3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability, and habitability

Leconte, Jérémy; Forget, F.; Charnay, Benjamin; Wordsworth, R.; Selsis, F.; Millour, Ehouarn; Spiga, Aymeric

doi:10.1051/0004-6361/201321042

Cited by 247 publications

(346 citation statements)

References 69 publications

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“…To really assess the possibility of water stability at the surface, inclusion of the water cycle, as in Leconte et al (2013), is mandatory.…”

Section: Discussionmentioning

confidence: 99%

Constraining physics of very hot super-Earths with theJames WebbTelescope. The case of CoRot-7b

Samuel¹,

Leconte²,

Rouan³

et al. 2014

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Context. Transit detection from space using ultra-precise photometry led to the first detection of super-Earths with solid surfaces: CoRot-7b and Kepler-10b. Because they lie only a few stellar radii from their host stars, these two rocky planets are expected to be extremely hot. Aims. Assuming that these planets are in a synchronous rotation state and receive strong stellar winds and fluxes, previous studies have suggested that they must be atmosphere-free and that a lava ocean is present on their hot dayside. In this article, we use several dedicated thermal models of the irradiated planet to study how observations with NIRSPEC on the James Webb Space Telescope (JWST) could further confirm and constrain, or reject the atmosphere-free lava ocean planet model for very hot super-Earths. Methods. Using CoRoT-7b as a working case, we explore the consequences on the phase-curve of a non tidal-locked rotation, with the presence/absence of an atmosphere, and for different values of the surface albedo. We then simulate future observations of the reflected light and thermal emission from CoRoT-7b with NIRSPEC-JWST and look for detectable signatures, such as time lag, of those peculiarities. We also study the possibility to retrieve the latitudinal surface temperature distribution from the observed SED. Results. We demonstrate that we should be able to constrain several parameters after observations of two orbits (42 h) thanks to the broad range of wavelengths accessible with JWST: i) the Bond albedo is retrieved to within ±0.03 in most cases. ii) The lag effect allows us to retrieve the rotation period within 3 h of a non phase-locked planet, whose rotation would be half the orbital period; for longer period, the accuracy is reduced. iii) Any spin period shorter than a limit in the range 30-800 h, depending on the thickness of the thermal layer in the soil, would be detected. iv) The presence of a thick gray atmosphere with a pressure of one bar, and a specific opacity higher than 10 −5 m −2 kg −1 is detectable. v) With spectra up to 4.5 μm, the latitudinal temperature profile can be retrieved to within 30 K with a risk of a totally wrong solution in 5% of the cases. This last result is obtained for a signal-to-noise ratio around 5 per resel, which should be reached on Corot-7 after a total exposure time of ∼70 h with NIRSPEC and only three hours on a V = 8 star. Conclusions. We conclude that it should thus be possible to distinguish the reference situation of a lava ocean with phase-locking and no atmosphere from other cases. In addition, obtaining the surface temperature map and the albedo brings important constraints on the nature or the physical state of the soil of hot super-Earths.

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“…To really assess the possibility of water stability at the surface, inclusion of the water cycle, as in Leconte et al (2013), is mandatory.…”

Section: Discussionmentioning

confidence: 99%

Constraining physics of very hot super-Earths with theJames WebbTelescope. The case of CoRot-7b

Samuel¹,

Leconte²,

Rouan³

et al. 2014

A&A

Self Cite

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“…We adopted the same temperature grids as in Leconte et al (2013) with values T = {110, 170, ..., 710} K and the same pressure grids with values p = {10 −3 ,10 −2 ,...,10 5 } mbar. The water volume mixing ratio could vary between 10 −7 to 1.…”

Section: Model Parametersmentioning

confidence: 99%

“…The bigger they are, the lower the albedo. In our model, the cloud ice particles have a size that varies depending on the water mixing ratio (see Leconte et al 2013 for details). In Yang et al (2013) the size is not indicated, but is said to be the same size as observed on Earth.…”

Section: Circular Orbitsmentioning

confidence: 99%

“…This is due to the higher Coriolis force that strengthens the mechanisms responsible for the equatorial super-rotation. The wave-mean flow interaction identified by Showman & Polvani (2011) and the three-way force balance identified by Showman et al (2013Showman et al ( , 2015 both affect the atmospheric circulation (see also Leconte et al 2013, for a discussion of the transition from stellar-antistellar circulation to super-rotation in the specific context of terrestrial planets). Figure 3 shows maps of the atmospheric temperature (color maps) and the wind pattern (with vectors) at an altitude of 10 km (corresponding to a pressure of 305 mbar for 1 L , 301 mbar for 10 −2 L , and 190 mbar for 10 −4 L ).…”

Section: Decreasing the Luminositymentioning

confidence: 99%

“…In Carone et al (2015), the Rossby wave transition region for an Earth-size planet is said to occur for a rotation period of 25 days, which is approximately the rotation period here (22.85 days). In the 1 L case, the rotation period was much longer and no Rossby wave could develop (e.g., Leconte et al 2013).…”

Section: Decreasing the Luminositymentioning

confidence: 99%

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Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Bolmont

Libert

Leconte

et al. 2016

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Unlike the Earth, which has a small orbital eccentricity, some exoplanets discovered in the insolation habitable zone (HZ) have high orbital eccentricities (e.g., up to an eccentricity of ∼0.97 for HD 20782 b). This raises the question of whether these planets have surface conditions favorable to liquid water. In order to assess the habitability of an eccentric planet, the mean flux approximation is often used. It states that a planet on an eccentric orbit is called habitable if it receives on average a flux compatible with the presence of surface liquid water. However, because the planets experience important insolation variations over one orbit and even spend some time outside the HZ for high eccentricities, the question of their habitability might not be as straightforward. We performed a set of simulations using the global climate model LMDZ to explore the limits of the mean flux approximation when varying the luminosity of the host star and the eccentricity of the planet. We computed the climate of tidally locked ocean covered planets with orbital eccentricity from 0 to 0.9 receiving a mean flux equal to Earth's. These planets are found around stars of luminosity ranging from 1 L to 10 −4 L . We use a definition of habitability based on the presence of surface liquid water, and find that most of the planets considered can sustain surface liquid water on the dayside with an ice cap on the nightside. However, for high eccentricity and high luminosity, planets cannot sustain surface liquid water during the whole orbital period. They completely freeze at apoastron and when approaching periastron an ocean appears around the substellar point. We conclude that the higher the eccentricity and the higher the luminosity of the star, the less reliable the mean flux approximation.

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The evolution of habitable climates under the brightening Sun

2015

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On water-dominated planets, warming from increased solar insolation is strongly amplified by the water vapor greenhouse feedback. As the Sun brightens due to stellar evolution, Earth will become uninhabitable due to rising temperatures. Here we use a modified version of the Community Earth System Model from the National Center for Atmospheric Research to study Earth under intense solar radiation. For small (≤10%) increases in the solar constant (S 0 ), Earth warms nearly linearly with climate sensitivities of~1 K/(W m À2) and global mean surface temperatures below 310 K. However, an abrupt shift in climate is found as the solar constant is increased to +12.5% S 0 . Here climate sensitivity peaks at~6.5 K/(W m À2 ), while global mean surface temperatures rise above 330 K. This climatic transition is associated with a fundamental change to the radiative-convective state of the atmosphere. Hot, moist climates feature both strong solar absorption and inefficient radiative cooling in the low atmosphere, thus yielding net radiative heating of the near-surface layers. This heating forms an inversion that effectively shuts off convection in the boundary layer. Beyond the transition, Earth continues to warm but with climate sensitivities again near unity. Conditions conducive to significant water loss to space are not found until +19% S 0 . Earth remains stable against a thermal runaway up to at least +21% S 0 , but at that point, global mean surface temperatures exceed 360 K, and water loss to space becomes rapid. Water loss of the oceans from a moist greenhouse may preclude a thermal runaway.

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3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability, and habitability

Cited by 247 publications

References 69 publications

Constraining physics of very hot super-Earths with theJames WebbTelescope. The case of CoRot-7b

Constraining physics of very hot super-Earths with theJames WebbTelescope. The case of CoRot-7b

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

The evolution of habitable climates under the brightening Sun

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