The Influence of a Substellar Continent on the Climate of a Tidally Locked Exoplanet

Lewis, Neil T.; Lambert, F. Hugo; Boutle, Ian; Mayne, Nathan J.; Manners, James; Acreman, David M.

doi:10.3847/1538-4357/aaad0a

Cited by 58 publications

(83 citation statements)

References 67 publications

(121 reference statements)

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“…The extent of this ozone removal is driven by the magnitude, frequency, and duration of the stellar activity. We find the planetary surface is potentially habitable in our calculations, in agreement with Boutle et al (2017), with a significant surface area with temperatures above 273 K. We did not consider ice-albedo feedback, following Shields et al (2013); Boutle et al (2017); Lewis et al (2018) who showed this effect is small for M dwarf planets. For our planetary calculations we adopted Earth-like CO 2 concentrations, but we acknowlege they are likely too low if there exists a carbonate-silicate negative feedback cycle (Walker et al 1981).…”

Section: Discussion and Concluding Remarkssupporting

confidence: 69%

“…The UM has been used previously to study the atmospheric physics of terrestrial exoplanets and hot Jupiters (e.g. Mayne et al (2014a,b); Boutle et al 2017; Lewis et al (2018); Drummond et al (2018)). We couple this model with the Chapman mechanism (Chapman 1930) that describes ozone chemistry in Earth's stratosphere with the hydrogen oxide catalytic cycle.…”

Section: Take Down Policymentioning

confidence: 99%

“…Temperature is approximately constant from an altitude of 2 km towards the surface on the day side, while there is a strong negative gradient on the night side over the same altitude range. Above 10 km, there is little difference between the distribution and values of air temperature and wind speed, suggesting an efficient transport of heat between the hemispheres (Yang & Abbot 2014;Lewis et al 2018). There is a strong peak in wind speed between 20 and 30 km, reflecting a jet stream structure.…”

Section: Hemispheric Mean 1-d Meteorological and Ozone Structurementioning

confidence: 99%

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Ozone chemistry on tidally locked M dwarf planets

Yates

Palmer

Manners

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We use the Met Office Unified Model to explore the potential of a tidally locked M dwarf planet, nominally Proxima Centauri b irradiated by a quiescent version of its host star, to sustain an atmospheric ozone layer. We assume a slab ocean surface layer, and an Earth-like atmosphere of nitrogen and oxygen with trace amounts of ozone and water vapour. We describe ozone chemistry using the Chapman mechanism and the hydrogen oxide (HOx, describing the sum of OH and HO2) catalytic cycle. We find that Proxima Centauri radiates with sufficient UV energy to initialize the Chapman mechanism. The result is a thin but stable ozone layer that peaks at 0.75 parts per million at 25 km. The quasi-stationary distribution of atmospheric ozone is determined by photolysis driven by incoming stellar radiation and by atmospheric transport. Ozone mole fractions are smallest in the lowest 15 km of the atmosphere at the substellar point and largest in the nightside gyres. Above 15 km the ozone distribution is dominated by an equatorial jet stream that circumnavigates the planet. The nightside ozone distribution is dominated by two cyclonic Rossby gyres that result in localized ozone hotspots. On the dayside the atmospheric lifetime is determined by the HOx catalytic cycle and deposition to the surface, with nightside lifetimes due to chemistry much longer than time-scales associated with atmospheric transport. Surface UV values peak at the substellar point with values of 0.01 W m−2, shielded by the overlying atmospheric ozone layer but more importantly by water vapour clouds.

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Section: Discussion and Concluding Remarkssupporting

confidence: 69%

Section: Take Down Policymentioning

confidence: 99%

Section: Hemispheric Mean 1-d Meteorological and Ozone Structurementioning

confidence: 99%

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Ozone chemistry on tidally locked M dwarf planets

Yates

Palmer

Manners

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The main focus of the theoretical modeling of exoplanets has been either the well observed hot Jupiter objects, or potentially habitable terrestrial planets. For terrestrial planets 3D General Circulation Models (GCMs) adapted from those used to study Earth, have been applied to explore the potential climates of, for example, Proxima Centauri b (Turbet et al 2016;Boutle et al 2017), the response of an Earth-like climate to weakened and intensified stellar irradiation (Leconte et al 2013;Charnay et al 2013, respectively), alongside studies including surface effects (Lewis et al 2018) and a dynamical ocean (e.g., Wolf et al 2017;Del Genio et al 2017). For hot Jupiters, gas-phase chemical equilibrium simulations have been performed, in 3D using GCMs, across a range of targets (e.g., Kataria et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Limits of the Primitive Equations of Dynamics for Warm, Slowly Rotating Small Neptunes and Super Earths

Mayne

Drummond

Debras

et al. 2019

ApJ

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We present significant differences in the simulated atmospheric flow for warm, tidally-locked small Neptunes and super Earths (based on a nominal GJ 1214b) when solving the simplified, and commonly used, primitive dynamical equations or the full Navier-Stokes equations. The dominant prograde, superrotating zonal jet is markedly different between the simulations which are performed using practically identical numerical setups, within the same model. The differences arise due to the breakdown of the so-called 'shallow-fluid' and traditional approximations, which worsens when rotation rates are slowed, and day-night temperature contrasts are increased. The changes in the zonal advection between simulations solving the full and simplified equations, give rise to significant differences in the atmospheric redistribution of heat, altering the position of the hottest part of the atmosphere and temperature contrast between the day and night sides. The implications for the atmospheric chemistry and, therefore, observations need to be studied with a model including a more detailed treatment of the radiative transfer and chemistry. Small Neptunes and super Earths are extremely abundant and important, potentially bridging the structural properties (mass, radius, composition) of terrestrial and gas giant planets. Our results indicate care is required when interpreting the output of models solving the primitive equations of motion for such planets.

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“…For all scenarios, we assumed that the planet is tidally locked. Tidal locking can have a profound effect on the climate circulation (Kite et al 2011;Wordsworth 2015;Koll & Abbot 2016;Carone et al 2018;Lewis et al 2018), and likely occurs on shorter timescales and for longer-period planets than previously determined (Barnes 2017). Given the relatively short tidal locking timescale for shortperiod planets, the assumption of tidal locking is sufficiently justified.…”

Section: Climate Modeling and Surface Temperaturementioning

confidence: 91%

Climate Modeling of a Potential ExoVenus

Kane

Ceja

Way

et al. 2018

ApJ

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The planetary mass and radius sensitivity of exoplanet discovery capabilities has reached into the terrestrial regime. The focus of such investigations is to search within the Habitable Zone where a modern Earth-like atmosphere may be a viable comparison. However, the detection bias of the transit and radial velocity methods lies close to the host star where the received flux at the planet may push the atmosphere into a runaway greenhouse state. One such exoplanet discovery, Kepler-1649b, receives a similar flux from its star as modern Venus does from the Sun, and so was categorized as a possible exoVenus. Here we discuss the planetary parameters of Kepler-1649b with relation to Venus to establish its potential as a Venus analog. We utilize the general circulation model ROCKE-3D to simulate the evolution of the surface temperature of Kepler-1649b under various assumptions, including relative atmospheric abundances. We show that in all our simulations the atmospheric model rapidly diverges from temperate surface conditions towards a runaway greenhouse with rapidly escalating surface temperatures. We calculate transmission spectra for the evolved atmosphere and discuss these spectra within the context of the James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSpec) capabilities. We thus demonstrate the detectability of the key atmospheric signatures of possible runaway greenhouse transition states and outline the future prospects of characterizing potential Venus analogs.

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The Influence of a Substellar Continent on the Climate of a Tidally Locked Exoplanet

Cited by 58 publications

References 67 publications

Ozone chemistry on tidally locked M dwarf planets

Ozone chemistry on tidally locked M dwarf planets

The Limits of the Primitive Equations of Dynamics for Warm, Slowly Rotating Small Neptunes and Super Earths

Climate Modeling of a Potential ExoVenus

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