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@ARTICLE{Krause:841715,
      author       = {Krause, Jens and Hoor, Peter and Engel, Andreas and
                      Ploeger, Felix and Grooß, Jens-Uwe and Bönisch, Harald and
                      Keber, Timo and Sinnhuber, Björn-Martin and Woiwode,
                      Wolfgang and Oelhaf, Hermann},
      title        = {{M}ixing and ageing in the polar lower stratosphere in
                      winter 2015/2016},
      journal      = {Atmospheric chemistry and physics / Discussions},
      volume       = {955},
      issn         = {1680-7367},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2018-00023},
      pages        = {1 - 32},
      year         = {2017},
      abstract     = {We present data from winter 2015/2016, which were measured
                      during the POLSTRACC (The Polar Stratosphere in a Changing
                      Climate) aircraft campaign between December 2015 and March
                      2016. The focus of this work is on the role of transport and
                      mixing between aged and potentially chemically processed air
                      masses from the stratosphere with mid and low latitude air
                      mass fractions with small transit times originating at the
                      tropical lower stratosphere. By combining measurements of
                      CO, N2O and SF6 we estimate the evolution of the relative
                      contributions of transport and mixing to the UTLS
                      composition over the course of the winter.We find an
                      increasing influence of aged stratospheric air partly from
                      the vortex as indicated by decreasing N2O and SF6 values
                      over the course of winter. Surprisingly we also found a mean
                      increase of CO by (3.00 ± 1.64) ppbV from January to
                      March relative to N2O in the lower stratosphere. We show
                      that this increase of CO is consistent with an increased
                      mixing of tropospheric air as part of the fast transport
                      mechanism in the lower stratosphere surf zone. The analysed
                      air masses were partly affected by air masses which
                      originated at the tropical tropopause and were
                      quasi-horizontally mixed into higher latitudes.This increase
                      of the tropospheric air fraction partly compensates for
                      ageing of the UTLS due to the diabatic descent of air masses
                      from the vortex by horizontally mixed, tropospheric
                      influenced air masses. This is consistent with simulated age
                      spectra from the Chemical Lagrangian Model of the
                      Stratosphere (CLaMS), which show a respective fractional
                      increase of tropospheric air with short transit times lower
                      than six months and a simultaneous increase of aged air from
                      deep stratospheric and vortex regions with transit times
                      larger than two years.We thus conclude that the lowermost
                      stratosphere in winter 2015/16 was affected by aged air from
                      the deep stratosphere and vortex region. These air masses
                      were significantly affected by increased mixing from the
                      lower latitudes, which led to a simultaneous increase of the
                      fraction of young air in the Arctic lowermost stratosphere
                      over the course of winter.},
      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)},
      pid          = {G:(DE-HGF)POF3-244},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/acp-2017-955},
      url          = {https://juser.fz-juelich.de/record/841715},
}