Temperature Anomalies During Late Boreal Winters With and Without Sudden Stratospheric Warming

The polar stratosphere in the Northern Hemisphere influences wintertime surface weather across Northern Eurasia, Eastern Canada, the Middle East, and the Eastern United States. This influence is pronounced following sudden stratospheric warmings (SSWs), during which the polar vortex is displaced from the pole or collapses. The surface impacts vary considerably and are challenging to predict. Here, we study the extratropical surface temperature anomalies in winters with and without SSW. Our analysis reveals a statistically significant surface impact of SSWs is observed in February and March, particularly when the Quasi-Biennial Oscillation (QBO) is in the easterly phase. During the westerly QBO phases, the SSW surface impact is less systematic. Surface anomalies in winters without SSW are also more pronounced in the late phase of eQBO winters. We further demonstrate that seasonal forecasts of SSW probability can be used to predict regional temperature anomalies especially in Northern Europe.