Altimetry over open ocean is a mature discipline, useful for process studies and operational forecasting. In coastal zones (the strip of land within a few tens of kilometres from a coast) data are often discarded because it is not known how to interpret or model land contamination effects on altimetric waveforms.
There are intrinsic difficulties in making corrections especially in the wet tropospheric component, high-frequency atmospheric and oceanic signals and tides.
The Sentinel-3 SRAL improved along-track resolution (approximately 250 m) in SAR mode facilitates sea surface height measurement close to the coast. The SRAL instrument is in SAR mode over coastal zones. The Level-2 SRAL/MWR products have a parameter indicating the distance to the coast as well as dedicated coastal geophysical corrections (e.g. Composite wet tropospheric correction).
New disseminated Level-1 products (Level-1A, Level-1B-s and Level-1B) allow improving sea surface height measurement over the coast through the possibility of improving and customising land contamination and retracking techniques.
Figure 1: Modification of the shape waveforms (in red) when a satellite altimeter approaches the coast entering the radar footprint, making the estimate of range and other derived quantities more difficult. (Credit: COASTALT)
For further information about ocean applications and services available, see: Copernicus website.