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| Titel |
The thermodynamic structure of summer Arctic stratocumulus and the dynamic coupling to the surface |
| VerfasserIn |
G. Sotiropoulou, J. Sedlar, M. Tjernström, M. D. Shupe, I. M. Brooks, P. O. G. Persson |
| 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 ; 14, no. 22 ; Nr. 14, no. 22 (2014-11-28), S.12573-12592 |
| Datensatznummer |
250119197
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| Publikation (Nr.) |
 copernicus.org/acp-14-12573-2014.pdf |
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| Zusammenfassung |
| The vertical structure of Arctic low-level clouds and Arctic boundary layer
is studied, using observations from ASCOS (Arctic Summer Cloud Ocean Study),
in the central Arctic, in late summer 2008. Two general types of cloud
structures are examined: the "neutrally stratified" and
"stably stratified" clouds. Neutrally stratified are mixed-phase clouds
where radiative-cooling near cloud top produces turbulence that generates a
cloud-driven mixed layer. When this layer mixes with the surface-generated
turbulence, the cloud layer is coupled to the surface, whereas when such an
interaction does not occur, it remains decoupled; the latter state is most
frequently observed. The decoupled clouds are usually higher compared to the
coupled; differences in thickness or cloud water properties between the two
cases are however not found. The surface fluxes are also very similar for
both states. The decoupled clouds exhibit a bimodal thermodynamic structure,
depending on the depth of the sub-cloud mixed layer (SCML): clouds with
shallower SCMLs are disconnected from the surface by weak inversions,
whereas those that lay over a deeper SCML are associated with stronger
inversions at the decoupling height. Neutrally stratified clouds generally
precipitate; the evaporation/sublimation of precipitation often enhances the
decoupling state. Finally, stably stratified clouds are usually lower,
geometrically and optically thinner, non-precipitating liquid-water clouds,
not containing enough liquid to drive efficient mixing through cloud-top
cooling. |
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