EGU21-4629, updated on 19 Apr 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Stratospheric modulation of cold air outbreaks and winter storms in the North Atlantic region and impacts on predictability

Hilla Afargan-Gerstman1, Iuliia Polkova2, Lukas Papritz1, Paolo Ruggieri3,4, Martin P. King5, Panos Athanasiadis4, Johanna Baehr1, Ole Wulff1, Michael Sprenger1, and Daniela I.V. Domeisen1
Hilla Afargan-Gerstman et al.
  • 1ETH Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland (
  • 2Institute of Oceanography, University of Hamburg, CEN, Hamburg, Germany
  • 3Department of Physics and Astronomy, University of Bologna, Italy
  • 4Euro-Mediterranean Center on Climate Change (CMCC), Bologna, Italy
  • 5Geophysical Institute, University of Bergen, Norway

Variability of the stratospheric polar vortex has the potential to influence surface weather by imposing negative North Atlantic Oscillation (NAO) conditions, associated with cold air outbreaks in the Arctic and a southward shift of the extratropical storm track. In particular, the likelihood of cold temperature extremes over the ocean, known as marine cold air outbreaks (MCAOs), have been associated with a range of hazardous conditions, including strong surface winds and the occurrence of extreme cyclones known as Polar Lows (PLs), posing risks for Arctic marine activity and infrastructure. Likewise, winter storms can lead to high damage potential in the extratropics due to their associated extreme winds.

Skillful predictions of MCAOs and extratropical winter storms on subseasonal timescales have been linked to the strength of the stratospheric polar vortex. Using ERA-Interim reanalysis (1979-2019) and ECMWF forecasts from the S2S Prediction Project database we investigate the stratospheric influence on surface extremes such as MCAOs and high-impact winter storms. Following weak stratospheric vortex extremes, anomalous circulation patterns accompanied by increased storminess over the eastern North Atlantic are found to be strong indicators for enhanced MCAOs in high- and mid-latitudes. Understanding the role of the stratosphere in subseasonal variability and predictability of cold air outbreaks and storm tracks during winter can provide a key for a reliable forecast of severe impacts.

How to cite: Afargan-Gerstman, H., Polkova, I., Papritz, L., Ruggieri, P., King, M. P., Athanasiadis, P., Baehr, J., Wulff, O., Sprenger, M., and Domeisen, D. I. V.: Stratospheric modulation of cold air outbreaks and winter storms in the North Atlantic region and impacts on predictability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4629,, 2021.


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