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基于集合降水预报的长江流域面雨量预报与应用

Prediction and application of area rainfall in the Yangtze River basin based on ensemble precipitation forecasting

  • 摘要: 基于2018—2021年欧洲中期天气预报中心集合降水预报数据开发了众数、平均数、最优百分位数、百分位数、概率等集合统计量面雨量预报产品。采用TS评分、相对作用特征(ROC)分析、评分综合表现图、Brier技巧评分等方法对长江流域的集合统计量面雨量预报与确定性面雨量预报开展对比检验评估。结果表明:对于大雨以上等级面雨量,平原流域评分高于山地流域,集合统计量预报性能整体优于确定性预报。不同子流域最优的集合统计量面雨量定量预报产品种类及排序存在差异,总体表现为50%百分位数产品最优,平均数次之,最优百分位数第三,基于综合检验结果推荐了长江各子流域排名前三的集合统计量面雨量定量预报产品。概率预报产品最优TS评分对应的概率预报值随面雨量量级增加而逐渐降低,15 mm (40 mm)量级的面雨量最优概率预报为50% (30%)。以最优TS评分为基准,向下浮动10%来获取面雨量概率预报参考区间,当集合统计量面雨量概率预报位于参考区间时预报价值较高。以2020年长江第5号洪水过程为例,开展概率预报与定量预报推荐产品相结合的集合统计量面雨量预报产品应用分析,进一步说明了集合统计量面雨量产品误差明显小于确定性预报。

     

    Abstract: Based on the ensemble precipitation prediction data of the European Centre for medium range weather forecast from 2018 to 2021, ensemble statistics area rainfall prediction products such as mode,mean,optimal percentile,percentile and probability have been developed. Threat score,bias score,relative operating characteristic (ROC) curve method,comprehensive performance diagram and brier skill score are used for verification to ensemble statistics area rainfall prediction products above heavy rain in the Yangtze River basin. Result shows that ensemble statistics area rainfall prediction products were superior to area rainfall forecasting calculated from deterministic precipitation prediction,and the score of plain area basin is higher than that of mountain basin for the area rainfall above heavy rain. There are differences in the types and ranking of the optimal areal rainfall quantitative prediction products in different sub basins of Yangtze River. The overall performance is that the median,mean and optimal percentile was the best,second and third in score among ensemble statistics area rainfall prediction products. The top three ideal ensemble statistics area rainfall prediction product were recommended according to the comprehensive verification result in each sub-basin of Yangtze River. The optimal probability forecast value corresponding to the best threat score of the probability forecast product gradually decreases with the increase of the area rainfall magnitude,and the optimal probability of area rainfall prediction above 15mm (40 mm) magnitude is 50%(30%). Taking the optimal TS score as the benchmark,the reference interval of areal rainfall probability forecast is obtained by floating down 10%. When the ensemble statistics areal rainfall probability forecast is located in the reference interval,the forecast reference value is higher. Taking the No. 5 flood process of the Yangtze River in 2020 as an example,the application analysis of the ensemble statistics area rainfall prediction product combining probability prediction and quantitative prediction recommendation products is carried out,which further shows that the error of the ensemble statistics area rainfall prediction product is significantly less than the deterministic forecast.

     

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