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| Titel |
Modelling of cirrus clouds – Part 2: Competition of different nucleation mechanisms |
| VerfasserIn |
P. Spichtinger, K. M. Gierens |
| 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 ; 9, no. 7 ; Nr. 9, no. 7 (2009-04-01), S.2319-2334 |
| Datensatznummer |
250007153
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| Publikation (Nr.) |
 copernicus.org/acp-9-2319-2009.pdf |
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| Zusammenfassung |
| We study the competition of two different freezing mechanisms
(homogeneous and heterogeneous freezing) in the same environment for
cold cirrus clouds. To this goal we use the recently developed and
validated ice microphysics scheme (Spichtinger and Gierens, 2009a) which distinguishes between ice classes according
to their formation process. We investigate cases with purely
homogeneous ice formation and compare them with cases where
background ice nuclei in varying concentration heterogeneously form
ice prior to homogeneous nucleation. We perform additionally a
couple of sensitivity studies regarding threshold humidity for
heterogeneous freezing, uplift speed, and ambient temperature, and
we study the influence of random motions induced by temperature
fluctuations in the clouds. We find three types of cloud evolution,
homogeneously dominated, heterogeneously dominated, and a mixed type
where neither nucleation process dominates. The latter case is prone
to long–lasting in–cloud ice supersaturation of the order 30% and
more. |
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