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| Titel |
A laboratory investigation into the aggregation efficiency of small ice crystals |
| VerfasserIn |
P. J. Connolly, C. Emersic, P. R. Field |
| 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. 4 ; Nr. 12, no. 4 (2012-02-21), S.2055-2076 |
| Datensatznummer |
250010740
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| Publikation (Nr.) |
 copernicus.org/acp-12-2055-2012.pdf |
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| Zusammenfassung |
| The aggregation of ice crystals and its temperature dependence is studied in
the laboratory using a large ice cloud chamber. This process is important to
the evolution of ice clouds in earth's atmosphere, yet there have been
relatively few laboratory studies quantifying this parameter and its
dependence on temperature. A detailed microphysical model is used to
interpret the results from the experiments and derive best estimates for the
aggregation efficiency as well as error bars. Our best estimates
for the aggregation efficiency, at temperatures other than
−15 °C, (in the interval −30≤T≤5 °C) are
mostly in agreement with previous findings, which were derived using a very
different approach to that described here. While the errors associated with
such experiments are reasonably large, statistically, at temperatures other
than −15, we are able to rule out aggregation efficiencies larger than
0.5 at the 75th percentile and rule out non-zero values at
−15 °C, whereas at −15 °C we can rule out values
higher than 0.85 and values lower than 0.35. The values of the aggregation
efficiency shown here may be used in model studies of aggregation, but care
must be taken that they only apply for the initial stages of aggregate
growth, with humidities at or close to water saturation, and for particles up
to a maximum size of ~500 μm. They may therefore find useful
application for modelling supercooled mid-level layer clouds that contain ice
crystals, which are known to be important radiatively. |
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