  The baroclinic instability problem is considered in the framework of
Laplacian tidal theory. The Hilbert space of the quasigeostrophic vorticity
budget is spanned by spheroidal functions. The fluid is linearly stable against
quasigeostrophic disturbances. As the essential source of irregular
ocean-atmosphere motions, baroclinic instability is ruled out by tidal theory.
The midlatitude beta-plane budget of vorticity fluxes is inconsistent with
basic laws of motion on the rotating spherical surface. Realistic numerical
simulations of global wave dynamics and dynamical circulation instabilities
require a covariant account of fluid motion on the spherical planet.
