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| Titel |
Supersaturation, dehydration, and denitrification in Arctic cirrus |
| VerfasserIn |
B. Kärcher |
| 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 ; 5, no. 7 ; Nr. 5, no. 7 (2005-07-20), S.1757-1772 |
| Datensatznummer |
250002979
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| Publikation (Nr.) |
 copernicus.org/acp-5-1757-2005.pdf |
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| Zusammenfassung |
| A polar cirrus case study is discussed with the help of a one-dimensional model with
explicit aerosol and ice microphysics. It is demonstrated that continuous cooling of
air in regions with small amounts of ice and slow ice deposition rates of water vapor
drives significant in-cloud supersaturations over ice, with potentially important
consequences for heterogeneous halogen activation. Radiatively important cloud properties
such as ice crystal size distributions are investigated, showing the presence of high
number concentrations of small crystals in the cloud top region at the tropopause, broad
but highly variable size spectra in the cloud interior, and mostly large crystals at the
cloud base. It is found that weakly forced Arctic cirrostratus are highly efficient at
dehydrating upper tropospheric air. Estimating nitric acid uptake in cirrus with an
unprecedented treatment of diffusion-limited trapping in growing ice crystals suggests
that such clouds could also denitrify upper tropospheric air masses efficiently, but a
closer comparison to suitable observations is needed to draw a definite conclusion on
this point. It is also shown that low temperatures, high ice supersaturations, and the
absence of ice above but close to the cloud top region cause efficient uptake of nitric
acid in background aerosol particles. |
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