2022年7月18—20日贵州持续性暴雨天气过程分析

Analysis of Continuous Rainstorm Process in Guizhou from July 18 to 20,2022

利用FNL 1°×1°再分析资料、FY-2H卫星TBB资料及常规气象观测资料,对2022年7月18—20日发生在贵州的一次持续性暴雨天气过程进行分析。结果表明:西太平洋副热带高压的西脊点在112°~116°E之间稳定维持,对850 hPa切变线的南压有阻碍作用,造成中尺度对流系统MCS在切变线附近发展增强,从而形成了此次持续性暴雨天气;强降水区上空700 hPa比湿≥11 g·kg^(-1),850 hPa比湿≥16 g·kg^(-1),且850 hPa水汽通量散度达-7×10^(-5)g·hPa^(-1)·cm^(-2)·s^(-1)以上,从近地面到300 hPa为一致的上升运动,其中心值达-1 Pa·s^(-1),近地面有高能舌存在,其中心值达360 K,同时低层暖平流和中层冷平流的共同作用降低了层结稳定度,为能量和潜热的释放提供了有利条件,进而增强了上升运动;在强降水发生的第Ⅰ阶段MCS呈团状结构,其大范围的云顶亮温TBB<-70℃,表明云体内上升运动发展强烈,是造成第Ⅰ阶段降水强度大的主要原因,当中α尺度对流云团分裂为多个中β尺度时,降水强度达到最强;第Ⅱ阶段和第Ⅲ阶段的MCS呈带状结构,其TBB<-70℃的范围较小,且产生暴雨的区域内TBB大多在-60℃左右,表明此阶段云体内的上升运动强度小于第Ⅰ阶段,降水强度远弱于第Ⅰ阶段,但由于云带在贵州中部一带稳定维持超过14 h,是造成第Ⅲ阶段暴雨影响区域最广,累积降水量最大的重要原因。

FNL 1°×1°reanalysis data,FY-2H satellite TBB data and conventional meteorological observation data are used to analyze a continuous rainstorm weather process that occurred in Guizhou from July 18 to 20,2022.The results show that the western ridge of the Western Pacific subtropical high was stable between 112°and 116°E,which hindered the southward movement of the 850 hPa shear line and caused the mesoscale convective system(MCS)to develop and strengthen near the shear line,thus forming the continuous rainstorm weather;the specific humidity of 700 hPa over the heavy rainfall area is more than 11 g·kg^(-1),850 hPa more than 16 g·kg^(-1),and the divergence of water vapor flux at 850 hPa is more than-7×10^(-5)g·hPa^(-1)·cm^(-2)·s^(-1).From near ground to 300 hPa,there is a consistent upward movement,its central value is -1 Pa·s^(-1),and there is a high-energy tongue near the ground,its central value is 360 K,meanwhile,the combined action of the low level warm advection and the middle level cold advection reduced the stratification stability and provided favorable conditions for the release of energy and latent heat,enhancing the ascending motion;in the first stage of heavy precipitation,the MCS showed a clumpy structure,and most of the cloud top brightness temperature(TBB)in the MCS region was lower than-70℃,indicating that the rising motion in the cloud body developed strongly,which was the main reason for the high precipitation intensity of the first stage,and when the scale of convective cloud split from the meso-αscale to the meso-βscale,the precipitation intensity reached the maximum;the MCS in the second and third stages showed a banded structure.The range of TBB below-70℃was small in the MCS,and the TBB in the rainstorm area was mostly around-60℃,which indicated that the intensity of upward movement in the cloud body was smaller than that in the first stage.Therefore,the precipitation intensity in the second and third stages was much weaker than that in the first stage.However,since the cloud belt was stable in the central part of Guizhou for more than 14 hours,the third stage rainstorm had the widest impact area and the largest cumulative precipitation.