Open AccessEffects of alternative cloud radiation parameterizations in a general circulation model
Author(s) -
Wan-Ho Lee,
Richard C. J. Somerville
Publication year - 1996
Publication title -
annales geophysicae
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.522
H-Index - 93
eISSN - 1432-0576
pISSN - 0992-7689
DOI - 10.1007/s00585-996-0107-6
Subject(s) - cloud forcing , shortwave , cloud feedback , longwave , environmental science , shortwave radiation , cloud albedo , cloud cover , climate model , cloud computing , radiative transfer , liquid water content , radiative forcing , atmospheric sciences , climate sensitivity , cloud height , parametrization (atmospheric modeling) , meteorology , climatology , climate change , radiation , computer science , physics , geology , oceanography , aerosol , quantum mechanics , operating system
Using the National Center for Atmospheric\udResearch (NCAR) general circulation model (CCM2), a suite of alternative cloud\udradiation parameterizations has been tested. Our methodology relies on perpetual\udJuly integrations driven by ±2 K sea surface temperature forcing. The tested\udparameterizations include relative humidity based clouds and versions of schemes\udinvolving a prognostic cloud water budget. We are especially interested in\udtesting the effect of cloud optical thickness feedbacks on global climate\udsensitivity. All schemes exhibit negative cloud radiation feedbacks, i.e., cloud\udmoderates the global warming. However, these negative net cloud radiation\udfeedbacks consist of quite different shortwave and longwave components between a\udscheme with interactive cloud radiative properties and several schemes with\udspecified cloud water paths. An increase in cloud water content in the warmer\udclimate leads to optically thicker middle- and low-level clouds and in turn\udnegative shortwave feedbacks for the interactive radiative scheme, while a\uddecrease in cloud amount leads to a positive shortwave feedback for the other\udschemes. For the longwave feedbacks, a decrease in high effective cloudiness for\udthe schemes without interactive radiative properties leads to a negative\udfeedback, while no distinct changes in effective high cloudiness and the\udresulting feedback are exhibited for the scheme with interactive radiative\udproperties. The resulting magnitude of negative net cloud radiation feed-back is\udlargest for the scheme with interactive radiative properties. Even though the\udsimulated values of cloud radiative forcing for the present climate using this\udmethod differ most from the observational data, the approach shows great promise\udfor the future