Ural Blocking as a Driver of Early-Winter Stratospheric Warmings

• Published in: Geophysical research letters Vol. 46; no. 10
• Main Author: Peings, Y.
• Format: Journal Article
• Language: English
• Published: United States American Geophysical Union 29.05.2019
• Subjects: Geology; GEOSCIENCES
• ISSN: 0094-8276; 1944-8007

This study explores the early-winter atmospheric response to Ural blocking anomalies in November, using a nudging technique to constrain the temperature and dynamics in a high-top atmospheric model. Persistent Ural blocking anomalies in November are associated with a warm Arctic/cold Siberia pattern and increased upward planetary waves entering the stratosphere, leading to a warming of the polar vortex. This stratospheric response then propagates in the troposphere, leading to increased occurrence of the negative North Atlantic Oscillation in December and January. In contrast, simulations with perturbed Barents-Kara sea ice and Siberian snow in November do not reproduce a significant atmospheric response. In simulations including a slab ocean, the Ural blocking induces Barents-Kara sea ice and Siberia snow anomalies that resemble composite analyses from observations. These results highlight Ural blocking variability in November as a robust driver of early-winter stratospheric warming while questioning causality between sea ice/snow and Ural blocking anomalies.