EVALUATION OF THE FORECAST FOR LANDED TYPHOONS BY GRAPES-REPS REGIONAL ENSEMBLE PREDICTION SYSTEM

ZHONG You-liang; CHEN Jing; WANG Jing; LV Kai; LI Xiao-li

doi:10.16032/j.issn.1004-4965.2017.06.016

Abstract：Based on the data of GRAPES-REPS Regional Ensemble Prediction System,four typhoons which landed in the coastal regions of Chinese continent for the period from July to September 2015 are evaluated by the methods of ensemble verification and diagnosis.The contents of evaluation included the typhoon track,landfall time and position and typhoon intensity as well as precipitation in order to be used better by forecasters.The results show that the average track by ensemble forecast is better than that of control forecast.The landed position of all ensemble members is quite different,which ranges from 20 to 340km,but observed landed positions of these four typhoons strike within the forecasts of ensemble members.The landed position errors of 24h and 48h ensemble average prediction are lower than that of control forecasts (82km and 197km).The results also showed that there are no obvious systematic errors of landed positions and the shorter the forecast time,the smaller error the landed position.For the landed time forecast,it is 2.5h ahead of ensemble members on average.For the intensity forecast of the typhoon,the minimum pressure and near-the-center maximum wind velocity are weak before landing and strong after landing with the observed landed position falling in the predicted values of ensemble members,which showed that GRAPES-REPS has the ability to make forecastsclose to the reality and exhibits the uncertainty of prediction.The AROC scores of precipitation category are from 0.59 to 0.76,which are positive for the forecaster.Thus,GRAPES-REPS can provide much more uncertainty information of typhoons track,landfall time,landfall position and intensity forecast than that of deterministic models,greatly improving the decision-making by forecaster.