VIIRS/NPP Nadir BRDF-Adjusted Reflectance Daily L3 Global 500m SIN Grid NRT

The VIIRS/NPP Nadir BRDF-Adjusted Reflectance Daily L3 Global 500 m SIN Grid Near Real Time (NRT), short-name VNP43IA4N product provides NBAR estimates at 500 meter (m) resolution. The VNP43IA4N product is produced daily using 16-day VIIRS data (i.e., the current day and the previous 15 days). The view angle effects are removed from the directional reflectances resulting in a stable and consistent Bidirectional Reflectance Distribution Function (BRDF) Adjusted Reflectance (NBAR) product.

The VNP43 algorithm uses the RossThick/Li-Sparse-Reciprocal (RTLSR) semi-empirical kernel-driven BRDF model, with the three kernel weights from VNP43IA1N to reconstruct surface anisotropic effects, correcting the directional reflectance to a common view geometry (VNP43IA4N), while also computing integrated black-sky albedo (BSA) at local solar noon and white-sky albedo (WSA) (VNP43IA3N). Researchers can use the BRDF model parameters with a simple polynomial, to obtain black-sky albedo at any solar illumination angle. Likewise, both the BSA and WSA Science Dataset (SDS) layers can be used with a simple polynomial, to manually estimate instantaneous actual albedo (blue-sky albedo). Additional details regarding the methodology are available in the Algorithm Theoretical Basis Document (ATBD) at https://www.umb.edu/editor_uploads/images/school_for_the_environment_cs….

The VNP43IA4N product includes six SDS layers for BRDF/Albedo mandatory quality and nadir reflectance for VIIRS imagery bands I1, I2, and I3.

该VIIRS/NPP垂向视场BRDF校正反射率每日L3全球500米SIN网格近实时(NRT)产品，简称VNP43IA4N，提供500米分辨率的NBAR估计。VNP43IA4N产品每日利用16天的VIIRS数据（即当前日及前15日）生成。通过从方向反射率中去除视场角度效应，该产品实现了稳定且一致的双向反射分布函数(BRDF)校正反射率(NBAR)。

VNP43算法采用罗斯厚/李稀疏-互易(RTLSR)半经验核驱动BRDF模型，从VNP43IA1N获取三个核权重以重建地表各向异性效应，校正方向反射率至共同视场几何形状(VNP43IA4N)，同时计算局部太阳正午的集成黑天反照率(BSA)和白色天空反照率(WSA)(VNP43IA3N)。研究者可以使用BRDF模型参数与简单的多项式相结合，获取任何太阳光照角度下的黑天反照率。同样，BSA和WSA科学数据集(SDS)层也可以通过简单的多项式进行使用，以手动估算即时实际反照率(蓝天反照率)。有关方法的详细信息，请参阅算法理论依据文件(ATBD)，链接为https://www.umb.edu/editor_uploads/images/school_for_the_environment_cs…。

VNP43IA4N产品包含六个SDS层，用于BRDF/Albedo强制性质量和VIIRS影像波段I1、I2和I3的垂向反射率。