MCD18A2: Daily and 3-Hour Photosynthetically Active Radiation at 1km Global Scale

MCD18A2 Version 6.2 provides daily global estimates of Photosynthetically Active Radiation (PAR) at 1-kilometer pixel resolution, with data points every 3 hours. The National Aeronautics and Space Administration (NASA) produces this combined MODIS Terra and Aqua product using a prototyping algorithm that incorporates multi-temporal signatures and look-up tables for aerosols and clouds. Improvements in this version include the use of shortwave infrared bands to reduce uncertainty in cloud- and snow-covered pixels and an updated multispectral algorithm.

Use Cases

• Modeling terrestrial ecosystem productivity based on incident solar radiation in the 400-700nm spectrum.
• Assessing cloud and aerosol impacts on surface light availability using the 3-hour PAR array.
• Improving land-surface model parameterization based on daily global PAR estimates at 1km resolution.
• Studying diurnal cycles of solar energy available for photosynthesis using the instantaneous PAR layers for each satellite overpass.

Strengths

• Algorithm improvements in Version 6.2, such as inclusion of shortwave infrared bands, significantly reduce estimation uncertainties in cloud- and snow-covered pixels.
• Provides both instantaneous PAR for each satellite overpass and a synthesized 3-hour PAR array.
• Global coverage at a 1-kilometer spatial resolution, produced daily.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Known data issues exist, requiring users to consult the MODIS/VIIRS Land Quality Assessment website for complete information.

Provenance

Source

National Aeronautics and Space Administration

Collection Method

Derived from combined MODIS Terra and Aqua satellite data using a prototyping algorithm with multi-temporal signatures and look-up tables.

Time Range

Daily production.

Freshness

Last updated 2026-03-12 23:37:18.261057; freshness should be verified.

Geography

Global.