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| Titel |
Effects of alternative cloud radiation parameterizations in a general circulation model |
| VerfasserIn |
Wan-Ho Lee, Richard C. J. Somerville |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 1 ; Nr. 14, no. 1, S.107-114 |
| Datensatznummer |
250012141
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| Publikation (Nr.) |
 copernicus.org/angeo-14-107-1996.pdf |
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| Zusammenfassung |
| Using the National Center for Atmospheric
Research (NCAR) general circulation model (CCM2), a suite of alternative cloud
radiation parameterizations has been tested. Our methodology relies on perpetual
July integrations driven by ±2 K sea surface temperature forcing. The tested
parameterizations include relative humidity based clouds and versions of schemes
involving a prognostic cloud water budget. We are especially interested in
testing the effect of cloud optical thickness feedbacks on global climate
sensitivity. All schemes exhibit negative cloud radiation feedbacks, i.e., cloud
moderates the global warming. However, these negative net cloud radiation
feedbacks consist of quite different shortwave and longwave components between a
scheme with interactive cloud radiative properties and several schemes with
specified cloud water paths. An increase in cloud water content in the warmer
climate leads to optically thicker middle- and low-level clouds and in turn
negative shortwave feedbacks for the interactive radiative scheme, while a
decrease in cloud amount leads to a positive shortwave feedback for the other
schemes. For the longwave feedbacks, a decrease in high effective cloudiness for
the schemes without interactive radiative properties leads to a negative
feedback, while no distinct changes in effective high cloudiness and the
resulting feedback are exhibited for the scheme with interactive radiative
properties. The resulting magnitude of negative net cloud radiation feed-back is
largest for the scheme with interactive radiative properties. Even though the
simulated values of cloud radiative forcing for the present climate using this
method differ most from the observational data, the approach shows great promise
for the future. |
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