CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models

CGILS—the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)—investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the "NESTS" negative cloud feedback and the "SCOPE" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence—Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations.

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Author Zhang, Minghua
Bretherton, Christopher
Blossey, Peter
Austin, Phillip
Bacmeister, Julio
Bony, Sandrine
Brient, Florent
Cheedela, Suvarchal
Cheng, Anning
Del Genio, Anthony
De Roode, Stephan
Endo, Satoshi
Franklin, Charmaine
Golaz, Jean-Christophe
Hannay, Cecile
Heus, Thijs
Isotta, Francesco
Dufresne, Jean-Louis
Kang, In-Sik
Kawai, Hideaki
Köhler, Martin
Larson, Vincent
Liu, Yangang
Lock, Adrian
Lohmann, Ulrike
Khairoutdinov, Marat
Molod, Andrea
Neggers, Roel
Rasch, Philip
Sandu, Irina
Senkbeil, Ryan
Siebesma, A.
Siegenthaler-Le Drian, Colombe
Stevens, Bjorn
Suarez, Max
Xu, Kuan-Man
von Salzen, Knut
Webb, Mark
Wolf, Audrey
Zhao, Ming
Publisher UCAR/NCAR - Library
Publication Date 2013-12-01T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Topic Category geoscientificInformation
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Metadata Date 2023-08-18T18:48:15.307026
Metadata Record Identifier edu.ucar.opensky::articles:13240
Metadata Language eng; USA
Suggested Citation Zhang, Minghua, Bretherton, Christopher, Blossey, Peter, Austin, Phillip, Bacmeister, Julio, Bony, Sandrine, Brient, Florent, Cheedela, Suvarchal, Cheng, Anning, Del Genio, Anthony, De Roode, Stephan, Endo, Satoshi, Franklin, Charmaine, Golaz, Jean-Christophe, Hannay, Cecile, Heus, Thijs, Isotta, Francesco, Dufresne, Jean-Louis, Kang, In-Sik, Kawai, Hideaki, Köhler, Martin, Larson, Vincent, Liu, Yangang, Lock, Adrian, Lohmann, Ulrike, Khairoutdinov, Marat, Molod, Andrea, Neggers, Roel, Rasch, Philip, Sandu, Irina, Senkbeil, Ryan, Siebesma, A., Siegenthaler-Le Drian, Colombe, Stevens, Bjorn, Suarez, Max, Xu, Kuan-Man, von Salzen, Knut, Webb, Mark, Wolf, Audrey, Zhao, Ming. (2013). CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models. UCAR/NCAR - Library. http://n2t.net/ark:/85065/d70z746s. Accessed 21 April 2025.

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