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@ARTICLE{Johansson:862203,
      author       = {Johansson, Sören and Santee, Michelle L. and Grooß,
                      Jens-Uwe and Höpfner, Michael and Braun, Marleen and
                      Friedl-Vallon, Felix and Khosrawi, Farahnaz and Kirner,
                      Oliver and Kretschmer, Erik and Oelhaf, Hermann and Orphal,
                      Johannes and Sinnhuber, Björn-Martin and Tritscher, Ines
                      and Ungermann, Jörn and Walker, Kaley A. and Woiwode,
                      Wolfgang},
      title        = {{U}nusual chlorine partitioning in the 2015/16 {A}rctic
                      winter lowermost stratosphere: {O}bservations and
                      simulations},
      journal      = {Atmospheric chemistry and physics / Discussions Discussions
                      [...]},
      volume       = {-},
      issn         = {1680-7375},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-02551},
      pages        = {1 - 38},
      year         = {2019},
      abstract     = {The Arctic winter 2015/16 was characterized by cold
                      stratospheric temperatures. Here we present a comprehensive
                      view of the temporal evolution of chlorine in the lowermost
                      stratosphere (LMS) over the course of this winter. We
                      utilize two-dimensional vertical cross sections of ozone
                      (O3) and chlorine nitrate (ClONO2), measured by the airborne
                      limb-imager GLORIA (Gimballed Limb Observer for Radiance
                      Imaging of the Atmosphere) during the POLSTRACC/GW-LCYCLE
                      II/GWEX/SALSA campaigns, to investigate in detail the
                      tropopause region. Observations from three long-distance
                      flights in January, February and March 2016 are discussed.
                      ClONO2 volume mixing ratios up to 1100 pptv were measured
                      at 380 K potential temperature in mesoscale structures.
                      Similar mesoscale structures are also visible in O3
                      measurements. Both trace gas measurements are applied to
                      evaluate simulation results from the chemistry transport
                      model CLaMS (Chemical Lagrangian Model of the Stratosphere)
                      and the chemistry climate model EMAC (ECHAM5/MESSy
                      Atmospheric Chemistry). These comparisons show agreement
                      within the expected performance of these models. Satellite
                      measurements from Aura/MLS (Microwave Limb Sounder) and
                      SCISAT/ACE-FTS (Atmospheric Chemistry Experiment – Fourier
                      Transform Spectrometer) provide an overview over the whole
                      winter and information about the stratospheric situation
                      above flight altitude. Time series of these satellite
                      measurements reveal unusually low hydrochloric acid (HCl)
                      and ClONO2 at 380 K from the beginning of January to the
                      end of February 2016, while chlorine monoxide (ClO) is
                      strongly enhanced. In March 2016, unusually rapid chlorine
                      deactivation into HCl is observed instead of deactivation
                      into ClONO2, the more typical pathway for deactivation in
                      the Arctic. Chlorine deactivation observed in the satellite
                      time series is well reproduced by CLaMS. Sensitivity
                      simulations with CLaMS demonstrate the influence of low
                      abundances of O3 and reactive nitrogen (NOy) due to ozone
                      depletion and sedimentation of NOy-containing particles,
                      respectively. On the basis of the different altitude and
                      time ranges of these effects, we conclude that the
                      substantial chlorine deactivation into HCl at 380 K arose
                      as a result of very low ozone abundances together with low
                      temperatures. Additionally, CLaMS estimates ozone depletion
                      of at least 0.4 ppmv at 380 K and 1.75 ppmv at
                      490 K, which is comparable to other extremely cold Arctic
                      winters. We have used CLaMS trajectories to analyze the
                      history of enhanced ClONO2 measured by GLORIA. In February,
                      most of the enhanced ClONO2 is traced back to chlorine
                      deactivation that had occurred within the past few days
                      prior to the GLORIA measurement. In March, after the final
                      warming, air masses in which chlorine has previously been
                      deactivated into ClONO2 have been transported in the
                      remnants of the polar vortex towards the location of
                      measurement for at least 11 days},
      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-2018-1227},
      url          = {https://juser.fz-juelich.de/record/862203},
}