Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-128
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
06 Mar 2017
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Satellite Measurements of Stratospheric GravityWaves over the Andes/Drake Passage Region Using a 3D S-Transform Technique
Corwin J. Wright1, Neil P. Hindley1, Lars Hoffmann2, M. Joan Alexander3, and Nicholas J. Mitchell1 1Centre for Space, Atmospheric and Oceanic Science, University of Bath, Bath, UK
2Jülich Supercomputing Centre, Forschungszentrum Jülich, Jülich, Germany
3Northwest Research Associates, Boulder, CO, USA
Abstract. Gravity waves (GWs) transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for applications such as weather and climate models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully-3D method for detecting and characterising GWs in the stratosphere. This method is based around a 3D Stockwell transform. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3D atmospheric temperature data from AIRS/Aqua over the altitude range 20–60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes, and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this technique over the region around the Southern Andes and Antarctic Peninsula, the largest known GW sources near the 60° S belt. Our analyses reveal the presence of strongly-intermittent highly-directionally-focused GWs with very high momentum fluxes (∼80–100 mPa or more at 30 km altitude). These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity vectors show clear observational evidence that these waves are strongly focused into the polar night wind jet, and thus may contribute significantly to the ''missing momentum'' at these latitudes.

Citation: Wright, C. J., Hindley, N. P., Hoffmann, L., Alexander, M. J., and Mitchell, N. J.: Satellite Measurements of Stratospheric GravityWaves over the Andes/Drake Passage Region Using a 3D S-Transform Technique, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-128, in review, 2017.
Corwin J. Wright et al.
Corwin J. Wright et al.
Corwin J. Wright et al.

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Short summary
We introduce a novel 3D method of measuring atmospheric gravity waves, based around a 3D Stockwell Transform. Our method lets us measure new properties, including wave intrinsic frequencies and phase and group velocities. We apply it to data from the AIRS satellite instrument over the Southern Andes for two consecutive winters. Our results show clear evidence that the waves measured are primarily orographic in origin, and that their group velocity vectors are focused into the polar night jet.
We introduce a novel 3D method of measuring atmospheric gravity waves, based around a 3D...
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