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| Titel |
Parameterizing ice nucleation rates using contact angle and activation energy derived from laboratory data |
| VerfasserIn |
J.-P. Chen, A. Hazra, Z. Levin |
| 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 ; 8, no. 24 ; Nr. 8, no. 24 (2008-12-15), S.7431-7449 |
| Datensatznummer |
250006509
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| Publikation (Nr.) |
 copernicus.org/acp-8-7431-2008.pdf |
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| Zusammenfassung |
| The rate of ice nucleation in clouds is not easily determined and large
discrepancies exist between model predictions and actual ice crystal
concentration measured in clouds. In an effort to improve the
parameterization of ice nucleating in cloud models, we investigate the rate
of heterogeneous ice nucleation under specific ambient conditions by knowing
the sizes as well as two thermodynamic parameters of the ice nuclei –
contact angle and activation energy. Laboratory data of freezing and
deposition nucleation modes were analyzed to derive inversely the two
thermodynamic parameters for a variety of ice nuclei, including mineral
dusts, bacteria, pollens, and soot particles. The analysis considered the
Zeldovich factor for the adjustment of ice germ formation, as well as the
solute and curvature effects on surface tension; the latter effects have
strong influence on the contact angle. Contact angle turns out to be a more
important factor than the activation energy in discriminating the nucleation
capabilities of various ice nuclei species. By extracting these
thermodynamic parameters, laboratory results can be converted into a
formulation that follows classical nucleation theory, which then has the
flexibility of incorporating factors such as the solute effect and curvature
effect that were not considered in the experiments. Due to various
uncertainties, contact angle and activation energy derived in this study
should be regarded as "apparent" thermodynamics parameters. |
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