台风路径数值预报实时订正技术及其集成应用

Real-Time Correction Method for Numerically Modeled Typhoon Tracks and Its Integrated Application

以台风路径数值预报的短时效预报偏差和目标时效(指所需订正的时效)的纬度预报为预报因子,采用多元线性回归方法建立了台风路径预报的偏差预估方程,继而对台风路径预报进行实时订正。本文以12 h为短时效,通过对欧洲中期天气预报中心确定性预报模式(ECMWF-IFS)和集合预报模式(ECMWF-EPS)的台风路径预报的应用,得到以下结论:2018年试报结果表明,24 h、36 h、48 h、60 h、72 h、84 h订正后的ECMWFIFS台风路径预报的平均距离误差分别比订正前减小了7.3 km、9.3 km、8.9 km、6.5 km、6.9 km、2.6 km,总体来说较强台风(指12 h的台风强度实况≥32.7 m s^-1)路径预报的订正效果更好。尝试了先对ECMWF-EPS各成员的台风路径预报进行订正,再进行集成预报,并对比了以下5种方式得到的台风路径预报:"订正后的确定性预报"、"所有集合预报成员集合平均"、"优选集合预报成员集合平均"、"所有集合预报成员先订正再集合平均"和"优选集合预报成员先订正再集合平均",2018年试报结果表明,对于平均距离误差,24 h和36 h"优选集合预报成员先订正再集合平均"最小,48 h和60 h"所有集合预报成员先订正再集合平均"最小,72 h和84 h"优选集合预报成员集合平均"最小,如果在业务中有针对性地进行应用,有望获得一个在各预报时效表现都较优异的台风路径客观综合预报结果。24 h、36 h、48 h、60 h"优选集合预报成员先订正再集合平均"的平均距离误差分别比"所有集合预报成员集合平均"减小了13.3 km、11.7 km、10.0 km、7.6 km,比中央气象台官方预报(对应的时效为12 h、24 h、36 h、48 h)减小了0.7 km、2.0 km、3.9 km、2.4 km。

Using the short-lead-time forecast bias and target-lead-time latitude forecast(i.e.,the lead time required to be corrected)of numerically forecasted typhoon tracks as the predictors,a track forecast bias prediction equation is established by multiple linear regression.The equation permits typhoon track forecast correction in real time.In this paper,12 h is taken as the short lead time,and the European Center for Medium-Range Weather Forecasts deterministic prediction system(ECMWF-IFS)and ensemble prediction system(ECMWF-EPS)for typhoon track forecasts are applied.The modeled forecast results from 2018 show that the mean track error of the corrected typhoon tracks forecasted by ECMWF-IFS at 24 h,36 h,48 h,60 h,72 h,and 84 h is reduced by 7.3 km,9.3 km,8.9 km,6.5 km,6.9 km,and 2.6 km,respectively,compared with those of uncorrected typhoon tracks.In general,the corrective effect is better for strong typhoons(observed intensity at 12 h≥32.7 m s^-1).First,the typhoon track forecast of each ensemble forecast member from ECMWF-EPS is corrected;the integrated forecast is then obtained.The typhoon track forecasts obtained by the following five methods are compared:"corrected deterministic prediction,""ensemble mean of all ensemble forecast members,""ensemble mean of selective ensemble forecast members,""ensemble mean of all corrected ensemble forecast members,"and"ensemble mean of corrected selective ensemble forecast members."The modeled forecast results from2018 show that"ensemble mean of corrected selective ensemble forecast members,""ensemble mean of all corrected ensemble forecast members,"and"ensemble mean of selective ensemble forecast members"yield the lowest track error at24 h and 36 h,48 h and 60 h,and 72 h and 84 h,respectively.When applied in a targeted manner in operational application,an objective comprehensive forecast result for typhoon tracks with excellent performance for each lead time is expected.At 24 h,36 h,48 h,and 72 h,the mean track error of"ensemble mean of corrected selective ensemble forecast members"is reduced by 13.3 km,11.7 km,10.0 km and 7.6 km,respectively,compared with those of"ensemble mean of all ensemble forecast members"and by 0.7 km,2.0 km,3.9 km,and 2.4 km,respectively,compared with those of the Central Meteorological Office official track forecast(with corresponding lead times of 12 h,24 h,36 h,and 48 h,respectively).