台风Utor登陆广东过程的数值研究

A Numerical Study of the Landfall of Typhoon Utor

台风Utor(0104)于2001年7月6日00时(UTC,下同)在广东汕尾地区登陆,带来比较严重的灾害性天气。以美国国家大气研究中心和宾州大学联合研制的第五代中尺度模式(MM5)为基础设计的台风预报模式比较准确地预报出台风Utor(0104)的移动路径(前24h的移动路径平均误差为68km)和天气现象的分布。在此基础上,设计了3个敏感性试验:①是把华南地区(26°N以南,110°E以东)的陆地变为海洋,②是把华南地区的山地变为平地,③是减小华南地区陆地的粗糙度,即取为近似于静风的洋面上的值。对比数值试验的结果表明:引起台风登陆后减弱的最主要因子是下垫面水汽供应的切断,其次是下垫面粗糙度(摩擦)的影响;地形作用能使迎风坡的降水明显增加,但对台风强度则没有明显的影响。

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.