广东省ECMWF降水集合预报统计量的检验与分析

Verification and Analysis of Statistics of Rainfall Ensemble Forecast by ECMWF in Guangdong Province

利用欧洲中期天气预报中心(ECMWF)的降水集合预报历史资料,对广东省86个地面气象站进行分级统计检验,分析集合统计量产品的预报效果。评分结果表明,降水量级越大,确定性预报与集合产品TS越低,对应最优分位数越高;对于冬季暴雨与前汛期晴雨,集合预报产品效果较好,TS分别达到0.50和0.66,对于前汛期暴雨效果则较差,TS在0.10左右。随着预报时效增加,集合预报TS逐渐减小,预报时效<72 h,前汛期集合TS下降幅度较大;预报时效>72 h,后汛期集合TS下降幅度较大。对于冬季和后汛期暴雨,集合预报相对于确定性预报有明显优势,并且预报时效越长,集合TS增幅越大。对于站点降水,在广东省东部和西南部沿海地区,确定性预报对暴雨的预报能力比较欠缺,而集合预报能显著改善这些地区的暴雨预报,部分站点的TS增幅能够达到0.20以上。

With the historical data of rainfall ensemble forecast by the European Center for Medium- range Weather Forecast （ECMWF） , we conducted a graded statistical verification of 86 surface stations in Guangdong province and analyzed the forecasting performance of ensemble statistics products. As shown in the result, the greater the order of magnitude of the rain and the lower the TS of deterministic forecasting and ensemble forecast products, the higher the corresponding quantile will be. The performance of the ensemble product is better for wintertime heavy rain and fine day/rain forecast in the annually first rainy season, with the TS being 0. 50 and 0. 66 respectively, than heavy rain forecast in the annually first rainy season, with the TS being about 0. 10. With the increase of forecast duration （ FD）, the TS of ensemble forecast decreases gradually; it drops significantly when the FD is less than 72 h for the heavy rain in the annually first rainy season, but it reduces remarkably when the FD is more than 72 h in the annually second rainy season. For the heavy rain in winter and the annually second rainy season, the ensemble forecast is much more advanta- geous over the deterministic forecast, and the longer the FD, the more the ensemble TS increases. The de- terministic forecast is less desirable for site-specific heavy rain in the coastal area of the eastern and south- western part of the province while the ensemble forecast can significantly improve it, with the increase of TS more than 0.20 in some sites.