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| Titel |
Thermodynamics of a dry atmosphere at different surface exchange rates and rotation speed |
| VerfasserIn |
Salvatore Pascale, Francesco Ragone, Valerio Lucarini, Yixiong Wang, Robert Boschi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075286
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| Zusammenfassung |
| We study the combined effect of the rotation speed Ω and of the surface exchange rate –
quantified by a surface turbulent relaxation timescale Ï – on the dissipative properties of an
Earth-like dry atmosphere. The rotation speed Ω is varied between one tenth and eight times
that of the Earth ΩE - 7.29 -
10-5 rad-1 and Ï from 45 minutes to 500 days. We study the
circulation regimes induced by such parametric variations through two key dimensionless
parameters, the thermal Rossby number Ro and the frictional dimensionless number
Ff. An extensive analysis is performed by using nonequilibrium thermodynamics
diagnostic tools such as material entropy production, efficiency, meridional heat
transport and kinetic energy dissipation. The thermal dissipation associated with the
sensible heat flux is found to depend mainly on the surface properties and to be
almost independent from the rotation rate, whereas the dissipation of kinetic energy
depends in a nontrivial way on both. Slowly rotating, axisymmetric circulations
(Ro > 1) have the highest mechanical dissipation when the surface drag is strong
(Ff - 10-3), but the highest efficiency for Ff - 10. For 0.01 < Ro < 1 the peak is
reached for Ff - 103 (Ï ~ 3 d), corresponding to the maximum activity of the
baroclinic eddies, the maximum meridional heat transport and the highest efficiency. At
high rotation rates (Ro < 10-2) there is a dramatic drop in the intensity of the
atmospheric energy cycle and in the meridional heat transport as the atmosphere tends
towards the radiative-convective equilibrium profile. When Ï is interpreted as an
internal parameter, our results also confirm the vagueness of the Maximum Entropy
Production Principle, since its applicability seems to be dependent on both the dissipative
functions and the dynamical regime. This study suggests the effectiveness of using
fundamental nonequilibrium thermodynamics to investigate the properties of planetary
atmospheres. |
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