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| Titel |
Ice nucleation properties of volcanic ash from Eyjafjallajökull |
| VerfasserIn |
C. R. Hoyle, V. Pinti, A. Welti, B. Zobrist, C. Marcolli, B. Luo, A. Höskuldsson, H. B. Mattsson, O. Stetzer, T. Thorsteinsson, G. Larsen, T. Peter |
| 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 ; 11, no. 18 ; Nr. 11, no. 18 (2011-09-27), S.9911-9926 |
| Datensatznummer |
250010103
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| Publikation (Nr.) |
 copernicus.org/acp-11-9911-2011.pdf |
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| Zusammenfassung |
| The ice nucleation ability of volcanic ash particles collected close
to the Icelandic volcano Eyjafjallajökull during its eruptions in
April and May 2010 is investigated experimentally, in the immersion
and deposition modes, and applied to atmospheric conditions by
comparison with airborne measurements and microphysical model
calculations. The number of ash particles which are active as ice
nuclei (IN) is strongly temperature dependent, with a very small
minority being active in the immersion mode at temperatures of
250–263 K. Average ash particles show only a moderate effect on ice
nucleation, by inducing freezing at temperatures between 236 K and
240 K (i.e. approximately 3–4 K higher than temperatures required
for homogeneous ice nucleation, measured with the same instrument). By
scaling the results to aircraft and lidar measurements of the
conditions in the ash plume days down wind of the eruption, and by
applying a simple microphysical model, it was found that the IN active
in the immersion mode in the range 250–263 K generally occurred
in atmospheric number densities at the lower end of those required to
have an impact on ice cloud formation. However, 3–4 K above the
homogeneous freezing point, immersion mode IN number densities a few
days down wind of the eruption were sufficiently high to have
a moderate influence on ice cloud formation. The efficiency of IN in
the deposition mode was found to be poor except at very cold
conditions (<238 K), when they reach an efficiency similar
to that of mineral dust with the onset of freezing at 10 %
supersaturation with respect to ice, and with the frozen fraction
nearing its maximum value at a supersaturation 20 %. In
summary, these investigations suggest volcanic ash particles to have
only moderate effects on atmospheric ice formation. |
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