Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

Yang, Jun; Cowan, Nicolas B.; Abbot, Dorian S.

doi:10.1088/2041-8205/771/2/l45

Cited by 377 publications

(530 citation statements)

References 42 publications

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“…1, bottom left). The albedo of the planet is about 0.25, which is significantly lower than in Yang et al (2013). This might be due to several differences in our simulations.…”

Section: Circular Orbitsmentioning

confidence: 67%

“…There are ice clouds above the substellar point at an altitude of 15 km; these clouds protect the substellar point. Yang et al (2013) determined that this mechanism allows the inner edge of the insolation HZ for synchronous planets to be closer than for non-synchronous planets.…”

Section: Circular Orbitsmentioning

confidence: 99%

“…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. Furthermore, Yang et al (2013) pointed out that the albedo of the planet strongly depends on the oceanic transport, which is not included here.…”

Section: Circular Orbitsmentioning

confidence: 99%

“…In Yang et al (2013) the size is not indicated, but is said to be the same size as observed on Earth. Furthermore, Yang et al (2013) pointed out that the albedo of the planet strongly depends on the oceanic transport, which is not included here. Finally, the biggest difference comes from the moist convection parametrization, which is chosen to be very simple with few free parameters in LMDZ (Manabe & Wetherald 1967).…”

Section: Circular Orbitsmentioning

confidence: 99%

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

Bolmont

Libert

Leconte

et al. 2016

A&A

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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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“…1, bottom left). The albedo of the planet is about 0.25, which is significantly lower than in Yang et al (2013). This might be due to several differences in our simulations.…”

Section: Circular Orbitsmentioning

confidence: 67%

Section: Circular Orbitsmentioning

confidence: 99%

Section: Circular Orbitsmentioning

confidence: 99%

Section: Circular Orbitsmentioning

confidence: 99%

See 2 more Smart Citations

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

Bolmont

Libert

Leconte

et al. 2016

A&A

View full text Add to dashboard Cite

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“…The areas with high P coincide with either the location of surfaces covered with sea ice or with the location of optically thick convective clouds. High values of planetary albedo 4,8,16,32,64,128,182,200,256, associated with deep convective clouds were already discussed in the case of synchronous rotation (Yang et al 2013) and in the case of rotation periods longer than 100 Earth-days . However, the impact of the ice albedo on the energy balance of slowly rotating planets has not yet been investigated.…”

Section: Surface Contribution To Planetary Albedomentioning

confidence: 74%

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

2017

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We investigate the influence of the rotation period (Prot) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing Prot and sea ice expands equatorwards. The cooling of the mean climate with increasing Prot is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation

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Delayed onset of runaway and moist greenhouse climates for Earth

Wolf

Toon

2014

Geophysical Research Letters

106

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As the Sun slowly grows brighter over its main sequence lifetime, habitability on Earth's surface will eventually become threatened probably leading to moist and then runaway greenhouse climates. One-dimensional climate models predict that a catastrophic thermal runaway will be triggered by a 6% increase in the solar constant above its present level. However, here simulations using a three-dimensional climate model with fixed carbon dioxide and methane indicate that surface habitability may be maintained at significantly larger solar constants. A 15.5% increase in the solar constant yields global mean surface temperatures of 312.9 K, well short of moist and runaway greenhouse states. Numerical limitations prevent simulation of climates much warmer than this. Nonetheless, our results imply that Earth's climate may remain safe against both water loss and thermal runaway limits for at least another 1.5 billion years and probably for much longer.

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Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

Cited by 377 publications

References 42 publications

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

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

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

Delayed onset of runaway and moist greenhouse climates for Earth

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