Dynamics of atmospheres with a non-dilute condensible component

Pierrehumbert, Raymond T.; Ding, Feng

doi:10.1098/rspa.2016.0107

Cited by 40 publications

(27 citation statements)

References 43 publications

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“…We next turn our attention to the simulation of relative humidity (RH), which is defined as the percentage of water vapor mixing ratio 3 relative to the saturation water vapor mixing ratio (Wallace & Hobbs 2016;Abbot 2018) and is a critical term for inferring habitability (Pierrehumbert 1995;Leconte et al 2013a;Pierrehumbert & Ding 2016) that can be affected by both radiative transfer and atmospheric dynamics. Relative humidity is higher in LMDG than in CAM3 at high altitude around the planet, both with and without clouds ( Fig.…”

Section: Relative Humiditymentioning

confidence: 99%

Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets: A 3D Model Intercomparison

Yang

Leconte

Wolf

et al. 2019

ApJ

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Robustly modeling the inner edge of the habitable zone is essential for determining the most promising potentially habitable exoplanets for atmospheric characterization. Global Climate Models (GCMs) have become the standard tool for calculating this boundary, but divergent results have emerged among the various GCMs. In this study we perform an intercomparison of standard GCMs used in the field on a rapidly rotating planet receiving a G-star spectral energy distribution and on a tidally locked planet receiving an M-star spectral energy distribution. Experiments both with and without clouds are examined. We find relatively small difference (within 8 K) in global-mean surface temperature simulation among the models in the G-star case with clouds. In contrast, the global-mean surface temperature simulation in the M-star case is highly divergent (20-30 K). Moreover, even differences in the simulated surface temperature when clouds are turned off are significant. These differences are caused by differences in cloud simulation and/or radiative transfer, as well as complex interactions between atmospheric dynamics and these two processes. For example we find that -2an increase in atmospheric absorption of shortwave radiation can lead to higher relative humidity at high altitudes globally and therefore a significant decrease in planetary radiation emitted to space. This study emphasizes the importance of basing conclusions about planetary climate on simulations from a variety of GCMs, and motivates the eventual comparison of GCM results with terrestrial exoplanet observations to improve their performance.

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Section: Relative Humiditymentioning

confidence: 99%

Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets: A 3D Model Intercomparison

Yang

Leconte

Wolf

et al. 2019

ApJ

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“…Large Λ corresponds to a slowly rotating planet, in which the Coriolis force is too week to support large temperature gradients. Such planets (with some caveats, discussed in Pierrehumbert & Ding (2016)) tend to have globally weak horizontal temperature gradients. Planets with Λ order unity or smaller are more Earthlike, with strong meridional (north-south) temperature gradients and strong zonal (east-west) jets.…”

Section: Scaling Theory For Tidally Locked Planetary Circulationmentioning

confidence: 99%

“…Λ is the Weak Temperature Gradient (WTG) parameter discussed in Pierrehumbert & Ding (2016) , and constitutes a nondimensional measure of the importance of the planet's rotation. Large Λ corresponds to a slowly rotating planet, in which the Coriolis force is too week to support large temperature gradients.…”

Section: Scaling Theory For Tidally Locked Planetary Circulationmentioning

confidence: 99%

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Linking the Climate and Thermal Phase Curve of 55 Cancri e

Hammond

Pierrehumbert

2017

ApJ

113

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The thermal phase curve of 55 Cancri e is the first measurement of the temperature distribution of a tidally locked Super-Earth, but raises a number of puzzling questions about the planet's climate. The phase curve has a high amplitude and peak offset, suggesting that it has a significant eastward hot-spot shift as well as a large day-night temperature contrast. We use a general circulation model to model potential climates, and investigate the relation between bulk atmospheric composition and the magnitude of these seemingly contradictory features. We confirm theoretical models of tidally locked circulation are consistent with our numerical model of 55 Cnc e, and rule out certain atmospheric compositions based on their thermodynamic properties. Our best-fitting atmosphere has a significant hotspot shift and day-night contrast, although these are not as large as the observed phase curve. We discuss possible physical processes which could explain the observations, and show that night-side cloud formation from species such as SiO from a day-side magma ocean could potentially increase the phase curve amplitude and explain the observations. We conclude that the observations could be explained by an optically thick atmosphere with a low mean molecular weight, a surface pressure of several bar and a strong eastward circulation, with night-side cloud formation a possible explanation for the difference between our model and the observations.

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“…The waterworld gains energy from incoming stellar radiation, and loses it via longwave emission and atmospheric escape. We describe this by the following equation (2), which is similar to those of Pierrehumbert (2010) and Lehmer et al (2017). However, we specifically account for radiative surface expansion in both the shortwave and longwave regimes:…”

Section: Energy Balancementioning

confidence: 99%

Atmospheric Evolution on Low-gravity Waterworlds

Arnscheidt

Wordsworth

Ding

2019

ApJ

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Low-gravity waterworlds (M 0.1M ⊕ ) are of interest for their potential habitability. The weakly bound atmospheres of such worlds have proportionally larger radiative surfaces and are more susceptible to escape. We conduct a unified investigation into these phenomena, combining analytical energy balance and hydrodynamic escape with line-by-line radiative transfer calculations. Because outgoing radiation is forced to increase with surface temperature by the expansion of the radiative surface, we find that these worlds do not experience a runaway greenhouse. Furthermore, we show that a long-lived liquid water habitable zone is possible for low-gravity waterworlds of sufficient mass. Its inner edge is set by the rate of atmospheric escape because a short-lived atmosphere limits the time available for life to evolve. In describing the physics of the parameter space transition from "planet-like" to "comet-like", our model produces a lower bound for habitability in terms of gravity. These results provide valuable insights in the context of the ongoing hunt for habitable exoplanets and exomoons.

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Dynamics of atmospheres with a non-dilute condensible component

Abstract: A contribution to the special feature 'Perspectives in astrophysical and geophysical Fluids' .Electronic supplementary material is available at

Cited by 40 publications

References 43 publications

Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets: A 3D Model Intercomparison

Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets: A 3D Model Intercomparison

Linking the Climate and Thermal Phase Curve of 55 Cancri e

Atmospheric Evolution on Low-gravity Waterworlds

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