Detection of pure swell in the Outer Río de la Plata, Argentina

DRAGANI, W.C.; SALIMBENI, ALEJANDRO; ALONSO, GUADALUPE; PEREZ, IAEL

Congreso; IV LatWaves; 2022

The presence of swell is widely known in the Outer Río de la Plata but, in general, always have been reported superimposed to the sea. A question which arises among regional specialists is whether or not events of pure swell (i.e. swell without sea) can occur in the Outer Río de la Plata. This work aims to detect and characterize possible events of pure swell at the Río de la Plata mouth. Wave parameters measured with a directional buoy (Datawell Waverider Mark II, period: 1996-2001), and wind measured at Carrasco and Aeroparque Jorge Newbery meteorological stations, and from NCEP/NCAR I Reanalysis, were used in this work. Based on data series of wave and wind parameters, a pure swell event is selected if the observed wave data had (i) periods greater than 8 s, (ii) heights greater than 0.5 m, (iii) differences between the directions of the wave and the wind of, at least, 90°, and (iv) event durations of at least 10 h. Using this set of criteria, 59 pure swell events were obtained at the Río de la Plata mouth between June 20, 1996, and November 17, 2001. It was obtained that pure swell is characterized by heights between 0.40 and 0.80 m, periods between 11 and 15 s, and propagation directions from the SE (60% of cases), SSE (20%), ESE (10%), E and S (less than 5% of cases). During pure swell conditions, the predominant wind is from the NW and N sectors, with intensities lower than 12 ms-1. Also, it was obtained that the frequency of occurrence of swell is maximum in winter, following the fall and the spring, and at last the summer. Consequently, the results presented here provide the first objective characterization of pure swell (i.e. uncontaminated of the sea) at the Outer Río de la Plata. Finally, the performance of four wave global models (Waverys, IFREMER, ERA5, and GFS) at the Outer Río de la Plata are discussed.