The Research On The Activity Of Southwest Vortex And Flood-producing Rainstorm Influencing South Of China

MICAPS data and NCEP 2.5×2.5°reanalyzed data during theyear 1996-2005 was used to make statistical research on the activity of southwest vortex and flood-producing vortex influencing south of china. The research reveals the climatic features such as frequency of vortex activity, producing origin, movement track, and intensity during the producing and moving procedure, and its lifetime, average circulation field, and precipitation features. And the allocation of influencing flood-producing synoptic system and its model graph were offered to provide evidence for forecasting on vortex and flood-producing storm rainfall in South of China.The "05.6" flood-producing storm rainfall in south of china was analyzed by means of synoptic system analysis and physic diagnosis.The results show that the weather backgrounds are abnormal flood-producing vortex activity and moving east and the advantageous allocation of weather situations. The interacting between flood-producing vortex and low level jet under special terrain condition is the main cause of the flood-producing storm rainfall.The water vapor transportation mainly came from south china sea.The flood-producing storm rainfall area and the precipitation intensity are agreement with the center of water vapor flux and water vapor convergence.The intercoupleing developed of strong divergence,intensive vorticity and intensive ascendant motion enhanced the the flood-producing storm rainfall.Based on the two-way nested non-hydrostatic mesoscale numerical model(MM5V36),the simulated experiment for developed flood-producing vortex is carried out on 24 hours of 20-21 June 2005. The results show that simulated flow fields,simulated height fileds and stimulated vorticity on 700hPa level are agreement with the observations. flood-producing vortex is shallow mesoscale convection system on 850～700hPa level.There are strong divergence and intensive vorticity in the center of flood-producing vortex.The simulated rainfall area and the precipitation intensity are agreement with the observations.