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淮河流域汛期面雨量多模式预报检验评估

The performance evaluation of the multi-model forecasting of areal rainfall for Huaihe River Basin during flood season

  • 摘要: 基于站点观测资料和四个数值模式预报资料,以2011—2012 年汛期(6—8 月)为例,评估四个模式对淮河流域15 个子单元客观面雨量预报效果。这四个模式为欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,简称ECMWF)全球模式、日本气象厅(Japan Meteorological Agency,简称JMA)全球模式、安徽省气象台业务中尺度模式MM5 (Mesoscale Model Version 5 )和WRF (Weather Research & Forecasting)。15 个子单元面雨量预报值采用网格算术平均法计算,面雨量实况值采用泰森多边形法计算。检验评估采用平均绝对误差、模糊评分、正确率以及TS 评分。检验评估结果表明: 1) ECMWF 预报效果整体上优于其他模式,尤其是在小雨到大雨等级优势明显;JMA、MM5 以及WRF 的预报效果依次降低。2) 各模式预报效果均表现出随降水等级(小雨、中雨、大雨、暴雨)增大而下降的趋势。3) 随预报时效 (24、48、72 h)延长,各模式预报效果逐渐下降。4) 分析典型个例发现,ECMWF、JMA 及WRF 对于24 h 预报时效的强、弱降水过程,预报效果存在较明显差异,对于强降水过程预报等级偏小;MM5 对于强、弱过程预报等级均有所偏大。

     

    Abstract: Based on the observations from conventional weather stations and the rainfall forecasts respectively obtained from four numerical weather prediction models of European Centre for Medium-Range Weather Forecasts (ECMWF), Japan Meteorological Agency (JMA), Mesoscale Model Version 5 (MM5) and Weather Research and Forecasting model (WRF) run by the Anhui Meteorological Observatory during flood season from 2011 to 2012, we evaluate the forecasting performances of the four numerical models mentioned above for the objective areal rainfall of 15 sub-basins in Huaihe River Basin. The forecasted areal rainfall of the 15 sub-basins is calculated by the grid arithmetic average method, while the empirical areal rainfall is calculated by Thiessen polygon method. Moreover, the scoring methods used to evaluate the performance include Mean Absolute Error (Ea), Fuzzy Grading (MP), Percentage Correct (PC) and Treat Score (TS). The evaluation results are as follows. 1) ECMWF performs better than other models as a whole; it clearly outperforms over others for light to heavy rain categories. Among the other 3 models, the performance decreases in order of JMA, MM5 and WRF. 2) The performances of the four models all decrease with the increasing grade of precipitation in order of light, moderate, heavy and torrential rain. 3) The performances of the four models all gradually decline with the extension of period of validity (i.e., 24 h, 48 h and 72 h). 4) By analyzing typical rain events, it is found that the grade of areal rainfall forecasted by ECMWF, JMA and WRF overestimate the weak precipitation while they underestimate the strong precipitation. MM5 overestimates both weak and strong precipitations.

     

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