Numerical Simulation And Diagnostic Analysis Of The Landfall Typhoon Rainstorm

Firstly, The process of landing Fujian of Typhoon "LongWang" is simulated byusing of MM5v3.6 in this paper. It is showed that MM5v3.6 can simulated mainrainstorm belt and its' distribution characteristic well. The formation of rainstorm inthe coastland of Fujian province has several main mechanisms:(1) the layer above theFujian coastland quite unsteady before and after typhoon landing;(2)because oftyphoon's unsymmetrical circumfluence, at the north of typhoon's heart, there werestrong wind speed, relative humidity, positive vorticity,convergence and verticalvelocity;(3) the higher and lower layers of rainstorm exists positive and negativehelicity column. The result showed that the model made a good effect on eithersimulating Fujian inland or seashore storms. The simulation experiment by controllingterrain showed that it was a great difference between the reinforcement results toinland seashore storm caused by the Fujian local terrain and the terrain made a moreoutstanding reinforcement effect to inland storm.Secondly, the terrain sensitivity test indicated that the special terrain in Fujianeastern coast could enhance the typhoon rainstorm distinctly. (a)The increase ofrainfall near the center of the typhoon has a close relation with the terrain;(b) Terraintendency and height can result in more uniformity of the precipitation distribution ;(c)Expect for the precipitation on the west of periphery of the typhoon. The precipitationenhancement extent appears counter of phase relationship with that of the typhooncenter or near the typhoon, especially on the region of the East Sea;(d) Thedistribution of typhoon precipitation presents the positive ad negative change as thegravity wave column wise under the influence of terrain.Finally, Simulation experiments of precipitation prediction with MM5v3.6'sdifferent parameterization schemes over Fujian. In order to test the forecast capabilityof MM5v3.6, four combinations of two different physical parameterization schemesare used in simulation tests of precipitation prediction. It is discovered that thecombinations of Grell cumulus parameterization and Mixed ice-phase in the secondnested grids are superior to the others, especially the center of downfall andrainstorm. The strongest rainstorm center was resulted in the unsymmetrical structureof typhoon "LongWang" through the structure sensitivity test.