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@ARTICLE{Hoffmann:811677,
      author       = {Hoffmann, Lars and Grimsdell, Alison W. and Alexander, M.
                      Joan},
      title        = {{S}tratospheric gravity waves at {S}outhern {H}emisphere
                      orographic hotspots: 2003–2014 {AIRS}/{A}qua observations},
      journal      = {Atmospheric chemistry and physics},
      volume       = {16},
      number       = {14},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2016-04063},
      pages        = {9381 - 9397},
      year         = {2016},
      abstract     = {Stratospheric gravity waves from small-scale orographic
                      sources are currently not well-represented in general
                      circulation models. This may be a reason why many
                      simulations have difficulty reproducing the dynamical
                      behavior of the Southern Hemisphere polar vortex in a
                      realistic manner. Here we discuss a 12-year record
                      (2003–2014) of stratospheric gravity wave activity at
                      Southern Hemisphere orographic hotspots as observed by the
                      Atmospheric InfraRed Sounder (AIRS) aboard the National
                      Aeronautics and Space Administration's (NASA) Aqua
                      satellite. We introduce a simple and effective approach,
                      referred to as the “two-box method”, to detect gravity
                      wave activity from infrared nadir sounder measurements and
                      to discriminate between gravity waves from orographic and
                      other sources. From austral mid-fall to mid-spring
                      (April–October) the contributions of orographic sources to
                      the observed gravity wave occurrence frequencies were found
                      to be largest for the Andes $(90 \%),$ followed by the
                      Antarctic Peninsula $(76 \%),$ Kerguelen Islands
                      $(73 \%),$ Tasmania $(70 \%),$ New Zealand $(67 \%),$
                      Heard Island $(60 \%),$ and other hotspots
                      $(24–54 \%).$ Mountain wave activity was found to be
                      closely correlated with peak terrain altitudes, and with
                      zonal winds in the lower troposphere and mid-stratosphere.
                      We propose a simple model to predict the occurrence of
                      mountain wave events in the AIRS observations using zonal
                      wind thresholds at 3 and 750 hPa. The model has
                      significant predictive skill for hotspots where gravity wave
                      activity is primarily due to orographic sources. It
                      typically reproduces seasonal variations of the mountain
                      wave occurrence frequencies at the Antarctic Peninsula and
                      Kerguelen Islands from near zero to over $60 \%$ with mean
                      absolute errors of 4–5 percentage points. The prediction
                      model can be used to disentangle upper level wind effects on
                      observed occurrence frequencies from low-level source and
                      other influences. The data and methods presented here can
                      help to identify interesting case studies in the vast amount
                      of AIRS data, which could then be further explored to study
                      the specific characteristics of stratospheric gravity waves
                      from orographic sources and to support model validation.},
      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:000381213300034},
      doi          = {10.5194/acp-16-9381-2016},
      url          = {https://juser.fz-juelich.de/record/811677},
}