Atmospheric Circulation and Thermal Phase-Curve Offset of Tidally and Non-Tidally Locked Terrestrial Exoplanets

TL;DR

This study uses an idealised general circulation model to explore how atmospheric dynamics influence thermal phase curves of Earth-like exoplanets with various orbital configurations, including non-tidally locked planets.

Contribution

It demonstrates how non-stationary substellar points affect atmospheric jets and thermal phase curve offsets, expanding understanding beyond tidally-locked planet models.

Findings

Thermal phase curve offset depends on substellar point velocity.

Non-tidally locked planets can have east or west hotspots.

Strong upper troposphere jets form in slowly rotating planets.

Abstract

Using an idealised general circulation model, we investigate the atmospheric circulation of Earth-like terrestrial planets in a variety of orbital configurations. We relax the common assumption of the planet being tidally-locked, and look at the role atmospheric dynamics can have in the observed thermal phase curve when the substellar point is non-stationary. In slowly rotating planets, a moving forcing can induce strong jets in the upper troposphere, both prograde and retrograde, sensitive to the speed and direction of the diurnal forcing. We find that, consistent with previous shallow water model experiments, the thermal phase curve offset is sensitive to the velocity of the substellar point moving across the surface of the planet. For a planet with a known orbital period, the results show that the observed hotspot on the planet could be either east or west of the substellar point, depending on whether the planet is tidally-locked or not.