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| Titel |
Ice nucleation properties of fine ash particles from the Eyjafjallajökull eruption in April 2010 |
| VerfasserIn |
I. Steinke, O. Möhler, A. Kiselev, M. Niemand, H. Saathoff, M. Schnaiter, J. Skrotzki, C. Hoose, T. Leisner |
| 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. 24 ; Nr. 11, no. 24 (2011-12-20), S.12945-12958 |
| Datensatznummer |
250010288
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| Publikation (Nr.) |
 copernicus.org/acp-11-12945-2011.pdf |
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| Zusammenfassung |
| During the eruption of the Eyjafjallajökull volcano in the south of Iceland
in April/May 2010, about 40 Tg of ash mass were emitted into the atmosphere.
It was unclear whether volcanic ash particles with
d < 10 μm facilitate the glaciation of clouds. Thus, ice
nucleation properties of volcanic ash particles were investigated in AIDA
(Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber
experiments simulating atmospherically relevant conditions. The ash sample
that was used for our experiments had been collected at a distance of 58 km
from the Eyjafjallajökull during the eruption period in April 2010. The
temperature range covered by our ice nucleation experiments extended from 219
to 264 K, and both ice nucleation via immersion freezing and deposition
nucleation could be observed. Immersion freezing was first observed at
252 K, whereas the deposition nucleation onset lay at 242 K and
RHice =126%. About 0.1% of the volcanic ash particles were
active as immersion freezing nuclei at a temperature of 249 K. For
deposition nucleation, an ice fraction of 0.1% was observed at around
233 K and RHice =116%. Taking ice-active surface site
densities as a measure for the ice nucleation efficiency, volcanic ash
particles are similarly efficient ice nuclei in immersion freezing mode
(ns,imm ~ 109 m−2 at 247 K) compared to certain mineral
dusts. For deposition nucleation, the observed ice-active surface site
densities ns,dep were found to be 1011 m−2 at 224 K and
RHice =116%. Thus, volcanic ash particles initiate deposition
nucleation more efficiently than Asian and Saharan dust but appear to be
poorer ice nuclei than ATD particles. Based on the experimental data, we have
derived ice-active surface site densities as a function of temperature for
immersion freezing and of relative humidity over ice and temperature for
deposition nucleation. |
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