The influence of stationary heating on time mean atmospheric flow forced to be equivalent barotropic

Abstract

In this paper, the use of an equivalent-barotropic model for the simulation of the atmospheric state, averaged over some time-interval, is discussed. This simulation may be arranged in such a way that the geopotential fields of the time-mean and barotropic flow are identical, implying that the real mean vertical velocity field is determined by the vertical velocity in the barotropic model and the eddy-transfer of heat or vorticity. As an application, the influence of stationary heating at the lower boundary of an equivalent-barotropic atmosphere is studied by using linear quasi-geostrophic theory. It appeared that the phase (with respect to the heating field) and amplitude of the forced waves are very sensitive to the mean zonal wind and the wavelength. On the basis of the results it is argued that some statistical relations concerning the large-scale ocean-atmosphere interaction may be explained by assuming that the anomaly field of the mean heating at the top of the boundary layer is directly proportional to the sea-surface temperature anomaly field.