FINITE-AMPLITUDE CONVECTION IN ROTATING SPHERICAL FLUID SHELLS

Finite-amplitude convection in rotating spherical fluid shells is cons idered for a variety of Prandtl numbers P and Rayleigh numbers Ra up t o about 10 times the critical value. Convection at low Rayleigh number s in the form of azimuthally periodic or weakly aperiodic drifting wav es is characterized by relatively low heat transport, especially for P less than or similar to 1. The transition to strongly time-dependent convection leads to a rapid increase of the heat transport with increa sing Rayleigh numbers. Onset of convection in the polar regions is del ayed, but contributes a disproportionate fraction of the heat transpor t at high Rayleigh number. The differential rotation generated by conv ection, the distributions of helicity, and the role of asymmetry with respect to the equatorial plane are also studied.