Search

With 30 years of uninterrupted observations and more than 15 successful missions, satellite altimetry is a mature technology for investigating sea state variability at decadal timescales with global coverage. However, deriving robust long-term statistics from multi-mission products requires careful processing of each mission product in order to ensure inter-mission consistency and long-term stability. Over the last three years, the ESA Sea State Climate Change Initiative has been performing a full reprocessing of the SGDR products from Jason-1, ENVISAT, Jason-2, Cryosat-2, SARAL, and Sentinel-3A. This reprocessing benefits from recently developed waveform retrackers, consistent data editing and inter-calibration methods and an adaptive denoising approach designed for the analysis of non-stationary and non-linear signals. In this study, we present the method to calibrate the Jason-2 reference data against in situ observations and inter-calibrate the other missions using comparisons with this reference at crossover ground points. The validation of the results uses in situ observations, model results from ERA-5 reanalysis and WW3-IFREMER hindcast, and cross-comparisons of independent missions . A particular focus is given on the coastal zone and on low and extreme sea state data in order to discuss the performance of this new altimeter product with respect to standard products provided by the space agencies.

International audience; The wave runup is known to depend on the offshore wave conditions and the beach slope. While most field studies on wave runup have focused on low-to-mild sloping sandy beaches, runup measurements on steep and irregular rocky beach profiles are still very sparse. Hence, little is known on the physical processes affecting the wave runup in such environments, and the range of applicability of empirical runup formula requires further investigation. This study focuses on the steep (0.1 < tan β < 0.4) rocky cliffs of Banneg Island, a small island of the Iroise Sea occasionally flooded during extreme water level events. A statistical parameter for extreme runup is derived from the measurements of pressure sensors deployed in the intertidal zone. Deep water wave parameters and highresolution topographic data are analyzed concurrently with runup time-series in order to assess the dependence of the runup on hydrodynamic conditions and foreshore slopes. The wave runup is shown to be strongly related to the surf-similarity parameter times the offshore significant wave height. Given the large topographic variability of the beach profile, the method used to compute the beach slope is shown to strongly affects the results.