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@ARTICLE{Thomas:23767,
      author       = {Thomas, A. and Borrmann, S. and Kiemle, C. and Adriani, A.
                      and Volk, M. and Beuermann, J. and Lepuchov, B. and Yushkov,
                      V. and Stefanutti, L.},
      title        = {{I}n-situ measurements of background aerosol and subvisible
                      cirrus near the tropical tropopause region},
      journal      = {Journal of Geophysical Research},
      volume       = {107},
      issn         = {0148-0227},
      address      = {Washington, DC},
      publisher    = {Union},
      reportid     = {PreJuSER-23767},
      pages        = {D24},
      year         = {2002},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {[1] In situ aerosol measurements were performed in the
                      Indian Ocean Intertropical Convergence Zone (ITCZ) region
                      during the Airborne Polar Experiment-Third European
                      Stratospheric Experiment on Ozone (APE-THESEO) field
                      campaign based in Mahe, Seychelles between 24 February and 6
                      March 1999. These are measurements of particle size
                      distributions with a laser optical particle counter of the
                      Forward Scattering Spectrometer Probe (FSSP)-300 type
                      operated on the Russian M-55 high-altitude research aircraft
                      Geophysica in the tropical upper troposphere and lower
                      stratosphere up to altitudes of 21 km. On 24 and 27 February
                      1999, ultrathin layers of cirrus clouds were penetrated by
                      Geophysica directly beneath the tropical tropopause at 17 km
                      pressure altitude and temperatures below 190 K. These layers
                      also were concurrently observed by the Ozone Lidar
                      Experiment (OLEX) lidar operating on the lower-flying German
                      DLR Falcon research aircraft. The encountered ultrathin
                      subvisual cloud layers can be characterized as (1)
                      horizontally extending over several hundred kilometers, (2)
                      persisting for at least 3 hours (but most likely much
                      longer), and (3) having geometrical thicknesses of 100-400
                      m. These cloud layers belong to the geometrically and
                      optically thinnest ever observed. In situ particle size
                      distributions covering diameters between 0.4 and 23 mum
                      obtained from these layers are juxtaposed with those
                      obtained inside cloud veils around cumulonimbus (Cb) anvils
                      and also with background aerosol measurements in the
                      vicinity of the clouds. A significant number of particles
                      with size diameters around 10 mum were detected inside these
                      ultrathin subvisible cloud layers. The cloud particle size
                      distribution closely resembles a background aerosol onto
                      which a modal peak between 2 and 17 mum is superimposed.
                      Measurements of particles with sizes above 23 mum could not
                      be obtained since no suitable instrument was available on
                      Geophysica. During the flight of 6 March 1999, upper
                      tropospheric and lower stratospheric background aerosol was
                      measured in the latitude band between 4degreesS and
                      19degreesS latitude. The resulting particle number densities
                      along the 56th meridian exhibit very little latitudinal
                      variation. The concentrations for particles with sizes above
                      0.5 m m encountered under these background conditions varied
                      between 0.1 and 0.3 particles/cm(3) of air in altitudes
                      between 17 and 21 km.},
      keywords     = {J (WoSType)},
      cin          = {ICG-I},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB47},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000181253700008},
      doi          = {10.1029/2001JD001385},
      url          = {https://juser.fz-juelich.de/record/23767},
}