一场突发性局地大暴雨触发作用的分析和探讨

利用多种非常规高时空分辨率观测资料并结合ERA5(ECMWF Reanalysis V5)再分析资料，分析了2019年6月2日长春市区的一场突发性局地大暴雨的中尺度特征，结果发现，低层或高层冷中心、暖湿气流和冷池出流三者之间不同的相互作用是该过程两段不同强度降水产生的根本原因：第一时段降水较强，并伴有强雷电和冰雹，700 hPa附近较弱冷中心在低层偏南风急流作用下北移至长春站北部并叠加在高层强冷中心之下，其下沉气流在边界层顶附近受该处降水形成的冷池和冷锋后部冷平流阻挡向南回流，冷池出流强度增强并在长春站附近迫使强暖湿气流抬升，长春站上空层结不稳定性加强，当上游对流云团东移至该地时强烈发展，回波强度超过60 dBZ,后向传播作用形成东西向线状对流，列车效应显著；第二时段降水相对较弱，仅伴有雷电，长春上空中低层仍为暖平流控制，高层冷空气继续加强并南压，其下沉气流在边界层顶附近受低层急流作用向北辐散，冷平流较强并与第一阶段强降水产生的冷池出流(较弱冷平流)在长春站附近辐合，迫使其低层相对较暖的气团抬升，700 hPa以下转为垂直上升运动，对流云团移至该处再次发展并与周围对流云团合并形成线状对...

Analysis and discussion on the triggering action of a locally sudden torrential rain

By using a variety of unconventional high spatial temporal resolution observation data and ERA5(ECMWF Reanalysis V5) reanalysis data,the mesoscale characteristics of a locally sudden torrential rain process occurred in Changchun City on June 2, 2019 were analyzed in detail. Results show that the different interactions between the cold center in the lower or upper layer, the warm and wet air and the cold pool outflow were the fundamental reason for two periods of precipitation with different intensities of this process:the precipitation in the first period accompanied by strong lightning and hail was strong. The weak cold center near 700 hPa moved northward to the north of Changchun Station under the action of low-level southerly jet, and superimposed under the high-level strong cold center. The downdraft near the top of boundary layer was blocked southward by the cold pool formed by the precipitation in northern Changchun station and the cold advection behind the cold front, which causedthe outflow of cold pool to increase in intensity and the warm moist air to rise near Changchun Station. The stratification instability over Changchun Station was strengthened. The upstream convective cloud clusters moved eastward over the place to strongly develop and formed an east-west linear convection group under the influence of the backward propagation action, the echo intensity exceeded 60 dBZ and the train effect was obvious. The second period precipitation was relatively weak, only accompanied by lightning. The upper layer of Changchun was still controlled by warm advection. The cold air at the upper level continued to strengthen and moved southward, and its downdraft diverged northward near the top of the boundary layer under the action of low-level jet. The strong cold advection converged with the cold pool outflow (weak cold advection) generated by the heavy rainfall in the first stage,which caused the relatively warm air mass in the lower level to rise. The vertical motion above Changchun station below 700 hPa turned into vertical upward motion. The upstream convective cloud clusters moved eastward over Changchun station to strongly developed again and formed a linear convection group by combining with the surrounding convective clouds.The two convergent airflows, however, were both cold advection and lacked the coordination of thermal conditions in the near-surface layer, which were not conducive to the strengthening and maintenance of updraft. The intensity did not exceed 55 dBZ and the strong echo centroid was low, with the holding time being short.