河北“23·7”特大暴雨过程的多尺度特征分析

Multi-scale Characteristics of the Torrential Rainfall in Hebei Province in July 2023

利用常规观测资料、ERA5再分析资料、FY-4G卫星的云顶亮温(Black Body Temperature,TBB)数据对河北地区2023年7月29日至8月2日出现的特大暴雨过程的大尺度环流背景及动、热力和水汽条件进行了分析。结果表明:暴雨期间副高与大陆高压打通,在河北北部形成了准东西向的“高压坝”,台风“杜苏芮”登陆后减弱为低空气旋,该气旋在副高西侧气流的引导下北上,受“高压坝”阻挡停滞于山西一带,在暴雨区上空形成东高西低的有利环流形势;中尺度对流系统在暴雨期间呈阶段性特征反复出现,先后以大范围的螺旋雨带、集中的旺盛对流、零散的对流云团对暴雨的维持产生了重要影响,降水的落区与TBB低值区对应较好;暴雨期间水汽条件充足,低空存在大范围的水汽辐合中心,低涡倒槽、暖式切变线和偏东南急流影响为暴雨提供了强盛的上升气流,太行山对水汽及气流的阻挡作用使得降水强度增强。

The large-scale circulation background and the dynamic,thermal,and water vapor conditions of the heavy rainstorm in Hebei Province from 29 Jul to 2 Aug 2023 were analyzed using conventional observation data,ERA5 reanalysis data,and Black Body Temperature(TBB)obtained from Satellite FY-4G.The results show that the subtropical high and continental high were connected during the rainstorm,forming a quasi-east–west“high-pressure barrier”in the north of Hebei Province.Typhoon Doksuri weakened to a low-level cyclone after landing,and under the guidance of the western flow of the subtropical high,it moved northward and stalled in Shanxi Province due to the“high-pressure barrier”,forming a favorable circulation background of high east and low west over the rainstorm area.The evolution of a mesoscale convective system involved during heavy rainstorms has complex characteristics,with widespread spiral rain bands,concentrated vigorous convection,and scattered convective clouds successively,significantly impacting the maintenance of heavy rainfall.The precipitation fallout zone corresponds well with the center of the TBB low value.The widespread center of moisture convergence in the low levels during heavy rainfall,combined with adequate moisture conditions,played a crucial role.The influence of the vortex inverted trough,warm shear,and the south–easterly low-level jets provided strong updrafts for the rainstorms,and the blocking effect of the Taihang Mountains on the involved water vapor and air currents intensified the precipitation.