The Movement Of Cold Air During Extratropical Transition Of MATSA And The Inducing Precipitation In Beijing And Tianjin

By employing the actual observational data of upper air and surface, typhoon MATSA is analyzed, the developing characteristic of the MATSA cloud system is analyzed using the data of FY-2C satellite cloud image, and the analysis of the different trait of thermal structure before and after extratropical transition is conducted by the use of NCEP reanalysis data, combining with the method of mesoscale Barnes filtering. In order to post the movement characteristic of the cold air during the process of extratropical transition, the whole process of MATSA making the landfall and going northward , thereafter extratropical transiting is simulated for 60h, using the Penn State -NCAR nonhydrostatic mesoscale model MM5(V3.7), the movement of the cold air is aborativly analyzed. In order to post the character in the process of the cold air, by its characters of low energy and dryness, and the physical quantity of potential vortex is imported. The results show that during the process of MATSA making the landfall and going northward, cold air of northwest rotates along with MATSA circulation from north to south first, and then goes northward from the south of the center of typhoon low, destroys the warm center of MATSA at last, inducing extratropical transition.Contemporarily, Using the Penn State -NCAR nonhydrostatic mesoscale model(MM5), the evolution of MATSA after making the landfall and the process of Tianjin and Beijing's precipitation is simulated for 48h. On the basis of the good result, the whole process of Tianjin and Beijing's precipitation and its influencing cloud system are aborativly analyzed. The cloud system of MATSA divide into west part and east one, when close to North China. Analyze from the developing condition of vapor and vertical velocity for these two pieces of cloud, indicate that the intensity and height of these two parts of cloud are completely different. The appearance of the west cloud is connected with the emergence of mesoscale convergence line at 850hPa stream field, while the role of the cold air is important.