CUAHSI CyberSeminar: Large-scale Snow Extent over Northern Hemisphere Lands
Presenter: Dr. David A. Robinson - Rutgers University, Department of Geography
Annual snow cover extent (SCE) over Northern Hemisphere (NH) lands averages 25.8 million square kilometers. It ranges from an average of 47.1 million sq. km. in January to 3.0 million sq. km. (mostly atop the Greenland Ice Sheet) in August. SCE is calculated at the Rutgers Global Snow Lab from daily SCE maps produced by meteorologists at the National Ice Center, who rely primarily on visible satellite imagery to construct the maps.
Annual SCE over NH lands has averaged lower since the late 1980s than earlier in the satellite era that began in the late 1960s. This is most evident from late winter through spring, and in the past decade has been exceedingly pronounced at high latitudes in May and June. The most recent four Mays have had four of the five lowest NH SCEs on record, with Eurasian (Eur) SCE at a record low in 2013. North American (NA) SCE achieved a record minimum in May 2010, but of late has not been as consistently low as over Eur. The past six Junes have seen record minimum SCEs over the NH and Eur, with five of these six Junes the lowest over NA. The recent early timing of arctic snowmelt appears to be occurring at an equivalent if not greater pace than the loss of summer Arctic sea ice extent.
While when projecting snow melt discharge it is much preferable to know the water equivalent of a snowpack (SWE) rather than its extent, the response of streamflow to seasonal SCE changes has been found to be significant within large basins in Siberia and the North American arctic. Along with an overview of continenal SCE kinematic, this hydrological relationship will be examined in this presentation, along with results looking at satellite microwave derived SWE and discharge, which also show promising results on a large scale.