THE CALCULATION OF THE DYNAMIC SEA-SURFACE TOPOGRAPHY AND THE ASSOCIATED FLOW-FIELD FROM ALTIMETRY DATA - A CHARACTERISTIC FUNCTION-METHOD

The quasi-stationary sea surface topography (QSST) and associated ocea nic circulation is determined by means of a characteristic function te chnique. The method was originally implemented in an ideal simplified case. The present application involves a 4 degrees x 4 degrees grid in spherical coordinates approximating the boundaries of the main ocean basins. The data field is provided by the first year of altimetric dat a from the TOPEX/POSEIDON mission. The method requires the numerical d etermination of the eigenfunctions spanning the streamfunction field a nd the associated characteristic functions from the balance equation. The former yields the flow field and the latter the surface height dis tribution, or QSST These functions are determined by the geometry and topography of the ocean basins and satisfy the linear steady-state dyn amical equations. They are defined within the basins only and avoid th e problems encountered when using functions defined over the entire sp here. The velocity field can be computed over the entire ocean area, i ncluding the equatorial regions. The coefficients of the height functi ons have been determined by fitting the surface height field provided by TOPEX altimetry. Seasonal variations have been computed by subtract ing a 32-cycle solution from each of the four 8-cycle seasonal solutio ns.