热带气象学报2024，Vol.40Issue(3)：411-424,14.DOI:10.16032/j.issn.1004-4965.2024.037
2020年夏季一次暴雨事件伴随干侵入的位涡及垂直运动诊断分析
Diagnostic Analysis of Potential Vorticity and Vertical Motion in a Torrential Rainfall Event Associated with Dry Intrusion in the Summer of 2020
摘要
Abstract
In the summer of 2020,frequent rainstorm events hit the Yangtze River Basin(YRB)in China.These rainstorms were closely related to the southward intrusion of high-value potential vorticity(PV)at the mid-to-high latitudes.Based on observational data and ERA5 reanalysis data,the dynamic mechanism of a rainstorm process in early July 2020 was investigated through PV diagnosis,vertical velocity decomposition,and backward trajectory tracking simulation.The results show that the southward PV intrusion,which was often coupled with dry intrusion processes,was related to the amplification of trough and ridge systems,as well as the PV advection caused by their convergence/divergence processes in the upper troposphere.Dynamically,the high-value PV intrusion in the upper troposphere and the PV development in the lower level jointly resulted in the tilting of isentropic surfaces,which was reflected in the change of vertical velocity component caused by the displacement of isentropic surfaces.The development of the vertical velocity component in relation to descending motion was attributed to the upper-level northerlies gliding along the isentropic surfaces,leading to a dry intrusion process.On the other hand,the southerlies continued to move along the sloping isentropic surfaces,persistently transporting water vapor upward.In such a manner,the condensation process accompanying the water vapor uplift further led to the development of the vertical velocity component related to non-diabatic heating,thereby reinforcing the vertical motion and triggering convection.After the onset of the convective motion,strong rainfall caused significant latent heat release in the middle and lower troposphere,which led to PV due to its vertical distribution that increased with height in the lower level.The enhanced vortices further promoted rainfall development by affecting the isentropic surface structure and vertical motion.It is the positive feedback mechanism among the PV,strong rainfall,and the three vertical motion components that maintained and promoted the rainstorm over the YRB.关键词
位涡/暴雨/干侵入/垂直运动/后向轨迹追踪Key words
potential vorticity/rainstorm/dry intrusion/vertical motion/backward trajectory tracking分类
天文与地球科学引用本文复制引用
金趁意,张冠舜,龙雨青..2020年夏季一次暴雨事件伴随干侵入的位涡及垂直运动诊断分析[J].热带气象学报,2024,40(3):411-424,14.基金项目
国家自然科学基金项目(42205065)资助 （42205065）
