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@ARTICLE{Poshyvailo:841716,
      author       = {Poshyvailo, Liubov and Müller, Rolf and Konopka, Paul and
                      Günther, Gebhard and Riese, Martin and Ploeger, Felix},
      title        = {{S}ensitivities of modelled water vapour in the lower
                      stratosphere: temperature uncertainty, effects of horizontal
                      transport and small-scale mixing},
      journal      = {Atmospheric chemistry and physics / Discussions},
      volume       = {1072},
      issn         = {1680-7375},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2018-00024},
      pages        = {1 - 29},
      year         = {2017},
      abstract     = {Water vapour (H2O) in the upper troposphere and lower
                      stratosphere (UTLS) is a key player for global radiation. A
                      realistic representation of H2O is critical for climate
                      model predictions of future climate change. Here, we
                      investigate the effects of current uncertainties in
                      tropopause temperature, horizontal transport and small-scale
                      mixing on simulated H2O in the lower stratosphere (LS).To
                      assess the sensitivities of simulated H2O, we use the
                      Chemical Lagrangian Model of the Stratosphere (CLaMS).
                      First, we examine CLaMS driven by two different reanalysis,
                      ERA-Interim and Japanese 55-year (JRA-55) reanalysis, to
                      investigate the robustness with respect to the
                      meteorological dataset. Second, we carry out CLaMS
                      simulations with transport barriers along latitude circles
                      (at the equator, 15° N/S and 35° N/S) to assess the
                      effects of horizontal transport. Third, we vary the strength
                      of parametrized small-scale mixing in CLaMS.Our results show
                      significant differences (about 0.5 ppmv) in simulated
                      stratospheric H2O due to uncertainties in the tropical
                      tropopause temperatures between current reanalysis datasets.
                      The JRA-55 based simulation is significantly moister when
                      compared to ERA-Interim, due to a warmer tropical tropopause
                      in JRA-55 reanalysis. The transport barrier experiments
                      demonstrate that the Northern Hemisphere (NH) subtropics
                      have a strong moistening effect on global stratospheric H2O.
                      Interhemispheric exchange shows only a very weak effect on
                      stratospheric H2O. Small-scale mixing mainly increases
                      troposphere–stratosphere exchange, causing an enhancement
                      of stratospheric H2O, particularly along the subtropical
                      jets and in the Asian monsoon region.The sensitivity studies
                      presented here provide new insights into the leading
                      processes that control stratospheric H2O, important for
                      assessing and improving climate model projections.},
      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) / HITEC - Helmholtz
                      Interdisciplinary Doctoral Training in Energy and Climate
                      Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-244 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/acp-2017-1072},
      url          = {https://juser.fz-juelich.de/record/841716},
}