Linking Siberian Snow Cover to Precursors of Stratospheric Variability

Previous research has linked wintertime Arctic Oscillation (AO) variability to indices of Siberian snow cover and upward wave activity flux in the preceding fall season. We will present, using monthly and daily gridded data, an analysis that links surface snow cover over Eurasia and vertical wave propagation into the stratosphere. Analysis of daily sea level pressure (SLP) and area-averaged 100hPa heat flux shows that in years with high October Eurasian snow cover extent, November SLP is significantly higher following the rapid advance of Eurasian snow cover and the 100hPa heat flux is significantly increased with a two-week lag to SLP. The vertical structure of the height field is analyzed and a westward-tilting pattern is found that extends all the way from the surface to the lower stratosphere, with largest normalized anomalies near the surface. These events occur nearly twice as often in high snow years compared to low snow years. The results suggest a unified chain of events: heavy snow in October, development of surface high pressure in early November, enhanced occurrence of westward-tilted ridging throughout the troposphere, and increased negative momentum transport into the lower polar stratosphere in late boreal fall.