Atmospheric Circulation and Thermal Phase-curve Offset of Tidally and Nontidally Locked Terrestrial Exoplanets

Abstract

Using an idealized 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 nonstationary. 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 hot spot on the planet could be either east or west of the substellar point, depending on whether the planet is tidally locked or not.