Using high sampling rate (10/20Hz) altimeter data for the observation of coastal surface currents: A case study over the northwestern Mediterranean Sea

• Published in: Journal of marine systems 2014-01, Vol.129, p.318-333
• Main Authors: Birol, Florence, Delebecque, Caroline
• Format: Article
• Language: English
• Subjects: Coastal currents; Data processing; Earth Sciences; LPC current; North-western Mediterranean Sea; Oceanography; Satellite altimetry; Sciences of the Universe; Signal-to-noise ratio
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2013.07.009

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). •The use of original full rate (10/20-Hz) altimeter measurements is evaluated relative to conventional 1-Hz data.•The number of near-coastal sea level data is higher when using directly the 10/20-Hz altimeter measurements.•The performance of original full rate altimeter data is quantified through a comparison with tide gauge observations.•By filtering full rate altimeter data we can obtain the same level of accuracy as we would using the classical 1-Hz data.•The use of original full rate altimeter data allows us to observe the variability of the circulation closer to the coast.