Simulated Phase-dependent Spectra of Terrestrial Aquaplanets in M Dwarf Systems

Wolf, Eric T.; Kopparapu, R.; Haqq-Misra, Jacob

doi:10.3847/1538-4357/ab184a

Cited by 29 publications

(25 citation statements)

References 72 publications

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“…This scheme was compared favorably against LBLRTM for warm, moist N 2 , H 2 O atmospheres (see Figure 1 in Kopparapu et al 2017). Note also that there is an analogous 68 spectral interval version of this radiation scheme, n68h2o, which was used in Wolf et al (2019) to yield better output spectral resolution for use in phase curve studies. This version has a full spectrum range from 0 to 42,087.00 cm −1 (0.238-infinity μm), with longwave and shortwave calculations computed over the entire spectral range.…”

Section: Radiative Transfermentioning

confidence: 99%

“…ExoCAM has been well-received and well-used since being made public. ExoCAM, and its ancestral versions, have been employed for a wide variety of studies, including the Faint Young Sun Paradox for Earth (Wolf & Toon 2013, 2014a, high-CO 2 atmospheres (Wolf et al 2018;Zhang et al 2021), runaway and moist greenhouse thresholds for Earth (Wolf & Toon 2014b, Earth-like extrasolar planets (Wolf et al 2017;Adams et al 2019;Kang 2019aKang , 2019bKang , 2019c, habitable zone exoplanets around M-dwarf stars (Kopparapu et al 2017;Wolf 2017;Haqq-Misra et al 2018;Komacek et al , 2020aKomacek et al , 2020bWolf et al 2019;Yang et al 2019a;Hu et al 2020;Rushby et al 2020;Suissa et al 2020b;Wei et al 2020;Chen et al 2021;May et al 2021;Song & Yang 2021), planets in circumbinary systems (Wolf et al 2020), and model intercomparison studies (Yang et al 2016(Yang et al , 2019bFauchez et al 2020Turbet et al 2021). ExoCAM results have also been used off-line in projects to drive photochemistry and observability studies (Afrin Badhan et al 2019;Suissa et al 2020a).…”

Section: Introductionmentioning

confidence: 99%

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ExoCAM: A 3D Climate Model for Exoplanet Atmospheres

Wolf¹,

Kopparapu

Haqq-Misra

et al. 2022

Planet. Sci. J.

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The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) project was initiated to compare 3D climate models that are commonly used for predicting theoretical climates of habitable zone extrasolar planets. One of the core models studied as part of THAI is ExoCAM, an independently curated exoplanet branch of the National Center for Atmospheric Research Community Earth System Model (CESM), version 1.2.1. ExoCAM has been used for studying atmospheres of terrestrial extrasolar planets around a variety of stars. To accompany the THAI project and provide a primary reference, here we describe ExoCAM and what makes it unique from standard configurations of CESM. Furthermore, we also conduct a series of intramodel sensitivity tests of relevant moist physical tuning parameters while using the THAI protocol as our starting point. A common criticism of 3D climate models used for exoplanet modeling is that cloud and convection routines often contain free parameters that are tuned to the modern Earth, and thus may be a source of uncertainty in evaluating exoplanet climates. Here, we explore sensitivities to numerous configuration and parameter selections, including a recently updated radiation scheme, a different cloud and convection physics package, different cloud and precipitation tuning parameters, and a different sea ice albedo. Improvements to our radiation scheme and the modification of cloud particle sizes have the largest effects on global mean temperatures, with variations up to ∼10 K, highlighting the requirement for accurate radiative transfer and the importance of cloud microphysics for simulating exoplanetary climates. However, for the vast majority of sensitivity tests, climate differences are small. For all cases studied, intramodel differences do not bias general conclusions regarding climate states and habitability.

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Section: Radiative Transfermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

ExoCAM: A 3D Climate Model for Exoplanet Atmospheres

Wolf¹,

Kopparapu

Haqq-Misra

et al. 2022

Planet. Sci. J.

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“…Briefly, Kopparapu et al (2017) use a modified version of the Community Atmosphere Model (CAM) version 4 (Neale et al 2010), called ExoCAM 2,3 that is suitable for exoplanet habitability studies. More details about the updates made to ExoCAM are given in Wolf (2017); Haqq-Misra et al (2018); Wolf et al (2019). Kopparapu et al (2017) explored 39 different configurations of an ocean-covered Earth-sized planet synchronously rotating around a late-M to mid-K star (T eff from 2600 K to 4500 K) in the HZ.…”

Section: Gcm Modelmentioning

confidence: 99%

Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

Suissa

Mandell

Wolf

et al. 2020

ApJ

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The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future. Understanding the atmospheres of these planets and determining the optimal strategy for characterizing them through transmission spectroscopy with our upcoming instrumentation is essential in order to constrain their environments. For this study, we present simulated transmission spectra of tidally locked Earth-sized ocean-covered planets around late-M to mid-K stellar spectral types, utilizing GCM modeling results previously published by Kopparapu et al. (2017) as inputs for our radiative transfer calculations performed using NASA's Planetary Spectrum Generator (psg.gsfc.nasa.gov; Villanueva et al. (2018)). We identify trends in the depth of H 2 O spectral features as a function of planet surface temperature and rotation rate. These trends allow us to calculate the exposure times necessary to detect water vapor in the atmospheres of aquaplanets through transmission spectroscopy with the upcoming James Webb Space Telescope (JWST) as well as several future flagship space telescope concepts under consideration (LUVOIR and OST) for a target list constructed from the TESS Input Catalog (TIC). Our calculations reveal that transmission spectra for water-rich Earth-sized planets around low-mass stars will be dominated by clouds, with spectral features < 20 ppm, and only a small subset of TIC stars would allow for the characterization of an ocean planet in the Habitable Zone. We thus present a careful prioritization of targets that are most amenable to follow-up characterizations with next-generation instrumentation, in order to assist the community in efficiently utilizing precious telescope time.

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“…If time-resolved observations are available, broadband photometric and polarimetric phase curves may be sensitive to the presence of liquid water oceans and land (Cowan & Strait 2013;Fujii et al 2017;Trees & Stam 2019). Other efforts have been proposed using high-resolution spectra and phase curves to probe atmospheric composition (Wolf et al 2019;Chen et al 2019), colors to identify qualitative planet type (Madden & Kaltenegger 2018), and albedo measurements to probe the existence of atmospheres (Mansfield et al 2019;Koll & Cronin 2019). However, all of these analyses either used 1D models that cannot capture the spatial heterogeneity of realistic climates, or relied on a relatively small number of model climates, making it difficult to quantify their robustness to model parameterizations and assumptions.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Challenges to Remote Sensing of Exo-Earths

Paradise,

Menou,

Lee

et al. 2021

Preprint

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Inferring the climate and surface conditions of terrestrial exoplanets in the habitable zone is a major goal for the field of exoplanet science. This pursuit will require both statistical analyses of the population of habitable planets as well as in-depth analyses of the climates of individual planets. Given the close relationship between habitability and surface liquid water, it is important to ask whether the fraction of a planet's surface where water can be a liquid, 𝜒 hab , can be inferred from observations. We have produced a diverse bank of 1,874 3D climate models and computed the full-phase reflectance and emission spectrum for each model to investigate whether surface climate inference is feasible with high-quality direct imaging or secondary eclipse spectroscopy. These models represent the outcome of approximately 200,000 total simulated years of climate and over 50,000 CPU-hours, and the roughly-100 GB model bank and its associated spectra are being made publicly-available for community use. We find that there are correlations between spectra and 𝜒 hab that will permit statistical approaches. However, spectral degeneracies in the climate observables produced by our model bank indicate that inference of individual climates is likely to be model-dependent, and inference will likely be impossible without exhaustive explorations of the climate parameter space. The diversity of potential climates on habitable planets therefore poses fundamental challenges to remote sensing efforts targeting exo-Earths.

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Simulated Phase-dependent Spectra of Terrestrial Aquaplanets in M Dwarf Systems

Cited by 29 publications

References 72 publications

ExoCAM: A 3D Climate Model for Exoplanet Atmospheres

ExoCAM: A 3D Climate Model for Exoplanet Atmospheres

Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

Fundamental Challenges to Remote Sensing of Exo-Earths

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