Atmospheric Circulation of Close‐in Extrasolar Giant Planets. I. Global, Barotropic, Adiabatic Simulations

We present results from a set of over 300 pseudospectral simulations of atmospheric circulation on extrasolar giant planets with circular orbits. The simulations are of high enough resolution (up to 341 total and sectoral modes) to resolve small-scale eddies and waves, required for reasonable physical accuracy. In this work, we focus on the global circulation pattern that emerges in a shallow, “equivalent-barotropic”, turbulent atmosphere on both tidally synchronized and unsynchronized planets. A full exploration of the large physical and numerical parameter-space is performed to identify robust features of the circulation. The model is validated with Solar System giant planets. For extrasolar giant planets with physical parameters similar to HD209458b—a presumably synchronized extrasolar giant planet representative in many dynamical respects—the circulation is characterized by the following features: 1) a coherent polar vortex that revolves around the pole in each hemisphere; 2) a low number—typically two or three— of slowly-varying, broad zonal (east-west) jets that form when the maximum jet speed – 2 – is comparable to, or somewhat stronger than, those observed on the planets in the Solar