How clear are the skies of WASP-80b?: 3D Cloud feedback on the atmosphere and spectra of the warm Jupiter
Authors
Nishil Mehta
Vivien Parmentier
Xianyu Tan
Elspeth K. H. Lee
Tristan Guillot
Lindsey S. Wiser
Taylor J. Bell
Everett Schlawin
Kenneth Arnold
Sagnick Mukherjee
Thomas P. Greene
Thomas G. Beatty
Luis Welbanks
Michael R. Line
Matthew M. Murphy
Jonathan J. Fortney
Kazumasa Ohno
Abstract
Close-in warm Jupiters orbiting M-dwarf stars are expected to exhibit diverse atmospheric chemistry, with clouds playing a key role in shaping their albedo, heat distribution, and spectral properties. We study WASP-80b, a warm Jupiter orbiting an M-dwarf star, using the latest JWST panchromatic emission and transmission spectra to comprehensively characterise its atmosphere, including cloud coverage, chemical composition, and particle sizes, and compare the observations with predictions from the General Circulation Models (GCM). We use a GCM, ADAM (ADvanced Atmospheric MITgcm, formerly known as SPARC/MITgcm), combined with the latest JWST data to study the atmosphere of WASP-80b. A cloud module with radiatively active, tracer-based clouds is integrated with the GCM to study the effects on the atmosphere and the spectrum. Our results indicate that both emission and transmission spectra of WASP-80b are best reproduced by cloudless GCMs or by atmospheres containing large cloud particles ($\geq 10~μ$m for Na$_2$S, $\geq 1~μ$m for KCl, and $\geq 5~μ$m for MgSiO$_3$), with smaller particles ruled out due to their strong radiative feedback. These findings emphasize the importance of particle size and composition in interpreting exoplanet atmospheric spectra and showcase the power of global modelling in constraining cloud properties. Among the expected clouds to form in WASP-80b, we show that only Na$_2$S clouds forming particles larger than 10 $μm$, KCl clouds larger than 1 $μm$, or MgSiO$_3$ clouds with particles larger than $5 μm$ can be compatible with the apparently cloudless emission and transmission spectra. Observations at shorter wavelengths in both emission and transmission could further distinguish between these cloudy scenarios and a truly cloudless atmosphere.
