3D Climate modelling of TRAPPIST-1 c with a Venus-like atmosphere: large-scale circulation and observational prospects

<p>In recent years, several Earth-sized exoplanets have been detected in short-period orbits of a few Earth days, around low-mass stars [<strong>1</strong>]. Despite their small size compared to gas giants, their close-in orbits combined with the small radius of the host star compared to our Sun&#8217;s make these worlds the best targets for atmospheric characterisation among rocky exoplanets. These worlds have stellar irradiation levels that can be several times that of the Earth, suggesting that a Venus-like climate is more likely [<strong>2</strong>]. Thus, the atmosphere of our neighbouring planet Venus presents a relevant case to address observational prospects.</p><p>The recent launch of the James Webb Space Telescope will advance the atmosphere and climate characterisation of nearby rocky exoplanets, with the support of upcoming ground-based observatories and space telescopes, such as the ESA/Ariel mission, scheduled for launch in 2029. The interpretation of the observables produced by these missions: reflectance, thermal emission and transmission spectra will need support from modelling studies of exoplanetary atmospheres. In particular, 3D Global Climate Models (GCMs) are critical for interpreting the observable signal&#8217;s modulations, as they provide synthetic top-of-the-atmosphere fluxes that can be disk-integrated as a function of the orbital phase. The spatial and temporal variability of these fluxes reflect the atmospheric variability of the simulated temperature and wind fields and provide insight over the large-scale circulation.</p><p>In this work, we used the Generic-GCM, developed at the&#160;<em>Laboratoire de M&#233;t&#233;orologie Dynamique</em>&#160;for exoplanet and paleoclimate studies [<strong>3, 4, 5</strong>], which includes a 3D dynamical core, common to all terrestrial planets, a planet-specific physical core, and an up-to-date generalised radiative transfer routine for variable atmospheric compositions.</p><p>We present the results of modelling highly irradiated rocky exoplanets orbiting an M-dwarf star, using a Venus-like atmosphere as a possible framework for the atmospheric conditions of TRAPPIST-1 c. We assumed synchronous rotation, zero eccentricity and obliquity, and a Venus-like atmosphere with 92-bar surface pressure and a radiatively active Venus-type global cloud cover. The results indicate an eastward shift of the peak thermal emission away from the sub-stellar point, suggesting an advection of warm air masses caused by a superrotation equatorial jet.</p><p>&#160;</p><p><strong>References:</strong></p><p>[1] Gillon et al. 2017. Nature. 542.</p><p>[2] Kane et al. 2018. ApJ. 869.</p><p>[3] Forget & Leconte, 2014. Phil. Trans R. Soc. A372.</p><p>[4] Turbet et al. 2016. A&A. 596. A112.</p><p>[5] Wordsworth et al. 2011. ApJL. 733. L48.</p><p>&#160;</p><p><strong>Acknowledgements:</strong></p><p>This work is supported by Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia (FCT) through the research grants UIDB/04434/2020, UIDP/04434/2020, P-TUGA PTDC/FIS-AST/29942/2017.</p>