Image of the Day: Satellite Spots Parched U.S. Landscape
As viewed via satellite, the massive 2012 U.S. drought shows up as an unhealthy brownish tint, centered on the High Plains and Midwest, but stretching from coast-to-coast. The image, generated by NASA's MODIS imager on its Terra and Aqua satellites, shows plant health in August 2012 compared to average conditions during the period from 2002 to 2012. Brown areas show where plant greenness was below average, whereas greens show vegetation that is more abundant than average (gray areas indicate a lack of available data).
As is immediately clear from this image, plants have not been very healthy lately in much of the country.
The map is based on an index called the Normalized Difference Vegetation Index, or NDVI, which is a measure of how plant leaves absorb visible light and reflect infrared light. According to NASA, drought-stressed vegetation reflects more visible light and less infrared than healthy vegetation.
As of September 18, about 65 percent of the lower 48 states were experiencing drought conditions. The 2012 U.S. drought, which came on suddenly and largely without warning, is comparable in severity and extent to the droughts of the 1930s era "Dust Bowl" years, as well as major droughts that affected the country in the 1950s.