基于TIGGE资料的流域概率性降水预报评估

Assessment of Probabilistic Precipitation Forecasts for the Huaihe Basin Using TIGGE Data

利用2008年7月1日至8月6日TIGGE-CMA资料存储中心的ECMWF、NCEP和CMA等业务中心1～10天的集合预报降水结果,结合淮河流域上游大坡岭—王家坝流域内19个站点的降水观测资料,对流域内的日降水预报效果进行了基于降水等级划分的确定性TS评分、概率性Brier评分以及考虑所有降水强度概率的百分位降水评估,并对2008年7月22—23日的强降水过程的预报效果进行了重点评估分析,探索了多模式概率预报降水面向流域的评估方法。结果表明,超级集合的TS评分和Brier评分优于单个中心的集合预报平均,集合平均由于平滑作用削弱了对长预报时效较强降水的预报能力;三套集合预报都体现部分成员具有捕捉实际降水的多种可能性;流域面雨量和单站百分位的分析表明:随着预报时效的延长,强降水的预报能力逐渐减弱,而超级集合由于考虑了更多的降水可能性,预报强降水的量级和空间分布同观测更为接近。

The precipitation forecasts of three prediction ensemble systems（ECMWF,NCEP and CMA） from the TIGGE-CMA archiving center（TIGGE,THORPEX Interactive Grand Global Ensemble） were assessed against observations of 19 stations located in the Dapoling-Wangjiaba sub-catchment of Huaihe Basin.It covers a period of 37-day beginning on July 1st,2008.The Threat Scores（TS）,the Brier Score and a percentile method were employed to assess the performance of the three ensemble prediction systems （EPSs） and their grand ensemble.The skills of probabilistic prediction of the heavy rain events occurring during 22—23 July 2008 were also investigated.The verifications of TS and Brier Scores showed that grand ensemble usually gives the best scores in any of the three EPSs.The verification of Brier Scores showed some members of any three EPSs captured the extreme events even a lead of 10 days.However, the probability skills were usually decreased by a simple ensemble mean.Grand ensemble increased the skill of probabilistic precipitation prediction.Whereas the simulation tends to more underestimate in comparison to the observation as the lead days range from 1 to 10 days.That means the probability forecasts are more skillful with a grand ensemble in comparison to a single EPS.The skills of probabilistic prediction with the grand ensemble were improved not only in space distribution of precipitation,but also in the intensity of it.