EGU24-11702, updated on 09 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Attributing the role of sudden stratospheric warming events in surface weather extremes and their impacts: insights from SNAPSI Working Group 2

William Seviour1, Amy Butler2, Chaim Garfinkel3, Peter Hitchcock4, and the SNAPSI Working Group 2*
William Seviour et al.
  • 1Dept of Mathematics and Statistics, University of Exeter, Exeter, UK (
  • 2NOAA Chemical Sciences Laboratory, Boulder, CO, USA
  • 3Fredy and Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerursalem, Jerusalem, Israel
  • 4Dept of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA
  • *A full list of authors appears at the end of the abstract

Sudden stratospheric warming events (SSWs)–in which the westerly polar vortex rapidly breaks down during winter–are  some of the most dramatic examples of dynamical variability in Earth’s atmosphere. It is now well established that SSWs are, on average, followed by large scale anomalies in near-surface circulation patterns, including an equatorward shift of the eddy driven jet that can persist for several months. These anomalies have, in turn, been related to an increase in the likelihood of a variety of high impact weather extremes. However, not all SSWs are followed by impactful weather events; equally, most winter weather extremes are not preceded by SSWs.

Here we will discuss the extent to which the occurrence of individual extreme weather events and their impacts can be attributed to polar stratospheric variability, drawing upon new results from the Stratospheric Nudging And Predictable Surface Impacts (SNAPSI) project (Working Group 2). This project involves a set of controlled subseasonal hindcast experiments, targeted at three SSW case study events, in which the stratospheric state can be either freely-evolving or nudged towards a climatological or observational state. These simulations reveal that the stratospheric evolution can more than double the regional risk of extreme temperature, rainfall, and snow events. We will go on to explore the attribution of the subsequent impacts of these weather extremes, including on the energy sector, health, and wildfires.  

SNAPSI Working Group 2:

William Seviour, Amy Butler, Chaim Garfinkel, Peter Hitchcock, Blanca Ayarzagüena, Hannah Bloomfield, Andrew Dowdy, Natalia Calvo, Justin Finkel, Gerbrand Koren, Richard Leeding, Eun-Pa Lim, Daniel de Maeseneire, Gabriele Messori, Regan Mudhar, Philip Rupp, Masakazu Taguchi, James Anstey, Dong-Chan Hong, Viatcheslav Kharin, Hera Kim, Jeff Knight, Daniele Mastrangelo, Michael Sigmond, Isla Simpson, Damien Specq, Tim Stockdale

How to cite: Seviour, W., Butler, A., Garfinkel, C., and Hitchcock, P. and the SNAPSI Working Group 2: Attributing the role of sudden stratospheric warming events in surface weather extremes and their impacts: insights from SNAPSI Working Group 2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11702,, 2024.

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