数值降水预报定量集成方法的业务应用

利用相似权重集成预报法对辽宁区域12个数值模式预报的降水量进行集成,并投入业务化应用。结果表明：通过对2009年5月1日至10月20日的24 h降水量预报进行TS评分,发现降水集成方法要优于12个集合成员的单个预报,同时也要优于简单的集合平均。试验表明,滞后时间和扩大圈数对集成预报效果影响很大,而单个的集合成员对集成预报效果影响较小。根据试验结果修改集成方法应用方案,按照不同降水量级和预报时效选择扩大的圈数,预报效果好于原方案,对大量级、长时效预报改进更明显,其中25 mm量级预报时效72 h的TS评分增加了20%或以上,具有实际应用价值。

Application of an ensemble method of quantitative precipitation forecasting

An ensemble method based on similar weights（also called ＂two-step method＂）was used to integrate the quantitative precipitation forecasts of the 12 numerical prediction models,and put them into the operational application.The results indicate that by comparing the TS scores of 24 hours precipitation forecast from May 1 to October 20,2009,the accuracy of precipitation forecast by the ensemble method is higher than by each single method of 12 ensemble members and by the ensemble average.Further experiments show that the effects of lag time and expanding grid number on the ensemble forecasts are significant,while that of the each single ensemble member is not significant.The application plan is modified according to these experiments：the expanded grid numbers depends on forecast period validity and precipitation level rather than similarity and if using the newest forecast method of ensemble members.The modified plan is better than the original plan,especially for long forecast period validity and high precipitation level.For example,TS score of 72 hours forecast period validity for 25 mm precipitation level could increase more than 20%.