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@ARTICLE{Braun:862202,
      author       = {Braun, Marleen and Grooß, Jens-Uwe and Woiwode, Wolfgang
                      and Johansson, Sören and Höpfner, Michael and
                      Friedl-Vallon, Felix and Oelhaf, Hermann and Preusse, Peter
                      and Ungermann, Jörn and Sinnhuber, Björn-Martin and
                      Ziereis, Helmut and Braesicke, Peter},
      title        = {{N}itrification of the lowermost stratosphere during the
                      exceptionally cold {A}rctic winter 2015/16},
      journal      = {Atmospheric chemistry and physics / Discussions Discussions
                      [...]},
      volume       = {108},
      issn         = {1680-7375},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-02550},
      pages        = {1 - 25},
      year         = {2019},
      abstract     = {The Arctic winter 2015/16 was characterized by
                      exceptionally cold stratospheric temperatures, favouring the
                      formation of polar stratospheric clouds (PSCs) from
                      mid-December until the end of February down to low
                      stratospheric altitudes. Observations by GLORIA (Gimballed
                      Limb Observer for Radiance Imaging of the Atmosphere) on
                      HALO (High Altitude and LOng range research aircraft) during
                      the PGS (POLSTRACC/GW-LCYLCE II/SALSA) campaign from
                      December 2015 to March 2016 allow an investigation of the
                      influence of denitrification on the lowermost stratosphere
                      (LMS) with a high spatial resolution. For the first time
                      vertical cross-sections of nitric acid (HNO3) along the
                      flight track and tracer-tracer correlations derived from the
                      GLORIA observations document detailed pictures of
                      wide-spread nitrification of the Arctic LMS during the
                      course of an entire winter. GLORIA observations show
                      large-scale structures and local fine structures with
                      strongly enhanced absolute HNO3 volume mixing ratios
                      reaching up to 11 ppbv at altitudes of 11 km in January
                      and nitrified filaments persisting until the middle of
                      March. Narrow streaks of enhanced HNO3, observed in
                      mid-January, are interpreted as regions recently nitrified
                      by sublimating HNO3-containing particles. Overall, a
                      nitrification of the LMS between 5.0 ppbv and 7.0 ppbv
                      at potential temperature levels between 350 and 380 K is
                      estimated. This extent of nitrification has never been
                      observed before in the Arctic lowermost stratosphere. The
                      GLORIA observations are compared with CLaMS (Chemical
                      Lagrangian Model of the Stratosphere) simulations. The
                      fundamental structures observed by GLORIA are well
                      reproduced, but differences in the fine structures are
                      diagnosed. Further, CLaMS predominantly underestimates the
                      spatial extent of maximum HNO3 mixing ratios derived from
                      the GLORIA observations as well as the enhancement at lower
                      altitudes. Sensitivity simulations with CLaMS including (i)
                      enhanced sedimentation rates in case of ice supersaturation
                      (to resemble ice nucleation on NAT), (ii) a global
                      temperature offset, (iii) modified growth rates (to resemble
                      aspherical particles with larger surfaces) and (iv)
                      temperature fluctuations (to resemble the impact of
                      small-scale mountain waves) mostly improve the agreement
                      with the GLORIA observations. The sensitivity simulations
                      suggest that details of particle microphysics play a
                      significant role for simulated LMS nitrification in January,
                      while air subsidence, transport and mixing become
                      increasingly important towards the end of the 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-2019-108},
      url          = {https://juser.fz-juelich.de/record/862202},
}