Sea Modeling by Microwave Altimetry

Abstract: In this note the applications of altimeter data to the monitoring of the sea surface height and, in particular, to the evaluation of large-scale oceanic currents are reviewed. The general problem of the altimeter measurement, with a special reference to the TOPEX/POSEIDON mission, is discussed. The decomposition of the sea surface height anomaly into its various components (tides, inverted barometer, steric height, height associated to geostrophic currents) is then considered. For each component a brief description of the physics of the associated phenomenon is given, along with references to the related recent scientific literature. A special emphasis is put on the determination of oceanic geostrophic currents. Therefore, the methods used to eliminate the components of the sea surface height anomaly not related to geostrophy are discussed. The derivation of near-surface currents and of depth-dependent currents with the aid of hydrographic data is considered in some detail. Finally, oceanic wind-driven models, in particular the time-dependent Sverdrup balance, are discussed in connection with altimeter data. 1