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@ARTICLE{Drdla:22111,
      author       = {Drdla, K. and Müller, R.},
      title        = {{T}emperature thresholds for chlorine activation and ozone
                      loss in the polar stratosphere},
      journal      = {Annales geophysicae},
      volume       = {30},
      issn         = {0992-7689},
      address      = {Kaltenburg, Lindau},
      publisher    = {Copernicus},
      reportid     = {PreJuSER-22111},
      pages        = {1055 - 1073},
      year         = {2012},
      note         = {We are grateful to Dave Fahey, Jens-Uwe Grooss, Thomas
                      Peter, Bob Portmann, Ross Salawitch, Susan Solomon, Simone
                      Tilmes, and Tobias Wegner for very helpful discussions and
                      for constructive critical comments. We thank Thomas Peter,
                      Ross Salawitch, Susan Solomon and a number of anonymous
                      referees for their thoughtful reviews. We also thank Tobias
                      Wegner very much for providing Figs. 1 and 2. This research
                      was supported in part by NASA's Earth Science Enterprise
                      through the Atmospheric Chemistry and Modeling Analysis
                      Program, NRA-02-OES-02 and by the European Union
                      EU-FP7-226365-RECONCILE grant. We are grateful to the United
                      Kingdom Met Office for providing meteorological analyses.},
      abstract     = {Low stratospheric temperatures are known to be responsible
                      for heterogeneous chlorine activation that leads to polar
                      ozone depletion. Here, we discuss the temperature threshold
                      below which substantial chlorine activation occurs. We
                      suggest that the onset of chlorine activation is dominated
                      by reactions on cold binary aerosol particles, without the
                      formation of polar stratospheric clouds (PSCs), i.e. without
                      any significant uptake of HNO3 from the gas phase. Using
                      reaction rates on cold binary aerosol in a model of
                      stratospheric chemistry, a chlorine activation threshold
                      temperature, T-ACL, is derived. At typical stratospheric
                      conditions, T-ACL is similar in value to T-NAT (within 1-2
                      K), the highest temperature at which nitric acid trihydrate
                      (NAT) can exist. T-NAT is still in use to parameterise the
                      threshold temperature for the onset of chlorine activation.
                      However, perturbations can cause T-ACL to differ from T-NAT:
                      T-ACL is dependent upon H2O and potential temperature, but
                      unlike T-NAT is not dependent upon HNO3. Furthermore, in
                      contrast to T-NAT, T-ACL is dependent upon the stratospheric
                      sulfate aerosol loading and thus provides a means to
                      estimate the impact on polar ozone of strong volcanic
                      eruptions and some geo-engineering options, which are
                      discussed. A parameterisation of T-ACL is provided here,
                      allowing it to be calculated for low solar elevation (or
                      high solar zenith angle) over a comprehensive range of
                      stratospheric conditions. Considering T-ACL as a proxy for
                      chlorine activation cannot replace a detailed model
                      calculation, and polar ozone loss is influenced by other
                      factors apart from the initial chlorine activation. However,
                      T-ACL provides a more accurate description of the
                      temperature conditions necessary for chlorine activation and
                      ozone loss in the polar stratosphere than T-NAT.},
      keywords     = {J (WoSType)},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {Atmosphäre und Klima / RECONCILE - Reconciliation of
                      essential process parameters for an enhanced predictability
                      of arctic stratospheric ozone loss and its climate
                      interactions. (226365)},
      pid          = {G:(DE-Juel1)FUEK491 / G:(EU-Grant)226365},
      shelfmark    = {Astronomy $\&$ Astrophysics / Geosciences,
                      Multidisciplinary / Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000306975300003},
      doi          = {10.5194/angeo-30-1055-2012},
      url          = {https://juser.fz-juelich.de/record/22111},
}