MCD18C2 v061

MODIS/Terra+Aqua Photosynthetically Active Radiation Daily 3-Hour L3 Global 0.05 Deg CMG

PI: Dongdong Wang


The MCD18C2 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 0.05 degree (5,600 meters at the equator) 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 MOD18C2 product are layers for instantaneous PAR array for each individual MODIS overpass and 3-hour PAR array along with a View Zenith Angle layer.

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Improvements/Changes from Previous Versions

  • The 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.
  • A polarization correction has been applied to the L1B Reflective Solar Bands (RSB).
  • The MCD18 suite has added CMG products (MCD18C1/MCD18C2).

Product Maturity

Validation at stage 1 has been achieved for the MODIS Surface Radiation products. Further details regarding MODIS land product validation for the MCD18 data products are available from the MODIS Land Team Validation site.

Collection and Granule


Characteristic Description
CollectionCombined MODIS
File Size~70 MB
Temporal Resolution< Daily
Temporal Extent2000-02-24 to Present
Spatial ExtentGlobal
Coordinate SystemGeographic Latitude and Longitude
File FormatHDF-EOS
Geographic Dimensions3600 km x 7200 km


Characteristic Description
Number of Science Dataset (SDS) Layers8
Columns/Rows3600 x 7200
Pixel Size5600 m


SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
GMT_0000_PAR Total PAR at GMT 00:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_0300_PAR Total PAR at GMT 03:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_0600_PAR Total PAR at GMT 06:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_0900_PAR Total PAR at GMT 09:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_1200_PAR Total PAR at GMT 12:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_1500_PAR Total PAR at GMT 15:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_1800_PAR Total PAR at GMT 18:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A
GMT_2100_PAR Total PAR at GMT 21:00 W/m² 32-bit floating point -1 N/A 0 to 700 N/A

See Table 4 in the User Guide for additional information on band dimensions.

Known Issues

For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website.

About the image

Combined MODIS Photosynthetically Active Radiation (PAR) data from the MCD18C2 global product, December 30, 2020.

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User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data


DOI: 10.5067/MODIS/MCD18C2.061