Abstract

Abstract This study aims to show that Lagrangian surface drifters are a suitable means of validating the mapping of oceanic mesoscale circulation by satellite altimetry. Tests are done using Geosat data to simulate drifter trajectories in the Azores-Madeira area. Multivariate objective analysis is then done to estimate the dynamic topography and its associated formal error using the velocity measurements obtained along drifter trajectories. This dynamic-topography field is compared with the reference field as given by Geosat data. Sensitivity to drifter number and energy level is studied. It is shown that with 25 drifters in a 500-km × 500-km area, the dynamic topography is obtained to within a formal accuracy of around 10%–20%. The difference between the estimated and reference fields is below 2 cm rms. These errors are smaller than the mapping errors induced by the space-time sampling of ERS-1 or TOPEX-POSEIDON satellites. According to these preliminary results, surface drifters are an efficient tool fo...

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