Validation and application of model/reanalysis sea-level data to the establishment of the reference hydrographic surface in Spanish waters

ABSTRACT Sea-level reanalysis data fields from the Iberia-Biscay-Ireland Monitoring and Forecasting Center (IBIre) were analysed and validated with coastal tide-gauge and vertical positioning data from 110 experimental stations, complemented with the Technical University of Denmark global ocean tide model and mean dynamic topography DTU10, in order to establish the reference hydrographic surface (RHS) for Spanish waters. IBIre fitting to experimental tidal ranges, with mean errors about 10 cm, improves the DTU10 results along the Iberian Mediterranean shore due to an adequate reproduction of the ‘radiational’ tides. Regarding the mean dynamic topography, errors were also about 10 cm both for IBIre and DTU10 fields, and about 50% of them is plausibly related to the experimental uncertainness arising from the different averaging periods of observed series. Fitting of IBIre results to experimental data provides orthometric/ellipsoidal heights of the lowest astronomical tide with mean errors between 7 and 10 cm. IBIre sea-level data have enough quality to constitute a reliable basis for an operative RHS in Spanish waters, and plausibly in other regions within its spatial coverage. Moreover, IBIre sea-level data have other potential applications to the study of climate/sea-level trends, and improvements of the accuracy in de-tiding satellite-altimetry data in the western Mediterranean Sea.