Mesoscale Feature And Orographic Sensitivity Test Of "07.7" Meiyu Front Rainstorm

The process of Meiyu front rainstorm occurred over Yangtz area during 8-9 July 2007("07.7" for short) is analyzed with NCEP global reanalysis data which is four times one day and cloud figure of FY-2C.The rainstorm took place during the period of long wave adjust after the dissipation of blocking pattern in the mid-high latitude. The Northwest stream in the front of ridge and the Southwest stream around subtropical high both affected the Yangtz area. Shear line and low vortex formed over Yangtz area with the interaction of South-west vortex, North-east vortex and subtropical high, which is the main mechanism of this process. Good allocation of high-level and low-level jet, vapor condition, thermodynamic condition and dynamical condition are found by diagnosis. Obvious mesoscale feature is found with mesoscale filter analysis and cloud figure. There're close relation between rainy place and the convergence of disturbance stream and the moving of the centre of disturbance. The main reason of the rainstorm is the development of mesoscale cloud mass and the interaction of these cloud masses. The rain occurred in the influencing and interaction area. In order to analyze the impact that different terrain take on different area, mesoscale numerical model WRF is used to make correlative orographic sensitivity test. The terrain of Dabieshan area and Huangshan area take different effect to the different rainy region during this process.