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@ARTICLE{Cirisan:154628,
      author       = {Cirisan, A. and Luo, B. P. and Engel, I. and Wienhold, F.
                      G. and Sprenger, M. and Krieger, U. K. and Weers, U. and
                      Romanens, G. and Levrat, G. and Jeannet, P. and Ruffieux, D.
                      and Philipona, R. and Calpini, B. and Spichtinger, P. and
                      Peter, T.},
      title        = {{B}alloon-borne match measurements of midlatitude cirrus
                      clouds},
      journal      = {Atmospheric chemistry and physics},
      volume       = {14},
      number       = {14},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2014-03918},
      pages        = {7341 - 7365},
      year         = {2014},
      abstract     = {Observations of high supersaturations with respect to ice
                      inside cirrus clouds with high ice water content (> 0.01 g
                      kg−1) and high crystal number densities (> 1 cm−3) are
                      challenging our understanding of cloud microphysics and of
                      climate feedback processes in the upper troposphere.
                      However, single measurements of a cloudy air mass provide
                      only a snapshot from which the persistence of ice
                      supersaturation cannot be judged. We introduce here the
                      "cirrus match technique" to obtain information about the
                      evolution of clouds and their saturation ratio. The aim of
                      these coordinated balloon soundings is to analyze the same
                      air mass twice. To this end the standard radiosonde
                      equipment is complemented by a frost point hygrometer,
                      "SnowWhite", and a particle backscatter detector, "COBALD"
                      (Compact Optical Backscatter AerosoL Detector). Extensive
                      trajectory calculations based on regional weather model
                      COSMO (Consortium for Small-Scale Modeling) forecasts are
                      performed for flight planning, and COSMO analyses are used
                      as a basis for comprehensive microphysical box modeling
                      (with grid scale of 2 and 7 km, respectively). Here we
                      present the results of matching a cirrus cloud to within
                      2–15 km, realized on 8 June 2010 over Payerne,
                      Switzerland, and a location 120 km downstream close to
                      Zurich. A thick cirrus cloud was detected over both
                      measurement sites. We show that in order to quantitatively
                      reproduce the measured particle backscatter ratios, the
                      small-scale temperature fluctuations not resolved by COSMO
                      must be superimposed on the trajectories. The stochastic
                      nature of the fluctuations is captured by ensemble
                      calculations. Possibilities for further improvements in the
                      agreement with the measured backscatter data are
                      investigated by assuming a very slow mass accommodation of
                      water on ice, the presence of heterogeneous ice nuclei, or a
                      wide span of (spheroidal) particle shapes. However, the
                      resulting improvements from these microphysical refinements
                      are moderate and comparable in magnitude with changes caused
                      by assuming different regimes of temperature fluctuations
                      for clear-sky or cloudy-sky conditions, highlighting the
                      importance of proper treatment of subscale fluctuations. The
                      model yields good agreement with the measured backscatter
                      over both sites and reproduces the measured saturation
                      ratios with respect to ice over Payerne. Conversely, the
                      $30\%$ in-cloud supersaturation measured in a massive 4 km
                      thick cloud layer over Zurich cannot be reproduced,
                      irrespective of the choice of meteorological or
                      microphysical model parameters. The measured supersaturation
                      can only be explained by either resorting to an unknown
                      physical process, which prevents the ice particles from
                      consuming the excess humidity, or – much more likely –
                      by a measurement error, such as a contamination of the
                      sensor housing of the SnowWhite hygrometer by a
                      precipitation drop from a mixed-phase cloud just below the
                      cirrus layer or from some very slight rain in the boundary
                      layer. This uncertainty calls for in-flight checks or
                      calibrations of hygrometers under the special humidity
                      conditions in the upper troposphere.},
      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},
      UT           = {WOS:000339934900013},
      doi          = {10.5194/acp-14-7341-2014},
      url          = {https://juser.fz-juelich.de/record/154628},
}