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[1] Satellite altimetry has proven to be a useful tool to study oceanic processes in the deep ocean. Over continental shelves, however, the aliasing of unresolved high-frequency signals of tidal and wind-induced origin is the source of long-wavelength errors that corrupt altimetry measurements and limit their use in shallow waters. In 2005, SSALTO/DUACS performed a complete reanalysis of altimeter data to accommodate the latest tidal model (GOT2000) and a correction for the aliased high-frequency signals using a hydrodynamic model MOG2D-G. This paper examines the quality and the performance of the newly released altimetry data over the northwest European shelf. This region is known for complex tides and for frequent storm surges. The newly corrected maps of sea level anomalies were compared with a previous altimetry product. Residual tidal aliasing was analyzed, and the impact of MOG2D-G and GOT2000 models was assessed. Altimeter records were compared with tide gauge measurements. This research showed a significant reduction in the contamination of data by high-frequency aliasing achieved through the use of the aforementioned models. However, aliased shallow-water tidal constituents pose a serious problem, and it is obvious that future tidal corrections should feature local tides. Nonaliased, physical sea level variability was also studied focusing on interannual, seasonal, and intra-annual (periods from 20 days to 1 year) modes. The magnitudes and the contributions of each mode to the total variance were estimated. It was demonstrated that the newly corrected data can successfully be used to study the variability of sea level over continental shelves.Citation: Volkov, D. L., G. Larnicol, and J. Dorandeu (2007), Improving the quality of satellite altimetry data over continental shelves,

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[1] The Indian Ocean tsunami, which occurred on December 26, 2004, was the first to be clearly observed using satellite altimeters. The wave amplitude observed in deep-ocean by TOPEX and Jason-1 was close to 60 cm about 2 hours after the earthquake. Envisat crossed the tsunami wave 3h15 after the earthquake and measured a 35 cm wave. Even though it flew over the tsunami 7h20 after the earthquake, GFO still observed a wave close to 20 cm. To better extract the tsunami signal from altimeter measurements, a specific ocean variability mapping technique is used. This technique proves to be mandatory for discriminating tsunami waves from other ocean signals. Altimeter signals are then compared with those derived from the CEA (Commissariat à l'Energie Atomique) model outputs. For the first time with altimeter data, peculiar short wavelengths signals along Jason-1 and Envisat profiles have been detected from the analysis of 20-Hz altimeter measurements. Such high wavenumber signals can be explained by the dispersive propagation of tsunami waves. These observations highlight the essential role of satellite altimeter measurements to better understand and to improve models of tsunami wave propagation and dissipation.