Trends in NHEMI Snow Cover

Tony Wood of the Philadelphia Inquirer writes in his Weather or Not column today about trends in NHEMI snow cover. Areal coverage has been decreasing and the spring melt has come earlier. An earlier post on NEWxSFC suggested similar trends.

Tony reports some interesting observations made by Rutgers University/s geography professor David Robinson and AER atmospheric scientist Judah Cohen on the subject and what it all might mean.

"First, and curiously, the snow cover in other seasons (summer, fall and winter) hasn't shown big changes, Robinson says.

"Second, after falling off in the late 1980s, reaching a record low in 1990, the snow cover rebounded - until three years ago. So the decreases in complete calendar years 2004, 2005 and 2006 could constitute an anomaly.

"Third, Robinson, who contributed to the blue-ribbon Intergovernmental Panel on Climate Change (IPCC) reports, says that one could make the interesting argument that the world is warmer because of less snow.

"It's a chicken-egg question," he says.

Judah Cohen adds...

"The physical mechanism isn't fully understood, Cohen says, but fall snow coverage evidently affects air pressure patterns that influence other changes: An above-normal snowpack in Siberia in October correlates with below-normal temperatures in the United States in winter.

"October is the key, Cohen believes, because when the sun is strongest (summer), the snow is scarce; when the snow cover peaks (winter), the sun is absent. October has both."

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Rutgers University Snow Lab
sCAST from AER...Inc