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@PHDTHESIS{Poshyvailo:878378,
      author       = {Poshyvailo, Liubov},
      title        = {{L}agrangian {S}imulation of {S}tratospheric {W}ater
                      {V}apour: {I}mpact of {L}arge-{S}cale {C}irculation and
                      {S}mall-{S}cale {T}ransport {P}rocesses},
      volume       = {503},
      school       = {Universität Wuppertal},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2020-02818},
      isbn         = {978-3-95806-488-1},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {126 S.},
      year         = {2020},
      note         = {Universität Wuppertal, Diss., 2020},
      abstract     = {The atmospheric global circulation, also referred to as the
                      Brewer-Dobson circulation, controls the composition of the
                      upper troposphere and lower stratosphere (UTLS). The UTLS
                      trace gas composition, in turn, crucially affects climate.
                      In particular, UTLS water vapour (H$_{2}$O) plays a
                      significant role in the global radiation budget. Therefore,
                      a realistic representation of H$_{2}$O and Brewer-Dobson
                      circulation, is critical for accurate model predictions of
                      future climate and circulation changes. This thesis is
                      structured in two main parts: focussing on the (i) effect of
                      model uncertainties (due to tropical tropopause temperature,
                      horizontal transport and small-scale mixing) on
                      stratospheric H$_{2}$O, and on the (ii) uncertainties in
                      estimating Brewer-Dobson circulation trends from the
                      observed H$_{2}$O trends. The results presented here are
                      based largely on stratospheric H$_{2}$O studies with the
                      Chemical Lagrangian Model of the Stratosphere (CLaMS).
                      Firstly, to investigate the robustness of simulated H${2}$O
                      with respect to different meteorological datasets, we
                      examine CLaMS driven by the ERA-Interim reanalysis from the
                      European Centre of Medium-Range Weather Forecasts, and the
                      Japanese 55-year Reanalysis (JRA-55). Secondly, to assess
                      the effects of horizontal transport, we carry out CLaMS
                      simulations, with transport barriers, along latitude
                      circles: at the equator, at 15$^{\circ}$ N/S and at
                      35$^{\circ}$ N/S. To investigate the sensitivity of
                      simulated H$_{2}$O regarding small-scale atmospheric mixing,
                      we vary the strength of parametrized small-scale mixing in
                      CLaMS. Finally, to assess the reliability of estimated
                      long-term Brewer-Dobson circulation changes from
                      stratospheric H$_{2}$O, we apply different methods of
                      calculating mean age of air trends involving two
                      approximations: instantaneous entry mixing ratio
                      propagation, and a constant correlation between mean age of
                      air and the fractional release factor of methane. The latter
                      assumption essentially means assuming a constant correlation
                      between the mean age of air and the mixing ratio of
                      long-lived trace gases. The results of this thesis show
                      significant differences in simulated stratospheric H$_{2}$O
                      (about 0.5 ppmv) due to uncertainties in the tropical
                      tropopause temperatures between the two reanalysis datasets,
                      JRA-55 and ERA-Interim. The JRA-55 based simulation is
                      significantly moister, when compared to ERA-Interim, due to
                      a warmer tropical tropopause of approximately 2 K. Moreover,
                      through introducing artificial transport barriers in CLaMS,
                      we suppress certain horizontal transport pathways. These
                      transport experiments demonstrate that the Northern
                      Hemisphere subtropics have a strong moistening effect on
                      global stratospheric H$_{2}$O. Interhemispheric exchange
                      shows only a very weak effect on stratospheric H$_{2}$O.
                      Small-scale mixing mainly increases troposphere-stratosphere
                      exchange, causing an enhancement of stratospheric H$_{2}$O,
                      particularly, along the subtropical jets in the summer
                      hemisphere and in the Northern hemispheric monsoon regions.
                      In particular, the Asian and American monsoon systems,
                      during boreal summer, turn out as regions especially
                      sensitive to changes in small-scale mixing. The estimated
                      mean age of air trends from stratospheric H$_{2}$O changes,
                      in general, are strongly determined by the assumed
                      approximations. Depending on the investigated region of the
                      stratosphere, and the considered period, the error of
                      estimated mean age of air trends can be large.
                      Interestingly, depending on the period, the effects from
                      both approximations can also be opposite, and may even
                      cancel out. The results of this thesis provide new insights
                      into the leading processes that control stratospheric
                      H$_{2}$O and its trends, and are therefore relevant for
                      improving climate model predictions. Furthermore, the
                      results of this work can be used for evaluating the
                      uncertainties of estimated stratospheric circulation changes
                      from global satellite measurements.},
      cin          = {IEK-7 / IBG-3},
      cid          = {I:(DE-Juel1)IEK-7-20101013 / I:(DE-Juel1)IBG-3-20101118},
      pnm          = {244 - Composition and dynamics of the upper troposphere and
                      middle atmosphere (POF3-244)},
      pid          = {G:(DE-HGF)POF3-244},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/878378},
}