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Using a Multiphysics Ensemble for Exploring Diversity in Cloud-Shortwave Feedback in GCMs.
- Source :
- Journal of Climate; Aug2012, Vol. 25 Issue 15, p5416-5431, 16p, 2 Charts, 9 Graphs, 2 Maps
- Publication Year :
- 2012
-
Abstract
- This study proposes a systematic approach to investigate cloud-radiative feedbacks to climate change induced by an increase of CO<subscript>2</subscript> concentrations in global climate models (GCMs). Based on two versions of the Model for Interdisciplinary Research on Climate (MIROC), which have opposite signs for cloud-shortwave feedback (ΔSW<subscript>cld</subscript>) and hence different equilibrium climate sensitivities (ECSs), hybrid models are constructed by replacing one or more parameterization schemes for cumulus convection, cloud, and turbulence between them. An ensemble of climate change simulations using a suite of eight models, called a multiphysics ensemble (MPE), is generated. The MPE provides a range of ECS as wide as the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel ensemble and reveals a different magnitude and sign of ΔSW<subscript>cld</subscript> over the tropics, which is crucial for determining ECS. It is found that no single process controls ΔSW<subscript>cld</subscript>, but that the coupling of two processes does. Namely, changing the cloud and turbulence schemes greatly alters the mean and the response of low clouds, whereas replacing the convection and cloud schemes affects low and middle clouds over the convective region. For each of the circulation regimes, ΔSW<subscript>cld</subscript> and cloud changes in the MPE have a nonlinear, but systematic, relationship with the mean cloud amount, which can be constrained from satellite estimates. The analysis suggests a positive feedback over the subsidence regime and a near-neutral or weak negative ΔSW<subscript>cld</subscript> over the convective regime in these model configurations, which, however, may not be carried into other models. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 08948755
- Volume :
- 25
- Issue :
- 15
- Database :
- Complementary Index
- Journal :
- Journal of Climate
- Publication Type :
- Academic Journal
- Accession number :
- 78299667
- Full Text :
- https://doi.org/10.1175/JCLI-D-11-00564.1