The solar energy available for photosynthesis, known as photosynthetically active radiation (PAR), is one of the important factors controlling the growth of plants and phytoplankton. It regulates the composition and evolution of marine and land-based ecosystems.

PAR refers to the wavelength range of incoming sunlight (roughly 400-700 nanometers) that can be absorbed by plants for photosynthesis. Knowing the spatial and temporal distribution of PAR is critical to understanding biogeochemical cycles of carbon, nutrients, and oxygen. These can impact water quality by stimulating or inhibiting the growth of organisms in the water.

NASA’s Earth-observing instruments, such as the MODIS instrument aboard the Aqua platform, can capture PAR data from around the world. Other related data include measures of leaf area index, gross primary production, and carbon fluxes.