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@ARTICLE{Robrecht:862870,
      author       = {Robrecht, Sabine and Vogel, Bärbel and Grooss, Jens-Uwe
                      and Rosenlof, K. and Thornberry, T. and Rollins, A. and
                      Krämer, Martina and Christensen, L. and Müller, Rolf},
      title        = {{M}echanism of ozone loss under enhanced water vapour
                      conditions in the mid-latitude lower stratosphere in summer},
      journal      = {Atmospheric chemistry and physics},
      volume       = {19},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-03057},
      pages        = {5805-5833},
      year         = {2019},
      abstract     = {Water vapour convectively injected into the mid-latitude
                      lowermost stratosphere could affect stratospheric ozone. The
                      associated potential ozone loss process requires low
                      temperatures together with elevated water vapour mixing
                      ratios. Since this ozone loss is initiated by heterogeneous
                      chlorine activation on liquid aerosols, an increase in
                      sulfate aerosol surface area due to a volcanic eruption or
                      geoengineering could increase the likelihood of its
                      occurrence. However, the chemical mechanism of this ozone
                      loss process has not yet been analysed in sufficient detail
                      and its sensitivity to various conditions is not yet clear.
                      Under conditions of climate change associated with an
                      increase in greenhouse gases, both a stratospheric cooling
                      and an increase in water vapour convectively injected into
                      the stratosphere are expected. Understanding the influence
                      of low temperatures, elevated water vapour and enhanced
                      sulfate particles on this ozone loss mechanism is a key step
                      in estimating the impact of climate change and potential
                      sulfate geoengineering on mid-latitude ozone.Here, we
                      analyse the ozone loss mechanism and its sensitivity to
                      various stratospheric conditions in detail. By conducting a
                      box-model study with the Chemical Lagrangian Model of the
                      Stratosphere (CLaMS), chemistry was simulated along a 7 d
                      backward trajectory. This trajectory was calculated
                      neglecting mixing of neighbouring air masses. Chemical
                      simulations were initialized using measurements taken during
                      the Studies of Emissions and Atmospheric Composition, Clouds
                      and Climate Coupling by Regional Surveys (SEAC4RS) aircraft
                      campaign (2013, Texas), which encountered an elevated water
                      vapour mixing ratio of 10.6 ppmv at a pressure level
                      around 100 hPa. We present a detailed analysis of the
                      ozone loss mechanism, including the chlorine activation,
                      chlorine-catalysed ozone loss cycles, maintenance of
                      activated chlorine and the role of active nitrogen oxide
                      radicals (NOx). Focussing on a realistic trajectory in a
                      temperature range from 197 to 202 K, a threshold in water
                      vapour of 10.6 ppmv has to be exceeded and maintained for
                      stratospheric ozone loss to occur. We investigated the
                      sensitivity of the water vapour threshold to temperature,
                      sulfate content, inorganic chlorine (Cly), inorganic
                      nitrogen (NOy) and inorganic bromine (Bry). The water vapour
                      threshold is mainly determined by the temperature and
                      sulfate content. However, the amount of ozone loss depends
                      on Cly, Bry and the duration of the time period over which
                      chlorine activation can be maintained. NOy affects both the
                      potential of ozone formation and the balance between
                      reactions yielding chlorine activation and deactivation,
                      which determines the water vapour threshold. Our results
                      show that in order to deplete ozone, a chlorine activation
                      time of 24 to 36 h for conditions of the water vapour
                      threshold with low temperatures must be maintained. A
                      maximum ozone loss of $9 \%$ was found for a 20 ppmv
                      water vapour mixing ratio using North American Monsoon (NAM)
                      tropopause standard conditions with a chemical box-model
                      simulation along a realistic trajectory. For the same
                      trajectory, using observed conditions (of 10.6 ppmv H2O),
                      the occurrence of simulated ozone loss was dependent on the
                      sulfate amount assumed. Detailed analysis of current and
                      future possibilities is needed to assess whether enhanced
                      water vapour conditions in the summertime mid-latitude lower
                      stratosphere lead to significant ozone loss},
      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:000466855400003},
      doi          = {10.5194/acp-19-5805-2019},
      url          = {https://juser.fz-juelich.de/record/862870},
}