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Abstract:
With the discovery of numerous exoplanets in the past 30 years, the number of known terrestrial planets, which are believed to host substantial atmospheres, has increased significantly and with it the likely range of parameters determining their yet-to-be-understood climates and circulations. In controlled laboratory studies, insights are gained into processes underlying circulations by systematically mapping flow regimes within a suitable parameter space. Motivated by this, several studies employ such a parametric approach for planetary atmospheres using simplified numerical models.In succession of those studies, the regimes of atmospheric general circulation patterns in Earth-like atmospheres are investigated by varying the planetary rotation rate and radiative equilibrium temperature profile using the dry dynamical core model setup EMIL within the MESSy framework updated for terrestrial planets containing a Newtonian cooling scheme. A superrotating, barotropically unstable cyclostrophic atmosphere is obtained at low rotation rates, turning geostrophic - first with regular and then chaotic baroclinic waves - with increasing rotation rates and eventually exhibiting multiple jets. These regimes, plus the quasi-axisymmetric one at low equator-to-pole temperature differences, are classified quantitatively by introducing several global indices validated by a clustering approach.These circulation regimes are interpreted in terms of the axisymmetric Held-Hou theory and the Quasi-Geostrophic theory. They are contrasted with the major features of the rotating annulus regime diagram, which includes an upper symmetric regime in contrast to the developed atmospheric model regime diagram. Finally, those considerations are used to place Venus, Mars, and Earth into an appropriate dynamical context.
