The climate time scale in the approach to radiative-convective equilibrium
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Emanuel_The climate time.pdf
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Author(s)
Emanuel, Kerry Andrew
Cronin, Timothy Wallace
Date Issued
October 2013
Journal
Journal of Advances in Modeling Earth Systems
Publisher
American Geophysical Union (AGU)
Citation
Cronin, Timothy W., and Kerry A. Emanuel. “The Climate Time Scale in the Approach to Radiative-Convective Equilibrium.” Journal of Advances in Modeling Earth Systems 5, no. 4 (October 29, 2013): 843–849. © 2013 American Geophysical Union
Version
Final published version
Abstract
In this paper, we discuss the importance of the surface boundary condition (fixed versus interactive surface temperature) for the long time scale of approach to Radiative-Convective Equilibrium (RCE). Using a simple linearized two-variable model for surface-atmosphere interaction, we derive an analytic expression for τ[subscript C], a long climate relaxation time scale that remains well defined and much longer than either mixing time scale of Tompkins and Craig (1998b), even in the limit that the heat capacity of the surface vanishes. We show that the size of τ[subscript C] is an intrinsic property of the coupling between the atmosphere and surface, and not a result of the thermal inertia of the surface alone. When the surface heat capacity is low, τ[subscript C] can be several times longer than expected, due to the effects of moisture on the effective heat capacity of the atmosphere. We also show that the theoretical expression for τ[subscript C] is a good predictor of best fit exponential relaxation time scales in a single-column model with full physics, across a range of surface temperatures and surface heat capacities.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Program in Atmospheres, Oceans, and Climate
Woods Hole Oceanographic Institution
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1002/jame.20049
