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New maps of snow cover produced by NASA’s Terra satellite show that this year’s snow line
stayed farther north than normal. When combined with land surface
temperature measurements, the observations confirm earlier National
Oceanic and Atmospheric Administration reports that the United States was
unusually warm and dry this past winter.
The above map shows snow cover over the continental United States from
February 2002 and is based on data acquired by the Moderate-Resolution Imaging Spectroradiometer
(MODIS). The amount of land covered by snow during this period was much lower than usual. With the exception of the western mountain ranges and the Great Lakes region, the country was mostly snow free. The solid red
line marks the average location of the monthly snow extent; white areas are
snow-covered ground. Snow was mapped at approximately 5 kilometer pixel resolution on a
daily basis and then combined, or composited, every eight days. If a pixel was
at least 50 percent snow covered during all of the eight-day periods that month, it was mapped as snow
covered for the whole month.