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| Titel |
Radiative impacts of cloud heterogeneity and overlap in an atmospheric General Circulation Model |
| VerfasserIn |
L. Oreopoulos, D. Lee, Y. C. Sud, M. J. Suarez |
| 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 ; 12, no. 19 ; Nr. 12, no. 19 (2012-10-04), S.9097-9111 |
| Datensatznummer |
250011496
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| Publikation (Nr.) |
 copernicus.org/acp-12-9097-2012.pdf |
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| Zusammenfassung |
| The radiative impacts of horizontal heterogeneity of layer cloud condensate,
and vertical overlap of both condensate and cloud fraction are examined with
the aid of a new radiation package operating in the GEOS-5 Atmospheric
General Circulation Model. The impacts are examined in terms of diagnostic
top-of-the atmosphere shortwave (SW) and longwave (LW) cloud radiative
effect (CRE) calculations for a range of assumptions and overlap parameter
specifications. The investigation is conducted for two distinct cloud
schemes, one that comes with the standard GEOS-5 distribution, and another
used experimentally for its enhanced cloud microphysical capabilities. Both
schemes are coupled to a cloud generator allowing arbitrary cloud overlap
specification. Results show that cloud overlap radiative impacts are
significantly stronger in the operational cloud scheme where a change of
cloud fraction overlap from maximum-random to generalized results in global
changes of SW and LW CRE of ~4 Wm−2, and zonal changes of up to
~10 Wm−2. This is an outcome of fewer occurrences (compared to
the other scheme) of large layer cloud fractions and fewer multi-layer
situations where large numbers of atmospheric layers are simultaneously
cloudy, both conditions that make overlap details more important. The impact
of the specifics of condensate distribution overlap on CRE is much weaker.
Once generalized overlap is adopted, both cloud schemes are only modestly
sensitive to the exact values of the overlap parameters. When one of the CRE
components is overestimated and the other underestimated, both cannot be
driven simoultaneously towards observed values by adjustments to cloud
condensate heterogeneity and overlap specifications alone. |
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