1. Changsha Meteorological Bureau,Changsha National Testbed for Comprehensive Meteorological Observation of CMA,Changsha 410205; 2. NO.96732 Troop of PLA,Shaoyang 422000
Abstract：In this paper,the conventional observation data,NCEP reanalysis data and satellite data are used to compare and analyze the two extreme rainstorm of "6.9" and "8.17" in Changsha urban area,looking for similarities and differences.The results show that the two rainstorm are mainly convective,and the maximum rainfall intensity is more than 90 mm/h.The "6.9" rainstorm occurred in the periphery of the subtropical high,and the "8.17" rainstorm occurred in the control area of the subtropical high.The water vapor sources of the two rainstorm are the same,the specific humidity is more than 16 g/kg,and the precipitation of the whole layer is more than 130 mm.The false equivalent potential temperature center of the lower layer is more than 360 K.The unstable situation is formed in the upper layer,and the energy is mainly concentrated in the lower layer.Both processes are influenced by the migration and development of beta mesoscale convective cells,and the mesoscale system moves slowly with a long impact time.Both of the two rainstorm were fine weather before the occurrence,and the ground was in a state of high temperature and high humidity.When there was cold advection,it could trigger local convective weather.The ground trough and convergence line strengthened the development of convection.
2025, Vol. 42 
