Tide model comparison over the Southwestern Atlantic Shelf

Abstract

Sea Surface Height (SSH) as measured by satellites has become a powerful tool for oceanographic and climate related studies. Whereas in the open ocean good accuracy has been achieved, more energetic dynamics and a number of calibration problems have limited applications over continental shelves and near the coast. Tidal ranges in the Southwestern Atlantic (SWA) continental shelf are among the highest in the world ocean, reaching up to 12 m at specific locations. This fact highlights the relevance of the accuracy of the tidal correction that must be applied to the satellite data to be useful in the region. In this work, amplitudes and phases of tidal constituents are extracted from five global tide models and three regional models and compared to the corresponding harmonics estimated from coastal tide-gauges (TGs) and satellite altimetry data. The Root-Sum-Square (RSS) of the misfit of the common set of the five tidal constituents solved by the models (M 2 , N 2 , S 2 , K 1 and O 1 ) is higher than 18 cm close to the coast for two of the regional models and higher than 24.5 cm for the rest of the models considered. Both values are too high to provide an accurate estimation of geostrophic non-tidal currents from satellite altimetry in the coastal region. On the other hand, the global model with the highest spatial resolution has a RSS lower than 4.5 cm over the continental shelf even when the non-linear M 4 overtide is considered. Comparison with in-situ current measurements suggests that this model can be used to de-tide altimetry data to compute large-scale patterns of SSH and associated geostrophic velocities. It is suggested that a local tide model with very high resolution that assimilates in-situ and satellite data should meet the precision 2 needed to estimate geostrophic velocities at a higher resolution both close to the coast and over the Patagonian shelf.

An investigation of ensemble-based assimilation of satellite altimetry and tide gauge data in storm surge prediction

“…Its one-third degree lat/lon resolution on the shelf is low, when compared to other current deterministic prediction models. In spite of its basic approach and coarseness, the SMARA model showed up to be comparable to global models with assimilation when validated with off-shore altimeter data (Saraceno et al 2010). Although coastal tidal ranges at the southern shelf are sub-estimated, its behaviour is well balanced throughout the Atlantic coast and the shelf.…”

Extraction of Tide Constituents by Harmonic Analysis Using Altimetry Satellite Data in the Brazilian Coast

“…It is a fact that the tide models have continually undergone tremendous improvements due to the use of orbital remotely sensed altimeter data in the last two to three decades or more. At the moment, most tide models have similar performances-that is, the tide output model differences are between a few centimeters and a maximum of 1 m in deep-water and shallow shelf regions, respectively (Zahran et al 2006;Saraceno et al 2010). The spatial resolution of GOT4.7 is 1 /28 3 1 /28, TPXO7.2 is 1 /48 3 1 /48, and FES2012 is 1 /168 3 1 /168.…”

“…The only question was whether TPXO7.2 or FES2012, which already includes remotely sensed altimeter data in its data assimilation process, could be considered an independent database for comparison with the HA results. Glorioso (2000) and Saraceno et al (2010) have discussed and justified the use of HA for comparison purposes based on the investigation of errors in the tide propagation scheme, which are particularly acute in areas of shallow water or complex bathymetry. Overall, their conclusions have pointed out that the errors are mainly due to low model skills over shelf and/or in some shallow water.…”

“…It is expected that a tide model with precise information about the mentioned physical parameters may accurately estimate, for example, the changes of a wave when it approaches the coast. Presently, there are no tidal models that include, in their contour conditions, precise information about bathymetry and the coastline of several regions and, the results from current tide models are still not very consistent near the coastal regions (Saraceno et al 2010). Several works have investigated the aforementioned problem and other related problems, for example, Schrama and Ray (1994), Smith and Sandwell (1997), Pascual et al (2006Pascual et al ( , 2007, Volkov et al (2007), and Ray (2008).…”

Research Article. Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

“…All these models comprise the eight diurnal and semi-diurnal constituents Q1, O1, P1, K1, N2, M2, S2, K2 in common with our regionalized model. For each of the models M and constituents w the RMS (root mean square) of the differences with respect to our regionalized model (index 0) was computed as [25] …”