This series of four images contains the Polar Stereographic projections of Second Generation Normalized Differential Vegetation Index (NDVI) data for the months of February, May, August and November 1996. The Second Generation images are in black and white only. The darker areas indicate dense, green vegetation, whereas the lighter areas are generally drier areas of the earth. The hole in the middle of the images is due to lack of coverage by the NOAA polar orbiter satellites (they travel a few degrees to one side of the poles, not directly over the poles, like their name would suggest). Note the general lack of green in the February Northern Hemisphere image because it is winter. Darker areas close to the equator indicate a permanent vegetation cover which is typical of tropical climates. As the growing season starts (in April or May), note the general darkening (greening) of the eastern United States and the California coast. Desert areas such as the Sahara are quite obvious in all four of these images and always have a very light appearance. The Nile River delta can be seen in all four images. The Nile stays green all year but is especially green in the August image. Once the growing season is complete, notice the general lightening of the November image over the United States. This indicates the vegetation is dying or dead. Interestingly, the area over India and Southeast Asia is much greener in the November image than the August image. This is due to the Monsoon season.
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