This visualization shows the NDVI anomaly in areas where maize, rice, soybeans, spring wheat or winter wheat are grown over the United States, Australia, Russia, Europe and southern Africa during certain years. Green colors indicate more than average vegetatation while orange colors indicate less productive areas.
Conditions in certain regions of the globe are suitable for growing particular crops but weather can alter the growing conditions in those regions throughout the year. Satellite data can gauge the health of plants, which is a good indicator of crop productivity. The satellite imagery used in this visualization shows changes in vegetation in regions where maize, rice, soybeans, spring wheat and winter wheat are grown.
The Normalized Difference Vegetation Index (NDVI) measures how dense and green plant leaves are which suggests overall vegetative health. Scientists calculate average NDVI values over a span of years to find out what is normal at each time of year. They then compare the current NDVI value for each day of year to the average computed over the set of base years to determine if the areas are more or less productive than the average. This comparison, called the NDVI Anomaly, is used in this visualization showing the changes in global crop production in regions of the globe and time periods when they experienced significant drought conditions. The NDVI anomaly images are useful as a measure of drought when compared to 'normal' plant health. In this visualization, areas of drought are shown in shades of orange, with the most severe drought being the brightest orange/yellow. Regions where crops are more productive than average are shown by shades of green where the brightest colors are the most productive.
This data was measured by the vegetation instrument Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. However, this instrument is not able to see the surface through clouds so there are regions where no data is collected on cloudy days. In these regions, the most recent prior days value is used up to 10 days before. Areas without data for ten or more days are designated as having no data. Areas with no data or areas that have a value close to average are shown in dark grey. Time periods when no data is available globally have been skipped in this visualization.
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