Comparative analysis on two rainstorm processes caused by typhoon Haikui(1211) after landfall

By using the comprehensive information of automatic weather observation and NCEP reanalysis data,this paper contrasts and analyses two rainstorm processes caused by the landing typhoon Haikui( 1211),which happened in Jiangsu with different convective features. It shows that the first-phase regional heavy rainstorm occurred near the typhoon circulation center and its north side. The circulation of typhoon was intact with a barotropic center during this time. Large-scale moisture convergence and strong ascending movement appeared near the circulation center and its north side in the easterly jet stream.These characteristics were beneficial for a regional rainstorm. The rainstorm occurred in a nearly neutral stratification,and precipitation distribution was more uniform with a gentler development,lower rainfall intensity and weaker convective activity. The second-phase heavy rainstorm occurred near the top of typhoon inverted trough,which was far from the circulation center. The cold thermal advection in the middle andupper atmosphere was helpful for the development of convective instability. During the process of precipitation development,obvious mesoscale disturbances appeared in the surface wind field,enhancing the local convergence and cyclonic vorticity. Furthermore,the development of surface frontal zone also strengthened the formation and development of mesoscale convective systems. The precipitation had significant mesoscale characteristics with rapid development,high rainfall intensity,strong convection,which led to a local heavy rainstorm.