Wind sea and swell discrimination in the outer Rio De La Plata Estuary, South Atlantic Ocean

Abstract

This study focuses on the comprehensive discrimination and characterization of wind-sea and swell dominating conditions in the outer Río de la Plata estuary (RDP). For that, time series of bulk wave parameters and wave spectra covering the period from 1996 to 2020 were analyzed. Results revealed that 57 % of the spectra exhibit double peaks indicating the prevalence of simultaneous wind-sea and swell events. To differentiate between wind-waves and swell cases, the Pierson–Moskowitz (PM) spectrum peak method was implemented. In this method, the ratio between the peak energy of a wave system and the energy of the PM spectrum with the same peak frequency is computed. If this ratio is greater than one, the wave system is categorized as wind-sea; otherwise, as swell. Later, a support vector network (SVM) classificator was applied to significant height (Hs)and peak period (Tp). Results indicate that a linear expression (Tp = 2.5 Hs + 3.3) optimally separates wind-sea and swell. The typical Hs were 1–2 m for wind-sea and 0.5–1 m for swell, with mean Tp values of 5.2 s and 10.5 s respectively. Wind-sea waves predominantly propagated from the E and S, while swell from the SE. Swell seasonality indicated the highest occurrence during the winter months and minimal occurrences during summer. Finally, the performance of the WAVERYS and IOWAGA products in predicting arrival times of swell at the RDP was evaluated. Both predicted an earlier arrival time for swell in over 70 % of the events. These results highlight the reliability of these global products in anticipating swell arrivals.