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Description

The VNP18A1 Version 2 is a NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Downward Shortwave Radiation (DSR) gridded Level 3 product. It is produced at 1 kilometer pixel resolution at daily intervals. DSR is the incident solar radiation over land surfaces in the shortwave spectrum (300-4,000 nanometers) and is a significant variable in land surface models (LSMs), receiving increased attention due to its importance for the management and operation of solar energy systems.

The VNP18 algorithm adapts the narrowband look-up table (LUT) approach to estimate DSR. The LUTs consider different types of loadings of aerosols and clouds at a variety of illumination and viewing geometry. The Algorithm Theoretical Basis Document (ATBD) is forthcoming and will provide additional details regarding the methodology used to create the data.

Provided in the VNP18A1 product are variables for instantaneous total, direct, and diffuse DSR, as well as 3-hour DSR, daily mean DSR, and a quality variable.

Version Description

Collection Version 2 Processing and Reprocessing

Product Summary

Platforms
Suomi-NPP
Instruments
VIIRS
Spatial Extent
N: 90 S: -90 E: 180 W: -180
Spatial Resolution
1000 Meters x 1000 Meters
Geographic Region
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2012-01-19 to Present
Temporal Resolution
1 Day
Data Partner
Land Science Investigator-led Processing System, Terrestrial Information Systems Laboratory, Earth Sciences Division, Sciences and Exploration Directorate, Goddard Space Flight Center, NASA (NASA/GSFC/SED/ESD/TISL/LandSIPS)
Land Processes Distributed Active Archive Center (LP DAAC)
Concept ID
C2631841562-LPCLOUD
Data State
ACTIVE
Processing Level
3
Published
Updated
Science Keywords
Reflectance,
Albedo,
Anisotropy,
Shortwave Radiation

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

Wang, D. (2025). VIIRS/NPP Downward Shortwave Radiation Daily L3 Global 1km SIN Grid V002 [Data set]. NASA Land Processes Distributed Active Archive Center. https://doi.org/10.5067/VIIRS/VNP18A1.002 Date Accessed: 2025-10-28

File Naming Convention

VNP18A1.A2025191.h06v03.002.2025209100439.h5

The file name begins with the Product Short Name (VNP18A1) followed by the Julian Date of Acquisition formatted as AYYYYDDD (A2025191), the Tile Identifier which is horizontal tile and vertical tile provided as hXXvYY (h06v03), the Version of the data collection (002), the Julian Date and Time of Production designated as YYYYDDDHHMMSS (2025209100439), and the Data Format (h5).

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
3hour_DSR 3-hour mean DSR W/m² float32 -1 -1 to 1400 N/A
Daily_Mean_DSR Daily Mean DSR W/m² float32 -1 -1 to 1400 N/A
Diffuse Instantaneous diffuse portion of DSR at VIIRS overpass W/m² float32 -1 -1 to 1400 N/A
Direct Instantaneous direct portion of DSR at VIIRS overpass W/m² float32 -1 -1 to 1400 N/A
DSR Instantaneous DSR at VIIRS overpass W/m² float32 -1 -1 to 1400 N/A
DSR_Quality DSR quality flag N/A uint8 N/A N/A to 4 N/A
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