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@ARTICLE{Spang:154218,
      author       = {Spang, R. and Günther, G. and Riese, M. and Hoffmann, L.
                      and Müller, Rolf and Griessbach, S.},
      title        = {{S}atellite observations of cirrus clouds in the {N}orthern
                      {H}emisphere lowermost stratosphere},
      journal      = {Atmospheric chemistry and physics / Discussions},
      volume       = {14},
      number       = {8},
      issn         = {1680-7375},
      reportid     = {FZJ-2014-03597},
      pages        = {12323 - 12375},
      year         = {2014},
      abstract     = {Here we present observations of the Cryogenic Infrared
                      Spectrometers and Telescopes for the Atmosphere (CRISTA) of
                      cirrus cloud and water vapour in August 1997 in the upper
                      troposphere and lower stratosphere (UTLS) region. The
                      observations indicate a considerable flux of moisture from
                      the upper tropical troposphere into the extra-tropical
                      lowermost stratosphere (LMS), resulting in the occurrence of
                      high altitude optically thin cirrus clouds in the LMS.The
                      locations of the LMS cloud events observed by CRISTA are
                      consistent with the tropopause height determined from
                      coinciding radiosonde data. For a hemispheric analysis in
                      tropopause relative coordinates an improved tropopause
                      determination has been applied to the ECMWF temperature
                      profiles. We found that a significant fraction of the cloud
                      occurrences in the tropopause region are located in the LMS,
                      even if a conservative overestimate of the cloud top height
                      (CTH) determination by CRISTA of 500 m is assumed. The
                      results show rather high occurrence frequencies $(∼5\%)$
                      up to high northern latitudes (70° N) and altitudes well
                      above the tropopause (>500 m at ∼350 K and above) in large
                      areas at mid and high latitudes.Comparisons with model runs
                      of the Chemical Lagragian Model of the Stratosphere (CLaMS)
                      over the CRISTA period show a reasonable consistency for the
                      retrieved cloud pattern. For this purpose a limb ray tracing
                      approach was applied through the 3-D model fields to obtain
                      integrated measurement information through the atmosphere
                      along the limb path of the instrument. The simplified cirrus
                      scheme implemented in CLaMS seems to cause a systematic
                      underestimation in the CTH occurrence frequencies in the LMS
                      with respect to the observations. The observations together
                      with the model results demonstrate the importance of
                      isentropic, quasi-horizontal transport of water vapour from
                      the sub-tropics and the potential for the occurrence of
                      cirrus clouds in the lowermost stratosphere and tropopause
                      region.},
      cin          = {IEK-7 / JSC},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013 / I:(DE-Juel1)JSC-20090406},
      pnm          = {411 - Computational Science and Mathematical Methods
                      (POF2-411)},
      pid          = {G:(DE-HGF)POF2-411},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/acpd-14-12323-2014},
      url          = {https://juser.fz-juelich.de/record/154218},
}