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| Titel |
Ice condensation on sulfuric acid tetrahydrate: Implications for polar stratospheric ice clouds |
| VerfasserIn |
T. J. Fortin, K. Drdla, L. T. Iraci, M. A. Tolbert |
| 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 ; 3, no. 4 ; Nr. 3, no. 4 (2003-07-09), S.987-997 |
| Datensatznummer |
250001133
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| Publikation (Nr.) |
 copernicus.org/acp-3-987-2003.pdf |
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| Zusammenfassung |
| The mechanism of ice nucleation to form
Type 2 PSCs is important for controlling the ice particle size and hence the possible dehydration in the polar winter
stratosphere. This paper probes heterogeneous ice nucleation on sulfuric acid
tetrahydrate (SAT). Laboratory experiments were performed using a thin-film, high-vacuum
apparatus in which the condensed phase is monitored via Fourier transform infrared spectroscopy and water pressure is monitored with the combination of an MKS
baratron and an ionization gauge. Results show that SAT is an efficient ice nucleus with
a critical ice saturation ratio of S*ice = 1.3 to 1.02 over the temperature range
169.8-194.5 K. This corresponds to a necessary supercooling of 0.1-1.3 K below the ice frost point.
The laboratory data is used as input for a microphysical/photochemical model to
probe the effect that this heterogeneous nucleation mechanism could have on
Type 2 PSC formation and stratospheric dehydration. In the model simulations, even a very small
number of SAT particles (e.g., 10-3 cm-3) result in ice nucleation on SAT as the dominant
mechanism for Type 2 PSC formation. As a result, Type 2 PSC formation is more
widespread, leading to larger-scale dehydration. The characteristics of the clouds are
controlled by the assumed number of SAT particles present, demonstrating that a proper
treatment of SAT is critical for correctly modeling Type 2 PSC formation and
stratospheric dehydration. |
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