Abstract
Satellite altimetry, measuring sea surface heights (SSHs), has unique capabilities to provide information about the ocean dynamics. In this paper, the skill of the original full rate (10/20Hz) measurements, relative to conventional 1-Hz data, is evaluated in the context of coastal studies in the Northwestern Mediterranean Sea. The performance and the question of the measurement noise are quantified through a comparison with different tide gauge sea level time series. By applying a specific processing, closer than 30km to the land, the number of valid data is higher for the 10/20-Hz than for the 1-Hz observations: +4.5% for T/P, +10.3 for Jason-1 and +13% for Jason-2. By filtering higher sampling rate measurements (using a 30-km cut-off low-pass Lanczos filter), we can obtain the same level of sea level accuracy as we would using the classical 1-Hz altimeter data. The gain in near-shore data results in a better observation of the Liguro–Provençal–Catalan Current. The seasonal evolution of the currents derived from 20-Hz data is globally consistent with patterns derived from the corresponding 1-Hz observations. But the use of higher frequency altimeter measurements allows us to observe the variability of the regional flow closer to the coast (~10–15km from land).
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