% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Spang:187218,
      author       = {Spang, Reinhold and Günther, Gebhard and Müller, Rolf and
                      Hoffmann, Lars and Griessbach, Sabine and Rolf, Christian
                      and Riese, Martin},
      title        = {{O}berservations of cirrus clouds in the lowermost
                      stratosphere: common feature, rare incident, or
                      observational artefact ?},
      journal      = {Geophysical research abstracts},
      volume       = {16},
      issn         = {1607-7962},
      address      = {Katlenburg-Lindau},
      publisher    = {Soc.},
      reportid     = {FZJ-2015-00891},
      pages        = {EGU2014-7297},
      year         = {2014},
      abstract     = {Ground based observations by lidar instruments show
                      evidential occurrence of optically and vertically thin
                      cirrus clouds in the lowermost stratosphere (LMS). The
                      knowledge about the potential formation processes of these
                      clouds, their occurrence and distribution, and their
                      radiative impact is very limited. Global observations of LMS
                      cirrus clouds by satellites would be very helpful to better
                      characterise these clouds. However, this is a difficult task
                      because the optical thickness of LMS cirrus is usually at
                      the edge of the detection limit (for space borne
                      limb-sounders) or even below (for infra red nadir
                      sounders).In addition, instrument characteristics can make
                      it difficult to judge if a cloud observation is inside the
                      LMS of just at or below the tropopause. Consequently it is
                      not really proven if LMS cirrus clouds are a rare occasion
                      or a globally common feature. We will give a brief overview
                      of the history of LMS cirrus observations from ground and
                      space borne sensors and are highlighting the sometimes
                      controversial discussion on the observation of clouds in the
                      LMS. Then we will focus on results from measurements of the
                      Cryogenic Infrared Spectrometers and Telescopes for the
                      Atmosphere (CRISTA) satellite instrument. CRISTA made a
                      number of snapshot measurements of the UT/LS during its two
                      Space Shuttle missions in 1994 and 1997. The measurements
                      demonstrate the potential of the IR limb viewing technique
                      to provide information on several trace constituents and
                      optically thin cirrus clouds with comparably high spatial
                      resolution. The CRISTA data are still unique for IR limb
                      sounders in the sense of vertical (1.5 km) and horizontal
                      (300-500 km) resolution as well as daily global coverage by
                      using three telescopes for three different viewing
                      directions simultaneously. The detection sensitivity for
                      optically thin cirrus clouds is extremely high. Depending on
                      the vertical and horizontal extent of a cirrus cloud, the
                      detection of an ice water content > 10-5g/m3 is achievable.
                      This detection limit is even better than for the CALIPSO
                      lidar, the most sensitive instrument currently in space. An
                      overview of CRISTA-2 water vapour and cirrus observations in
                      August 1997 will be given, and compared with corresponding
                      ECMWF reanalyses and simulations by the Chemical Lagrangian
                      Model of the Stratosphere (CLaMS). The observations indicate
                      a considerable flux of moisture from the upper tropical
                      troposphere into the extra-tropical lowermost stratosphere,
                      accompanied by high cirrus cloud occurrence frequencies even
                      at rather high northern latitudes (65N) and at altitudes
                      above the tropopause (around 350 K potential temperature).
                      The observations are compared with CLaMS simulations, which
                      include a simple parameterisation for cirrus cloud formation
                      and sedimentation of ice particles. The results suggest a
                      connection between isentropic, quasi-horizontal transport of
                      water vapour from the sub-tropics and the occurrence of
                      optically thin cirrus clouds in the lowermost stratosphere
                      well above the tropopause.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {234 - Composition and Dynamics of the Upper Troposphere and
                      Stratosphere (POF2-234)},
      pid          = {G:(DE-HGF)POF2-234},
      typ          = {PUB:(DE-HGF)16},
      url          = {https://juser.fz-juelich.de/record/187218},
}