Identificação de ciclones extratropicais geradores de ondas swell na costa Oeste do Ceará

Abstract

Due to the increase of usage and occupation of the coastal zone in the world and the investment in these areas, the meteorological and oceanographic studies, specilly concerning gravity waves, since they are some of the main modifiers of this environment, gain importance. In this context, this study has as goal indentify the areas in which the swell that arrive at the western coast of Ceará state are generated. For the analysis of the wave field, we used the results of the wave propagation model WaveWatch III for the years between 1979 and 2015, validated against observational data from a buoy at Pecém Port (3o32’2"S, 38o47’58"W) for the years 1997- 2001. For the estimation of the swell generation areas, the Ridge Line method was used, wich identifies the distance between the observation point and the region of wave generation through the ocean surface gravity wave dispersion relation in deep water. Sea level pressure and wind intensity and direction at the surface from the National Center of Environmental Prediction were used for the identification of the atmospheric systems which generated the swell identified at the Ceará coast. The validation indicated that the results of the WaveWatch III were more accpetable on the months of August, September and October (Hs); April, September, October and November (Tp); and September and October (Dp). From the analysis of the swell events during these months for the WaveWatch III time-series, 53 swell events with period largest than 18 seconds were identified reaching the coast. In general, the swell identified at Ceará coast is generated by tropical and extratropical cyclones at the North Atlantic, between 35o N and 65o N. These events of dispersive arrival are identified mostly during months of December, January and February, since this is the time-period most suitable for the generation of these potentially wave-generating atmospheric systems, which waves can arrive with high energy at the northern coast of northeastern Brazil.