Based on conventional observation data from weather stations of Zhejiang Province and its surrounding and ERA-Interim reanalysis data from March to May during 2007-2016, the circulation characteristics and meso-scale conceptual model of warm sector rainfall processes in spring in Zhejiang Province were analyzed and summarized. The results show that the cloud was more, the precipitation was small, the temperature was high and the daily temperature difference was small during warm sector weathers in spring in Zhejiang Province. The warm sector rainfall processes were divided into four types according to 850 hPa wind field, and they were the southwestern airflow pattern, warm shear northward extending pattern, cold shear approaching pattern and southeastern airflow pattern, respectively. The warm sector rainfall for cold shear approaching pattern was the strongest, and then followed by warm shear northward extending pattern, their precipitation was large in the southwest and was small in the northeast, while that for southeastern airflow pattern was the smallest. Meso-scale analysis found that the warm sector rainfall often appeared in the dense isoline area of θse on 850 hPa and the convergence upward area of intersection of southeasterly airflow near surface and low-level southwesterly airflow over the coastal of Zhejiang, and rain belt paralleled to θse isolines. The baroclinic instability which caused by residual cold air near surface and temperature difference between land and sea could significantly increase the precipitation of warm sector.
