The Numerical Simulation Research Of The Rainstorm Of Typhoon 0010 "Bilis"

Firstly, The process of landing Fujian of Typhoon "Bilis" is simulated by using of MM5 Model in this paper. It is showed that MM5 can simulate main rainstorm belt and its' distribution characteristic well. The formation of rainstorm in the coastland of Fujian province has several main mechanisms:(l) the layer above the Fujian coastland quite unsteady before and after typhoon landing. (2)because of typhoon's unsymmetrical circumfluence, at the north of typhoon's heart , there were strong wind speed, relative humidity, positive vorticity , convergence and vertical velocity. (3) the higher and lower layers of rainstorm exists positive and negative helicity column. (4) the high layers exist positive moist potential vorticity center and the low layers exist negative moist potential vorticity center.Secondly, the terrain sensitivity test indicated that the special terrain in Fujian eastern coast could enhance the typhoon rainstorm distinctly. By comparing face rain of each three hours in three different regions, analyzing vertical velocity in different schemes and horizontal flow field during different time, it was found that when the multiplied result of mountain grads and vertical cross wind velocity reached maximum, the terrain has most notable effectiveness on enhancing typhoon rainstorm.Thirdly, the water vapor Analyses and Experiments showed that the water vapor changing has great influence on the rainfall and typhoon itself intensity. The result of single level vapor sensitivity experiments showed that the vapor has different effect on precipitation. For different levers, it has most obvious effect on 850hPa, and for different districts, the most notable effect takes place in mid-northern territory in Fujian.Finally, it is discovered the strongest rainstorm center was resulted in the unsymmetrical structure of typhoon "Bilis" through the structure sensitivity test.