A parametric study of atmospheric superrotation on Venus-like planets: Effects of oblique angle of planetary rotation axis

Parametric experiments of superrotation on slowly rotating planets, such as Venus, were conducted. The oblique angle of the planetary rotation axis is one of the most important parameters in the dynamics of the superrotation. New relationships are found for the maximum mean zonal flow, meridional flow, and equatorpole temperature difference. For low obliquity, the dynamic state alternates between weak and strong superrotations with a period of about 10000 days in the phase space, and small fluctuations of about 1000 days are also seen. Fully-developed superrotation is maintained by meridional circulation and waves in the case of a slightly oblique angle. However, it is not formed in the case of a highly oblique angle, since the vertical transport of angular momentum due to meridional circulation is ineffective at the solstices. The superrotational wind becomes larger with decreasing obliquity.