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

作　　者：金趁意 张冠舜 龙雨青 JIN Chenyi;ZHANG Guanshun;LONG Yuqing(Shangqiu Meteorological Service,Shangqiu,Henan 476000,China;Guangzhou Institute of Tropical and Marine Meteorology,China Meteorological Administration,Guangzhou 510641,China;Guangdong Provincial Key Laboratory of Reginal Numerical Weather Prediction,Guangzhou 510641,China)

机构地区：[1]河南省商丘市气象局,河南商丘476000 [2]中国气象局广州热带海洋气象研究所,广东广州510641 [3]中国气象局/广东省区域数值天气预报重点实验室,广东广州510641

出　　处：《热带气象学报》2024年第3期411-424,共14页Journal of Tropical Meteorology

基　　金：国家自然科学基金项目(42205065)资助。

摘　　要：2020年夏季我国长江流域频繁的暴雨事件与中、高纬度高位势涡度(简称位涡)南侵过程有关。基于观测和ERA5再分析资料,本文利用位涡诊断、垂直速度分解以及后向轨迹追踪模拟的方法对7月上旬一次暴雨过程进行了动力学归因研究。结果表明:中、高纬度高位涡的侵入往往伴随干侵入的发生,高位涡南侵与高层槽、脊系统振幅增大及其辐合/辐散过程对位涡的平流有关。动力上,高位涡侵入和低空位涡增强会导致等熵面的倾斜发展,反映在等熵面位移造成的垂直速度分量变化上;高空偏北风沿等熵面的下滑导致下沉垂直运动分量发展,进而形成干侵入过程;相反,偏南风沿等熵面的上升运动会向高层持续输送水汽,水汽抬升凝结导致与非绝热加热相关的垂直速度分量发展,进一步导致抬升运动加强,触发对流起始。对流发生后,强降水引起对流层中、低层的潜热释放,因其垂直分布在低空随高度增加而制造位涡,增强的低涡通过影响等熵面结构和垂直运动促进降水进一步增强,位涡、强降水以及与三个垂直速度分量之间的正反馈机制是长江流域暴雨维持和发展的重要原因。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 maintaine

关 键 词：位涡 暴雨 干侵入 垂直运动 后向轨迹追踪 

分 类 号：P458.121.1[天文地球—大气科学及气象学]