Repeated Cyclogenesis on Hot-Exoplanet Atmospheres with Deep Heating

TL;DR

This study uses high-resolution simulations to show that deep heating in hot-exoplanet atmospheres causes repeated cyclogenesis and turbulence, leading to observable differences in thermal flux compared to shallow heating models.

Contribution

It introduces a new dynamic equilibrium state with cyclonic storms caused by deep heating, expanding understanding of atmospheric dynamics on hot exoplanets.

Findings

Deep heating induces repeated cyclonic storms.

Thermal flux varies significantly with heating depth.

Turbulence and mixing occur on a timescale of about 3 planetary rotations.

Abstract

Most current models of hot-exoplanet atmospheres assume shallow heating, a strong day-night differential heating near the top of the atmosphere. Here we investigate the effects of energy deposition at differing depths in a model tidally locked gas-giant exoplanet. We perform high-resolution atmospheric flow simulations of hot-exoplanet atmospheres forced with idealized thermal heating representative of shallow and deep heating (i.e., stellar irradiation strongly deposited at $\sim 10^3$ Pa and $\sim 10^5$ Pa pressure levels, respectively). Unlike with shallow heating, the flow with deep heating exhibits a new dynamic equilibrium state, characterized by repeated generation of giant cyclonic storms that move away westward once formed. The formation is accompanied by a burst of heightened turbulence, leading to the production of small-scale flow structures and large-scale mixing of temperature on a timescale of $\sim 3$ planetary rotations. Significantly, while effects that could be important (e.g., coupled radiative flux and convectively excited gravity waves) are not included, over a timescale of several hundred days the simulations robustly show that the emergent thermal flux depends strongly on the heating type and is distinguishable by current observations.