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@ARTICLE{Ern:823849,
      author       = {Ern, Manfred and Trinh, Quang Thai and Kaufmann, Martin and
                      Krisch, Isabell and Preusse, Peter and Ungermann, Jörn and
                      Zhu, Yajun and Gille, John C. and Mlynczak, Martin G. and
                      Russell III, James M. and Schwartz, Michael J. and Riese,
                      Martin},
      title        = {{S}atellite observations of middle atmosphere gravity wave
                      absolute momentum flux and of its vertical gradient during
                      recent stratospheric warmings},
      journal      = {Atmospheric chemistry and physics},
      volume       = {16},
      number       = {15},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2016-06489},
      pages        = {9983 - 10019},
      year         = {2016},
      abstract     = {Sudden stratospheric warmings (SSWs) are circulation
                      anomalies in the polar region during winter. They mostly
                      occur in the Northern Hemisphere and affect also surface
                      weather and climate. Both planetary waves and gravity waves
                      contribute to the onset and evolution of SSWs. While the
                      role of planetary waves for SSW evolution has been
                      recognized, the effect of gravity waves is still not fully
                      understood, and has not been comprehensively analyzed based
                      on global observations. In particular, information on the
                      gravity wave driving of the background winds during SSWs is
                      still missing.We investigate the boreal winters from
                      2001/2002 until 2013/2014. Absolute gravity wave momentum
                      fluxes and gravity wave dissipation (potential drag) are
                      estimated from temperature observations of the satellite
                      instruments HIRDLS and SABER. In agreement with previous
                      work, we find that sometimes gravity wave activity is
                      enhanced before or around the central date of major SSWs,
                      particularly during vortex-split events. Often, SSWs are
                      associated with polar-night jet oscillation (PJO) events.
                      For these events, we find that gravity wave activity is
                      strongly suppressed when the wind has reversed from eastward
                      to westward (usually after the central date of a major SSW).
                      In addition, gravity wave potential drag at the bottom of
                      the newly forming eastward-directed jet is remarkably weak,
                      while considerable potential drag at the top of the jet
                      likely contributes to the downward propagation of both the
                      jet and the new elevated stratopause. During PJO events, we
                      also find some indication for poleward propagation of
                      gravity waves. Another striking finding is that obviously
                      localized gravity wave sources, likely mountain waves and
                      jet-generated gravity waves, play an important role during
                      the evolution of SSWs and potentially contribute to the
                      triggering of SSWs by preconditioning the shape of the polar
                      vortex. The distribution of these hot spots is highly
                      variable and strongly depends on the zonal and meridional
                      shape of the background wind field, indicating that a pure
                      zonal average view sometimes is a too strong simplification
                      for the strongly perturbed conditions during the evolution
                      of SSWs.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {244 - Composition and dynamics of the upper troposphere and
                      middle atmosphere (POF3-244) / HITEC - Helmholtz
                      Interdisciplinary Doctoral Training in Energy and Climate
                      Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-244 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000383144600002},
      doi          = {10.5194/acp-16-9983-2016},
      url          = {https://juser.fz-juelich.de/record/823849},
}