The level-4 MODIS global Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation (FPAR) product is composited every 8 days at 1-kilometer resolution on a Sinusoidal grid. This product was created to make MODIS products for the North American Carbon Program (NACP) more easily accessible and useable by streamlining access to MODIS land data products. These products are tailored for modeling efforts by providing the preprocessing necessary to create gap-filled and QA-filtered data for of only the layers of interest to investigators, thus saving individuals hours of data acquisition and processing.

The LAI variable defines the number of equivalent layers of leaves relative to a unit of ground area, whereas FPAR measures the proportion of available radiation in the photosynthetically active wavelengths that are absorbed by a canopy. Both variables are used as satellite-derived parameters for calculating surface photosynthesis, evapotranspiration, and net primary production, which in turn are used to calculate terrestrial energy, carbon, water cycle processes, and biogeochemistry of vegetation.

For the details of the temporal smoothing and the spatial gap filling algorithms used, see the User Guide for MOD09GFS and MOD15GFS products.