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

Minghua Zhang (1) , Peter N. Blossey (2) , Marat F. Khairoutdinov (1) , Phillip H. Austin (3) , Julio T. Bacmeister (4) , Sandrine Bony (5) , Florent Brient (5) , Suvarchal K. Cheedela (6) , Anthony D. del Genio (7) , Stephan R. de Roode (8) , Satoshi Endo (9) , Jean-Christophe Golaz (10) , Bjorn Stevens (6) , Francesco Alessandro Isotta (11) , Charmaine N. Franklin (12) , Anning Cheng (13) , In-Sik Kang (14) , Hideaki Kawai (15) , Yangang Liu (9) , Kuan-Man Xu (13) , Martin Koehler (16) , Adrian P. Lock (17) , Andrea M. Molod (18) , Cecile Hannay (4) , Ming Zhao (10) , Ulrike Lohmann (11) , Roel A. J. Neggers (19) , Philip Rasch (20) , Irina Sandu (6) , Colombe Siegenthaler-Le Drian (11) , Ryan Senkbeil (21) , Thijs Heus (6) , Christopher S. Bretherton (2) , Max J. Suarez (18) , Audrey Wolf (7) , A. Pier Siebesma (19) , Knut von Salzen (22) , Mark J. Webb (17) , Vincent E. Larson (21) , Jean-Louis Dufresne (5)

1 ITPA - Institute for Terrestrial and Planetary Atmospheres [Stony Brook]
2 Department of Atmospheric Sciences [Seattle]
3 University of British Columbia [Vancouver]
4 ESRL - NOAA Earth System Research Laboratory
5 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
6 MPI-M - Max-Planck-Institut für Meteorologie
7 GISS - NASA Goddard Institute for Space Studies
8 Department of Geoscience and Remote Sensing [Delft]
9 Brookhaven Natl Lab, Dept Environm Sci, Upton, NY 11973 USA
10 GFDL - NOAA Geophysical Fluid Dynamics Laboratory
11 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
12 CSIRO, Ctr Australian Weather & Climate Res, Aspendale, Vic, Australia
13 LaRC - NASA Langley Research Center [Hampton]
14 Seoul Natl Univ, Sch Earth & Environm Sci, Seoul, South Korea
15 Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan
16 ECMWF - European Centre for Medium-Range Weather Forecasts
17 MOHC - Met Office Hadley Centre
18 GMAO - Global Modeling and Assimilation Office
19 KNMI - Royal Netherlands Meteorological Institute
20 Pacific NW Natl Lab, Richland, WA 99352 USA
21 Univ Wisconsin, Dept Math Sci, Milwaukee, WI 53201 USA
22 Canadian Ctr Climate Modelling & Anal, Victoria, BC, Canada

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.

Domaines: Océan, Atmosphère

Minghua Zhang, Peter N. Blossey, Marat F. Khairoutdinov, Phillip H. Austin, Julio T. Bacmeister, et al.. CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models. Journal of Advances in Modeling Earth Systems, 2013, 5 (4), pp.826-842. ⟨10.1002/2013ms000246⟩. ⟨hal-01091226⟩