Modelling Non-Condensing Compositional Convection for Applications to Super-Earth and Sub-Neptune Atmospheres

Abstract

Compositional convection is atmospheric mixing driven by density variations caused by compositional gradients. Previous studies have suggested that compositional gradients of atmospheric trace species within planetary atmospheres can impact convection and the final atmospheric temperature profile. In this work, we employ 3D convection resolving simulations using Cloud Model 1 (CM1) to gain a fundamental understanding of how compositional variation influences convection and the final atmospheric state of exoplanet atmospheres. We perform 3D initial value problem simulations of non-condensing compositional convection for Earth-Air, ${\mathrm{H}}_2$, and $\mathrm{C}{\mathrm{O}}_2$ atmospheres. Conventionally, atmospheric convection is assumed to mix the atmosphere to a final, marginally stable state defined by a unique temperature profile. However, when there is compositional variation within an atmosphere, a continuous family of stable end states is possible, differing in the final state composition profile. Our CM1 simulations are used to determine which of the family of possible compositional end states is selected. Leveraging the results from our CM1 simulations, we develop a dry convective adjustment scheme for use in General Circulation Models (GCMs). This scheme relies on an energy analysis to determine the final adjusted atmospheric state. Our convection scheme produces results that agree with our CM1 simulations and can easily be implemented in GCMs to improve modelling of compositional convection in exoplanet atmospheres.

References in corpus (10)

• Mass-Radius Relationships for Solid Exoplanets
• Habitability and Biosignatures of Hycean Worlds
• Condensation-inhibited convection in hydrogen-rich atmospheres: Stability against double-diffusive processes and thermal profiles for Jupiter, Saturn, Uranus, and Neptune
• Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System
• Earth shaped by primordial H${}_2$ atmospheres
• TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). Motivations and protocol version 1.0
• Atmospheric convection plays a key role in the climate of tidally-locked terrestrial exoplanets: insights from high-resolution simulations
• Convective inhibition with an atmosphere, I: super-critical cores on sub-Neptune/super-Earths
• Effects of Radius and Gravity on the Inner Edge of the Habitable Zone
• Idealised 3D simulations of diabatically-forced Ledoux convection. Application to the atmosphere of hot rocky exoplanets

Cited by in corpus (3)

• A 3D picture of moist-convection inhibition in hydrogen-rich atmospheres: Implications for K2-18 b
• Convective shutdown in the atmospheres of lava worlds
• 3D Modeling of Moist Convective Inhibition in Idealized Sub-Neptune Atmospheres