2016年7月华北特大暴雨过程河北南部垂直风切变观测特征

Vertical Wind Shear Observational Characteristics in South Hebei During the Torrential Rain Process in North China in July 2016

利用气象观测站小时雨量、不同探测手段得到的高空风资料,对2016年7月19—20日华北特大暴雨过程中河北南部降雨不同阶段水平风的垂直变化特征进行分析。结果表明:(1)在河北南部,太行山沿山一带到山前平原、平原东部分布着两片短时强降雨区,前者强度更强,体现了地形迎风坡对降雨的增幅作用。(2)本次过程中,3种探测手段计算的深层垂直风切变具有一致的变化规律。西部山区和山前平原降雨显著增强阶段,环境风维持强深层垂直风切变,相应的u风差也显著增强,有利于迎风坡降雨增强。降雨结束时,深层垂直风切变为弱垂直风切变。(3)强降雨阶段,水平风垂直切变矢量基本上呈现单一方向顺时针切变,且低层风垂直切变较大。降雨结束阶段,水平风垂直切变矢量方向变化复杂。(4)太行山脉高度以下的东风不断增强,最大东风分量达到8~28 m/s,有利于山区和山前降雨的增强。

Based on hourly rainfall data from automatic meteorological stations,upper horizontal wind data by different detection methods in South Hebei,this study explored the observational characteristics of upper horizontal wind data with different precipitation stages during the torrential rain in 19-20 July 2016. It is found that,firstly,two short-time heavy rainfall regions appeared along the Taihang Mountains to the piedmont plain,and eastern plain in south Hebei,while the former was more intensive and relating to the terrain. Secondly,the deep vertical wind shear calculated by different detection methods had similar varying tendency;Strong deep vertical wind shear was maintained at the stage of rainfall increasing significantly in the western mountain to the piedmont plain,and the difference of the zonal wind speed correspondingly increased too,strengthening the rainfall in the windward slope. The deep vertical wind shear became weak after the rain. Thirdly,at the stage of heavy rain,horizontal wind vertical shear vector had significant clockwise-curved attribute and strong low-level vertical wind shear magnitude,and after the rain,horizontal wind vertical shear vector had clutter attribute. Finally,the easterly wind speed below the height of the Taihang Mountains was increasing,with the maximum easterly wind speed up to 28 m/s,which was in favor of strengthening the rainfall along the Taihang Mountains to the piedmont plain.