STUDY OF BAROTROPIC MODEL FLOWS: INTERMITTENCY, WAVES AND PREDICTABILITY.

The regime flows corresponding to the barotropic nondivergent equation with forcing, drag and subgrid-scale are studied using spectral models on the plane and on the sphere. The flow regimes obtained exhibit clear evidence of the existence of an entrophy-cascading inertial range, together with a reverse energy cascade toward small wavenumbers. It is shown, however, that the entrophy cascade is not associated with the k** minus **3 spectral slope expected from the Kolmogorov-Kraichnan theory of two-dimensional turbulence; the slopes obtained are significantly steeper. This apparent paradox is tentatively resolved by a phenomenological theory of space-time intermittency in two dimensions. The effect of differential rotation in connection with Rossby wave propagation is also studied.