A Numerical Study of the Landfall of Typhoon Utor

Typhoon Utor(0104) made landfall to Shanwei of Guangdong province at 00 UTC on 6 July 2001 and caused severe and disastrous weather. The numerical prediction system based on the Fifth-generation NCAR/Penn State University Mesoscale Model (MM5) successfully predicts Utors moving track and distribution of weather phenomena.Three sensitivity experiments were designed for studying the effects of topography and land process in South China based on the typhoon intensity and weather distribution:① changing the land of South China into the ocean (Exp B),② reducing South China terrain to flat with surface roughness unchanged (Exp C),③ reducing the surface roughness of South China to 10~(-4) m (Exp D). The experiment results show that the decay of landing typhoon is mainly due to the decrease of water vapor supply from the surface, secondly the increase of surface frictions. The precipitation distribution is considerably affected by the topography of South China, that is, the precipitation amount on the up-slope is much more than on the down-slope.The topography,however,has little effect on the decay of typhoon Utor.