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Earth System Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 2 | Copyright
Earth Syst. Dynam., 9, 647-661, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 24 May 2018

Research article | 24 May 2018

Interannual variability in the gravity wave drag – vertical coupling and possible climate links

Petr Šácha1,2, Jiri Miksovsky1, and Petr Pisoft1 Petr Šácha et al.
  • 1Department of Atmospheric Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic
  • 2Faculty of Sciences, Universidade de Vigo, Ourense, Spain

Abstract. Gravity wave drag (GWD) is an important driver of the middle atmospheric dynamics. However, there are almost no observational constraints on its strength and distribution (especially horizontal). In this study we analyze orographic GWD (OGWD) output from Canadian Middle Atmosphere Model simulation with specified dynamics (CMAM-sd) to illustrate the interannual variability in the OGWD distribution at particular pressure levels in the stratosphere and its relation to major climate oscillations. We have found significant changes in the OGWD distribution and strength depending on the phase of the North Atlantic Oscillation (NAO), quasi-biennial oscillation (QBO) and El Niño–Southern Oscillation. The OGWD variability is shown to be induced by lower-tropospheric wind variations to a large extent, and there is also significant variability detected in near-surface momentum fluxes. We argue that the orographic gravity waves (OGWs) and gravity waves (GWs) in general can be a quick mediator of the tropospheric variability into the stratosphere as the modifications of the OGWD distribution can result in different impacts on the stratospheric dynamics during different phases of the studied climate oscillations.

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Short summary
The paper investigates variability in the gravity wave drag in the stratosphere in connection with climate phenomena like the El Niño–Southern Oscillation. This link represents a possible mechanism of tropospheric influence on the higher atmospheric layers, a mechanism of utmost importance that has not been studied in detail yet. The results illustrate that there are indeed significant changes in the gravity wave drag distribution and strength depending on the phase of the studied oscillations.
The paper investigates variability in the gravity wave drag in the stratosphere in connection...