Numerical Simulation And Diagnostic Analysis Of Heavy Rainfall Caused By No.0509 Typhoon "Matsa"

An analysis of the action process of No.0509 typhoon "Matsa" is made with NCEP objective analysis data in this work firstly. It is revealed that the subtropical high is the direct influencing system of No.0509 typhoon's moving route. Based on FY-2C satellite visible pictures, the development of typhoon is performed. It shows the causes of typhoon intensity weakening slowly, and the favorable environment of typhoon heavy rainfall generating.By using observations from Doppler radar, the typhoon rainfall is studied. Using synoptic diagnostic methods, the typhoon rainfall is analyzed with NCEP objective analysis data, the conventional observational datasets. It is found that the coupling of low-level and upper-level jets is an important cause of this heavy rainfall. Analyzing multiform physical quantity shows that the variations of chief physical quantity in the process of storm are indicators to the counterparts of precipitation in a certain sense.The meso-scale numerical model (MM5V3.7) is used to simulate the typhoon heavy rainfall process. Using the model output with high spatial and temporal resolution, we study the characteristic and mechanism of the rainfall in more detail. The asymmetry structure of typhoon flow results in the asymmetry distribution of rainfall. The modified non-geostrophic wet Q vector diagnostic analysis shows that the vector is favorable for diagnosing the heavy rainfall process. The distribution and evolution of 500hPa modified non-geostrophic wet Q vector divergence field are good indicators to the distribution and evolution of typhoon heavy rainfall, as well as its convergence intensity. The diagnosis of vertical helicity turns out that the horizontal distribution of 650hPa vertical helicity is a good indicator to the distribution of rainfall, the positive big center to the center of heavy rainfall. Through analyzing MPV, it is showed that low air is symmetry instability and convection instability when heavy rainfall happening. The development of relative MPV is a good indicator to the development of rainfall.