Northern Hemisphere Weekly and Monthly Snow Cover

The U.S. National Earth Satellite Service (NESS) created hand-drawn Northern Hemisphere maps of snow and ice boundaries on a weekly basis starting in 1966. A satellite meteorologist would use visible satellite data to determine the change in snow and ice boundaries from the previous week, and confirm any drastic changes with surface station observations. Since these maps were the only complete record of snow and ice extent, providing spatially-continuous coverage versus the historical daily point observations taken mainly in populated areas, they were digitized by the Climatology Program at the University of Nebraska onto a 190.5 km resolution polar-stereographic grid, and then objectively analyzed to produce various other snow cover products.