From Super-Earths to Mini-Neptunes: Implications of a Surface on Atmospheric Circulation

It is well known that planets with radii between that of Earth and Neptune have been the most commonly detected to date. To classify these planets as either terrestrial or gaseous, typically we turn to mass-radius relations and composition curves to determine the likelihood of such a planet being rocky or gaseous. While these methods have set a likely transition radius of approximately 1.5 R⊕, we cannot expect that any change between terrestrial and gaseous compositions will be a sharp cutoff, and composition curve predictions result in ambiguous designations for planets right near this transition radius. In this work, we present 3D general circulation models (GCMs) of transition planets, wherein we study the effects of a surface on observable quantities such as the latitudinal variations and eclipse depths. We present our updated GCM, validated on the circulation of Earth, before discussing our modeling choices for this transition planet. Finally, we discuss the results of this study and explore the prospects of detecting the presence of a surface through observations of secondary eclipses in the future.