Scientist Tom Painter examines the differences between pure and dirty snow. A rise in dust can be a critical influence on snow-fed water supplies in the American West.
This pair of maps shows average percent snow cover in December 2008 and February 2009, the first and last months of meteorological winter in the Northern Hemisphere.
Afghanistan was one of many countries in southern and central Asia suffering through extreme cold and snow in January 2008. Most of the country was covered with snow when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this photo-like image on January 20.