VIIRS/NPP BRDF/Albedo Quality Daily L3 Global 500m SIN Grid V001

The VNP43IA2 Version 1 data product was decommissioned on July 31, 2025. Users are encouraged to use the [VNP43IA2](https://doi.org/10.5067/VIIRS/VNP43IA2.002) and [VJ143IA2](https://doi.org/10.5067/VIIRS/VJ143IA2.002) Version 2 data products.

The NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Bidirectional Reflectance Distribution Function (BRDF) and Albedo Quality (VNP43IA2) Version 1 product provides BRDF and Albedo quality at 500 meter (m) resolution. The VNP43IA2 product is produced daily using 16 days of VIIRS data and is weighted temporally to the ninth day, which is reflected in the file name. The VNP43IA2 product provides information regarding band quality and days of valid observation within a 16-day period for the VIIRS imagery bands. The VNP43 data products are designed to promote the continuity of NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo data product suite.

The VNP43 algorithm uses the RossThick/Li-Sparse-Reciprocal (RTLSR) semi-empirical kernel-driven BRDF model, with the three kernel weights from [VNP43IA1](https://doi.org/10.5067/VIIRS/VNP43IA2.001) to reconstruct surface anisotropic effects, correcting the directional reflectance to a common view geometry ([VNP43IA4](https://doi.org/10.5067/VIIRS/VNP43IA4.001)), while also computing integrated black-sky albedo (BSA) at local solar noon and white-sky albedo (WSA) ([VNP43IA3](https://doi.org/10.5067/VIIRS/VNP43IA3.001)). 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).

The VNP43IA2 data product provides a total of 11 SDS layers including: BRDF/Albedo band quality (inversion information) and days of valid observation within a 16-day period for VIIRS imagery bands I1, I2, and I3, as well as land water type class flag, snow BRDF albedo class flag, local solar noon, albedo uncertainty and the platform name.

Known Issues
* The abnormally high activation of the high aerosol flag in the Collection 1 (C1) VNP09 product has impacted downstream products. The VNP43 BRDF/Albedo/NBAR product is affected by reducing the number of otherwise acceptable observations used as input to characterize surface anisotropy. This effect (most obvious over arid bright surfaces) results in a reduced number of high quality full BRDF model inversions. Therefore, users should be aware that bright arid surfaces (normally associated with high quality BRDF/Albedo/NBAR retrievals) are likely to be somewhat represented by lower quality results in C1. VNP09 has been corrected for Collection 2 (C2). Therefore, users should avoid substantive use of C1 VNP43 over arid regions (and wait for C2 products). In any event, users are always strongly encouraged to download and use the extensive QA data provided in VNP43[I-M]A2, in addition to the briefer mandatory QA provided as part of the VNP43[I-M]A1, 3 and 4 products.
* For complete information about known issues please refer to the [MODIS/VIIRS Land Quality Assessment website](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=VIIRS).

VNP43IA2 版本1数据产品已于2025年7月31日正式退役。建议用户使用[VNP43IA2](https://doi.org/10.5067/VIIRS/VNP43IA2.002)与[VJ143IA2](https://doi.org/10.5067/VIIRS/VJ143IA2.002)的版本2数据产品。

NASA/NOAA的Suomi国家极轨伙伴卫星（Suomi National Polar-orbiting Partnership，Suomi NPP）搭载的可见光红外成像辐射计套件（Visible Infrared Imaging Radiometer Suite，VIIRS）双向反射分布函数（Bidirectional Reflectance Distribution Function，BRDF）与反照率质量（VNP43IA2）版本1产品，提供分辨率为500米的BRDF与反照率质量数据。VNP43IA2产品基于16天的VIIRS观测数据每日生成，并在时间维度上加权至第9天，该加权信息将反映在文件名中。该产品可提供VIIRS成像波段的波段质量信息，以及16天周期内的有效观测天数数据。VNP43系列数据产品旨在延续美国国家航空航天局（NASA）中分辨率成像光谱仪（Moderate Resolution Imaging Spectroradiometer，MODIS）BRDF/反照率数据产品套件的业务连续性。

VNP43算法采用RossThick/Li-Sparse-Reciprocal（RTLSR）半经验核驱动BRDF模型，从[VNP43IA1](https://doi.org/10.5067/VIIRS/VNP43IA2.001)获取三个核权重值，以重构地表各向异性效应，将方向反射率校正至统一观测几何（对应[VNP43IA4](https://doi.org/10.5067/VIIRS/VNP43IA4.001)），同时计算当地太阳正午时刻的黑体反照率（Black-sky Albedo，BSA）与白体反照率（White-sky Albedo，WSA）（对应[VNP43IA3](https://doi.org/10.5067/VIIRS/VNP43IA3.001)）。研究人员可通过简单多项式结合BRDF模型参数，获取任意太阳照射角度下的黑体反照率。同理，黑体反照率与白体反照率科学数据集（Science Dataset，SDS）图层可结合简单多项式，手动估算瞬时实际反照率（蓝天反照率）。更多方法学细节可参阅《算法理论基础文档（Algorithm Theoretical Basis Document，ATBD）》。

VNP43IA2数据产品共包含11个科学数据集图层，具体包括：BRDF/反照率波段质量（反演信息）、VIIRS成像波段I1、I2、I3在16天周期内的有效观测天数，以及陆地水域类型分类标志、积雪BRDF反照率分类标志、当地太阳正午时刻、反照率不确定性与平台名称。

已知问题
* Collection 1（C1）版本VNP09产品中高气溶胶标志出现异常高激活的情况，对下游产品造成了影响。VNP43系列BRDF/反照率/NBAR产品受此影响，用于表征地表各向异性的可用观测数量有所减少。该效应在干旱亮地表区域最为显著，会导致高质量完整BRDF模型反演的数量降低。因此，用户需注意，原本应具备高质量BRDF/反照率/NBAR反演结果的干旱亮地表区域，在C1版本中可能表现为较低质量的反演结果。VNP09产品已在Collection 2（C2）版本中完成修正，因此用户应避免在干旱区域大量使用C1版本的VNP43产品，可等待C2版本数据发布。无论如何，强烈建议用户除使用VNP43[I-M]A1、3和4产品附带的简要强制质量评估数据外，同时下载并使用VNP43[I-M]A2产品中提供的全面质量评估数据。
* 如需获取完整的已知问题信息，请参阅[MODIS/VIIRS陆地质量评估网站](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=VIIRS)