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TIGGE技术对西南地区地面要素预报性能的分析

Performance analysis of surface element forecast of TIGGE ensemble forecast in southwest China

  • 摘要: 基于TIGGE中欧洲中期天气预报中心和美国国家环境预报中心全球集合预报系统(EC_GEPS和NCEP_GEPS)的2016年1月1日-2017年12月31日连续2 a的预报资料,对两套系统在西南地区10 d以内的2 m温度和24 h定量降水预报进行检验评估和综合分析。2 m温度预报检验结果表明:EC_GEPS和NCEP_GEPS的2 m温度控制预报和集合平均预报的均方根误差均普遍偏高且NCEP_GEPS总体而言优于EC_GEPS;两套系统集合平均均方根误差相对于控制预报改进不明显;集合离散度均明显偏低;Talagrand分布均呈现出非常明显的"J型"分布特征,Outlier评分普遍偏高且EC_GEPS的Outlier评分明显低于NCEP_GEPS;从集合最小值到集合最大值,随着集合百分位的增大,各个预报时效的均方根误差逐渐减小,集合最大值预报技巧最高。降水预报检验结果表明:EC_GEPS和NCEP_GEPS的24 h定量降水预报的Talagrand分布总体而言均呈现出"L型"分布特征且NCEP_GEPS更加明显;NCEP_GEPS各个预报时效的Outlier评分均普遍偏高且明显高于EC_GEPS;EC_GEPS的降水概率预报技巧明显优于NCEP_GEPS;EC_GEPS的70%集合百分位预报技巧最高,NCEP_GEPS的80%集合百分位预报技巧最高。EC_GEPS和NCEP_GEPS在西南地区的2 m温度预报和降水预报均存在一定的系统性误差,进行相应的集合预报系统性偏差订正应该能较好地改进预报技巧。

     

    Abstract: Based on the global ensemble forecast data of EC and NCEP in TIGGE database from January 1, 2016 to December 31, 2017, the 2 m air temperature and 24 h accumulated rain forecasts within 10 days of the two systems in southwest China are verified and analyzed. The 2 m air temperature verification results show that the root mean square error of control forecast and ensemble mean of EC_GEPS and NCEP_GEPS are generally very high, especially higher for EC_GEPS. For each forecast lead time, the root mean square error of ensemble mean forecast is basically equal to that of the control forecast, and the ensemble spread is significantly low. The Talagrand distributions all showed a "J" distribution characteristics. The outlier score is generally high, and the outlier score of EC_GEPS is significantly lower than that of NCEP_GEPS. From the minimum ensemble forecast to the maximum ensemble forecast, with the increase of the ensemble percentiles, the root mean square error of each forecast lead time decreases gradually, and the root mean square error of the maximum ensemble forecast is the lowest. The 2 m air temperature verification results show that the Talagrand distribution of 24 h accumulated rain for each forecast lead time of EC_GEPS and NCEP_GEPS generally show a certain "L" distribution characteristics, which is more obvious for NCEP_GEPS. The outlier scores of NCEP_GEPS for each forecast lead time are generally high, and much higher than those of EC_GEPS. The rainfall ensemble prediction skill of EC_GEPS is much better than that of NCEP_GEPS. The prediction skill of 70% ensemble percentile forecast of EC_GEPS is optimal among all ensemble percentile forecasts, and the prediction skill of 80% ensemble percentile forecast of NCEP_GEPS is optimal among all ensemble percentile forecasts. Both EC_GEPS and NCEP_GEPS have some systematic errors in the 2 m air temperature forecast and precipitation forecast in Southwest China. Therefore, conducting corresponding systematic error correction for the ensemble forecast should improve the forecast technique.

     

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