Numerical Study On The Torrential Rainfall Process In Southwest China

In this dissertation, a durative severe heavy rain process in the east of Sichuan Basin in Sep. 2004 was analyzed. Firstedly, using NCEP-FNL global reanalysis grid data analysed this vortex, and then the numerical experiment by WRF was conducted to reproduce this process, based on the analysed conclusion, corresponding sensitivity experiments were designed, in order than, analysed conclusion can be confirmed.Circumfluence analysis indicated that two trough and one wedge is the extrusive characteristic of this process; at on time, typhoon SANGDA formed on the west Pacific Ocean moved northwestly is the distinct characteristic different from general Southwast Vortex, typhoon blocked Subtropical high moved and weakened eastwardly, induced the Southwast Vortex stagnated in the Southwast region for a long time, and solicitated a durative severe heavy rain. Moisture analysis indicated that except the moisture form the South China Sea, the infection of typhoon also can't be ignored. Jet stream from Southwast had signifiable contact with precipitation of Vortex.The numerical model successfully simulated this process, the intensity of precipitation and the rainfall region are right, so it is the bases for the sensitivity experiment.Terrain effect sensitivity experiment indicated that the special terrain of Sichuan Basin to the form, the development, and the maintaince of vortex, when the terrain hight was reduced to the 1/2 of originally, the precipitation of east of Sichuan Basin reduced distinctly, and the weather systerm down an up changed, the advantaged physiscal condition was weakened also. The moisture transportation is the most important condition of rainfall, In this process, moisture sensitivity experiment indicated that the jet stream of lower level is the mostly dynamical conditon, the trumcation of east moisture transportation made little changs to the precipitation of this region, so the South China Sea is the primary moisture source of the rainfall, the typhoon only offered the dynamical conditon. When the typhoon is weakened, the precipitation and the weather systems are all have no obvious changes, may have some imporments to do, for the sensitivity procepts or the skills of modeling.