Extended Abstract

800 hPa (a,b, arrow indicates position for vertical section) , vertical sections of Cz and simulated radarreflectivity (shading, only ≥10 dBz). (a)(c) 1800 UTC 21 Aug. (b)(d) 0600 UTC 22 Aug.Fig.5 displays distributions of and 6 h accumulated rainfall on 800 hPa andCzvertical sections of Cz and simulated radar reflectivity. It is found that the high value areaof Cz on lower layer is a good index to strong convection and heavy rainfall region intyphoon circulation.5. ConclusionThe mechanism of rainfall change associated typhoon Winnie has been discussed basedon satellite data and MM5 outputs in its ET process.The results indicate that the rainfall distribution displays remarkable asymmetry. Theheavy rainfall mainly occurs in the north at first, then the northeast and southeast part oftyphoon circulation, going around typhoon center clockwise during ET process.It is found that the environmental vertical shear becomes stronger under the interactionbetween the remnant and upper westerly trough during ET process, and results in the rainfallconcentrated in the left side of downstream of the shear. Meanwhile, the vertical structure oftyphoon vortex is slantwise against height, and the heavy rainfall occurs in the slantingdirection. On the other hand, the rainfall variation also is related to the thermal advectionactivity in the remnant of typhoon circulation. The heavy rainfall is associated with warm airadvection at 700hPa. Moreover, the vertical component of convective vorticity vector canreflect the impacts of wind vertical shear and front in ET typhoon circulation. Its high valuearea has a good relationship with heavy rainfall on lower layer .Acknowledgments. This work was financed by the National Grand Fundamental Research 973 Programof China (Grant nos. 2009CB421504 ), and the National Natural Science Foundation of China (Grant nos.40730948, 40975032).ReferencesChen Lianshou, Xu Xiangde, Luo Zhexian and Wang Jizhi. Introduction to Tropical Cyclone Dynamics,Beijing:Meteorological Press. 2002.317ppCHEN S Y S, KNAFF J A and MARKS F D Jr. Effect of vertical wind shear and storm motion on tropicalcyclone rainfall asymmetries deduced from TRMM. Mon Wea Rev, 2006, 134:3190-3208.FRANK W M and RITCHIE E A. Effects of environmental flow upon tropical cyclone structure. MonWea Rev, 1999, 127:2044-2061Gao S, Wang X and Zhou Y. 2004a: Generation of generalized moist potential vorticity in a frictionlessand moist adiabatic flow. Geophys. Res. Lett., 31, L12113,1-4Harr P A, Elsberry E L. Extratropical transition of tropical cyclones over the western North Pacific. Part I:Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 2000, 128:2613-2633Klein P M, Harr P A, Elsberry R L. Extratropical transition of western North Pacific tropical cyclones: Anoverview and conceptual model of the transformation stage. Wea. Forecasting, 2000, 15: 373-395Li Ying, Chen Lianshou, Lei Xiaotu. Numerical study of impacts of upper-level westerly trough on theextratropical transition process of Typhoon Winnie (1997). Acta Meteorologica Sinica,2006,64(5):552-563Niu Xuexin, Du Huiliang, Liu Jianyong. 2005. The numerical simulation of rainfall and precipitationmechanism associated with typhoon Sinlaku (0216) . Acta Meteor Sinica, 63(1):57-63SHUANZHU GAO, ZHIYONG MENG, FUQING ZHANG and LANCE F. BOSART. ObservationalAnalysis of Heavy Rainfall Mechanisms Associated with Severe Tropical Storm Bilis (2006) after ItsLandfall. Mon Wea Rev, 2009, 137: 1881-1897.Zhu Peijun, Chen Min, Tao Zuyu, et al. Numerical simulation of typhoon Winnie(1997) after landfall. PartII: Structure evolution analysis. Acta Meteorologica Sinica (in Chinese), 2002, 60(5):560-567-36-