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@ARTICLE{Keber:887691,
      author       = {Keber, Timo and Bönisch, Harald and Hartick, Carl and
                      Hauck, Marius and Lefrancois, Fides and Obersteiner, Florian
                      and Ringsdorf, Akima and Schohl, Nils and Schuck, Tanja and
                      Hossaini, Ryan and Graf, Phoebe and Jöckel, Patrick and
                      Engel, Andreas},
      title        = {{B}romine from short-lived source gases in the
                      extratropical northern hemispheric upper troposphere and
                      lower stratosphere ({UTLS})},
      journal      = {Atmospheric chemistry and physics},
      volume       = {20},
      number       = {7},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-04352},
      pages        = {4105 - 4132},
      year         = {2020},
      abstract     = {We present novel measurements of five short-lived
                      brominated source gases (CH2Br2, CHBr3, CH2ClBr, CHCl2Br and
                      CHClBr2). These rather short-lived gases are an important
                      source of bromine to the stratosphere, where they can lead
                      to depletion of ozone. The measurements have been obtained
                      using an in situ gas chromatography and mass spectrometry
                      (GC–MS) system on board the High Altitude and Long Range
                      Research Aircraft (HALO). The instrument is extremely
                      sensitive due to the use of chemical ionization, allowing
                      detection limits in the lower parts per quadrillion (ppq,
                      10−15) range. Data from three campaigns using HALO are
                      presented, where the upper troposphere and lower
                      stratosphere (UTLS) of the northern hemispheric mid-to-high
                      latitudes were sampled during winter and during late summer
                      to early fall. We show that an observed decrease with
                      altitude in the stratosphere is consistent with the relative
                      lifetimes of the different compounds. Distributions of the
                      five source gases and total organic bromine just below the
                      tropopause show an increase in mixing ratio with latitude,
                      in particular during polar winter. This increase in mixing
                      ratio is explained by increasing lifetimes at higher
                      latitudes during winter. As the mixing ratios at the
                      extratropical tropopause are generally higher than those
                      derived for the tropical tropopause, extratropical
                      troposphere-to-stratosphere transport will result in
                      elevated levels of organic bromine in comparison to air
                      transported over the tropical tropopause. The observations
                      are compared to model estimates using different emission
                      scenarios. A scenario with emissions mainly confined to low
                      latitudes cannot reproduce the observed latitudinal
                      distributions and will tend to overestimate organic bromine
                      input through the tropical tropopause from CH2Br2 and CHBr3.
                      Consequently, the scenario also overestimates the amount of
                      brominated organic gases in the stratosphere. The two
                      scenarios with the highest overall emissions of CH2Br2 tend
                      to overestimate mixing ratios at the tropical tropopause,
                      but they are in much better agreement with extratropical
                      tropopause mixing ratios. This shows that not only total
                      emissions but also latitudinal distributions in the
                      emissions are of importance. While an increase in tropopause
                      mixing ratios with latitude is reproduced with all emission
                      scenarios during winter, the simulated extratropical
                      tropopause mixing ratios are on average lower than the
                      observations during late summer to fall. We show that a good
                      knowledge of the latitudinal distribution of tropopause
                      mixing ratios and of the fractional contributions of
                      tropical and extratropical air is needed to derive
                      stratospheric inorganic bromine in the lowermost
                      stratosphere from observations. In a sensitivity study we
                      find maximum differences of a factor 2 in inorganic bromine
                      in the lowermost stratosphere from source gas injection
                      derived from observations and model outputs. The
                      discrepancies depend on the emission scenarios and the
                      assumed contributions from different source regions. Using
                      better emission scenarios and reasonable assumptions on
                      fractional contribution from the different source regions,
                      the differences in inorganic bromine from source gas
                      injection between model and observations is usually on the
                      order of 1 ppt or less. We conclude that a good
                      representation of the contributions of different source
                      regions is required in models for a robust assessment of the
                      role of short-lived halogen source gases on ozone depletion
                      in the UTLS.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000524488200003},
      doi          = {10.5194/acp-20-4105-2020},
      url          = {https://juser.fz-juelich.de/record/887691},
}