Greenness of the Conterminous U.S.
Overview of the Greenness of the Conterminous U.S.
Satellite derived vegetation index maps of the contiguous United States have been available since 1989. The vegetation index maps, or more commonly called "greenness" maps, are produced every week using the latest information on the growth and condition of the vegetation.
The greenness maps show the health and vigor of the vegetation. Generally healthy vegetation is considered an indicator of favorable climatic and environmental conditions. While poor vegetation condition is indicative of droughts and diminished productivity. The USGS greenness maps can be used to evaluate the vegetation condition of a region. The greenness maps are produced with a spatial resolution of 1-km. At this scale the greenness maps are most useful for countywide, statewide, and regional evaluation of vegetation condition.
The greenness maps are used by government agencies and private industry for a wide variety of applications. Some examples are agricultural assessment, grazing land management, grassland and forest fire danger assessment, and drought monitoring.
One of the most important aspects of the USGS greenness mapping is the more than 20-year history of information. Over the last 20 years, droughts have come and gone, there have been years when the vegetation has been lush from ample rain, and there have been the "normal" years. From all of this information it is possible to determine the departure from normal for vegetation condition, much like is done for precipitation.
As a result, it is possible to compare this week`s vegetation condition with normal conditions. An above normal condition could indicate wetter or warmer than normal conditions while a below normal condition could indicate colder or dryer than normal conditions. The interpretation of departure from normal will depend on the season and geography of a region.
The greenness maps are digital images that can be used on any computer. The images are available in two basic forms. Most of the images you will see here are GIF formatted images that can viewed by a browser or most imagery viewing applications. The greenness images are also available in binary format that is more suitable for analytical image processing. Thus the greenness images can be used for visual assessment of conditions or for quantitative analysis of biophysical conditions.