Numerical Simulation And Diagnostic Analysis Of AERE Typhoon Heavy Rainfall In 2004

An analysis of the macroscale circulation in the No. 0418 typhoon AERE process is made in this work. It is revealed that typhoon AERE making landfall Fujian province several times is mainly induced together by revolving each other between two typhoon, barring of high pressure and the strong Northern current beside landmass . By using observations from Doppler radar, the meso-scale spiral bands is studied and then the meso-scale characteristics of typhoon heavy rainfall is discovered. Analyzing the physics structure of vorticity, divergence, vertical velocity etc. indicated the physics fields are favorable for the occurance of the heavy rain over Fujian where the physics values are well according to the heavy rainstorm positions.The meso-scale numerical model MM5(V3.7) is used to simulate the heavy rain process. Using the model output with high spatial and temporal resolution, we study the characteristic and mechanism of the rainfall in more detail.It turns out that the distributing and evolution of helicity is a indicator of typhoon heavy rainstorm in a certain sense. The change of helicity can reflect the movement and development of synoptic system and the position and intensity of the rainstorm. Through analyzing MPV during the heavy rainstorm process , it is showed that is wet symmetry instability above rainstorm area. Q vector divergence field on vertical section plane along NE-SW direction on Fujian coast submit piece form district of convergence and divergence, have reflected meso-scale character.Meso-scale terrain affects obviously the location and intensity of precipitation cell , and it makes northeast area in Fujian province precipitation increase. Sensitive tests show that latent heat release acts a decisive role in the formation of the meso-scale systems. The effect caused by the variation of initial humidity field on simulation of rainfall area and intensity gradually decreases along with the increase of integration period. The amount of water vapor which is necessary for the formation of precipitation is not only determined by the initial field, but also affected by the water vapor transportation from tropical ocean to Fujian area.