Simulating the Coastal Ocean Circulation Near the Cape Peninsula Using a Coupled Numerical Model

Abstract

A coupled numerical hydrodynamic model is presented for the Cape Peninsula region of South Africa. The model is intended to support a range of interdisciplinary coastal management and research applications, given the multifaceted socio-economic and ecological value of the study area. Calibration and validation are presented, with the model reproducing the mean circulation well. Maximum differences between modelled and measured mean surface current speeds and directions of 3.9 × 10−2 m s−1 and 20.7°, respectively, were produced near Cape Town, where current velocities are moderate. At other measurement sites, the model closely reproduces mean surface and near-bed current speeds and directions and outperforms a global model. In simulating sub-daily velocity variability, the model’s skill is moderate, and similar to that of a global model, where comparison is possible. It offers the distinct advantage of producing information where the global model cannot, however. Validation for temperature and salinity is provided, indicating promising performance. The model produces a range of expected dynamical features for the domain including upwelling and vertical current shear. Nuances in circulation patterns are revealed; specifically, the development of rotational flow patterns within False Bay is qualified and an eddy in Table Bay is identified.

A wave-driven surface circulation feature in Table Bay

“…For example, although dissipation due to depthinduced breaking, whitecapping and friction is considered, low-frequency swell dissipation, which can affect orbital motion in lower layers, is not. For more comprehensive information on calibration and validation, the reader is referred to de Vos et al (2021). The development of the circulation patterns discussed in Section 3.2 was found to be insensitive to the choice of boundary forcing configuration (with astronomic water level and Riemann types having been tested) and parameter settings (such as bottom roughness and bottom wave stress formulations and coefficients), with these choices affecting mainly wave and current vector accuracies.…”

“…Further relevance of the implications of these findings lies in the context of maritime safety. With considerable boating and shipping traffic of both a recreational and commercial nature operating in Table Bay, accurate marine weather and ocean forecasting are important (de Mey et al 2009;Fossati and Piedra-Cueva 2013;de Vos et al 2021). Although the effect of surface gravity waves as a risk factor to maritime activity has been established (de Vos and Rautenbach 2019), the direct effect of surface ocean currents is less clear.…”

Prediksi Perubahan Garis Pantai Di Pantai Tanjung Lesung, Kec. Panimbang, Kabupaten Pandeglang, Banten (Studi Kasus: 2022-2047)

“…Banyaknya proses abrasi dan akresi di daerah tanjung kemungkinan disebabkan oleh adanya dinamika oseanografi yang lebih kompleks. Dinamika oseanografi tersebut diantaranya gelombang dan angin yang lebih tinggi (Vos et al, 2021).…”

Evaluation of coastal hydrodynamic performance using statistical analysis at the Kelantan coast, Malaysia

“…While, numerical models using a mathematical formulation that has been described as hydrodynamic processes to represent coastal processes well (Blacka et al, 2007). However, the performance of the coastal models need to be calibrated and verified with sufficient observed data because of the complex elements in the coastal area (De Vos et al, 2021;Prasetyo et al, 2018). Several numerical models have been demonstrated to identify the best approach for understanding hydrodynamics characteristics due to dynamic environment in coastal area; and these models are recently being used as an effective tool to help in decision making such as MIKE 21 developed by DHI, also known as Denmark Hydraulic Institute, (2011).…”