Acoustic propagation in the Brazil current system off the Southeastern coast

The Brazil Current (BC) is perhaps the less studied subtropical boundary current of the world ocean. Within this region, the BC develops vigorous meanders and rings. A combination of numerical simulations and observational studies are important tools to unravel these phenomena. Direct current measurements are rare and usually too short to depict the mean, long term circulation patterns. Similarly, quasi-synoptic hydrographic data in the region is sparse. Acoustic waves are an efficient tool for covering large regions of the water column in a synoptic way. Acoustic tomography can be therefore useful to better predict through inversion for the effective sound speed field and its assimilation to a circulation model the oceanographic fields of interest (temperature, salinity, density). Such information is particularly important for initialization and data assimilation to regional models for which small and meso-scale processes are of fundamental interest. In this paper, a preliminary study of acoustic propagation modeling through two vertical sections off the Brazilian southeastern coast is presented. Actual hydrographic data from DEPROAS 2003 sea trial serve to construct the physical parameters that characterize these sections