EGU2020-19025, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-19025
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Impact of the North Atlantic Warming Hole on Sensible Weather

Melissa Gervais1,3, Jeffrey Shaman2, and Yochanan Kushnir3
Melissa Gervais et al.
  • 1Department of Meteorology and Atmospheric Sciences, Penn State, University Park PA, United States of America (mmg62@psu.edu)
  • 2Columbia University, New York, United States of America (jls106@cumc.columbia.edu)
  • 3Lamont-Doherty Earth Observatory, Columbia University, United States of America (kushnir@ldeo.columbia.edu)

In future climate projections there is a notable lack of warming in the North Atlantic subpolar gyre, known as the North Atlantic warming hole (NAWH). The NAWH has been previously shown to contribute to a poleward shift and eastward elongation of the North Atlantic jet that constitutes an additional important driver of future changes in the North Atlantic jet using a set of large-ensemble atmosphere simulations with the Community Earth System model.  The current study investigates the impact of the warming hole on sensible weather, particularly over Europe using the same simulations. North Atlantic jet regimes are classified within the model simulations by applying self-organizing maps to winter daily wind speeds on the dynamic tropopause. The NAWH is found to increase the prevalence of jet regimes with stronger and more poleward jets.  A previously identified transient eddy-mean response to the NAWH that leads to downstream enhancements of wind speeds is found to be dependent on the jet regimes. These localized regime-specific changes vary by latitude and strength, combining to form the broad increase in seasonal mean wind speeds over Eurasia. Impacts on surface temperature and precipitation within the various North Atlantic jet regimes are also investigated. A large decrease in surface temperature over Eurasia is found to be associated with the NAWH in regimes where air masses are advected over the subpolar gyre.  Precipitation is found to be locally suppressed over the warming hole region and increased directly downstream. The impact of this downstream response on coastal European precipitation is dependent on the strength of the NAWH.

How to cite: Gervais, M., Shaman, J., and Kushnir, Y.: Impact of the North Atlantic Warming Hole on Sensible Weather, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19025, https://doi.org/10.5194/egusphere-egu2020-19025, 2020

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Display material version 1 – uploaded on 27 Apr 2020
  • AC1: Comment on EGU2020-19025, Melissa Gervais, 05 May 2020

    Q: Hilla Gerstman, ETH (05:00) Melissa, have you looked what drives the changes in the jet regime?

    A: Yes, it seems the dominant impact on the jet regime is a transient-eddy mean response.  We had identified such process in the time mean sense.  In the context of regimes you can see that depending on the regime we can have greater or smaller <v'T'> that feeds in to strengthen the North Atlantic jet.  The jet is typically strengthened / elongated where the jet resides in each regime.  This leads to their being strengthenings in different locations depending on the regime.  This averages to a broad increase in the seasonal average.