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@ARTICLE{Hauck:878699,
      author       = {Hauck, Marius and Bönisch, Harald and Hoor, Peter and
                      Keber, Timo and Ploeger, Felix and Schuck, Tanja J. and
                      Engel, Andreas},
      title        = {{A} convolution of observational and model data to estimate
                      age of air spectra in the northern hemispheric lower
                      stratosphere},
      journal      = {Atmospheric chemistry and physics},
      volume       = {20},
      number       = {14},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-03017},
      pages        = {8763 - 8785},
      year         = {2020},
      abstract     = {Derivation of mean age of air (AoA) and age spectra from
                      atmospheric measurements remains a challenge and often
                      requires output from atmospheric models. This study tries to
                      minimize the direct influence of model output and presents
                      an extension and application of a previously established
                      inversion method to derive age spectra from mixing ratios of
                      long- and short-lived trace gases. For a precise description
                      of cross-tropopause transport processes, the inverse method
                      is extended to incorporate air entrainment into the
                      stratosphere across the tropical and extratropical
                      tropopause. We first use simulations with the Chemical
                      Lagrangian Model of the Stratosphere (CLaMS) to provide a
                      general proof of concept of the extended principle in a
                      controllable and consistent environment, where the method is
                      applied to an idealized set of 10 trace gases with
                      predefined constant lifetimes and compared to reference
                      model age spectra. In the second part of the study we apply
                      the extended inverse method to atmospheric measurements of
                      multiple long- and short-lived trace gases measured aboard
                      the High Altitude and Long Range (HALO) research aircraft
                      during the two research campaigns
                      POLSTRACC–GW-LCYCLE–SALSA (PGS) and Wave-driven
                      Isentropic Exchange (WISE). As some of the observed species
                      undergo significant loss processes in the stratosphere, a
                      Monte Carlo simulation is introduced to retrieve age spectra
                      and chemical lifetimes in stepwise fashion and to account
                      for the large uncertainties. Results show that in the
                      idealized model scenario the inverse method retrieves age
                      spectra robustly on annual and seasonal scales. The
                      extension to multiple entry regions proves reasonable as our
                      CLaMS simulations reveal that in the model between $50 \%$
                      and $70 \%$ of air in the lowermost stratosphere has
                      entered through the extratropical tropopause (30–90∘ N
                      and S) on annual average. When applied to observational data
                      of PGS and WISE, the method derives age spectra and mean AoA
                      with meaningful spatial distributions and quantitative
                      range, yet large uncertainties. Results indicate that
                      entrainment of fresh tropospheric air across both the
                      extratropical and tropical tropopause peaked prior to both
                      campaigns, but with lower mean AoA for WISE than PGS data.
                      The ratio of moments for all retrieved age spectra for PGS
                      and WISE is found to range between 0.52 and 2.81 years. We
                      conclude that the method derives reasonable and consistent
                      age spectra using observations of chemically active trace
                      gases. Our findings might contribute to an improved
                      assessment of transport with age spectra in future studies.},
      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:000555471200001},
      doi          = {10.5194/acp-20-8763-2020},
      url          = {https://juser.fz-juelich.de/record/878699},
}