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| Titel |
Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments |
| VerfasserIn |
C. Hoose, O. Möhler |
| 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. 20 ; Nr. 12, no. 20 (2012-10-29), S.9817-9854 |
| Datensatznummer |
250011538
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| Publikation (Nr.) |
 copernicus.org/acp-12-9817-2012.pdf |
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| Zusammenfassung |
| A small subset of the atmospheric aerosol population has the ability to
induce ice formation at conditions under which ice would not form without
them (heterogeneous ice nucleation). While no closed theoretical description
of this process and the requirements for good ice nuclei is available,
numerous studies have attempted to quantify the ice nucleation ability of
different particles empirically in laboratory experiments. In this article,
an overview of these results is provided. Ice nucleation "onset" conditions
for various mineral dust, soot, biological, organic and ammonium sulfate
particles are summarized. Typical temperature-supersaturation regions can be
identified for the "onset" of ice nucleation of these different particle
types, but the various particle sizes and activated fractions reported in
different studies have to be taken into account when comparing results
obtained with different methodologies. When intercomparing only data obtained
under the same conditions, it is found that dust mineralogy is not a
consistent predictor of higher or lower ice nucleation ability. However, the
broad majority of studies agrees on a reduction of deposition nucleation by
various coatings on mineral dust. The ice nucleation active surface site
(INAS) density is discussed as a simple and empirical normalized measure for
ice nucleation activity. For most immersion and condensation freezing
measurements on mineral dust, estimates of the temperature-dependent INAS
density agree within about two orders of magnitude. For deposition nucleation
on dust, the spread is significantly larger, but a general trend of
increasing INAS densities with increasing supersaturation is found. For soot,
the presently available results are divergent. Estimated average INAS
densities are high for ice-nucleation active bacteria at high subzero
temperatures. At the same time, it is shown that INAS densities of some other
biological aerosols, like certain pollen grains, fungal spores and diatoms,
tend to be similar to those of dust. These particles may owe their high ice
nucleation onsets to their large sizes. Surface-area-dependent
parameterizations of heterogeneous ice nucleation are discussed. For
immersion freezing on mineral dust, fitted INAS densities are available, but
should not be used outside the temperature interval of the data they were
based on. Classical nucleation theory, if employed with only one fitted
contact angle, does not reproduce the observed temperature dependence for
immersion nucleation, the temperature and supersaturation dependence for
deposition nucleation, and the time dependence of ice nucleation.
Formulations of classical nucleation theory with distributions of contact
angles offer possibilities to overcome these weaknesses. |
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