一次台风残涡引发的天津局地暴雨中尺度对流过程分析

本文利用欧洲中心再分析资料、FY-2G卫星云导风资料，多普勒雷达组网资料、风廓线、加密自动站资料，分析了2017年8月2日由北上台风残涡引起的天津局地暴雨过程中的中尺度对流过程，研究其触发条件，并探讨了形成原因。结果表明：在局地对流发生前，天津中北部地面附近并没有较好的动力以及湿度条件，且存在扰动逆温，扰动温度负值区（冷垫）厚度达到50 hPa以上，较大的水平风垂直切变在东南斜升气流下，水平涡管发生扭曲，产生垂直涡度，在边界层以上正负涡度之间形成辐合线，触发条件不稳定能量释放，在天津中北部产生局地对流，对流在触发后不断发展并向西北方向移动，与其西北侧线状多单体合并，导致天津北部的短时强降水天气。

Analysis of mesoscale convection process of heavy rain in Tianjin caused by a typhoon remnant vortex

We analyzed the mesoscale convection process of a local rainstorm in Tianjin caused by the typhoon remnant vortex using the reanalysis data from the European Center, cloud driving wind data from FY-2G satellite, two Doppler radar network data from Tanggu in Tianjin and Cangzhou in Hebei province, wind profiles and observations from the automatic stations.The triggering conditions and causes were studied as well.The results show that before the local convection occurring, there are no good dynamical and humidity conditions near the ground in the north-central part of Tianjin.There is an anomalous temperature inversion layer.The thickness of the negative anomalous temperature (cold pad) area exceeds 50 hPa.A larger wind vertical shear exists under the southeast tilting airflow to make the horizontal vortex tubes distorted and results in a vertical vorticity.Above the boundary layer, a convergence line forms between the positive and negative vorticities, which triggers release of the unstable energy.Consequently, a local convection process develops over the north-central Tianjin and moves northwestwards, merging with its northwest linear polymer, which leads the short-time heavy rainfall in the northern Tianjin.