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| Titel |
Assessment of some parameterizations of heterogeneous ice nucleation in cloud and climate models |
| VerfasserIn |
J. A. Curry, V. I. Khvorostyanov |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 2 ; Nr. 12, no. 2 (2012-01-27), S.1151-1172 |
| Datensatznummer |
250010553
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| Publikation (Nr.) |
 copernicus.org/acp-12-1151-2012.pdf |
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| Zusammenfassung |
| Several different types of parameterization of heterogeneous ice nucleation
for cloud and climate models have been developed over the past decades,
ranging from empirically-derived expressions to parameterizations of ice
crystal nucleation rates derived from theory, including the parameterization
developed by the authors that includes simultaneous dependence on the
temperature and saturation ratio, hereafter referred to as KC.
Parameterizations schemes that address the
deliquescence-heterogeneous-freezing (DHetF), which combines the modes of
condensation freezing and immersion freezing, are assessed here in the
context of thermodynamic constraints, laboratory measurements, and recent
field measurements. It is shown that empirical schemes depending only on the
ice saturation ratio or only on temperature can produce reasonable crystal
concentrations, but ice crystal nucleation is thermodynamically prohibited
in certain regions of the temperature-saturation ratio phase space. Some
recent empirical parameterizations yield clouds that are almost entire
liquid at temperatures as low as −35 °C in contrast to cloud
climatology. Reasonable performance of the KC ice nucleation scheme is
demonstrated by comparison with numerous data from several recent field
campaigns, laboratory data, climatology of cloud phase-state. Several
mis-applications of the KC parameterization that appeared recently in the
literature are described and corrected. It is emphasized here that a correct
application of the KC scheme requires integration of the individual
nucleation rates over the measured size spectrum of ice nuclei that
represent a fraction or several fractions of the environmental aerosol with
specific ice nucleation properties. The concentration in these fractions can
be substantially smaller than that of the total aerosol, but greater than
the crystal concentration measured by an experimental device. Simulations
with temperature-dependent active site area or with several IN fractions
having different properties show that ice nucleation in the KC scheme occurs
in a wide temperature range of 10–20 °C, which depends on IN properties.
Simulation with a spectral bin model and correct application of KC scheme
adequately describes ice nucleation via the DHetF mode and yields crystal
concentrations and phase state close to those measured in the single-layer
stratocumulus cloud observed in the Mixed Phase Arctic Cloud Experiment
(MPACE). An assessment of some deficiencies in current parcel modeling
methods and cloud chamber observations and their impact on parameterization
development and evaluation is provided. |
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