VNP43C4 v001

VIIRS/NPP BRDF/Albedo Nadir BRDF-Adjusted Reflectance Daily L3 Global 0.05 Deg CMG


PI: Crystal Schaaf

Description

The Suomi National Polar-Orbiting Partnership (S-NPP) NASA Visible Infrared Imaging Radiometer Suite (VIIRS) Bidirectional Reflectance Distribution Function (BRDF) and Albedo Nadir BRDF-Adjusted Reflectance Daily Global 0.05 Degree Climate Modeling Grid (CMG) Version 1 product (VNP43C4) is derived from the 30 arc second CMG VNP43D Version 1 product suite. VNP43C3 is generated daily from all available high-quality reflectance data over a 16-day moving window emphasizing the ninth day of the retrieval period, which is reflected in the Julian date in the filename. The VNP43 algorithm uses the RossThick/Li-Sparse-Reciprocal (RTLSR) semi-empirical kernel-driven BRDF model, with the three kernel weights from VNP43C1 to compute NBAR values for the VIIRS Day/Night band (DNB), and moderate resolution bands M1 through M5, M7, M8, M10, and M11. The algorithm removes view angle effects from directional reflectances to model the values as if they were collected from a nadir view at local solar noon. The quality and inversion status of the majority of the underlying 30 arc second pixels is provided as well as the percentage of the underlying pixels that were present or were snow covered. Users are encouraged to assess the quality information before using the BRDF/Albedo data. This 0.05 degree (5,600 meters at the equator) CMG product covers the entire globe for use in climate simulation models.

The VNP43C4 product includes 10 layers containing NBAR values for VIIRS DNB and moderate resolution bands M1 through M5, M7, M8, M10, and M11. Along with the NBAR data for the 10 bands are five ancillary layers for uncertainty, quality, local solar noon, percent finer resolution inputs, and snow cover. A low-resolution browse image is also available showing NBAR bands M5, M4, and M3 as a red, green, blue (RGB) image in JPEG format.

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Characteristics

Product Maturity

Validation at stage 1 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

Collection

Characteristic Description
CollectionS-NPP VIIRS
DOI10.5067/VIIRS/VNP43C4.001
File Size~90 MB
Temporal ResolutionDaily
Temporal Extent2012-01-19 to Present
Spatial ExtentGlobal
Coordinate SystemGeographic Latitude and Longitude
DatumN/A
File FormatHDF-EOS5
Geographic DimensionsGlobal

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers15
Columns/Rows7200 x 3600
Pixel Size5600 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
BRDF_Albedo_Uncertainty BRDF inversion information N/A 16-bit unsigned integer 32767 N/A 0 to 32766 0.001
BRDF_Quality BRDF and albedo quality information N/A 8-bit unsigned integer 255 N/A 0 to 5 N/A
Local_Solar_Noon Local solar noon zenith angle Degree 8-bit unsigned integer 255 N/A 0 to 90 N/A
Nadir_Reflectance_DNB Nadir reflectance for Day/Night band (0.7 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M1 Nadir reflectance for band M1 (0.412 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M10 Nadir reflectance for band M10 (1.61 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M11 Nadir reflectance for band M11 (2.25 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M2 Nadir reflectance for band M2 (0.445 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M3 Nadir reflectance for band M3 (0.488 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M4 Nadir reflectance for band M4 (0.555 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M5 Nadir reflectance for band M5 (0.672 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M7 Nadir reflectance for band M7 (0.865 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Nadir_Reflectance_M8 Nadir reflectance for band M8 (1.240 μm) N/A 16-bit signed integer 32767 N/A 0 to 10000 0.0001
Percent_Inputs Percent finer resolution data which contributed to the CMG Percent 8-bit unsigned integer 255 N/A 0 to 100 N/A
Percent_Snow Percent of underlying data flagged as snow Percent 8-bit unsigned integer 255 N/A 0 to 100 N/A

Quality bit index

Value Description
0 Best quality, 100% with full inversions
1 Good quality, 75% or more with best full inversions and 90% or more with full inversions
2 Relative good quality, 75% or more with full inversions
3 Mixed, 75% or less full inversions and 25% or less fill values
4 All magnitude inversions or 50% or less fill values
5 50% or more fill values
255 Fill value

Product Quality

The quality and inversion status of the majority of the underlying 30 arc second pixels is provided as well as the percentage of the underlying pixels that were present or were snow covered. Therefore, quality should be considered when using this product for quantitative results. Product accuracy/uncertainty information can be found in section 4 of the Algorithm Theoretical Basis Document (ATBD).

Known Issues

The VIIRS Land Surface Reflectance product (VNP09) flags a larger number of retrievals as ‘High Aerosol’ in the quality layer as compared to the MODIS reflectance product. The inaccurately flagged high aerosol quality flags cause the BRDF retrieval algorithm to incorrectly reject the observations and switch from full inversion (high quality retrieval) to magnitude inversion (low quality retrieval) in the mid to high latitude, arid lands, and tropical vegetative regions.

Documentation

Using the Data

Tools

Citation

DOI: 10.5067/VIIRS/VNP43C4.001

About the Image

VIIRS RGB Nadir BRDF-Adjusted Reflectance data from the VNP43C4 global product acquired January 1, 2017.

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