Exo-Nephology: 3D simulations of cloudy hot-Jupiter atmospheres with the Met Office 'Unified Model'

Thursday 5 July, 17:10

Evidence of clouds in hot-Jupiter atmospheres spans from variability of and offsets in planetary phase curves, to muted absorption features in transmission spectra. The latter, attributed to the opaque nature of cloud condensate decks and/or haze, make atmospheric characterisation challenging. Using the verified Met Office Global Circulation Model (GCM) the ‘Unified Model’ (UM) and a kinetic, microphysical cloud formation code, we perform 3D simulations of radiatively-active prognostic cloudy hot-Jupiter atmospheres. Our model considers homogeneous nucleation of seed particles, mixed-composition heterogeneous surface growth (condensation) and evaporation, cloud particle advection, gravitational settling, absorption and scattering. We focus on the well-studied HD209458b and investigate the structure and evolution of cloud particles in response to the atmospheric dynamics and reveal the importance of cloud scattering on the thermal evolution of the atmosphere. To connect with current observables, we present synthetic model phase curves and transmission spectra obtained directly from our 3D cloud-coupled GCM and discuss the implications of the distribution of our cloud particles on phase curve offsets and variability. We explore the potential for the detection of features in our cloudy transmission spectrum with JWST MIRI, and probe the importance of cloud particle sizes and composition on the ability to characterise the atmospheres of these exotic planets.

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