Earth${}^{\prime }$s polar night boundary layer as an analogue for dark side inversions on synchronously rotating terrestrial exoplanets

Abstract

A key factor in determining the potential habitability of synchronously rotating planets is the strength of the atmospheric boundary layer inversion between the dark side surface and the free atmosphere. Here we analyse data obtained from polar night measurements at the South Pole and Alert Canada, which are the closest analogues on Earth to conditions on the dark sides of synchronously rotating exoplanets without and with a maritime influence, respectively. On Earth, such inversions rarely exceed 30 K in strength, because of the effect of turbulent mixing induced by phenomena such as so-called mesoscale slope winds, which have horizontal scales of 10s to 100s of km, suggesting a similar constraint to near-surface dark side inversions. We discuss the sensitivity of inversion strength to factors such as orography and the global-scale circulation, and compare them to a simulation of the planet Proxima Centauri b. Our results demonstrate the importance of comparisons with Earth data in exoplanet research, and highlight the need for further studies of the exoplanet atmospheric collapse problem using mesoscale and eddy-resolving models.

arXiv commentAccepted by Astrophysical Journal Letters; 14 pages, 3 figures

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• Prospects for water vapor detection in the atmospheres of temperate and arid rocky exoplanets around M-dwarf stars
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• 3D simulations of TRAPPIST-1e with varying CO2, CH4 and haze profiles
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• Meta-modelling the climate of dry tide locked rocky planets
• Lightning activity on a tidally locked terrestrial exoplanet in storm-resolving simulations for a range of surface pressures