The hydrothermodynamics of upwelling and downwelling events as a consequence of successively wind field changes are investigated using a 1 1/2 layer numerical model for open and limited coastal regions. The model includes the essential dynamical processes. Solutions are found in a regional ocean basin and are forced by non-uniform and time-dependent wind fields. The study case is the Cabo Frio Coast (Rio de Janeiro, Brazil), a very sensitive hydrodynamic coastal system, where the passage of cold fronts modifies completely the NE wind prevailing pattern (favourable to upwelling events) to SW winds (favourable to downwelling). The model is successful in simulating many features of observed patterns. Initially, the numerical experiments include a simple corner coastline shape, relevant to the Cabo Frio region, to understand the mechanisms and to clarify the relative importance of different factors in producing the strong property gradients typical of upwelling areas. The coastal ocean is forced by different wind patterns including non-permanent wind field rotations. Later, the goal of this paper, the observed SST variability during typical summer months in the coastal region of Cabo Frio, is simulated numerically. The change of SST is reproduced with a good degree of approximation, when upwelling and downwelling events take place. The role of some physical processes and the initial conditions is clarified, isolating their effects. The obtained results demonstrate that the existing theory of upper layer dynamics formulated in the proposed simple model account for the observed phenomena on occasion of upwelling-downwelling cycles caused by variable wind in space and time. © 2003 Elsevier Ltd. All rights reserved.