Sensitivity study on the main tidal constituents of the Gulf of Tonkin by using the frequency-domain tidal solver in T-UGOm

Abstract

Abstract. Consequences of tidal dynamics on hydro-sedimentary processes are a recurrent issue in estuarine and coastal processes studies, and accurate tidal solutions are a prerequisite for modeling sediment transport, especially in macro-tidal regions. The motivation for the study presented in this publication is to implement and optimize a model configuration that will satisfy this prerequisite in the frame of a larger objective in order to study the sediment dynamics and fate from the Red River Delta to the Gulf of Tonkin from a numerical hydrodynamical–sediment coupled model. Therefore, we focus on the main tidal constituents to conduct sensitivity experiments on the bathymetry and bottom friction parameterization. The frequency-domain solver available in the hydrodynamic unstructured grid model T-UGOm has been used to reduce the computational cost and allow for wider parameter explorations. Tidal solutions obtained from the optimal configuration were evaluated from tide measurements derived from satellite altimetry and tide gauges; the use of an improved bathymetry dataset and fine friction parameter adjustment significantly improved our tidal solutions. However, our experiments seem to indicate that the solution error budget is still dominated by bathymetry errors, which is the most common limitation for accurate tidal modeling.

Variability of the Red River Plume in the Gulf of Tonkin as Revealed by Numerical Modeling and Clustering Analysis

“…Due to the variable horizontal grid, the coastal area near the RR mouths has a fine horizontal resolution of 300 m, while near the open boundary, the grid size can increase to 4500 m (Figure 2A). As the coastal area adjacent to the RR delta is characterized by a complex topography, with many islands and islets, a considerable effort has been devoted to the construction of the model bathymetry and shorelines and is described in Piton et al (2020). In particular, the bathymetry is reconstructed from GEBCO 2014 combined with other sources and field surveys.…”

“…The Gulf of Tonkin (16.9 • N -21.9 • N, 105.6 • E -110 • E) is a small shelf sea located east of Vietnam and south of China with depth less than 100 m (Figure 1A). It is a meso-tidal region, dominated by diurnal constituents (K1, O1) as described for instance by Nguyen et al (2014) and Piton et al (2020). The ocean circulation of the Gulf of Tonkin (hereafter GOT) has been examined by several authors (e.g., Ding et al, 2013;Gao et al, 2014;Rogowski et al, 2019; for a recent review see Piton et al, 2021).…”

Background stratification impacts on internal tide generation and abyssal propagation in the western equatorial Atlantic and the Bay of Biscay

“…The T-UGOm (Toulouse Unstructured Grid Ocean model) has been used to simulate the ITs. Initially developed to resolve the two-dimensional tidal equations (Piton et al, 2020;Lyard et al, 2021a), this model has been extended to resolve the three-dimensional tidal equations in the frequency domain (Nugroho, 2017;Lyard et al, 2021b). The model configuration is set to be hydrostatic and with a free surface.…”

Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing

“…The differences between observed and modeled sea level can be explained by: (i) the location of the tide gauges near the coast, or near islands, where the model grid is too coarse to resolve local processes, or (ii) the sensitivity to the bottom drag parameterization in the numerical model. Simulated tides are sensitive to the bathymetry, the bottom roughness and to the friction law (linear, quadratic, and logarithmic) (Toublanc et al, 2018;Piton et al, 2020). Despite these differences and since the Bay of Biscay is energetic in M2 and S2 tidal harmonics, the numerical model performance is satisfactory for the simulations of tides.…”