气团订正对静止卫星成像仪资料同化在台风预报中的改进效果研究

IMPROVED TYPHOON TRACK PREDICTION WITH GOES-13/15 IMAGER RADIANCE AIR MASS CORRECTION AND ASSIMILATION

基于美国台风预报系统(Hurricane Weather Research and Forecasting,HWRF),研究了气团订正方法对GOES-13/15静止卫星成像仪资料同化效果的改进作用,选取了2012年6月23日生成于大西洋地区的台风Debby作为研究对象,通过一组对照试验比较了气团订正前后台风路径和初始场相关物理量的差异,结果表明:气团订正能显著减小GOES-13/15静止卫星成像仪资料的系统偏差,明显提高台风路径的预报效果,气团订正使得预报的台风路径与观测路径的平均偏差和标准差降低了30%左右,提前6 h实现了台风路径的正确转向。物理机制分析表明,经过气团订正后的静止卫星资料增强了位于台风东南侧副热带高压的强度,同时增加了台风东部的温度和比湿,在引导气流和大气温、湿场的共同作用下,台风预报路径实现了正确转向。

In this study,radiance observations of four infrared channels from GOES-13 and GOES-15 imagers are directly assimilated using the National Centers for Environmental Prediction(NCEP)Hurricane Weather Research and Forecasting(HWRF)model.Selecting the landfalling tropical storm Debby generated in the Atlantic on June 23,2012 as a case,we compare the differences between tropical storm Debby’s track and its physical variables of initial field with and without air mass correction through a pair of assimilation and forecast experiments.It is shown that the deviation of GOES-13/15 imagers is reduced significantly,and the track forecast of Debby improves much after air mass correction.In addition,the mean and standard deviation between observed and forecast track are reduced by 30%and prediction captures the directional turn of tropical storm track 6 hours earlier than forecast without air mass correction.Analysis of physical mechanism shows that the assimilated GOES data of air mass correction enhances the southeastern subtropical anticyclone of the tropical storm and increases the eastern temperature and moisture of Debby.Under the influence of steering flow,air temperature and moist,the track forecast achieves the correct prediction of the turn of typhoon’s track.