# Overcast on Osiris: 3D radiative-hydrodynamical simulations of a cloudy hot Jupiter using the parameterised, phase-equilibrium cloud formation code EddySed

## TL;DR

This study uses 3D radiative-hydrodynamical simulations with a parameterised cloud model to show clouds significantly affect the thermal and optical structure of a hot Jupiter's atmosphere, improving observational matches.

## Contribution

First application of fully coupled cloud radiative feedback in 3D simulations of HD 209458b using the EddySed parameterised cloud model, highlighting the importance of cloud effects.

## Key findings

- Cloud radiative feedback markedly alters atmospheric structure.
- Cloud properties are sensitive to sedimentation efficiency and deep atmosphere profiles.
- Simulated observations better match actual data with clouds included.

## Abstract

We present results from 3D radiative-hydrodynamical simulations of HD 209458b with a fully coupled treatment of clouds using the EddySed code, critically, including cloud radiative feedback via absorption and scattering. We demonstrate that the thermal and optical structure of the simulated atmosphere is markedly different, for the majority of our simulations, when including cloud radiative effects, suggesting this important mechanism can not be neglected. Additionally, we further demonstrate that the cloud structure is sensitive to not only the cloud sedimentation efficiency (termed $f_{\textrm{sed}}$ in EddySed), but also the temperature-pressure profile of the deeper atmosphere. We briefly discuss the large difference between the resolved cloud structures of this work, adopting a phase-equilibrium and parameterised cloud model, and our previous work incorporating a cloud microphysical model, although a fairer comparison where, for example, the same list of constituent condensates is included in both treatments, is reserved for a future work. Our results underline the importance of further study into the potential condensate size distributions and vertical structures, as both strongly influence the radiative impact of clouds on the atmosphere. Finally, we present synthetic observations from our simulations reporting an improved match, over our previous cloud-free simulations, to the observed transmission, HST WFC3 emission and 4.5 $\mu$m Spitzer phase curve of HD 209458b. Additionally, we find all our cloudy simulations have an apparent albedo consistent with observations.