Simulating Titan’s tropospheric circulation with the Portable University Model of the Atmosphere

Grieger, B.; Segschneider, Joachim; Keller, H. U.; Rodin, A. V.; Lunkeit, Frank; Kirk, Edilbert; Fraedrich, Klaus

doi:10.1016/j.asr.2003.08.079

Cited by 13 publications

(11 citation statements)

References 15 publications

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“…Therefore, what reviewed here as well as the ongoing studies on the entropy production and efficiency of the Earth system may be of help for studying the thermodynamics of the atmosphere of celestial bodies. Thus, it is encouraging to observe that various models belonging to the PLASIM family have already been adapted to study the atmospheres of Titan [15] and Mars [52], and that intercomparison projects on the modeling of the Venusian atmosphere (see http://www.issbern.ch/workshops/venusclimate/) and Martian atmosphere (see http://www.atm.ox.ac.uk/user/ newmanc/workshop/intercomp.html) are ongoing. Figure 12: Difference in the value and position of the peak of the ocean poleward meridional enthalpy transport between the SRESA1B and the preindustrial simulations for the northern hemisphere (first panel) and for the southern hemisphere (second panel).…”

Section: Discussionmentioning

confidence: 99%

Energetics of Climate Models: Net Energy Balance and Meridional Enthalpy Transport

Lucarini¹,

Ragone²

2011

Reviews of Geophysics

118

152

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[1] We analyze the publicly released outputs of the simulations performed by climate models (CMs) in preindustrial (PI) and Special Report on Emissions Scenarios A1B (SRE-SA1B) conditions. In the PI simulations, most CMs feature biases of the order of 1 W m −2 for the net global and the net atmospheric, oceanic, and land energy balances. This does not result from transient effects but depends on the imperfect closure of the energy cycle in the fluid components and on inconsistencies over land. Thus, the planetary emission temperature is underestimated, which may explain the CMs' cold bias. In the PI scenario, CMs agree on the meridional atmospheric enthalpy transport's peak location (around 40°N/S), while discrepancies of ∼20% exist on the intensity. Disagreements on the oceanic transport peaks' location and intensity amount to ∼10°and ∼50%, respectively. In the SRESA1B runs, the atmospheric transport's peak shifts poleward, and its intensity increases up to ∼10% in both hemispheres. In most CMs, the Northern Hemispheric oceanic transport decreases, and the peaks shift equatorward in both hemispheres. The Bjerknes compensation mechanism is active both on climatological and interannual time scales. The total meridional transport peaks around 35°in both hemispheres and scenarios, whereas disagreements on the intensity reach ∼20%. With increased CO 2 concentration, the total transport increases up to ∼10%, thus contributing to polar amplification of global warming. Advances are needed for achieving a self-consistent representation of climate as a nonequilibrium thermodynamical system. This is crucial for improving the CMs' skill in representing past and future climate changes.Citation: Lucarini, V., and F. Ragone (2011), Energetics of climate models: Net energy balance and meridional enthalpy transport, Rev. Geophys., 49, RG1001,

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Section: Discussionmentioning

confidence: 99%

Energetics of Climate Models: Net Energy Balance and Meridional Enthalpy Transport

Lucarini¹,

Ragone²

2011

Reviews of Geophysics

118

152

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“…Nonetheless, this requires re-examining in more quantitative terms the scale analysis discussed in this paper and assess its limitations, Second, a detailed examination of the Lorenz energy cycle and entropy production of other celestial objects of the solar system seems of great relevance for its own sake and for understanding the relevance of the thermodynamical bounds proposed here. It is encouraging to note that various models 39 belonging to the PLASIM family (Fraedrich et al 2005) have already been adapted to study the atmospheres of Titan (Grieger et al 2004) and Mars (Stenzel at al. 2007), thus allowing for an integration of satellite and model data.…”

Section: Discussionmentioning

confidence: 99%

New Results on the Thermodynamic Properties of the Climate System

Lucarini

Fraedrich

Ragone

2011

Journal of the Atmospheric Sciences

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In this paper the authors exploit two equivalent formulations of the average rate of material entropy production in the climate system to propose an approximate splitting between contributions due to vertical and eminently horizontal processes. This approach is based only on 2 D radiative fields at the surface and at the top of atmosphere. Using 2D fields at the top of atmosphere alone, lower bounds to the rate of material entropy production and to the intensity of the Lorenz energy cycle are derived. By introducing a measure of the efficiency of the planetary system with respect to horizontal thermodynamic processes, it is possible to gain insight into a previous intuition on the possibility of defining a baroclinic heat engine extracting work from the meridional heat flux. The approximate formula of the material entropy production is verified and used for studying the global thermodynamic properties of climate models (CMs) included in the Program for Climate Model Diagnosis and Intercomparison (PCMDI)/phase 3 of the Coupled Model Intercomparison Project (CMIP3) dataset in preindustrial climate conditions. It is found that about 90% of the material entropy production is due to vertical processes such as convection, whereas the large-scale meridional heat transport contributes to only about 10% of the total. This suggests that the traditional two-box models used for providing a minimal representation of entropy production in planetary systems are not appropriate, whereas a basic but conceptually correct description can be framed in terms of a four-box model. The total material entropy production is typically 55 mW m(-2) K(-1), with discrepancies on the order of 5%, and CMs' baroclinic efficiencies are clustered around 0.055. The lower bounds on the intensity of the Lorenz energy cycle featured by CMs are found to be around 1.0-1.5 W m(-2), which implies that the derived inequality is rather stringent. When looking at the variability and covariability of the considered thermodynamic quantities, the agreement among CMs is worse, suggesting that the description of feedbacks is more uncertain. The contributions to material entropy production from vertical and horizontal processes are positively correlated, so that no compensation mechanism seems in place. Quite consistently among CMs, the variability of the efficiency of the system is a better proxy for variability of the entropy production due to horizontal processes than that of the large-scale heat flux. The possibility of providing constraints on the 3D dynamics of the fluid envelope based only on 2D observations of radiative fluxes seems promising for the observational study of planets and for testing numerical models

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“…The meridional circulation of Titan is largely unknown from observations although the seasonal change in Titan's brightness is evidence of meridional transport of aerosols and reversal of the meridional flow around the equinox [ Lorenz et al , 2004]. Virtually all Titan GCMs predict the presence of a thermally direct either pole‐to‐pole or equator‐to‐pole Hadley cell extending from the surface with upwelling at low southern latitudes in the season of Huygens entry [ Hourdin et al , 1995; Tokano et al , 1999, 2001; Rannou et al , 2002, 2006; Hourdin et al , 2004; Grieger et al , 2004]. Therefore, the measured upward flow in the troposphere is likely to be part of the tropospheric thermally direct cell.…”

Section: Discussionmentioning

confidence: 99%

Vertical atmospheric flow on Titan as measured by the HASI instrument on board the Huygens probe

Mäkinen

Harri

Tokano

et al. 2006

Geophysical Research Letters

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On January 14, 2005, the Huygens probe descended on the surface of Titan, the largest moon of Saturn and the only moon in the Solar system with a substantial atmosphere. After the deployment of the main parachute and the release of the heat shield at an altitude of about 150 km, the local pressure and temperature were measured by HASI (Huygens Atmospheric Structure Instrument) all the way down to the surface. These measurements have now been used to determine the vertical component of the atmospheric flow along the trajectory of the probe. The average flow direction is rising below about 40 km and sinking above that, with features that loosely match the strong shears in the horizontal wind profile obtained by radio telemetry. The prevalence of sinking motion in the stratosphere is an unexpected result for the given latitude, suggesting a layered atmosphere with a large thermally indirect cell. Wiggles superposed on the main upward flow are evidence of inertial instability characteristic of equatorial regions, pointing to a latitudinal shear of zonal wind throughout the lower atmosphere.

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Simulating Titan’s tropospheric circulation with the Portable University Model of the Atmosphere

Cited by 13 publications

References 15 publications

Energetics of Climate Models: Net Energy Balance and Meridional Enthalpy Transport

Energetics of Climate Models: Net Energy Balance and Meridional Enthalpy Transport

New Results on the Thermodynamic Properties of the Climate System

Vertical atmospheric flow on Titan as measured by the HASI instrument on board the Huygens probe

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