“CMA北京模式”中三种不同阵风诊断方案在北京地区大风预报中的评估

Evaluation of three different gust diagnostic schemes in the CMA-BJ for gale forecasting over Beijing

  • 摘要: 数值模式预报是阵风预报的重要途径之一,对“中国气象局北京快速更新循环数值预报系统(简称CMA北京模式)”中AFWA、UPP、IUM三种阵风诊断方案在北京地区大风预报中的性能进行了分析评估。两次大风过程的分析以及各季节大风预报的批量试验检验结果显示:三种方案的阵风预报存在明显差异,IUM方案的阵风预报能力优势明显。IUM方案对冷空气大风和雷暴大风预警都有较好的指示意义。其对2020年3月18日冷空气大风过程中大风起始时间、大风区位置和演变以及过程极大风速均有较好的预报效果,对2020年8月2日雷暴大风过程中大风区范围预报偏大且位置存在偏差,但对大风预警的指示意义最强。IUM方案的阵风风速预报整体偏强,但对各个季节达到或超过5级阵风的等级预报较为准确。总体而言,IUM方案对北京地区大风预报性能较好,基于该方案制作的阵风预报产品可为大风预报提供有力支撑。

     

    Abstract: Numerical prediction is one of the important ways to forecast gust. This study analyzed and evaluated the performance of the three gust diagnostic schemes (AFWA, UPP and IUM) in the CMA-BJ for gale forecasting over Beijing. Subjective analysis on two extreme gale processes as well as objective validation on batch experiments of each season indicated that there are significant differences in the gust forecasting using the three schemes, and the forecasting with the IUM scheme shows significant advantages. The IUM scheme performs relatively well on forecasting gales associated with both cold air and thunderstorms. For the gale on 18 March 2020, which was induced by cold air invasion, the scheme shows good performance on the forecast of starting and ending time, the location and evolution, and the maximum value during the entire period of the gale. For the gale on 2 August 2020, which was generated by a thunderstorm, the scheme overestimates the gale area and shows certain biases in the location of the gale. However, the scheme issues warning for gale, which is the most significant. Moreover, the gust speed predicted by the IUM scheme has positive biases at all seasons, but the forecasts of gales equal to or greater than level 5 are more consistent with observations. In general, the IUM scheme performs better than the other two schemes for the gale forecasting over Beijing, and can provide strong support for the gale forecasting.

     

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