The Role of snow cover in the Northern Hemisphere winter to summer transition

This paper examines the role of North Hemisphere snow cover in the linkage between the winter North Atlantic Oscillation (NAO) and the summer Northern Annular Mode (NAM). This transition is partially supported by the persistence of the NAO-induced snow cover anomalies and the asymmetric thermal distribution induced by summer snow cover. We define an index of subpolar temperature difference which links winter NAO with the subsequent summer NAM. The index is also significant in the linkage between summer and winter climates and can be used as an useful predictor of the upcoming winter NAO.