Thermodynamics of a Global-Mean State of the Atmosphere—A State of Maximum Entropy Increase

Ozawa, Hisashi; Ohmura, Atsumu

doi:10.1175/1520-0442(1997)010<0441:toagms>2.0.co;2

Cited by 86 publications

(128 citation statements)

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“…There is some evidence (Lorenz, 2003;Paltridge, 1975) that horizontal heat transport on the Earth may adjust itself to maximize dissipation (or entropy production), apparently also the case with Titan and Mars (Lorenz et al, 2001). Ozawa and Ohmura (1997) present a 1D radiative-convection model (with shortwave absorption) with the vertical convective flux selected to maximize entropy production-without regard to any critical lapse rate-and find that the observed terrestrial atmosphere seems consistent with this idea. It is of interest that the predicted convective fluxes [54,77,89,96, 101] W m −2 for τ = [1,2,3,4,5] are exactly in agreement with our Eq.…”

Section: Discussionmentioning

confidence: 92%

“…This discrepancy is due in part to the nongreyness of the real atmosphere (any window IR emission to space cannot participate in convection), and in part due to the fact that of the incident shortwave 240 W m −2 that is not reflected to space, some significant fraction is absorbed in the atmosphere. Previous model studies (e.g., Ozawa and Ohmura, 1997;Pujol and Fort, 2002) assume the shortwave opacity is related linearly with the infrared optical depth, and that only ∼ 140 W m −2 is absorbed at the surface. As well as reducing the flux available at the surface, this absorption warms the atmosphere and thus lowers the temperature gradient driving convection.…”

Section: Analytic Expressionsmentioning

confidence: 99%

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A simple expression for vertical convective fluxes in planetary atmospheres

Lorenz

McKay

2003

Icarus

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We explore the vertical convective flux F c in a radiative-convective grey atmosphere. An expression of the form F c = F s τ o /(C + Dτ o ) appears useful, where F s is the shortwave flux absorbed at the base of an atmosphere with longwave optical depth τ o and C and D are constants. We find excellent agreement with an idealized grey radiative-convective model with no shortwave absorption for D = 1 and C = 1 ∼ 2 depending on the surface-atmosphere temperature contrast and on the imposed critical lapse rate. Where shortwave absorption is correlated with longwave opacity, as in the atmospheres of Earth and Titan, C = 2, D = 2 provides an excellent fit, validated against the present terrestrial situation and the results of a nongrey model of Titan's strongly antigreenhouse atmosphere under a wide range of conditions. The expression may be useful for studying the energetics of planetary climates through time where there is insufficient data to constrain more elaborate models.

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Section: Discussionmentioning

confidence: 92%

Section: Analytic Expressionsmentioning

confidence: 99%

A simple expression for vertical convective fluxes in planetary atmospheres

Lorenz

McKay

2003

Icarus

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“…The value obtained by MEP closely matched the empirical value used in the model. While Paltridge (1975) originally hypothesized maximum convective heat flux in the vertical, several authors have demonstrated that MEP is applicable to convection in the vertical as well (Ozawa and Ohmura 1997;Pujol and Fort 2002;Pujol 2003;Lorenz and Mckay 2003;Kleidon 2004a).…”

Section: Demonstration Of Mep States: Examplesmentioning

confidence: 99%

Nonequilibrium thermodynamics and maximum entropy production in the Earth system

Kleidon

2009

Naturwissenschaften

149

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The Earth system is maintained in a unique state far from thermodynamic equilibrium, as, for instance, reflected in the high concentration of reactive oxygen in the atmosphere. The myriad of processes that transform energy, that result in the motion of mass in the atmosphere, in oceans, and on land, processes that drive the global water, carbon, and other biogeochemical cycles, all have in common that they are irreversible in their nature. Entropy production is a general consequence of these processes and measures their degree of irreversibility. The proposed principle of maximum entropy production (MEP) states that systems are driven to steady states in which they produce entropy at the maximum possible rate given the prevailing constraints. In this review, the basics of nonequilibrium thermodynamics are described, as well as how these apply to Earth system processes. Applications of the MEP principle are discussed, ranging from the strength of the atmospheric circulation, the hydrological cycle, and biogeochemical cycles to the role that life plays in these processes. Nonequilibrium thermodynamics and the MEP principle have potentially wide-ranging implications for our understanding of Earth system functioning, how it has evolved in the past, and why it is habitable. Entropy production allows us to quantify an objective direction of Earth system change (closer to vs further away from thermodynamic equilibrium, or, equivalently, towards a state of MEP). When a maximum in entropy production is reached, MEP implies A. Kleidon (B) Max-Planck-Institut für Biogeochemie, Postfach 10 01 64, 07701 Jena, Germany e-mail: akleidon@bgc-jena.mpg.de that the Earth system reacts to perturbations primarily with negative feedbacks. In conclusion, this nonequilibrium thermodynamic view of the Earth system shows great promise to establish a holistic description of the Earth as one system. This perspective is likely to allow us to better understand and predict its function as one entity, how it has evolved in the past, and how it is modified by human activities in the future.

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“…This places the maximization of GPP on a fundamental principle, one that applies not only to biological processes, but also to purely physical processes such as atmospheric turbulence (e.g. Paltridge, 1975;Paltridge, 1978;Ozawa & Ohmura, 1997;Lorenz et al, 2001;Kleidon et al, 2003;Kleidon et al, 2006). However, further evaluations and comparison to observations would be necessary to confirm that present-day climatic conditions are indeed optimal to the terrestrial biosphere.…”

Section: S238mentioning

confidence: 99%

Quantifying the biologically possible range of steady-state soil and surface climates with climate model simulations

Kleidon

2006

Biologia

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Abstract:The terrestrial biosphere shapes the exchange fluxes of energy and mass at the land surface. The diversity of plant form and functioning can potentially result in a wide variety of possible climatic conditions at the land surface and in the soil, which in turn feed back to more or less suitable conditions for terrestrial productivity. Here, I use sensitivity simulations to vegetation form and functioning with a global climate model to quantify this possible range of steady-states ("PROSS") of the surface energy-and mass balances. The surface energy-and water balances over land are associated with substantial sensitivity to vegetation parameters, with precipitation varying by more than a factor of 2, and evapotranspiration by a factor of 5. This range in biologically possible climatic conditions is associated with drastically different levels of vegetation productivity. Optimum conditions for maximum productivity are close to the simulated climate of present-day conditions. These results suggest the conclusions that (a) climate does not determine vegetation form and function, but merely constrains it, and (b) the emergent climatic conditions at the land surface seem to be close to optimal for the functioning of the terrestrial biosphere.

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Thermodynamics of a Global-Mean State of the Atmosphere—A State of Maximum Entropy Increase

Cited by 86 publications

References 9 publications

A simple expression for vertical convective fluxes in planetary atmospheres

A simple expression for vertical convective fluxes in planetary atmospheres

Nonequilibrium thermodynamics and maximum entropy production in the Earth system

Quantifying the biologically possible range of steady-state soil and surface climates with climate model simulations

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