Abstract:Based on the conventional observation data, automatic station data, Doppler radar data and NCEP 1°×1° reanalysis data, the convection cells that formed and developed in the lower troposphere in the easterly airflow are analyzed and the local short term severe precipitation in Nanjing during YOG (Youth Olympic Games) opening ceremony caused by the convection cells is also studied. Moreover, the formation mechanism of the convection in the shallow layer of the easterly airflow, the radar characteristics and the reasons of the convection cells reversely moving in the precipitation cloud system during the rainfall are discussed. The results show that the lower troposphere over Nanjing blows easterly wind while the middle above layer is dominated by the southwesterly wind. The transition zone between them corresponds to a dry layer which was formed by dry air carried by a northerly air in the middle troposphere. The overlapping of the dry layer on the shallow easterly warm airflow promotes the development of the convective unstable stratification in the mid and low troposphere. Local convergence by the surface wind disturbance and surface non frontogenesis baroclinic zone inspires the formation of the convection in the easterly airflow. The structures of the two kinds of reversely propagating convective cells in the precipitation echo have obvious differences. The barycenter height, vertical extension thickness and the prevailing background wind in the layer determine the propagation and movement of the convective cells.