基于多模式和网格预报产品融合的降水预报释用方法

Interpretation Method of Fusion Grid Precipitation Forecast Based on Various Precipitation Forecast Products

网格降水的预报准确率是精细化天气预报业务的核心问题。利用多家数值模式和国家气象中心逐3 h网格降水预报指导产品,以格点降水实况分析资料为参照,在客观评估模式表现的基础上,提出多模式和网格降水预报产品融合的降水预报释用方法。研究表明:给定降水阈值,不同降水产品的预报性能有显著差异,存在预报表现好的降水产品漏报,而其他降水产品命中的情况;对确定性单模式来说,在降水检验阈值给定的条件下,预报降水量超出阈值越大,其空报的可能性越低。检验三种降水产品72 h时效内逐3 h降水量,晴雨预报的降水漏报次数明显低于空报次数,基于该特性,可以利用不同模式未预报降水的格点来消除空报。以检验为基础,选用前期表现好的降水预报为背景场,使用高阈值融合满足条件的其他强降水预报产品,使用低阈值消除弱降水空报。回算表明,相对背景场,该方法可以同时提高强降水的TS评分和晴雨预报准确率。

Improving the accuracy of grid precipitation forecasting is an important direction for refined weather forecasting.This paper uses the precipitation grid reanalysis data as a reference to objectively evaluate the precipitation forecast of different numerical models and the forecast performance of the National Meteorological Centre’s grid precipitation guidance products.Based on the verification results,a precipitation forecast interpretation method is proposed which fuses various precipitation forecast products.The main conclusions are as follows.Under the same precipitation threshold,the forecast performance of different precipitation products is significantly different,and there are cases in which the precipitation products with good forecast performance are missed,while other precipitation products are obtained.For the deterministic single model,the greater the forecast precipitation exceeds the verified threshold,the lower the possibility of an false alarm is.Verify the 3 h precipitation forecast for the three products with a valid time of 72 hours,for sunny or rainy day forecast,the number of omission of precipitation is significantly lower than the number of false alarms,which can be used to eliminate weak precipitation.On the basis of the verification,we select a model forecast that performed well in the previous period as the background field,and use a high threshold to fuse heavy precipitation,and use a low threshold to eliminate false alarm of weak precipitation.The results show that the forecast performance of fused precipitation can be improved.