3D Model Uncertainty in Estimating the Inner Edge of the Habitable Zone

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Jun Yang1, Dorian S Abbot1, Eric T Wolf2, Jeremy Leconte3, Timothy M Merlis4, Daniel D.B. Koll1, Colin Goldblatt5, Feng Ding1, Francois Forget6 and Brian Toon7, (1)University of Chicago, Chicago, IL, United States, (2)University of Colorado at Boulder, Boulder, CO, United States, (3)LMD, CNRS, Paris, France, Paris, France, (4)McGill University, Montreal, QC, Canada, (5)University of Victoria, Victoria, BC, Canada, (6)CNRS, Paris Cedex 16, France, (7)University of Colorado at Boulder, Department of Atmospheric and Oceanic Sciences, Boulder, CO, United States
Accurate estimates of the width of the habitable zone are critical for determining which exoplanets are potentially habitable and estimating the frequency of Earth-like planets in the galaxy. Recently, the inner edge of the habitable zone has been calculated using 3D atmospheric general circulation models (GCMs) that include the effects of subsaturation and clouds, but different models obtain different results. We study potential sources of differences in five GCMs through a series of comparisons of radiative transfer, clouds, and dynamical cores for a rapidly rotating planet around the Sun and a synchronously rotating planet around an M star. We find that: (1) Cloud parameterization leads to the largest differences among the models; (2) Differences in water vapor longwave radiative transfer are moderate as long as the surface temperature is lower than 360 K; (3) Differences in shortwave absorption influences atmospheric humidity of synchronously rotating planet through a positive feedback; (4) Differences in atmospheric dynamical core have a very small effect on the surface temperature; and (5) Rayleigh scattering leads to very small differences among models. These comparisons suggest that future model development should focus on clouds and water vapor radiative transfer.