ECMWF极端天气指数在新疆强降水预报中的检验评估

Evaluation of Extreme Forecast Index from ECMWF in Severe Precipitation Forecast in Xinjiang

使用2015年10月—2018年9月欧洲中期天气预报中心集合预报系统(ECMWFEPS)逐日降水极端天气指数(EFI)预报资料,分析新疆区域降水EFI产品与强降水的对应关系并得到预报阈值。结果表明:预报的EFI与实况降水量存在正相关关系,随着降水量增加,EFI预报结果具有线性增加趋势,说明EFI对强降水有一定的指示意义。各量级降水预报的最高TS评分随着预报时效的增加而减小,且随着降水量等级的增大而减小。不同季节暴量降水发生站次为夏季最多,冬季最少,对应的EFI阈值大都在0.4~0.6,夏季EFI值范围在0.2~0.7,夏季更易发生暴量降水。随着预报时效增加,暴量降水发生站点频次最多所对应的EFI值逐渐减小。随着降水量级增加,空报率减小幅度不大,但漏报率增加。

Based on the daily precipitation extreme forecast index(EFI)from ECMWF global ensemble prediction system(EPS)from October 2015 to September 2018,the relationship between EFI and severe precipitation was analyzed,and the predicted threshold was obtained.Results show a positive correlation between EFI and observed precipitation.With the increase of precipitation,EFI shows a linear increasing trend,which indicates that EFI has a certain guiding significance for heavy precipitation.The maximum threat score(TS)of each magnitude precipitation decreases with the increase of advanced forecast time,also decreases with the increase of precipitation intensity.The frequency of rainstorm differ in different seasons,most in summer and least in winter,and the corresponding EFI threshold almost ranges from 0.4~0.6,and 0.2~0.7 in summer.Rainstorm is more likely to occur in summer.With the increase of advanced forecast time,the EFI value corresponding to the station with most rainstorms decreases gradually.With the increase of precipitation magnitude,the rate of vacancy forecast decreases slightly,but the rate of missing forecast increases.