Satellite data can be used to monitor the health of plant life from space. The Normalized Difference Vegetation Index (NDVI) provides a simple numerical indicator of the health of vegetation which can be used to monitoring changes in vegetation over time. This animation shows the seasonal changes in vegetation by fading between average monthly NDVI data from 2004. The loop begins on September 24 and repeats six times during one full rotation of the globe at a rate of one frame per day. The fade for each month is complete on the 15th of each month.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0