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ECMWF 降水极端天气指数在安徽省的应用评估

Assessment and applications of precipitation Extreme Forecast Index (EFI) from ECMWF to Anhui province

  • 摘要: 使用2012 年10 月—2014 年9 月欧洲中期天气预报中心(ECMWF)全球集合预报系统逐日降水、5 d 和10 d 累计降水极端天气指数(EFI)预报资料,分析了降水EFI 和强降水、降水气候距平的统计关系。结果表明: 整体而言,降水EFI 大值区和强降水具有较好对应关系,EFI 越大,发生强降水的可能性越大,但随着预报时效增加,EFI 的指示作用逐渐下降;对逐日降水EFI 大值区和降水落区TS 评分表明,在最优TS 评分条件下,EFI 阈值随着降水量级增加而增大,随着预报时效增加而降低;冬半年(10—3 月) 5 d 和10 d 累计降水EFI 对过程降水的指示意义优于夏半年(4—9 月),但当EFI 超过0.4时,随其增加,不同季节对应降水气候距平均迅速增加;另外,5 d 累计降水EFI 对过程降水的指示作用优于10 d 累计降水EFI。

     

    Abstract: In this study, the precipitation Extreme Forecast Index (EFI) from ECMWF global ensemble prediction system (EPS) from October 2012 to September 2014, including 1d, 5d and 10 d accumulated precipitation EFI, were used to evaluate the statistical relationship between EFI and severe precipitation and its anomaly, respectively. Results indicate that the high value center of EFI corresponds to severe precipitation zone. The greater the EFI is, the higher the probability that severe precipitation events occurred is. But as the forecast time length increases, the indicative significance of EFI becomes less evident. TS scores of the high value center of EFI for daily precipitation and the precipitation area show that to obtain the best TS score, the thresholds of EFI increase with the increase of precipitation grades and decrease with the increase of forecast time length. The indicative significance of EFI for 5 d and 10 d accumulated precipitation to heavy rainfall in the cold seasons (from October to March the following year) is better than that in the warm seasons (from April to September). When EFI is greater than 0.4, the precipitation climate anomalies increase quickly with the increase both 5 d and 10 d accumulated precipitation. In addition, the indicative significance of EFI for 5 d accumulated precipitation is better than that for 10 d accumulated precipitation.

     

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