Abstract:Based on the routine observational data, FY2C TBB data, radar data, NCEP reanalysis data and LAPS analysis data, a comparative analysis on mesoscale characteristics of two torrential rain processes in Hunan Province in June 2011 was analyzed. The results show that: The two processes belong to the type of low vortex and cold trough rainstorm, but their mesoscale characteristics, precipitation nature and environmental conditions are different. The rainstorm on 9 June 2011 is generated by a meso β scale low vortex, which is stable and immobile during the process. The satellite image manifests a mesoscale convective cloud cluster which develops severely, and the radar echoes are convective precipitation echoes in the earlier stage and transform to convective stratiform mixed clouds echoes in the later stage. In comparison, the rainstorm on 13 June 2011 is mainly produced by mesoscale convective shear lines which maintain for a long time and move slowly. The satellite images show it a convective cloud band that exits for a long time, and the radar echoes are convective stratiform mixed clouds echoes. The establishment of vapour transfer channels and strong convergence of water vapor in the middle and low troposphere provide favorable conditions for the mesoscale convective system. The two severe rainstorms both occur in the unstable stratifications with high temperature and humidity and strong ascending motions. The ascending movements caused by the dynamic forcing in the frontal zone enhance upward transfer of energy and water vapor from low levels. The obvious compensation descending airflows appear on the north and south sides of the deep vertical motion in the first process, but in the second process, the ascending motion is inclined, and the compensation descending airflows only appear on the south side.