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尺度分析降水检验方法在暴雨评估中的应用

An application of the scale analysis precipitation verification method in rainstorm assessment

  • 摘要: 随着数值预报技术的不断发展,气象领域对精细化降水预报评估提出了更高的要求。常规降水检验仅能提供降水综合技巧,无法获取降水预报深层误差分布规律,难以定位误差来源。为深入了解高分辨率模式极端降水预报误差特征,选取2024年华北混合型强降水个例,基于尺度分析的降水检验方法开展精细化降水预报误差评估,并利用2023年夏季检验结果验证结论的一致性和可靠性。个例检验结果表明,不同分辨率模式检验结果较为一致,其中模式中雨预报技巧最佳,大雨和暴雨预报误差最集中的尺度均为48 km,均方误差MSE百分比达20%以上,大暴雨降水预报在典型风暴尺度上几乎没有预报技巧。CMA-MESO区域模式季节检验显示大雨和暴雨误差集中在24—96 km尺度范围,检验结果具有较强的稳健性,该范围是小尺度湿对流过程初始误差经过24 h时间积分后形成的关键误差尺度,与该尺度相关的对流扰动过程如典型的重力波动、斜压不稳定触发等物理过程值得重点关注。

     

    Abstract: With the continuous advancement of numerical forecasting techniques, the meteorological community has imposed higher requirements on the evaluation of high-resolution precipitation forecasts. Conventional precipitation verification approaches can only provide a comprehensive assessment of forecast skills, which fail to capture the intrinsic distribution of forecast errors and identify the error sources. To gain deeper insights into error characteristics of extreme precipitation forecasts in high-resolution models, a case study of a mixed-type heavy precipitation event in North China in 2024 was selected for comprehensive analysis. A verification methodology based on scale analysis was employed to evaluate forecast errors in high-resolution precipitation predictions, and the consistency and reliability of the conclusions were validated using verification results from the summer of 2023. The case study results indicate that the verification results exhibit a high degree of consistency across various models of different resolutions. Notably, the models exhibit the highest forecasting skill score in predicting moderate rain, whereas forecast errors for heavy and torrential rain are predominantly concentrated at a scale of 48 km, with the mean squared error percentage (MSE%) exceeding 20%. For extremely heavy rain, the models exhibit minimal forecasting skill at the typical storm scale. The seasonal verification of the CMA-MESO regional model further indicates that forecast errors for heavy and torrential rain are concentrated within the 24–96 km scale range, confirming the reliability of the verification results. This scale range has been identified as the critical error scale, primarily caused by the 24-hour time integration of initial errors in small-scale moist convective processes. Physical processes related to convective perturbation weather processes associated with this scale, such as gravity waves and the triggering of baroclinic instability, warrant particular attention.

     

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