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@ARTICLE{Krmer:7554,
      author       = {Krämer, M. and Schiller, C. and Afchine, A. and Bauer, R.
                      and Gensch, I. and Mangold, A. and Schlicht, S. and Spelten,
                      N. and Sitnikov, N. and Borrmann, S. and de Reus, M. and
                      Spichtinger, M. and P.},
      title        = {{I}ce supersaturations and cirrus cloud crystal numbers},
      journal      = {Atmospheric chemistry and physics},
      volume       = {9},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {PreJuSER-7554},
      pages        = {3505 - 3522},
      year         = {2009},
      note         = {Funding for the campaigns was granted by the BMBF within
                      the "Ozonforschungsprogramm" and the "Angewandte Klima- und
                      Atmosphiirenforschung" programme, by the EU DG XII within
                      Framework Programmes 5 and 6, and by ESA within the ENVISAT
                      validation programme. Water vapour measurements by FLASH and
                      data preparation was supported by the Russian Foundation for
                      Basic Research grants No. 06-05-64165-a and 07-05-00486-a.
                      This work was partly supported by the European Commission
                      within the framework of the Marie Curie Fellowship "Impact
                      of mesoscale dynamics and aerosols on the life cycle of
                      cirrus clouds (IMDALCC)".},
      abstract     = {Upper tropospheric observations outside and inside of
                      cirrus clouds indicate water vapour mixing ratios sometimes
                      exceeding water saturation. Relative humidities over ice
                      (RHice) of up to and more than $200\%$ have been reported
                      from aircraft and balloon measurements in recent years.From
                      these observations a lively discussion continues on whether
                      there is a lack of understanding of ice cloud microphysics
                      or whether the water measurements are tainted with large
                      uncertainties or flaws.Here, RHice in clear air and in ice
                      clouds is investigated. Strict quality-checked aircraft in
                      situ observations of RHice were performed during 28 flights
                      in tropical, mid-latitude and Arctic field experiments in
                      the temperature range 183-240 K. In our field measurements,
                      no supersaturations above water saturation are found.
                      Nevertheless, super- or subsaturations inside of cirrus are
                      frequently observed at low temperatures (<205 K) in our
                      field data set. To explain persistent RHice deviating from
                      saturation, we analysed the number densities of ice crystals
                      recorded (luring 20 flights. From the combined analysis -
                      using conventional microphysics - of supersaturations and
                      ice crystal numbers, we show that the high, persistent
                      supersaturations observed inside of cirrus can possibly be
                      explained by unexpected, frequent very low ice crystal
                      numbers that could scarcely be caused by homogeneous ice
                      nucleation. Heterogeneous ice formation or the suppression
                      of freezing might better explain the observed ice crystal
                      numbers.Thus, our lack of understanding of the high
                      supersaturations, with implications for the microphysical
                      and radiative properties of cirrus, the vertical
                      redistribution of water and climate, is traced back to the
                      understanding of the freezing process at low temperatures.},
      keywords     = {J (WoSType)},
      cin          = {ICG-1},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB790},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK406},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000266968200003},
      url          = {https://juser.fz-juelich.de/record/7554},
}