Intra-seasonal variation of the wintertime Polar/Eurasia pattern

WE investigated the intra-seasonal variation of the winter Polar/Eurasia (PEU) pattern, the dominant circulation pattern over the Eurasian continent, during the period 1979/80-2021/22. The PEU events have centers of action over western Europe, the Urals and the Siberian-Mongolian region. The development of PEU events is associated with a Rossby wave train triggered by anomalous horizontal divergent winds over the North Atlantic and the European continent. Diagnostic analysis based on the quasi-geostrophic geopotential height tendency equation suggests that the cross-frequency dynamics play an important role in the formation and decay of the western Europe center, as well as the formation of the Siberian-Mongolian center. The sole effect of the low-frequency forcing primarily contributes to the life cycle of the Urals center and the decay of the Siberian-Mongolian center. The effect of the cross-frequency forcing and the low-frequency forcing on the PEU centers of action is predominantly due to their advection component. The cross-frequency forcing in Europe involves an interaction between the extratropical storm activity and the low-frequency flow, where the development and decay of PEU events are associated with contrasting storm track anomalies extending from the North Atlantic to the European continent. Overall, the evolution of the intra-seasonal PEU pattern is mainly due to the internal dynamic processes over the extratropics.

Automated summary

This study investigates the intra-seasonal variation of the winter Polar/Eurasia pattern and finds that PEU events primarily occur over western Europe, the Urals, and the Siberian-Mongolian region. The research reveals the significant role of cross-frequency dynamics in the formation and decay of these circulation patterns, while low-frequency forcing mainly affects the life cycle of the Urals center and the decay of the Siberian-Mongolian center.