Implications of a Surface on Atmospheric Circulation

Atmospheres of gaseous and terrestrial planets have been well studied, with most work focussing on only one of these types of planets. However, with the understanding that a transition between the two populations of planets occurs around 1.6 Earth Radii, a natural question arises: For planets near this transition, are there significant differences in atmospheric circulation when a surface is introduced into the atmosphere? In this work, we present the first results from a 3D General Circulation Model modified to study the entire range of planetary sizes from Earth-like to Neptune-like, with the ability to focus in on planetary sizes that are equally likely to be gaseous or terrestrial. Using the same modeling framework for both types of planets allows us to make direct comparisons and predictions for how a surface affects the circulation of planets near the transition between gaseous and terrestrial compositions. Further, for exoplanets with ambiguous densities, we make predictions for the observability of these differences as an independent way to differentiate between gaseous and terrestrial probabilities when aerosols limit our ability to directly constrain atmospheric composition. 

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