“…Similar problems to the one presented in (1.1) have been studied by several authors, who in different ways inspected the well-posedness issues and the asymptotic analysis of models for geophysical flows. For example, in the context of compressible fluids, we refer to [7], [29], [32] for the first works on 2-D viscous shallow water models (see also [17], [19], [20] for the inviscid case), to [22], [23], [26], [27] for the barotropic Navier-Stokes system and to [37] for weakly compressible and inviscid fluids (see also [25] for other singular limits in thermodynamics of viscous fluids). In the compressible case, the fact that the pressure is a given function of the density implies a double advantage in the analysis: on the one hand, one can recover good uniform bounds for the oscillations (from the reference state) of the density; on the other hand, at the limit, one disposes of a stream-function relation between the densities and the velocities.…”