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Description

The MCD18A1 Version 6.2 is a Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua combined Downward Shortwave Radiation (DSR) gridded Level 3 product produced daily at 1 kilometer pixel resolution with estimates of DSR every 3 hours. DSR is incident solar radiation over land surfaces in the shortwave spectrum (300-4,000 nanometers) and is an important variable in land-surface models that address a variety of scientific and application issues. The MCD18 products are based on a prototyping algorithm that uses multi-temporal signatures of MODIS data to derive surface reflectance and then calculate incident DSR using the look-up table (LUT) approach. The LUTs consider different types of loadings of aerosols and clouds at a variety of illumination/viewing geometry. Global DSR products are generated from MODIS and geostationary satellite data. Additional details regarding the methodology used to create the data are available in the Algorithm Theoretical Basis Document (ATBD).

Provided in the MOD18A1 product are layers for instantaneous DSR array for each individual MODIS overpass and 3-hour DSR array along with a View Zenith Angle layer.

Known Issues

Version Description

The following changes and improvements were implemented for inputs to MODIS Version 6.2 DSR data products: (1) MODIS shortwave infrared bands are included in the retrieval algorithm, which significantly reduces estimation uncertainties in cloud- and snow-covered pixels, (2) Inclusion of a new multispectral algorithm has been implemented to replace the blue band retrieval algorithm, and (3) An improved climatology of surface spectral and broadband albedo was produced and used in the retrieval algorithm.

Product Summary

Platforms
Terra ,
Aqua
Instruments
MODIS
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
1000 Meters x 1000 Meters
Spatial Reference System(s)
MODIS Sinusoidal Tiling System
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2000-02-24 to Present
Temporal Resolution
3 Hour
Data Partner
Land Processes Distributed Active Archive Center (LP DAAC) ,
MODIS Adaptive Processing System, Terrestrial Information Systems Laboratory, Earth Sciences Division, Science and Exploration Directorate, Goddard Space Flight Center, NASA (NASA/GSFC/SED/ESD/TISL/MODAPS)
Concept ID
C2486249220-LPCLOUD
Data State
ACTIVE
Number of Files/Granules
2803545
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. (2024). MODIS/Terra+Aqua Surface Radiation Daily/3-Hour L3 Global 1km SIN Grid V062 [Data set]. NASA Land Processes Distributed Active Archive Center. https://doi.org/10.5067/MODIS/MCD18A1.062 Date Accessed: 2026-02-14

File Naming Convention

MCD18A1.A2025182.h00v08.062.2025204054932.hdf

The file name begins with the Product Short Name (MCD18A1) followed by the Julian Date of Acquisition formatted as AYYYYDDD (A2025182), the Tile Identifier which is horizontal tile and vertical tile provided as hXXvYY (h00v08), the Version of the data collection (062), the Julian Date and Time of Production designated as YYYYDDDHHMMSS (2025204054932), and the Data Format (hdf).

Documents

USER'S GUIDE

ALGORITHM THEORETICAL BASIS DOCUMENT (ATBD)

PRODUCT QUALITY ASSESSMENT

SCIENCE DATA PRODUCT VALIDATION

GENERAL DOCUMENTATION

Publications Citing This Dataset

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
Diffuse Instantaneous diffuse DSR at MODIS overpass W/m² float32 -1 0 to 1400 N/A
Direct Instantaneous direct DSR at MODIS overpass W/m² float32 -1 0 to 1400 N/A
DSR Instantaneous total DSR at MODIS overpass W/m² float32 -1 0 to 1400 N/A
DSR_Quality Quality flag N/A uint8 4 0 to 2 N/A
GMT_0000_DSR Total DSR at GMT 00:00 W/m² float32 -1 0 to 1400 N/A
GMT_0300_DSR Total DSR at GMT 03:00 W/m² float32 -1 0 to 1400 N/A
GMT_0600_DSR Total DSR at GMT 06:00 W/m² float32 -1 0 to 1400 N/A
GMT_0900_DSR Total DSR at GMT 09:00 W/m² float32 -1 0 to 1400 N/A
GMT_1200_DSR Total DSR at GMT 12:00 W/m² float32 -1 0 to 1400 N/A
GMT_1500_DSR Total DSR at GMT 15:00 W/m² float32 -1 0 to 1400 N/A
GMT_1800_DSR Total DSR at GMT 18:00 W/m² float32 -1 0 to 1400 N/A
GMT_2100_DSR Total DSR at GMT 21:00 W/m² float32 -1 0 to 1400 N/A
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