Based on conventional meteorological observation data of Zhejiang Province, ERA5 hourly reanalysis data (0.25°×0.25°) and blackbody brightness temperature (TBB) of FY-4A satellite, the two rainstorm processes occurring on June 3 and June 30 in 2020 were compared and analyzed. The results are as follows: (1) The rainstorm on June 3 (short for “6·03”) occurred in the background of monsoon trough, and there were southwest flow in front of the trough at 500 hPa and warm shear at 850 hPa over Zhejiang Province,while the rain storm on June 30 (short for “6·30”) occurred in the background of northeast cold vortex, there were confluence of cold and warm air at 500 hPa and cold shear at 850 hPa. For two rainstorm processes, their rainfall areas were similar, all concentrating in west Zhejiang and presenting east-west belt distribution. But for the “6·30” process, the rainfall area was wider, both the center rainfall and process rainfall were larger, the hourly rainfall intensity was stronger, and the duration of heavy rainfall was longer. (2) Both two rainstorm processes were convective unstable precipitation, but the heavy rainfall areas were in different positions of the jet stream. The “6·03” process was a warm shear type rainstorm in the warm region, the “train effect” of convective cloud clusters was significant and precipitation was located in the strong convergence area of water vapor flux in front of the jet. During the “6·30”, the Meiyu front was a westerly convergence frontogenesis, and the convective cloud clusters presented a backward propagation path, the precipitation was located in the strong convergence area of water vapor flux near the jet axis. The maximum convergence area of water vapor flux and intensity at 700 hPa corresponded to the falling area and intensity of heavy precipitation in the next six hours, which had a certain reference in rainstorm forecast in the Meiyu season. (3) Due to different precipitation types, the corresponding frontogenesis was different, and the height of the frontal zone indicating one hour heavy rainfall was also different. So in the forecast of rainstorm in the Meiyu season, the correspondence of different precipitation types and frontogenesis at different heights should be fully considered.

Based on the ground intensive observation data, NCEP FNL reanalysis data, FY-2G satellite cloud images and dual polarization radar data, the influences of Typhoon Lekima (1909) on extreme heavy precipitation in the coast of Zhejiang Province were analyzed and discussed. The results show that the intensity of Typhoon Lekima was strong, the range was wide, and the intensity weakened slowly and movement was slow after the typhoon landing, which caused the extreme heavy precipitation in the coast of Zhejiang Province. The low values of black body temperature (TBB) matched with the centers of heavy rainfall for a long time, and the train effect and enhancement of southeasterly jet anticipated the amplification of heavy rainfall. The high value zones of ZH, KDP and ZDR of dual polarization radar were consistent, which indicated there were plenty of big water drops over the coastal areas of Zhejiang. The atmospheric precipitable water consistently maintained high-value with 70 to 80 mm over extreme heavy precipitation area, and the continuous and exuberant southwesterly and easterly jets transported water vapour to Zhejiang. Meanwhile, the center of positive vorticity coincided with the center of strong convergence in lower troposphere, and the height of convection development was very high, which were conductive to the amplification of heavy rainfall. Moreover, the vertical motion of apparent heat source (Q1) and apparent water vapor sink (Q2) was dominant. The peak value of Q1 and Q2 appeared alternately, and the corresponding height of the former was higher than that of the latter, which was beneficial to latent heat releasing and heavy rainfall maintaining.