Patchy nightside clouds on ultra-hot Jupiters: General Circulation Model simulations with radiatively active cloud tracers

Abstract

The atmospheres of ultra-hot Jupiters have been characterized in detail through recent phase curve and low-and high-resolution emission and transmission spectroscopic observations. Previous numerical studies have analyzed the effect of the localized recombination of hydrogen on the atmospheric dynamics and heat transport of ultra-hot Jupiters, finding that hydrogen dissociation and recombination lead to a reduction in the day-to-night contrasts of ultra-hot Jupiters relative to previous expectations. In this work, we add to previous efforts by also considering the localized condensation of clouds in the atmospheres of ultra-hot Jupiters, their resulting transport by the atmospheric circulation, and the radiative feedback of clouds on the atmospheric dynamics. To do so, we include radiatively active cloud tracers into the existing MITgcm framework for simulating the atmospheric dynamics of ultrahot Jupiters. We take cloud condensate properties appropriate for the high-temperature condensate corundum from CARMA cloud microphysics models. We conduct a suite of GCM simulations with varying cloud microphysical and radiative properties, and we find that partial cloud coverage is a ubiquitous outcome of our simulations. This patchy cloud distribution is inherently set by atmospheric dynamics in addition to equilibrium cloud condensation, and causes a cloud greenhouse effect that warms the atmosphere below the cloud deck. Nightside clouds are further sequestered at depth due to a dynamically induced high-altitude thermal inversion. We post-process our GCMs with the Monte Carlo radiative transfer code gCMCRT and find that the patchy clouds on ultra-hot Jupiters do not significantly impact transmission spectra but can affect their phase-dependent emission spectra.

The Mantis Network II: examining the 3D high-resolution observable properties of the UHJs WASP-121b and WASP-189b through GCM modelling

“…Coupled cloud formation models to the GCM in the UHJ regime (e.g. Komacek et al 2022) will be enlightening to see if TiO can be cold trapped in the case of WASP-121b. Potential cold trapping of TiO was investigated for HD 209458b in Parmentier et al (2013).…”

“…This likely the case for some UHJ planets (e.g. Helling et al 2021;Komacek et al 2022), with clouds mostly confined to the nightside hemisphere. However, due to the significant added computational expense of modelling clouds in hot Jupiter GCMs (e.g.…”

Spatially-resolving the terminator: Variation of Fe, temperature and winds in WASP-76 b across planetary limbs and orbital phase

“…Such clouds form at pressures of 10 −2 -10 −3 bar depending on the temperature, consistent with our opacity decks for the night side of log(𝑃 cl /bar) = −2.08 +0.44 −0.53 (evening side, 𝜙 = −0.04 -− 0.02) and log(𝑃 cl /bar) = −3.33 +0.80 −0.91 (morning side, 𝜙 = 0.02 -0.04). Recent work has also shown that patchy clouds may be present on the night side of UHJs but that they only weakly affect terminator observations (Komacek et al 2022).…”

“…Including winds into atmospheric models is also of particular importance given that there are also a growing number of high-resolution studies which have constrained these on the terminator (Brogi et al 2016;Flowers et al 2019;Seidel et al 2021). In addition, recent work has also shown that cloud formation on the night side of UHJs is strongly dependent on the atmospheric dynamics (Komacek et al 2022) and these clouds can affect phase-dependent emission spectra.…”