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| Titel |
Dynamical states of low temperature cirrus |
| VerfasserIn |
D. Barahona, A. Nenes |
| 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. 8 ; Nr. 11, no. 8 (2011-04-26), S.3757-3771 |
| Datensatznummer |
250009647
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| Publikation (Nr.) |
 copernicus.org/acp-11-3757-2011.pdf |
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| Zusammenfassung |
| Low ice crystal concentration and sustained in-cloud supersaturation,
commonly found in cloud observations at low temperature, challenge our
understanding of cirrus formation. Heterogeneous freezing from effloresced
ammonium sulfate, glassy aerosol, dust and black carbon are proposed to
cause these phenomena; this requires low updrafts for cirrus characteristics
to agree with observations and is at odds with the gravity wave spectrum in
the upper troposphere. Background temperature fluctuations however can establish a "dynamical equilibrium" between ice production and
sedimentation loss (as opposed to ice crystal formation during the first
stages of cloud evolution and subsequent slow cloud decay) that explains low
temperature cirrus properties. This newly-discovered state is favored at low
temperatures and does not require heterogeneous nucleation to occur (the
presence of ice nuclei can however facilitate its onset). Our understanding
of cirrus clouds and their role in anthropogenic climate change is reshaped,
as the type of dynamical forcing will set these clouds in one of two
"preferred" microphysical regimes with very different susceptibility to
aerosol. |
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