Anomalous Eurasian snow extent and the wintertime AO

Abstract

The winter mode of the Arctic Oscillation (AO) is the dominating influence on extratropical winter climate variability in the Northern Hemisphere (NH) . The phase of the Arctic Oscillation is characterized by trends in temperature, precipitation, air pressure, and storm tracks over the North Atlantic region, and affects northeastern North America, Europe, and parts of the Mediterranean. While predictability of the AO phase would benefit socioeconomic sectors in these densely populated regions by enabling greater foreknowledge of energy demands, precipitation intensity, and storm frequency, it is currently not particularly skillful. Previous studies have demonstrated a link between autumn snow over Eurasia and the AO mode and have proposed a dynamical pathway describing the mechanism that links them. The goal of this thesis is to present new evidence of a significant relationship between anomalous snow cover and the winter AO phase. Observational evidence of a significant link between extremely high (low) October snow extent anomalies over Eurasia and the negative (positive) AO winter phase is presented. Significant positive (negative) vertical wave activity flux (WAF) anomalies in the stratosphere during December and January are shown to occur following autumns with significantly high (low) snow extent, supporting the dynamical pathway proposed in previous studies. It is concluded that a significant mean snow extent anomaly over Eurasia in October could serve as a predictor for the AO phase of the following winter.