Abstract:

In order to implement the localized application of ECMWF (European Centre for Medium-Range Weather Forecasting) model well and improve the accuracy of precipitation forecast in Sichuan Province, the systematic deviation characteristics of forecast of precipitation with various magnitudes from ECMWF model were analyzed from July to September during 2020-2021. The result shows that the rain days forecasted by ECMWF model are more than the observations in Sichuan Province from July to September during 2020-2021, especially in Panxi region and western Sichuan Plateau. The heavy rain days forecasted by the model are more than the observations in southwestern Basin and Panxi region, while they are less than the observations in southern Basin. Then, the correction experiment about 24-hour cumulative precipitation forecast was carried out based on quantile mapping method, and it was applied to heavy rainfall forecast. After the correction using quantile mapping method, the TS (Threat Score) of forecast of rainstorm and above is improved by 7%-15%, and the TS of forecast of precipitation with various magnitudes is 2%-4% higher than the multi-model integrated objective forecast products. The POD (Probability of Detection) of forecast of heavy rain, rainstorm and above is improved by 10%-20%. The corrected location of rain belt in particular rainstorm areas is closer to the actual.

Key words: ECMWF model, quantile mapping method, precipitation forecast correction, precipitation forecast test, Sichuan Province

摘要：

为做好ECMWF（European Centre for Medium-Range Weather Forecasting）模式本地化释用，提高四川省降水预报准确率，对四川省2020—2021年7—9月模式各量级降水预报系统性偏差规律分析发现，该模式预报的雨日较实况偏多，尤其是攀西地区和川西高原；预报的大雨日数盆地西南部及攀西地区多于实况，而盆地南部少于实况。然后，基于分位数映射法对模式预报的24 h累积降水开展大量级降水订正试验与检验。基于分位数映射法订正后，暴雨及以上量级TS（Threat Score）提高7%~15%，且各量级降水TS均高于多模式集成客观预报产品2%~4%，大雨及以上、暴雨及以上量级命中率提高10%~20%，订正后雨带位置特别是暴雨落区与实况更接近。

关键词: ECMWF模式, 分位数映射法, 降水预报订正, 降水预报检验, 四川省