Analysis on Circulation Evolution and Influence System of Two Rare Heavy Rainstorm Processes

Based on conventional meteorological observation data and ECWMF data, using synoptic analysis method, comparative analysis of two rare heavy rainstorms(July 28-30, 2007 and July 22-24, 2010) in Henan Province was conducted, and the evolution of circulation situation and its influence system were diagnosed. The results showed that(1) the rainstorm process in 2007 was cut-off low-vortex type gradually changing to the long-wave trough type, and the rainstorm process in 2010 was two high coexistence type.(2) Main influence systems of Henan rainstorm included subtropical high, Qinghai-Tibet high, westerly trough, vortex, shear line, high-and low-level jet and low vortex moving along the shear line.(3) The low-level southwest jet provided water vapor conditions for the occurrence of rainstorm weather. The upper westerly jet provided strong dynamic uplift conditions for the rainstorm process. The high-altitude strong divergence area on the right side of the high-altitude jet axis often corresponded to the rainstorm center.(4) The cyclonic convergence of low vortex provided a dynamic uplift mechanism in the middle layer. Cooperated with large-scale circulation field, it also provided sufficient water vapor and energy for rainstorm occurrence.(5) In the two processes, the main ground systems causing rainstorm were static front and cold front.(6) The surface mesoscale systems causing the two rainstorms were mesoscale low vortex and shear line.