% 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”.

@PHDTHESIS{Meyer:22871,
      author       = {Meyer, Jessica},
      title        = {{I}ce {C}rystal {M}easurements with the {N}ew {P}article
                      {S}pectrometer {NIXE}-{CAPS}},
      volume       = {160},
      school       = {Universität Wuppertal},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-22871},
      isbn         = {978-3-89336-840-2},
      series       = {Schriften des Forschungszentrums Jülich : Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      year         = {2013},
      note         = {Record converted from VDB: 12.11.2012; Universität
                      Wuppertal, Diss., 2012},
      abstract     = {Mixed-phase clouds consist of liquid droplets and ice
                      crystals and appear in the temperature range between
                      0$^{◦}$C and 40$^{◦}$C. They are in the focus of recent
                      research because model studies indicate that their degree of
                      glaciation have an impact on the cloud radiative properties.
                      Up to now, mainly the measurement of bulk liquid and ice
                      water content is used to investigate the mixed-phase cloud
                      glaciation process. This study, for the first time, presents
                      extensive size resolved laboratory and aircraft based
                      in-situ mixed-phase cloud observations. For this purpose,
                      the Novel Ice EXpEriment - Cloud and Aerosol Particle
                      Spectrometer (NIXE-CAPS), an established cloud particle
                      instrument, but equipped with an additional depolarization
                      detector to distinguish ice crystals and liquid droplets, is
                      used. The complete set of measured parameters includes
                      concentration and phase of cloud particles in the size range
                      of 0.61 $\mu$m to 937.5 $\mu$m. Here, the dependence of
                      mixed-phase cloud glaciation on the initial number of ice
                      active aerosol, relative humidity and temperature is
                      investigated for clouds generated in the AIDA cloud chamber
                      and for natural clouds observed on board of the British
                      aircraft BAE146 during the COALESC campaign over the UK in
                      2011. A significant difference in the degree of glaciation
                      is found for AIDA mixed-phase clouds evolved in either sub-
                      or supersaturated humidity conditions with respect to water
                      (RHw). The droplet concentration in supersaturated RHw
                      regimes is constantly high (around 500 cm$^{−3}$) over the
                      whole temperature range, since the droplets do not evaporate
                      (dropletice coexisting regime). Under subsaturated
                      conditions where evaporation of droplets occurs
                      (Wegener-Bergeron-Findeisen regime), their concentrations
                      decrease with temperature from about 100 cm$^{−3}$ at 270
                      K to 1 cm$^{−3}$ at 235 K. This decrease in droplet
                      concentration is most likely caused by the increasing
                      difference of the water vapor saturation pressure with
                      respect to liquid and ice. Hence, the droplet concentration
                      in mixed phase clouds seems to be mainly driven by the
                      dynamic situation. The number of ice nuclei in the AIDA
                      chamber and thus the ice crystal concentration of the AIDA
                      clouds was constantly high. In the droplet-ice coexistence
                      regime, where also high liquid droplet concentrations are
                      observed, the resultant number fraction of frozen cloud
                      particles is only about 10 \% for all temperatures. In
                      contrast, in the subsaturated Wegener-Bergeron-Findeisen
                      regime, the ice number fraction increases with decreasing
                      droplet concentration from about 20 \% at 270 K up to 80 \%
                      at 235 K. Thus, the colder AIDA clouds in the
                      Wegener-Bergeron-Findeisen regions show a high degree of
                      glaciation which is expected for Wegener-Bergeron-Findeisen
                      conditions, but complete glaciation does not occur.
                      Nevertheless, the ice mass fraction is very close to 100 \%,
                      since the remaining particles classified as droplets are
                      only small. The COALESC natural clouds are found to be
                      almost all in theWegener-Bergeron-Findeisen regime with
                      droplet numbers decreasing with temperature, as for the AIDA
                      clouds. However, the number of ice nuclei in the atmosphere
                      is much lower than in the AIDA chamber. Thus, the ice number
                      fraction observed for the COALESC natural clouds ranges only
                      from about 2 \% at 270 K up to 20 \% at 235 K. It is much
                      lower than for the respective AIDA clouds which glaciated in
                      an environment with a very high number of ice nuclei. The
                      measurements in the AIDA and COALESC mixed-phase clouds
                      illustrate how the degree of glaciation in mixed-phase
                      clouds is determined by both the thermodynamic situation of
                      the cloud and the number of ice nuclei, and, most
                      interestingly, that coexistence of droplets and ice is
                      possible in natural mixed-phase clouds in the
                      Wegener-Bergeron-Findeisen regime, where complete glaciation
                      is believed to be the most probable state.},
      cin          = {IEK-7},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK491},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/22871},
}