Thermal radiation of magma ocean planets using a 1-D radiative-convective model of H2O-CO2 atmospheres

Abstract : This paper presents an updated version of the simple 1D radiative-convective H2O-CO2 atmospheric model from Marcq [2012] and used by Lebrun et al. [2013] in their coupled interior-atmosphere model. This updated version includes a correction of a major miscalculation of the outgoing longwave radiation (OLR), and extends the validity of the model (P-coordinate system, possible inclusion of N2, improved numerical stability). It confirms the qualitative findings of Marcq [2012], namely (1) the existence of a blanketing effect in any H2O-dominated atmosphere: the outgoing longwave radiation (OLR) reaches an asymptotic value, also known as Nakajima's limit and first evidenced by Nakajima et al. [1992], around 280W/m2 neglecting clouds, significantly higher than our former estimate from Marcq[2012]. (2) The blanketing effect breaks down for a given threshold temperature Tϵ, with a fast increase of OLR with increasing surface temperature beyond this threshold, making extrasolar planets in such an early stage of their evolution easily detectable near 4μm provided they orbit a red dwarf. Tϵ2O surface pressure, but increasing CO2 pressure leads to a slight decrease of Tϵ. (3) clouds act both by lowering Nakajima's limit by up to 40%, and by extending the blanketing effect, raising the threshold temperature Tϵ by about 10%.
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Submitted on : Wednesday, July 19, 2017 - 9:28:13 AM
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Emmanuel Marcq, Arnaud Salvador, Hélène Massol, Anne Davaille. Thermal radiation of magma ocean planets using a 1-D radiative-convective model of H2O-CO2 atmospheres. Journal of Geophysical Research. Planets, Wiley-Blackwell, 2017, 122 (7), pp.1539-1553. ⟨10.1002/2016JE005224⟩. ⟨insu-01564674⟩



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