A New 2D Energy Balance Model for Simulating the Climates of Rapidly and Slowly Rotating Terrestrial Planets

Abstract

Abstract Energy balance models (EBMs), alongside radiative–convective climate models and global climate models (GCMs), are useful tools for simulating planetary climates. Historically, planetary and exoplanetary EBMs have solely been 1D latitudinally dependent models with no longitudinal dependence, until the study of Okuya et al., which focused on simulating synchronously rotating planets. Following the work of Okuya et al., I have designed the first 2D EBM (PlaHab) that can simulate N2–CO2–H2O–H2 atmospheres of both rapidly and synchronously rotating planets, including Mars, Earth, and exoplanets located within their circumstellar habitable zones. PlaHab includes physics for both water and CO2 condensation. Regional topography can be incorporated. Here, I have specifically applied PlaHab to investigate the present Earth, early Mars, TRAPPIST-1 e, and Proxima Centauri b, representing examples of habitable (and potentially habitable) worlds in our solar system and beyond. I compare my EBM results against those of other 1D and 3D models, including those of the recent Trappist-1 Habitable Atmosphere comparison project. Overall, the EBM results are consistent with those of other 1D and 3D models, although inconsistencies among all models continue to be related to the treatment of clouds and other known differences between EBMs and GCMs, including heat transport parameterizations. Although 2D EBMs are a relatively new entry in the study of planetary/exoplanetary climates, their ease of use, speed, flexibility, wide applicability, and greater complexity (relative to 1D models) may indicate an ideal combination for the modeling of planetary and exoplanetary atmospheres alike.