Atmospheric circulation of tidally locked exoplanets: II. Dual-band radiative transfer and convective adjustment

TL;DR

This paper advances 3D atmospheric models of exoplanets by integrating dual-band radiative transfer and convective adjustment, enhancing realism in simulating temperature profiles and circulation patterns.

Contribution

It introduces a novel combination of radiative transfer and convective schemes into 3D exoplanet atmospheric simulations, bridging purely dynamical models and more comprehensive radiative ones.

Findings

Temperature-pressure profiles vary with atmospheric composition.

Presence or absence of temperature inversions depends on radiative processes.

Hot spot offsets are robust indicators of atmospheric dynamics.

Abstract

Improving upon our purely dynamical work, we present three-dimensional simulations of the atmospheric circulation on Earth-like (exo)planets and hot Jupiters using the GFDL-Princeton Flexible Modeling System (FMS). As the first steps away from the dynamical benchmarks of Heng, Menou & Phillipps (2011), we add dual-band radiative transfer and dry convective adjustment schemes to our computational setup. Our treatment of radiative transfer assumes stellar irradiation to peak at a wavelength shorter than and distinct from that at which the exoplanet re-emits radiation ("shortwave" versus "longwave"), and also uses a two-stream approximation. Convection is mimicked by adjusting unstable lapse rates to the dry adiabat. The bottom of the atmosphere is bounded by a uniform slab with a finite thermal inertia. For our models of hot Jupiters, we include an analytical formalism for calculating temperature-pressure profiles, in radiative equilibrium, which accounts for the effect of collision-induced absorption via a single parameter. We discuss our results within the context of: the predicted temperature-pressure profiles and the absence/presence of a temperature inversion; the possible maintenance, via atmospheric circulation, of the putative high-altitude, shortwave absorber expected to produce these inversions; the angular/temporal offset of the hot spot from the substellar point, its robustness to our ignorance of hyperviscosity and hence its utility in distinguishing between different hot Jovian atmospheres; and various zonal-mean flow quantities. Our work bridges the gap between three-dimensional simulations which are purely dynamical and those which incorporate multi-band radiative transfer, thus contributing to the construction of a required hierarchy of three-dimensional theoretical models.