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@ARTICLE{Mller:844122,
      author       = {Müller, Rolf and Grooß, Jens-Uwe and Zafar, Abdul Mannan
                      and Robrecht, Sabine and Lehmann, Ralph},
      title        = {{T}he maintenance of elevated active chlorine levels in the
                      {A}ntarctic lower stratosphere through {HC}l null cycles},
      journal      = {Atmospheric chemistry and physics},
      volume       = {18},
      number       = {4},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2018-01597},
      pages        = {2985 - 2997},
      year         = {2018},
      abstract     = {The Antarctic ozone hole arises from ozone destruction
                      driven by elevated levels of ozone destroying ("active")
                      chlorine in Antarctic spring. These elevated levels of
                      active chlorine have to be formed first and then maintained
                      throughout the period of ozone destruction. It is a matter
                      of debate how this maintenance of active chlorine is brought
                      about in Antarctic spring, when the rate of formation of HCl
                      (considered to be the main chlorine deactivation mechanism
                      in Antarctica) is extremely high. Here we show that in the
                      heart of the ozone hole (16–18km or 85–55hPa, in the
                      core of the vortex), high levels of active chlorine are
                      maintained by effective chemical cycles (referred to as HCl
                      null cycles hereafter). In these cycles, the formation of
                      HCl is balanced by immediate reactivation, i.e. by immediate
                      reformation of active chlorine. Under these conditions,
                      polar stratospheric clouds sequester HNO3 and thereby cause
                      NO2 concentrations to be low. These HCl null cycles allow
                      active chlorine levels to be maintained in the Antarctic
                      lower stratosphere and thus rapid ozone destruction to
                      occur. For the observed almost complete activation of
                      stratospheric chlorine in the lower stratosphere, the
                      heterogeneous reaction HCl + HOCl is essential; the
                      production of HOCl occurs via HO2 + ClO, with the HO2
                      resulting from CH2O photolysis. These results are important
                      for assessing the impact of changes of the future
                      stratospheric composition on the recovery of the ozone hole.
                      Our simulations indicate that, in the lower stratosphere,
                      future increased methane concentrations will not lead to
                      enhanced chlorine deactivation (through the reaction
                      CH4 + Cl  ⟶  HCl + CH3) and that extreme ozone
                      destruction to levels below  ≈ 0.1ppm will occur until
                      mid-century.},
      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:000426556500005},
      doi          = {10.5194/acp-18-2985-2018},
      url          = {https://juser.fz-juelich.de/record/844122},
}