In this paper we introduce the new concept of directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface retrieved from satellite observations. This surface DLER describes Lambertian (isotropic) surface reflection which is extended with a dependence on the satellite viewing geometry. We apply this concept to data of the GOME-2 satellite instruments to create a global database of the reflectivity of the Earth's surface, providing surface DLER for 26 wavelength bands between 328 and 772 nm as a function of the satellite viewing angle via a second-degree polynomial parameterisation. The resolution of the database grid is 0.25^∘ by 0.25^∘, but the real, intrinsic spatial resolution varies over the grid from 1.0^∘ by 1.0^∘ to 0.5^∘ by 0.5^∘ down to 0.25^∘ by 0.25^∘ by applying dynamic gridding techniques. The database is based on more than 10 years (2007–2018) of GOME-2 data from the MetOp-A and MetOp-B satellites.The relation between DLER and bi-directional reflectance distribution function (BRDF) surface reflectance is studied using radiative transfer simulations. For the shorter wavelengths (λ<500 nm), there are significant differences between the two. For instance, at 463 nm the difference can go up to 6 % at 30^∘ solar zenith angle. The study also shows that, although DLER and BRDF surface reflectances have different properties, they are comparable for the longer wavelengths (λ>500 nm). Based on this outcome, the GOME-2 surface DLER is compared with MODIS surface BRDF data from MODIS band 1 (centred around 645 nm) using both case studies and global comparisons. The conclusion of this validation is that the GOME-2 DLER compares well to MODIS BRDF data and that it does so much better than the non-directional LER database. The DLER approach for describing surface reflectivity is therefore an important improvement over the standard isotropic (non-directional) LER approaches used in the past.The GOME-2 surface DLER database can be used for the retrieval of atmospheric properties from GOME-2 and from previous satellite instruments like GOME and SCIAMACHY. It will also be used to support retrievals from the future Sentinel-5 UVNS (ultraviolet, visible, near-infrared, and short-wave infrared) satellite instrument.

中文翻译：

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由 GOME-2 卫星仪器测量的地球表面定向相关朗伯等效反射率 (DLER)

在本文中，我们介绍了从卫星观测中获得的地球表面定向相关朗伯等效反射率 (DLER) 的新概念。该表面 DLER 描述了朗伯（各向同性）表面反射，其扩展依赖于卫星观察几何形状。我们将此概念应用于 GOME-2 卫星仪器的数据，以创建地球表面反射率的全球数据库，提供 328 至 772 nm之间 26 个波长带的表面 DLER 作为卫星视角的函数，通过第二个-多项式参数化。数据库网格的分辨率为 0.25 ^∘ × 0.25 ^∘，但实际的固有空间分辨率在网格上从 1.0 ^{∘ 变化}通过应用动态网格技术，从 1.0 ^∘到 0.5 ^∘到 0.5 ^∘到 0.25 ^∘到 0.25 ^∘。该数据库基于 MetOp-A 和 MetOp-B 卫星超过 10 年（2007-2018 年）的 GOME-2 数据。 DLER 与双向反射分布函数 (BRDF) 表面反射率之间的关系使用辐射研究转移模拟。对于较短的波长（λ <500  nm），两者之间存在显着差异。例如，在 463  nm 处的差异可以在 30 ^∘处达到 6 %太阳天顶角。该研究还表明，尽管 DLER 和 BRDF 表面反射率具有不同的特性，但它们在较长波长（λ > 500  nm）方面具有可比性。基于这一结果，将 GOME-2 表面 DLER 与来自 MODIS 波段 1（以 645 nm为中心）的 MODIS 表面 BRDF 数据进行比较 ) 使用案例研究和全球比较。该验证的结论是，GOME-2 DLER 与 MODIS BRDF 数据相比效果很好，并且比非定向 LER 数据库做得好得多。因此，描述表面反射率的 DLER 方法是对过去使用的标准各向同性（非定向）LER 方法的重要改进。 GOME-2 表面 DLER 数据库可用于从 GOME-2 和从以前的卫星仪器，如国美和 SCIAMACHY。它还将用于支持未来 Sentinel-5 UVNS（紫外线、可见光、近红外和短波红外）卫星仪器的检索。