DOI: 10.1007/s00382-016-3301-6
Scopus记录号: 2-s2.0-84982957461
论文题名: Which way will the circulation shift in a changing climate? Possible nonlinearity of extratropical cloud feedbacks
作者: Tandon N.F. ; Cane M.A.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2017
卷: 48, 期: 2017-11-12 起始页码: 3759
结束页码: 3777
语种: 英语
英文关键词: Atmospheric circulation
; Climate change
; Cloud feedback
; Cloud microphysics
英文摘要: In a suite of idealized experiments with the Community Atmospheric Model version 3 coupled to a slab ocean, we show that the atmospheric circulation response to CO2 increase is sensitive to extratropical cloud feedback that is potentially nonlinear. Doubling CO2 produces a poleward shift of the Southern Hemisphere (SH) midlatitude jet that is driven primarily by cloud shortwave feedback and modulated by ice albedo feedback, in agreement with earlier studies. More surprisingly, for CO2 increases smaller than ~25 %, the SH jet shifts equatorward. Nonlinearities are also apparent in the Northern Hemisphere, but with less zonal symmetry. Baroclinic instability theory and climate feedback analysis suggest that as the CO2 forcing amplitude is reduced, there is a transition from a regime in which cloud and circulation changes are largely decoupled to a regime in which they are highly coupled. In the dynamically coupled regime, there is an apparent cancellation between cloud feedback due to warming and cloud feedback due to the shifting jet, and this allows the ice albedo feedback to dominate in the high latitudes. The extent to which dynamical coupling effects exceed thermodynamic forcing effects is strongly influenced by cloud microphysics: an alternate model configuration with slightly increased cloud liquid (LIQ) produces poleward jet shifts regardless of the amplitude of CO2 forcing. Altering the cloud microphysics also produces substantial spread in the circulation response to CO2 doubling: the LIQ configuration produces a poleward SH jet shift approximately twice that produced under the default configuration. Analysis of large ensembles of the Canadian Earth System Model version 2 demonstrates that nonlinear, cloud-coupled jet shifts are also possible in comprehensive models. We still expect a poleward trend in SH jet latitude for timescales on which CO2 increases by more than ~25 %. But on shorter timescales, our results give good reason to expect significant equatorward deviations. We also discuss the implications for understanding the circulation response to small external forcings from other sources, such as the solar cycle. © 2016, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/53205
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Physics, University of Toronto, 60 St. George St., Toronto, ON, Canada; Department of Earth and Environmental Sciences, Lamont–Doherty Earth Observatory, Columbia University, New York, NY, United States
Recommended Citation:
Tandon N.F.,Cane M.A.. Which way will the circulation shift in a changing climate? Possible nonlinearity of extratropical cloud feedbacks[J]. Climate Dynamics,2017-01-01,48(2017-11-12)