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Weather and Climate Dynamics An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/wcd-2020-23
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wcd-2020-23
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 26 May 2020

Submitted as: research article | 26 May 2020

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This preprint is currently under review for the journal WCD.

Tropopause-level planetary wave source and its role in two-way troposphere–stratosphere coupling

Lina Boljka1 and Thomas Birner2 Lina Boljka and Thomas Birner
  • 1Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
  • 2Meteorological Institute, Ludwig-Maximilians-Universität München, Munich, Germany

Abstract. Atmospheric planetary waves play a fundamental role in driving stratospheric dynamics, including sudden stratospheric warming (SSW) events. It is well established that the bulk of the planetary wave activity originates near the surface. However, recent studies have pointed to a planetary wave source near the tropopause that may play an important role in the development of SSWs. Here we analyse the dynamical origin of this wave source and its impact on stratosphere–troposphere coupling, using an idealised model and a quasi-reanalysis. It is shown that the tropopause-level planetary wave source is associated with nonlinear wave–wave interactions and subsequent resonance as well as with transient wave decay. The resulting planetary waves may then propagate deep into the stratosphere, where they dissipate and may help to force SSWs. We find that when an SSW is preceded by the tropopause wave source, it is followed by a robust downward impact, decelerating the tropospheric zonal mean zonal winds between 40–60° N several weeks later. Unlike this robust response following the tropopause wave source events, we do not find such a robust downward impact following the SSWs preceded by surface wave source events. This suggests that the tropopause wave source could potentially be used as one of the predictors of not only SSWs, but their downward impact as well.

Lina Boljka and Thomas Birner

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Status: open (until 07 Jul 2020)
Status: open (until 07 Jul 2020)
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Lina Boljka and Thomas Birner

Lina Boljka and Thomas Birner

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Latest update: 07 Jul 2020
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Short summary
This study addresses the origin and impacts of a source of large-scale atmospheric waves in the lower stratosphere, which has not been examined before. This wave source is caused by interactions of waves of smaller scales. Here we show that as it lies in the lower stratosphere, this wave source can precede extreme events in the stratosphere and that such events can then lead to a robust response of the tropospheric weather patterns several weeks later (potential for long-term forecasting).
This study addresses the origin and impacts of a source of large-scale atmospheric waves in the...
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