A Scaling Theory for Atmospheric Heat Redistribution on Rocky Exoplanets

Daniel D. B. Koll

Published 2019-07-30Version 1

Atmospheric heat redistribution shapes the remote appearance of rocky exoplanets but there is currently no easy way to predict a planet's heat redistribution from its physical properties. In this paper I derive an analytical scaling theory for the heat redistribution on tidally locked rocky exoplanets. The main parameters of the theory are a planet's equilibrium temperature, its surface pressure, and its broadband longwave optical thickness. I validate the theory against general circulation model simulations of TRAPPIST-1b, GJ1132b, and LHS 3844b. I find that heat redistribution becomes efficient, and a planet's observable thermal phase curve and secondary eclipse start to deviate significantly from that of a bare rock, once surface pressure exceeds O(1) bar. These results thus bridge the gap between theory and imminent observations with the James Webb Space Telescope. They can also be used to parameterize the effect of 3D atmospheric dynamics in 1D models, thereby improving the self-consistency of such models.