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@ARTICLE{PoshyvailoStrube:909082,
      author       = {Poshyvailo-Strube, Liubov and Müller, Rolf and
                      Fueglistaler, Stephan and Hegglin, Michaela Imelda and
                      Laube, Johannes C. and Volk, C. Michael and Ploeger, Felix},
      title        = {{H}ow can {B}rewer–{D}obson circulation trends be
                      estimated from changes in stratospheric water vapour and
                      methane?},
      journal      = {Atmospheric chemistry and physics},
      volume       = {22},
      number       = {15},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2022-02999},
      pages        = {9895 - 9914},
      year         = {2022},
      note         = {open access},
      abstract     = {The stratospheric meridional overturning circulation, also
                      referred to as the Brewer–Dobson circulation (BDC),
                      controls the composition of the stratosphere, which, in
                      turn, affects radiation and climate. As the BDC cannot be
                      directly measured, one has to infer its strength and trends
                      indirectly. For instance, trace gas measurements allow the
                      calculation of average transit times.Satellite measurements
                      provide information on the distributions of trace gases for
                      the entire stratosphere, with measurements of particularly
                      long temporal and dense spatial coverage available for
                      stratospheric water vapour (H2O). Although chemical
                      processes and boundary conditions confound interpretation,
                      the influence of methane (CH4) oxidation on H2O in the
                      stratosphere is relatively straightforward, and thus H2O is
                      an appealing tracer for transport analysis despite these
                      caveats. In this work, we explore how mean age of air trends
                      can be estimated from the combination of stratospheric H2O
                      and CH4 data, by carrying out a proof of concept within the
                      model environment of the Chemical Lagrangian Model of the
                      Stratosphere (CLaMS). In particular, we assess the
                      methodological uncertainties related to the two commonly
                      used approximations of (i) instantaneous stratospheric entry
                      mixing ratio propagation and (ii) constant correlation
                      between mean age and the fractional release factor of CH4.
                      Performing various sensitivity studies with CLaMS, we test
                      different methods of the mean age of air trend estimation,
                      and we aim to provide simple and practical advice on the
                      adjustment of the used approximations for obtaining more
                      reliable mean age of air trends from the measurements of H2O
                      and CH4.Our results show that the estimated mean age of air
                      trends from the combination of stratospheric H2O and CH4
                      changes may be significantly affected by the assumed
                      approximations. Depending on the investigated stratospheric
                      region and the considered period, the error in estimated
                      mean age of air trends can be large, especially in the lower
                      stratosphere. For particular periods, the errors from the
                      two approximations can lead to opposite effects, which may
                      even cancel out. Finally, for a more reliable estimate of
                      the mean age of air trends, we propose adjusting the
                      approximation method by using an idealized age spectrum to
                      propagate stratospheric entry mixing ratios. The findings of
                      this work can be used for assessing the uncertainties in
                      stratospheric BDC trend estimation from global satellite
                      measurements.},
      cin          = {IEK-7 / IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013 / I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2112 - Climate Feedbacks (POF4-211) / 2173 -
                      Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2112 / G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000835274100001},
      doi          = {10.5194/acp-22-9895-2022},
      url          = {https://juser.fz-juelich.de/record/909082},
}