Regime e variabilidade de ondas no Atlântico Tropical

Abstract

Waves are important components of the ocean’s dynamics, being responsible, once they reach the shore, for the sediments transport and for impacting on harbor activities and navigation. The aim of this work is to evaluate the wave climatology and its long time variability over the Tropical Atlantic. For this purpose, we used significant height, peak period and wave direction data obtained from the model WaveWatch III (WW3), from 1979 to 2015. We have observed that the waves’ characteristics for the study area are related to the trade winds and the occurrence of tropical and extratropical cyclones. The location of the Intertropical Convergence Zone (ITCZ) and its meridional oscillation have an influence on the observed seasonal variations. Our results have shown that the predominant wave directions are from North to Northeast , for most parts of the northern coast of Brazil, and from East to Southeast, for the east coast. The periods of higher occurrence are smaller than 10 s (sea waves) and the wave heights, from 1.5 m to 2.5 m. We have found long term variations of 25 cm (0.69 cm/year) for the wave heights, 0.5 s (0.014s/year) for the wave periods and 5% (0.13%/year) for the wave directions. The causes for these variations are still not well known, although they might be related to the climate change. When comparing the results obtained from the WW3 model with the ERA-Interim results and in situ data, we observed that the WW3 model did not behave properly for the coastal area, which requires attention when applied for coastal management and activities. We could not conclude which of the two models (WW3 or ERA) was more representative for the area of interest. Therefore, further research is needed for an effective validation of the models for the study area.