Satellite observed changes in the Northern Hemisphere snow cover phenology and the associated radiative forcing and feedback between 1982 and 2013

Abstract

Quantifying continental-scale changes in snow cover phenology (SCP) and evaluating their associated radiative forcing and feedback is essential for meteorological, hydrological, ecological, and societal purposes. However, the current SCP research is inadequate because few published studies have explored the long-term changes in SCP, as well as their associated radiative forcing and feedback in the context of global warming. Based on satellite-observed snow cover extent (SCE) and land surface albedo datasets, and using a radiative kernel modeling method, this study quantified changes in SCP and the associated radiative forcing and feedback over the Northern Hemisphere (NH) snow-covered landmass from 1982 to 2013. The monthly SCE anomaly over the NH displayed a significant decreasing trend from May to August (-0.89 106 km2 decade-1), while an increasing trend from November to February (0.65 106 km2 decade-1) over that period. The changes in SCE resulted in corresponding anomalies in SCP. The snow onset date (D o) moved forward slightly, but the snow end date (D e) advanced significantly at the rate of 1.91 days decade-1, with a 73% contribution from decreased SCE in Eurasia (EU). The anomalies in D e resulted in a weakened snow radiative forcing of 0.12 (0.003) W m-2 and feedback of 0.21 (0.005) W m-2 K-1, in melting season, over the NH, from 1982 to 2013. Compared with the SCP changes in EU, the SCP anomalies in North America were relatively stable because of the clearly contrasting D e anomalies between the mid- and high latitudes in this region.