3D Climate modelling of TRAPPIST-1 c with a Venus-like atmosphere: large-scale circulation and observational prospects
Authors: Quirino Diogo , Gilli Gabriella , Navarro Thomas , Turbet Martin , Fauchez Thomas , Machado Pedro 
Published: March 2022

&lt;p&gt;In recent years, several Earth-sized exoplanets have been detected in short-period orbits of a few Earth days, around low-mass stars [&lt;strong&gt;1&lt;/strong&gt;]. 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&amp;#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 [&lt;strong&gt;2&lt;/strong&gt;]. Thus, the atmosphere of our neighbouring planet Venus presents a relevant case to address observational prospects.&lt;/p&gt;&lt;p&gt;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&amp;#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.&lt;/p&gt;&lt;p&gt;In this work, we used the Generic-GCM, developed at the&amp;#160;&lt;em&gt;Laboratoire de M&amp;#233;t&amp;#233;orologie Dynamique&lt;/em&gt;&amp;#160;for exoplanet and paleoclimate studies [&lt;strong&gt;3, 4, 5&lt;/strong&gt;], 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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] Gillon et al. 2017. Nature. 542.&lt;/p&gt;&lt;p&gt;[2] Kane et al. 2018. ApJ. 869.&lt;/p&gt;&lt;p&gt;[3] Forget &amp; Leconte, 2014. Phil. Trans R. Soc. A372.&lt;/p&gt;&lt;p&gt;[4] Turbet et al. 2016. A&amp;A. 596. A112.&lt;/p&gt;&lt;p&gt;[5] Wordsworth et al. 2011. ApJL. 733. L48.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;This work is supported by Funda&amp;#231;&amp;#227;o para a Ci&amp;#234;ncia e a Tecnologia (FCT) through the research grants UIDB/04434/2020, UIDP/04434/2020, P-TUGA PTDC/FIS-AST/29942/2017.&lt;/p&gt;