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| Titel |
In-situ observations and modeling of small nitric acid-containing ice crystals |
| VerfasserIn |
C. Voigt, B. Kärcher, H. Schlager, C. Schiller, M. Krämer, M. Reus, H. Vössing, S. Borrmann, V. Mitev |
| 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 ; 7, no. 12 ; Nr. 7, no. 12 (2007-06-27), S.3373-3383 |
| Datensatznummer |
250005098
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| Publikation (Nr.) |
 copernicus.org/acp-7-3373-2007.pdf |
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| Zusammenfassung |
| Measurements in nascent ice forming regions are very rare and help
understand cirrus cloud formation and the interactions of trace
gases with ice crystals. A tenuous cirrus cloud has been probed with
in-situ and remote sensing instruments onboard the high altitude
research aircraft Geophysica M55 in the tropical upper troposphere.
Besides microphysical and optical particle properties, water
(H2O) and reactive nitrogen species (NOy) have been
measured. In slightly ice supersaturated air between 14.2 and
14.9 km altitude, an unusually low ice water content of
0.031 mg m−3 and small ice crystals with mean radii of
5 µm have been detected. A high nitric acid to water
molar ratio (HNO3/H2O) of 5.4×10−5 has been
observed in the ice crystals, about an order of magnitude higher
compared to previous observations in cirrus at temperatures near
202 K. A model describing the trapping of HNO3 in growing
ice particles shows that a high HNO3 content in ice crystals
is expected during early growth stages, mainly originating from
uptake in aerosol particles prior to freezing. Water vapor
deposition on ice crystals and trapping of additional HNO3
reduces the molar ratio to values close to the ratio of
HNO3/H2O in the gas phase while the cloud ages. |
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