This paper is the second part of companion papers describing the development of GRASP approach for aerosol and surface retrieval from Sentinel-5P/TROPOMI. Here we focus on the S5P/TROPOMI GRASP aerosol and surface products global validation and systematic intercomparison with other products from independent instruments and algorithms. Specifically, we have validated the S5P/TROPOMI GRASP, Suomi-NPP/VIIRS DB and MODIS/TERRA DT + DB aerosol products with the ground-based AERONET referenced measurements using the same methodology and intercompare the validation results. In addition, the global pixel-to-pixel intercomparisons of the aerosol products (AOD, fine/coarse mode AOD and SSA) are performed over different surfaces, i.e., ocean and land surface with different NDVIs. Besides, we compared the S5P/TROPOMI GRASP, MODIS MCD43 surface BRDF/albedo as well as OMI, GOME-2 and SCIAMACHY Lambertian-Equivalent Reflectivity (LER) albedo climatology developed by Royal Netherlands Meteorological Institute (KNMI) with the surface reference dataset generated based on the synergetic retrieval of AERONET and S5P/TROPOMI measurements. Finally, the intercomparisons of the surface BRDF and albedo datasets were performed globally at the UV, VIS, NIR and SWIR parts of the spectrum. Overall, generally good agreement was observed between independent aerosol and surface datasets with a high percentage of pixels satisfying the Optimal and Target requirements. We would emphasize two advantages for TROPOMI/GRASP aerosol and surface products: (i) it provides spectral AOD together with detailed aerosol properties, such as fine/coarse mode AOD, spectral AAOD and SSA at UV, VIS, NIR and SWIR wavelengths, which are important for constraining aerosol environmental and climate effects; (ii) the TROPOMI/GRASP aerosol and surface products are globally retrieved simultaneously in a fully consistent manner.

中文翻译：

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使用 GRASP 算法扩展 S5P/TROPOMI 的气溶胶和表面表征。第二部分：全球验证和比对


本文是姊妹篇的第二部分，描述了从 Sentinel-5P/TROPOMI 进行气溶胶和表面反演的 GRASP 方法的开发。在这里，我们重点关注 S5P/TROPOMI GRASP 气溶胶和表面产品的全球验证以及与来自独立仪器和算法的其他产品的系统比对。具体来说，我们使用相同的方法通过地面 AERONET 参考测量来验证 S5P/TROPOMI GRASP、Suomi-NPP/VIIRS DB 和 MODIS/TERRA DT + DB 气溶胶产品，并对验证结果进行相互比较。此外，气溶胶产品（AOD、精细/粗略模式AOD和SSA）的全局像素间比较是在不同表面（即具有不同NDVI的海洋和陆地表面）上进行的。此外，我们还比较了荷兰皇家气象研究所（KNMI）开发的S5P/TROPOMI GRASP、MODIS MCD43表面BRDF/反照率以及OMI、GOME-2和SCIAMACHY朗伯等效反射率（LER）反照率气候学与生成的表面参考数据集基于 AERONET 和 S5P/TROPOMI 测量值的协同检索。最后，在光谱的 UV、VIS、NIR 和 SWIR 部分对表面 BRDF 和反照率数据集进行了全局比较。总体而言，独立气溶胶和表面数据集之间普遍存在良好的一致性，其中很大一部分像素满足最佳和目标要求。 我们要强调 TROPOMI/GRASP 气溶胶和表面产品的两个优势：(i) 它提供光谱 AOD 以及详细的气溶胶特性，例如 UV、VIS、NIR 和 SWIR 波长下的细/粗模式 AOD、光谱 AAOD 和 SSA，这对于限制气溶胶环境和气候影响很重要； (ii) TROPOMI/GRASP 气溶胶和表面产品以完全一致的方式在全球范围内同时检索。