Accuracy evaluation of global tidal models in the Bohai Sea via the combination of tide gauges and GFO satellite altimeters

Abstract

Accuracy assessments of global tide models are essential for practical applications such as navigation and tidal correction in satellite altimetry. Traditionally, model accuracy assessment is performed by comparing global tide models with point-based tide gauges which are spatially limited in terms of number and location. To address the issue of the scarcity of tide gauges in the sea areas of interest, previous studies have introduced tide-favourable Topex/Poseidon (T/P)-Jason series as supplements in the course of model evaluation. However, the overlap of T/P-Jason series in model construction and evaluation may destroy the reliability of their evaluation results. In this study, we evaluate the accuracy of five popular global tide models (EOT20, FES2014, TPXO9, HAMTIDE12, and DTU16) in the Bohai Sea via the combination of four tide gauges and ∼8-year Geosat Follow-On (GFO) satellite altimeter records. The wide coverage of GFO data and their independence from analyzed global tide models guarantee the reliability of our findings. The results from GFO data and tide gauges are highly consistent, both revealing the superiority of FES2014 and the poor performances of TPXO9 and HAMTIDE12 in the Bohai Sea. The performances of FES-referenced models (EOT20 and DTU16) are generally good but slightly worse than that of FES2014. Of note, tidal amplitudes of eight major constituents derived from TPXO9 are abnormally small in the Bohai Sea. As water depths decrease, the errors of all five global tide models elevate notably, indicting the challenges in modelling coastal tides which may necessitate further exploration and improvements.