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@ARTICLE{Hindley:868088,
      author       = {Hindley, Neil P. and Wright, Corwin J. and Smith, Nathan D.
                      and Hoffmann, Lars and Holt, Laura A. and Alexander, M. Joan
                      and Moffat-Griffin, Tracy and Mitchell, Nicholas J.},
      title        = {{G}ravity waves in the winter stratosphere over the
                      {S}outhern {O}cean: high-resolution satellite observations
                      and 3-{D} spectral analysis},
      journal      = {Atmospheric chemistry and physics},
      volume       = {19},
      number       = {24},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-06679},
      pages        = {15377 - 15414},
      year         = {2019},
      abstract     = {Atmospheric gravity waves play a key role in the transfer
                      of energy and momentum between layers of the Earth's
                      atmosphere. However, nearly all general circulation models
                      (GCMs) seriously under-represent the momentum fluxes of
                      gravity waves at latitudes near 60∘ S, which can lead to
                      significant biases. A prominent example of this is the
                      “cold pole problem”, where modelled winter stratospheres
                      are unrealistically cold. There is thus a need for
                      large-scale measurements of gravity wave fluxes near
                      60∘ S, and indeed globally, to test and constrain GCMs.
                      Such measurements are notoriously difficult, because they
                      require 3-D observations of wave properties if the fluxes
                      are to be estimated without using significant limiting
                      assumptions. Here we use 3-D satellite measurements of
                      stratospheric gravity waves from NASA's Atmospheric Infrared
                      Sounder (AIRS) Aqua instrument. We present the first
                      extended application of a 3-D Stockwell transform (3DST)
                      method to determine localised gravity wave amplitudes,
                      wavelengths and directions of propagation around the entire
                      region of the Southern Ocean near 60∘ S during austral
                      winter 2010. We first validate our method using a synthetic
                      wavefield and two case studies of real gravity waves over
                      the southern Andes and the island of South Georgia. A new
                      technique to overcome wave amplitude attenuation problems in
                      previous methods is also presented. We then characterise
                      large-scale gravity wave occurrence frequencies, directional
                      momentum fluxes and short-timescale intermittency over the
                      entire Southern Ocean. Our results show that highest wave
                      occurrence frequencies, amplitudes and momentum fluxes are
                      observed in the stratosphere over the mountains of the
                      southern Andes and Antarctic Peninsula. However, we find
                      that around $60 \%–80 \%$ of total zonal-mean momentum
                      flux is located over the open Southern Ocean during
                      June–August, where a large “belt” of increased wave
                      occurrence frequencies, amplitudes and fluxes is observed.
                      Our results also suggest significant short-timescale
                      variability of fluxes from both orographic and
                      non-orographic sources in the region. A particularly
                      striking result is a widespread convergence of gravity wave
                      momentum fluxes towards latitudes around 60∘ S from the
                      north and south. We propose that this convergence, which is
                      observed at nearly all longitudes during winter, could
                      account for a significant part of the under-represented flux
                      in GCMs at these latitudes.},
      cin          = {JSC},
      ddc          = {550},
      cid          = {I:(DE-Juel1)JSC-20090406},
      pnm          = {511 - Computational Science and Mathematical Methods
                      (POF3-511)},
      pid          = {G:(DE-HGF)POF3-511},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000503444400003},
      doi          = {10.5194/acp-19-15377-2019},
      url          = {https://juser.fz-juelich.de/record/868088},
}