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Article

Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model

Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade de Lisboa, 1049-004 Lisboa, Portugal
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Author to whom correspondence should be addressed.
Academic Editor: Ian Young
J. Mar. Sci. Eng. 2021, 9(2), 153; https://doi.org/10.3390/jmse9020153
Received: 13 January 2021 / Revised: 27 January 2021 / Accepted: 28 January 2021 / Published: 2 February 2021
(This article belongs to the Special Issue Extreme Waves)
The influence of the Agulhas Current on the wave field is investigated. The study is conducted by performing high resolution spectral wave model simulations with and without ocean currents. The validation of the numerical simulations is performed for the Significant Wave Height (Hs) using all possible satellite altimetry data available in the study region for a winter period of 2018. Wave spectra and extreme waves parameters are examined in places where waves and current are aligned in the Agulhas Current. Sentinel-1 (S1) wave mode Synthetic Aperture Radar (SAR) spectra are used to estimate the composites of the Hs and BFI (Benjamin–Feir Index). SAR computed BFI and Hs were compared with the respective composites obtained from the Simulating Waves Nearshore (SWAN) model. From the Hs composites using SAR data and modeled data, it can be concluded that the Hs maxima values are distributed in the Agulhas Current Retroflection (ACR) and also in the southern limit of the domain that is affected by the strong circumpolar winds around Antarctic. In addition, the BFI composites exhibit the highest values in the ACR and some few values are observed in the southern border as occurred with the Hs. The results of this study indicate that there is direct correlation between the Agulhas Current strength, the Hs and the BFI. It was found that the modeled directional wave spectra are broadened when the ocean current is considered in the simulation. The analysis of the modeled wave spectra is performed over eddies, rings and meanders in the Agulhas Current region. The transformation of the wave spectra due to current refraction is discussed based on the numerical simulations. The effect of the Agulhas Current on the spectral shape is explored. The spectral wave energy grows when the wave and the current are aligned, resulting in peaked, elongated and widened spectra. A decrease of the peak period was observed before the occurrence of maximum values of BFI, which characterize abnormal sea states. View Full-Text
Keywords: extreme waves; Agulhas Current; wave-current interactions; SAR wave mode; SWAN; BFI extreme waves; Agulhas Current; wave-current interactions; SAR wave mode; SWAN; BFI
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MDPI and ACS Style

Ponce de León, S.; Guedes Soares, C. Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model. J. Mar. Sci. Eng. 2021, 9, 153. https://doi.org/10.3390/jmse9020153

AMA Style

Ponce de León S, Guedes Soares C. Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model. Journal of Marine Science and Engineering. 2021; 9(2):153. https://doi.org/10.3390/jmse9020153

Chicago/Turabian Style

Ponce de León, Sonia; Guedes Soares, C. 2021. "Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model" J. Mar. Sci. Eng. 9, no. 2: 153. https://doi.org/10.3390/jmse9020153

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