VNP43IA4 v001

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

PI: Crystal Schaaf


The NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Nadir Bidirectional Reflectance Distribution Function (BRDF) Adjusted Reflectance (NBAR) Version 1 product provides NBAR estimates at 500 meter (m) resolution. The VNP43IA4 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 view angle effects are removed from the directional reflectances, resulting in a stable and consistent NBAR product. 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 to reconstruct surface anisotropic effects, correcting the directional reflectance to a common view geometry (VNP43IA4), while also computing integrated black-sky albedo (BSA) at local solar noon and white-sky albedo (WSA) (VNP43IA3). 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 VNP43IA4 product includes six SDS layers for BRDF/Albedo mandatory quality and nadir reflectance for VIIRS imagery bands I1, I2, and I3. A low-resolution browse image is also available showing NBAR bands I1, I2, and I1 as an RGB (red, green, blue) image in JPEG format.

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Product Maturity

Validation at stage 3 has been achieved for the VIIRS BRDF/Albedo product suite. Visit the VIIRS Land Product Quality Assessment website for additional information on validation and product maturity status.

Collection and Granule


Characteristic Description
CollectionSuomi NPP VIIRS
File Size~16.7 MB
Temporal ResolutionDaily
Temporal Extent2012-01-17 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
File FormatHDF-EOS5
Geographic Dimensions1200 km x 1200 km


Characteristic Description
Number of Science Dataset (SDS) Layers6
Columns/Rows2400 x 2400
Pixel Size500 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
BRDF_Albedo_Band_Mandatory_Quality_I1 BRDF/Albedo mandatory quality for band I1 N/A 8-bit unsigned integer 255 N/A 0 to 1 N/A
BRDF_Albedo_Band_Mandatory_Quality_I2 BRDF/Albedo mandatory quality for band I2 N/A 8-bit unsigned integer 255 N/A 0 to 1 N/A
BRDF_Albedo_Band_Mandatory_Quality_I3 BRDF/Albedo mandatory quality for band I3 N/A 8-bit unsigned integer 255 N/A 0 to 1 N/A
Nadir_Reflectance_I1 Nadir BRDF/Albedo Reflectance at local solar noon for band I1 N/A 16-bit signed integer 255 N/A 0 to 10000 0.0001
Nadir_Reflectance_I2 Nadir BRDF/Albedo Reflectance at local solar noon for band I2 N/A 16-bit signed integer 255 N/A 0 to 10000 0.0001
Nadir_Reflectance_I3 Nadir BRDF/Albedo Reflectance at local solar noon for band I3 N/A 16-bit signed integer 255 N/A 0 to 10000 0.0001

Product Quality

Product Quality information can be found in the ATBD in Table 9. Product accuracy/uncertainty information can be found in Section 4. Additional quality information can be found in the VNP43IA2 data product.

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.

About the image

A RGB composite of the VNP43IA4 nadir reflectance bands over Southeastern Australia from October 29, 2018.

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User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data


DOI: 10.5067/VIIRS/VNP43IA4.001