the squall line echo was large(200300 km),the center intensity was strong(6070 dBZ),the strong echo top was high(78 km),and the moving speed was fast(5570 km·h^(-1)).In a word,the formation and development of squall line was the main reason for the occurrence of large-scale thunderstorm and gale in central and eastern Henan Province.