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@ARTICLE{Braun:866358,
      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 $2015\–2016$},
      journal      = {Atmospheric chemistry and physics},
      volume       = {19},
      number       = {21},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-05514},
      pages        = {13681 - 13699},
      year         = {2019},
      abstract     = {The Arctic winter 2015–2016 was characterized by
                      exceptionally low 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-LCYCLE II–SALSA) campaign from
                      December 2015 to March 2016 allow the investigation of the
                      influence of denitrification on the lowermost stratosphere
                      (LMS) with a high spatial resolution. Two-dimensional
                      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
                      enhanced absolute HNO3 volume mixing ratios reaching up to
                      11 ppbv at altitudes of 13 km in January and nitrified
                      filaments persisting until the middle of March. Narrow
                      coherent structures tilted with altitude of enhanced HNO3,
                      observed in mid-January, are interpreted as regions recently
                      nitrified by sublimating HNO3-containing particles. Overall,
                      extensive nitrification of the LMS between 5.0 and
                      7.0 ppbv at potential temperature levels between 350 and
                      380 K is estimated. 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 HNO3 maxima derived from the GLORIA
                      observations as well as the overall nitrification of the
                      LMS. Sensitivity simulations with CLaMS including (i)
                      enhanced sedimentation rates in case of ice supersaturation
                      (to resemble ice nucleation on nitric acid trihydrate
                      (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) slightly improved the
                      agreement with the GLORIA observations of individual
                      flights. However, no parameter could be isolated which
                      resulted in a general improvement for all flights. Still,
                      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 for the simulated
                      HNO3 distributions 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},
      UT           = {WOS:000496725700004},
      doi          = {10.5194/acp-19-13681-2019},
      url          = {https://juser.fz-juelich.de/record/866358},
}