Preprints
https://doi.org/10.5194/acp-2019-630
https://doi.org/10.5194/acp-2019-630

  06 Aug 2019

06 Aug 2019

Review status: this preprint has been withdrawn by the authors.

Geographical distributions of mesospheric gravity wave activity before and after major sudden stratospheric warmings observed by Aura/MLS

Klemens Hocke1,2, Jonas Hagen1, Franziska Schranz1, and Leonie Bernet1,2 Klemens Hocke et al.
  • 1Institute of Applied Physics, University of Bern, Bern, Switzerland
  • 2Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland

Abstract. Observations of the global distribution of mesospheric gravity wave activity are rare. To our knowledge there exist only a few articles showing global maps of gravity wave potential energy in the mesosphere derived from observations of the instrument SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) on NASA's satellite TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics). In the present study, we find that the geopotential height (GPH) measurements of the instrument MLS (Microwave Limb Sounder) on NASA's satellite Aura are sensitive to mesospheric gravity waves with horizontal wavelengths between 200 and 1500 km. We apply a data analysis which evaluates the standard deviation of horizontal GPH perturbations at a fixed pressure level and along the orbit of the sounding volume of Aura/MLS. The orographic waves from the Southern Andes in August serve as a test signal for the horizontal resolution and sensitivity of the method. We find enhanced gravity wave activity in the lower, middle, and upper mesosphere in a small region over the Southern Andes. It seems that the horizontal resolution of the mesospheric gravity wave maps provided by Aura/MLS is higher than those of TIMED/SABER. We apply the method to estimate the global distributions of mesospheric gravity wave activity before and after the major sudden stratospheric warmings (SSWs) of January 21, 2006, January 24, 2009, and January 6, 2013 using 30 day intervals of Aura/MLS observations of GPH. It seems that the gravity wave activity in the lower mesosphere over the subtropical convection regions of the summer hemisphere are decreased after the SSW of January 21, 2006. The gravity wave activity in the lower and middle mesosphere over middle and high latitudes (40° N to 70° N) of the winter hemisphere is decreased after the SSW of January 24, 2009. The major SSW of January 6, 2013 is preceded by enhanced mesospheric gravity wave activity over Eurasia at high latitudes (40° N to 60° N). This asymmetric gravity wave activity in the lower mesosphere is coincident with a long-lasting stay of the stratospheric polar vortex mainly in the Eurasian longitude sector before the SSW of January 6, 2013. In case of the SSW 2009 and SSW 2013, the gravity wave activity is enhanced at latitudes poleward of 70° N in the lower and middle mesosphere after the SSWs.

This preprint has been withdrawn.

Klemens Hocke et al.

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Interactive discussion

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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Klemens Hocke et al.

Klemens Hocke et al.

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This preprint has been withdrawn.

Short summary
The dense sampling of geopotential height (GPH) profiles of the microwave limb sounder (MLS) on NASA's satellite Aura is appropriate for detection of mesospheric gravity waves. Up to now, the global distribution of mesospheric gravity wave activity is relatively unknown. The study focuses on the relation of mesospheric gravity waves to major sudden stratospheric warmings.
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