Northern Hemisphere snow cover extent during the satellite era

Satellite-derived maps of Northern Hemisphere continental snow cover extent (SCE) began being produced by National Oceanic and Atmospheric Administration meteorologists in the late 1960s. Map data have been used in national and international assessments of climate variability and change, and in investigations regarding the role of snow cover in the climate system. Despite their proven climate utility, meteorological forecasting has been the driving force behind producing these maps. As such, changes (documented and undocumented) in mapping methodologies have occurred over time, without a focus on their climatological continuity. In particular, 1999 brought a change from weekly to daily maps and a greatly increased resolution to the map's digitized grid. Members of the Rutgers Global Snow Lab have kept a watchful eye on changes and have developed a satellite SCE climate data record (CDR). This presentation will introduce this new CDR, discussing where the most notable changes from the previous environmental data record lie. The temporal and spatial dimensions of SCE over the past four decades will be assessed. Late winter through early summer SCE showed a sharp reduction in the late 1980s, levels that have continued to remain below the first half of the satellite era. Meanwhile, fall through mid winter SCE has not shown much change, with the fall continuing to show the greatest interannual variability. Recently, negative SCE anomalies have occurred more frequently over Eurasia than in North America.