How well do multi-satellite products capture the space-time dynamics of precipitation? Part I: five products assessed via a wavenumber-frequency decomposition
How well do multi-satellite products capture the space-time dynamics of precipitation? Part I: five products assessed via a wavenumber-frequency decomposition
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DOI：
10.1175/jhm-d-21-0075.1
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发表时间：
2021-08
影响因子：
3.8
通讯作者：
C. Guilloteau;E. Foufoula‐Georgiou;P. Kirstetter;J. Tan;G. Huffman
中科院分区：
文献类型：
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作者：
C. Guilloteau;E. Foufoula‐Georgiou;P. Kirstetter;J. Tan;G. Huffman
随着更多全球卫星降水产品的出现，为了给在水文建模、气候研究和其他应用中降水时空特征的捕捉效果提供指导，对它们进行更仔细的评估是至关重要的。在此，我们提出一种时空傅里叶频谱分析，并定义了一套指标，用于评估风暴系统的空间组织、降水特征的传播速度和方向，以及卫星产品再现参考“地面实况”产品变异性的时空尺度（“有效分辨率”）。我们通过一个具有丰富时空结构的风暴系统案例研究，展示了该方法如何与我们的物理直觉相关联。然后，我们对美国东南部两年期间的五种高分辨率多卫星产品（CMORPH、GSMaP、IMERG - 早期、IMERG - 最终和PERSIANN - CCS）进行了评估。与参考的地面雨量计 - 雷达数据集（GV - MRMS）相比，所有五种卫星产品都显示出大致一致的时空功率谱密度，这表明在降水系统的平均形态和动力学方面具有一致性。然而，在波长小于200公里和周期小于4小时的情况下频谱功率的不足表明所有卫星产品都过于“平滑”。在这些精细尺度上，这些产品与雨量计 - 雷达参考数据的频谱相干性水平也较低，这表明在捕捉降水特征的位置和时间方面存在差异。从时空频谱相干性来看，与其他产品相比，IMERG - 最终产品在解析降水直至200公里和4小时尺度的时空动力学方面表现出更优的能力。
As more global satellite-derived precipitation products become available, it is imperative to evaluate them more carefully for providing guidance as to how well precipitation space-time features are captured for use in hydrologic modeling, climate studies and other applications. Here we propose a space-time Fourier spectral analysis and define a suite of metrics which evaluate the spatial organization of storm systems, the propagation speed and direction of precipitation features, and the space-time scales at which a satellite product reproduces the variability of a reference “ground-truth” product (“effective resolution”). We demonstrate how the methodology relates to our physical intuition using the case study of a storm system with rich space-time structure. We then evaluate five high-resolution multi-satellite products (CMORPH, GSMaP, IMERG-early, IMERG-final and PERSIANN-CCS) over a period of two years over the southeastern US. All five satellite products show generally consistent space-time power spectral density when compared to a reference ground gauge-radar dataset (GV-MRMS), revealing agreement in terms of average morphology and dynamics of precipitation systems. However, a deficit of spectral power at wavelengths shorter than 200 km and periods shorter than 4 h reveals that all satellite products are excessively “smooth”. The products also show low levels of spectral coherence with the gauge-radar reference at these fine scales, revealing discrepancies in capturing the location and timing of precipitation features. From the space-time spectral coherence, the IMERG-final product shows superior ability in resolving the space-time dynamics of precipitation down to 200 km and 4 h scales compared to the other products.