Abstract
Abstract. EOT20 is the latest in a series of empirical ocean tide (EOT) models derived using residual tidal analysis of multi-mission satellite altimetry at DGFI-TUM. The amplitudes and phases of 17 tidal constituents are provided on a global 0.125∘ grid based on empirical analysis of seven satellite altimetry missions and four extended missions. The EOT20 model shows significant improvements compared to the previous iteration of the global model (EOT11a) throughout the ocean, particularly in the coastal and shelf regions, due to the inclusion of more recent satellite altimetry data as well as more missions, the use of the updated FES2014 tidal model as a reference to estimated residual signals, the inclusion of the ALES retracker and improved coastal representation. In the validation of EOT20 using tide gauges and ocean bottom pressure data, these improvements in the model compared to EOT11a are highlighted with the root sum square (RSS) of the eight major tidal constituents improving by ∼ 1.4 cm for the entire global ocean with the major improvement in RSS (∼ 2.2 cm) occurring in the coastal region. Concerning the other global ocean tidal models, EOT20 shows an improvement of ∼ 0.2 cm in RSS compared to the closest model (FES2014) in the global ocean. Variance reduction analysis was conducted comparing the results of EOT20 with FES2014 and EOT11a using the Jason-2, Jason-3 and SARAL satellite altimetry missions. From this analysis, EOT20 showed a variance reduction for all three satellite altimetry missions with the biggest improvement in variance occurring in the coastal region. These significant improvements, particularly in the coastal region, provide encouragement for the use of the EOT20 model as a tidal correction for satellite altimetry in sea-level research. All ocean and load tide data from the model can be freely accessed at https://doi.org/10.17882/79489 (Hart-Davis et al., 2021). The tide gauges from the TICON dataset used in the validation of the tide model, are available at https://doi.org/10.1594/PANGAEA.896587 (Piccioni et al., 2018a).
Highlights
The regular fluctuations of the sea surface caused by ocean tides have intrigued and fascinated scientists for centuries based on their influence on oceanic processes
EOT20 follows a similar scheme as the former model, EOT11a, consisting of three major steps: the creation of an sea level anomaly (SLA) product including the correction of a reference ocean tide model; the estimation of the residual tides based on this SLA product; and the combination of the reference model with the residual tides to form a new global ocean tide model
Significant changes and additions have been done to EOT20 with the objective of improving coastal estimations. These changes are in the reference tide model used in the residual analysis, the use of more recent developments in coastal altimetry, the increased coverage of satellite altimetry based on the launching of further missions (e.g. Jason-3), the use of an accurate land–sea mask onto the model output data, and using a triangular grid for the residual analysis
Summary
The regular fluctuations of the sea surface caused by ocean tides have intrigued and fascinated scientists for centuries based on their influence on oceanic processes. EOT11a (Savcenko and Bosch, 2012), the latest in a series of global ocean tide models developed at DGFI-TUM, is an example of a semi-empirical tide model developed using residual tidal analysis of multi-mission satellite altimetry. The model has continued to be developed, with regional studies being conducted by Piccioni et al (2021) based on improvements being made in the coastal region These improvements are largely driven by the progresses in accuracy and precision of altimetry measurements in the coastal zone and the use of the updated FES2014 (Lyard et al, 2020) tide model as the reference model for the residual tidal analysis.
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