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@ARTICLE{Ploeger:862448,
      author       = {Ploeger, Felix and Legras, B. and Charlesworth, Edward and
                      Yan, Xiaolu and Diallo, Mohamadou Abdoulaye and Konopka,
                      Paul and Birner, Th. and Tao, Mengchu and Engel, A. and
                      Riese, Martin},
      title        = {{H}ow robust are stratospheric age of air trends from
                      different reanalyses?},
      journal      = {Geophysical research abstracts},
      volume       = {21},
      number       = {9},
      issn         = {1029-7006},
      address      = {Katlenburg-Lindau},
      publisher    = {Soc.},
      reportid     = {FZJ-2019-02760},
      pages        = {EGU2019-2171},
      year         = {2019},
      abstract     = {An accelerating Brewer–Dobson circulation (BDC) is a
                      robust signal of climate change in model predictions but has
                      been questioned by trace gas observations. We analyse the
                      stratospheric mean age of air and the full age spectrum as
                      measures for the BDC and its trend. Age of air is calculated
                      using the Chemical Lagrangian Model of the Stratosphere
                      (CLaMS) driven by ERA-Interim, JRA-55 and MERRA-2 reanalysis
                      data to assess the robustness of the representation of the
                      BDC in current generation meteorological reanalyses. We find
                      that the climatological mean age significantly depends on
                      the reanalysis, with JRA-55 showing the youngest and MERRA-2
                      the oldest mean age. Consideration of the age spectrum
                      indicates that the older air for MERRA-2 is related to a
                      stronger spectrum tail, which is likely associated with
                      weaker tropical upwelling and stronger recirculation.
                      Seasonality of stratospheric transport is robustly
                      represented in reanalyses, with similar mean age variations
                      and age spectrum peaks. Long-term changes from 1989 to 2015
                      turn out to be similar for the reanalyses with mainly
                      decreasing mean age accompanied by a shift of the age
                      spectrum peak towards shorter transit times, resembling the
                      forced response in climate model simulations to increasing
                      greenhouse gas concentrations. For the shorter periods,
                      1989–2001 and 2002–2015, the age of air changes are less
                      robust. Only ERA-Interim shows the hemispheric dipole
                      pattern in age changes from 2002 to 2015 as viewed by recent
                      satellite observations. Consequently, the representation of
                      decadal variability of the BDC in current generation
                      reanalyses appears less robust and is a major uncertainty of
                      modelling the BDC.},
      month         = {Apr},
      date          = {2019-04-07},
      organization  = {Vienna (Austria), 7 Apr 2019 - 12 Apr
                       2019},
      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:000467412800004},
      doi          = {10.5194/acp-19-6085-2019},
      url          = {https://juser.fz-juelich.de/record/862448},
}