Thermal convection in rotating systems

Convection in rotating systems exhibits a rich variety of phenomena not only because of the additional parameter of rotation but also because in addition to the static solution there exist other non-convecting states corresponding to thermal wind solutions from which convective states bifurcate. In this review, cases of geophysical and astrophysical relevance are emphasized. The two problems of convection in horizontal fluid layers heated from below and rotating either about a vertical (case A) or a horizontal (case B) axis of rotation serve as an introduction to the subject since they characterize convection in polar and equatorial regions of spherical shells. The contrasting properties of the two cases have been exhibited by linear and nonlinear theories and by experimental observations. Recently studied features include the generation of mean zonal flows by convection in case B and the unusual occurrence in case A of an infinite number of steady states all of which are unstable.