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降雨条件下风廓线雷达探测大气垂直速度综合算法改进

Improved Retrieval of Atmospheric Vertical Velocity from Wind Profiler Radar under Rainfall Conditions

  • 摘要: 中国气象局风廓线雷达业务网在降雨环境下功率谱密度数据信号没能有效区分降水与湍流信号,计算得到的大气垂直速度和水平风速等基本产品,会出现明显偏差,甚至错误。本文基于业务运行需求设计了功率谱数据多个技术环节的处理方法和核心算法,并建立了综合算法处理流程,经检验效果良好。噪声电平估计关键技术采用Savitzky-Golay滤波替代滑动平均对谱线进行预处理,并设计功率谱排序后的滑动Z检验的噪声电平估计方法,经仿真验证,结果明显好于已有的多种算法。文中定义的功率谱信号识别检测方法,经过多种统计算法和物理检查处理,可以准确获取降水发生时的双峰信号,经高斯拟合,计算得到平均速度,能够区分大气湍流垂直运动和降水下落速度。利用上述改进的大气垂直运动识别综合算法对北京观象台风廓线雷达2023年7月30日降雨过程进行了综合验证。结果表明,该算法可以很好地适用于晴空、降雨等天气条件,区分大气垂直运动和降水下降速度,实时反映降雨时大气和降水的运动状态。经该算法处理后得到的大气湍流垂直运动与欧洲中期天气预报中心第5代再分析资料(ERA5)十分接近,而现有业务使用的大气垂直速度在降雨环境下反映的是降水下落速度,将降水下落速度误判为大气垂直运动,与实际情况存在明显误差。

     

    Abstract: The operational wind profiler radar network of the China Meteorological Administration cannot reliably distinguish precipitation and turbulence signals in PSD (power spectral density) data during rainfall. This limitation causes significant deviations, or even errors in the retrieved atmospheric vertical and horizontal wind speed products. Based on operation requirements, this article designs processing methods and core algorithms for multiple technical aspects of power spectrum data, and establishes a comprehensive algorithm processing flow. The results have been tested and proven to be effective. Among them, the key technology for noise level estimation employs Savitzky-Golay filtering instead of moving average for preprocessing spectral lines, and designs a noise level estimation method based on sliding Z-test after power spectrum sorting. Simulation results show that the performance is significantly better than that of existing algorithms. Additionally, the power spectrum signal recognition and detection method outlined in the article can precisely capture the bimodal signals indicative of precipitation through the application of various statistical algorithms and physical verification processes. Following Gaussian fitting, the mean velocity is calculated, enabling differentiation between vertical motion caused by atmospheric turbulence and the falling velocity of precipitation. Validation using Beijing radar observations on 30 July 2023, shows that the proposed algorithm accurately distinguishes atmospheric motion from precipitation fall velocity under all conditions, aligning with the fifth-generation ECMWF reanalysis data. In contrast, current operational products misinterpret precipitation fall velocity as atmospheric motion, resulting in substantial retrieval errors.

     

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