Changes of Snow Cover, Temperature, and Radiative Heat Balance over the Northern Hemisphere

Abstract Contemporary large-scale changes in satellite-derived snow cover were examined over the Northern Hemisphere extratropical land (NEL) areas. These areas encompass 55% of the land in the Northern Hemisphere. Snow cover (S) transient regions, the “centers of action” relative to interannual variations of snow cover, were identified for the years 1972–1992. During these years a global retreat in snow cover extent (SE) occurred in the second half of the hydrologic year (April–September). Mean annual SE has decreased by 10% (2.3 × 106 km2). Negative trends account for one-third to one-half of the interannual continental variance of SE. The historical influence of S on the planetary albedo and outgoing longwave radiation (OLR) is investigated. The mean annual response of the S feedback on the radiative balance (RB) is negative and suggests a large-scale heat redistribution. During autumn and early winter (up to January), however, the feedback of S on the planetary RB may he positive. Only by February doe...