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

Energy balance models (EBMs), alongside radiative-convective climate models (RCMs) 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-rotating 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 present Earth, early Mars, TRAPPIST-1e 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 (THAI) comparison project. Overall, 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 two-dimensional 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.Comment: Accepted into The Planetary Science Journal (35 pages, 12 Figures, 4 Tables

A more comprehensive habitable zone for finding life on other planets

The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are CO2 and H2O. Although the classical HZ is an effective navigational tool, recent HZ formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. Here, I review the planetary and stellar processes considered in both classical and newer HZ formulations. Supplementing the classical HZ with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. Such improved HZ tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets.Comment: Published in Geosciences. Invited review for the "Planetary Evolution and Search for Life on Habitable Planets" Special Issue (58 pages, 15 Figures, 1 Table). Fixed a typo in Table 1 and updated acknowledgements (was not fixed in v2). http://www.mdpi.com/2076-3263/8/8/280/ht