Séminaire Exoplanètes / |
| « Modéliser l''atmosphères de planètes fortement irradiées: comment sauver la terre du runaway greenhouse ? » |
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Jérémy Leconte |
| Because current exoplanets detection methods are biased toward shorter period orbits, most planets discovered to date have a higher equilibrium temperature than the Earth. If water is available at the surface, it could be evaporated, leading to the so-called runaway or moist greenhouse that determines the inner edge of the traditional habitable zone. However, so far, emphasis has been put on 1D radiative convective models, which cannot well predict the impact of clouds, or the non-linear effect of spatial inhomogeneities which can dominate in the case of close in exoplanets for which the rotation rate is synchronized with the orbital motion. Using a new generic 3D GCM developed at LMD for exoplanet studies, I will first give new estimates of the critical flux above which runaway greenhouse is triggered on an ocean-bearing world like the Earth. I will show that clouds have a stabilizing feedback on the climate and thus push the inner edge of the habitable zone closer to the star than usually inferred from 1D models. I will also show how the classical runaway greenhouse can be avoided if water is present only in limited amount. In particular, we will demonstrate that a bistable climate regime can exist on these objects. |
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mardi 30 avril 2013 - 14:30 Salle Daniel Chalonge Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |