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Description

The MCD18A2 Version 6.1 dataset was decommissioned on June 1, 2024. Users are encouraged to use the MCD18A2 Version 6.2 data product.

The MCD18A2 Version 6.1 is a Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua combined Photosynthetically Active Radiation (PAR) gridded Level 3 product produced daily at 1 kilometer pixel resolution with estimates of PAR every 3 hours. PAR is incident solar radiation in the visible spectrum (400-700 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 PAR 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 PAR 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 MOD18A2 product are layers for instantaneous PAR array for each individual MODIS overpass and 3-hour PAR array along with a View Zenith Angle layer.

Known Issues

Version Description

The following changes and improvements were implemented for inputs to MODIS Version 6.1 Land Cover data products: (1) Version 6.1 Level-1B (L1B) products have been improved by undergoing various calibration changes that include: changes to the response-versus-scan angle (RVS) approach that affects reflectance bands for Aqua and Terra MODIS, corrections to adjust for the optical crosstalk in Terra MODIS infrared (IR) bands, and corrections to the Terra MODIS forward look-up table (LUT) update for the period 2012 – 2017, and (2) A polarization correction has been applied to the L1B Reflective Solar Bands (RSB).

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 2024-06-01
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
C2484080763-LPCLOUD
Data State
DEPRECATED
Number of Files/Granules
0
Processing Level
3
Published
Updated
Science Keywords
Reflectance ,
Albedo ,
Anisotropy

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. (2021). MODIS/Terra+Aqua Photosynthetically Active Radiation Daily/3-Hour L3 Global 1km SIN Grid V061 [Data set]. NASA Land Processes Distributed Active Archive Center. https://doi.org/10.5067/MODIS/MCD18A2.061 Date Accessed: 2026-02-15

File Naming Convention

MCD18A2.A2024153.h04v10.061.2024178065847.hdf

The file name begins with the Product Short Name (MCD18A2) followed by the Julian Date of Acquisition formatted as AYYYYDDD (A2024153), the Tile Identifier which is horizontal tile and vertical tile provided as hXXvYY (h04v10), the Version of the data collection (061), the Julian Date and Time of Production designated as YYYYDDDHHMMSS (2024178065847), 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

Filters
Title Year Author
Estimation of land surface incident shortwave radiation from Geostationary Advanced Himawari Imager and Advanced Baseline Imager observations using an optimization method Zhang, Y.
Forest fragmentation impacts the seasonality of Amazonian evergreen canopies Nunes, M. H.
A new index assessing the viability of PAR application projects used to validate PAR models Ferrera-Cobos, F.
Combination of models to generate the first PAR maps for Spain Ferrera-Cobos, F.
A new set of MODIS land products (MCD18)—Downward shortwave radiation and photosynthetically active radiation Wang, D.
Exploration of machine learning techniques in emulating a coupled soil canopy atmosphere radiative transfer model for multi-parameter estimation from satellite observations Shi, H.
SHOWING 6 OF 6

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 PAR at MODIS overpass W/m² float32 -1 0 to 700 N/A
Direct Instantaneous direct PAR at MODIS overpass W/m² float32 -1 0 to 700 N/A
GMT_0000_PAR Total PAR at GMT 00:00 W/m² float32 -1 0 to 700 N/A
GMT_0300_PAR Total PAR at GMT 03:00 W/m² float32 -1 0 to 700 N/A
GMT_0600_PAR Total PAR at GMT 06:00 W/m² float32 -1 0 to 700 N/A
GMT_0900_PAR Total PAR at GMT 09:00 W/m² float32 -1 0 to 700 N/A
GMT_1200_PAR Total PAR at GMT 12:00 W/m² float32 -1 0 to 700 N/A
GMT_1500_PAR Total PAR at GMT 15:00 W/m² float32 -1 0 to 700 N/A
GMT_1800_PAR Total PAR at GMT 18:00 W/m² float32 -1 0 to 700 N/A
GMT_2100_PAR Total PAR at GMT 21:00 W/m² float32 -1 0 to 700 N/A
PAR Instantaneous total PAR at MODIS overpass W/m² float32 -1 0 to 700 N/A
PAR_Quality Quality flag Bit Field uint8 N/A N/A N/A
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