This composite image over the continental United States wasproduced with data acquired by the Moderate-resolution ImagingSpectroradiometer (MODIS) during the period March 24 - April 8, 2000.The image is a map of the density of the plant canopycovering the ground. It is the first in a series of images over the continental U.S. produced by the MODIS Land Discipline Group (refer to this site June 2 & 5 for the next two images in the series).
The image is a MODIS data product called "Leaf Area Index," whichis produced by radiometrically measuring the visible and nearinfrared energy reflected by vegetation. The Leaf Area Indexprovides information on the structure of plant canopy, showing howmuch surface area is covered by green foliage relative to total landsurface area. In this image, dark green pixels indicate areas wheremore than 80 percent of the land surface is covered by green vegetation, lightgreen pixels show where leaves cover about 10 to 50 percent of theland surface, and brown pixels show virtually no leaf coverage.
The more leaf area a plant has, the more sunlight it can absorb forphotosynthesis. Leaf Area Index is one of a new suite of measurements that scientists use to understand how the Earth's land surfaces are changing over time. Their goal is to use these measurements to refine computer models well enough to simulate how the land biosphere influences the natural cycles ofwater, carbon, and energy throughout the Earth system.
This image is the first of its kind from the MODIS instrument,which launched in December 1999 aboard the Terra spacecraft. MODISbegan acquiring scientific data on February 24, 2000, when it firstopened its aperture door. The MODIS instrument and Terra spacecraftare both managed by NASA's Goddard Space Flight Center, Greenbelt, MD.
References & Resources
Image courtesy Steven Running, MODIS Land Group Member, University of Montana
