A NOTE ON THE BAROTROPIC RESPONSE OF SEA-LEVEL TO TIME-DEPENDENT WINDFORCING

This study examines the extent to which sea level variations at period s between 30 days and 1 year and spatial scales greater than 1000 km c an be described by the wind-driven linear barotropic vorticity dynamic s. The TOPEX/POSEIDON altimetric observations of sea level and the win d products of the National Meteorological Center are used as the datab ase for the study. Each term of the linear barotropic vorticity equati on was evaluated by averaging over regions of 10 degrees x 10 degrees. In most of the open ocean the result of the analysis suggests that th e sea level variabilities at the scales considered cannot be fully des cribed by the equation; the apparent net vorticity change is more than what can be explained by the local wind stress curl. In the few regio ns where the wind stress curl is strong enough to balance the vorticit y budget, predominantly in the northeast Pacific and the southeast Pac ific, the balance is basically achieved in terms of the time-dependent topographic Sverdrup relation, namely, the balance between the advect ion of the planetary vorticity plus the topography-induced vorticity a nd the forcing by the wind stress curl.