A new framework for isolating individual feedback processes in coupled general circulation climate models. Part I: formulation |
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Authors: | Jianhua Lu Ming Cai |
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Institution: | (1) Department of Meteorology, Florida State University, Tallahassee, FL 32306, USA |
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Abstract: | This paper proposes a coupled atmosphere–surface climate feedback–response analysis method (CFRAM) as a new framework for
estimating climate feedbacks in coupled general circulation models with a full set of physical parameterization packages.
The formulation of the CFRAM is based on the energy balance in an atmosphere–surface column. In the CFRAM, the isolation of
partial temperature changes due to an external forcing or an individual feedback is achieved by solving the linearized infrared
radiation transfer model subject to individual energy flux perturbations (external or due to feedbacks). The partial temperature
changes are addable and their sum is equal to the (total) temperature change (in the linear sense). The decomposition of feedbacks
is based on the thermodynamic and dynamical processes that directly affect individual energy flux terms. Therefore, not only
those feedbacks that directly affect the TOA radiative fluxes, such as water vapor, clouds, and ice-albedo feedbacks, but
also those feedbacks that do not directly affect the TOA radiation, such as evaporation, convections, and convergence of horizontal
sensible and latent heat fluxes, are explicitly included in the CFRAM. In the CFRAM, the feedback gain matrices measure the
strength of individual feedbacks. The feedback gain matrices can be estimated from the energy flux perturbations inferred
from individual parameterization packages and dynamical modules. The inter-model spread of a feedback gain matrix would help
us to detect the origins of the uncertainty of future climate projections in climate model simulations. |
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Keywords: | Climate feedback Global warming Climate sensitivity |
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