@InProceedings{ViannaMene:2002:CuSeLe,
               author = "Vianna, Marcio L. and Menezes, Viviane V. de",
                title = "Currents and sea level off the Northeast Brazilian coast",
                 year = "2002",
         organization = "Simp{\'o}sio Brasileiro de Oceanografia, 1.",
             keywords = "OCEANOGRAFIA.",
             abstract = "The region of the North Brazil Current (NBC)Retroflection in the 
                         northern hemisphere has been studied since the 80{\"{\i}}s by 
                         Johns and collaborators (Johns et al., 1998), who disclosed the 
                         importance of the annual cycle, the 25-40 day and 60-90 day 
                         oscillations in relation to NBC ring shedding. Upstream, with no 
                         rings in the NBC, near Fortaleza, no long-term data was ever 
                         published to date. This work describes our effort to study sea 
                         level and currents over the NE Brazil shelf in the last 8 years. 
                         We deployed and maintained 3 Tide Gauges (TG)at Fortaleza and 
                         TERMISA over the northern shelf (3S-4S)and at Tamandar{\'e} (8S), 
                         and two ADCP bottom moorings, and obtained some time series data 
                         kindly given to us by INPH and Petrobr{\'a}s. There are presently 
                         three current meter time series records available: two ADCP 
                         moorings (July 2000-March 2001, 20m and 30m depths, 037W)at the 
                         mid and outer shelf, and one standard current meter mooring off 
                         Paracur{\'u} (August 1995-March 1996, 40m isobath, 039W, surface 
                         data). Hourly wind station data sets from two stations were also 
                         made available to us, one at the coast and one at the offshore 
                         site off Paracur{\'u}. The ADCP data were studied by EOF 
                         analysis, which confirmed the well-known barotropic nature of the 
                         observed currents on the continental shelf. The principal 
                         component time series were analyzed by Multichannel Singular 
                         Spectrum Analysis (MSSA). After removal of tidal signals, the 
                         low-frequency signal vector spectra show a dominant spectral peak 
                         at 57 day period at both ADCP sites, with currents strongly 
                         polarized in the longshore direction. The Paracuru currents, and 
                         the contemporaneous TG data, present the same spectral bands as 
                         the Johns current meter data. These oscillations are shown to be 
                         wind-forced by a complex EOF-MSSA analysis. We also used ERS wind 
                         scatterometer data to extend this analysis to the NBC 
                         Retroflection area, and obtained similar correlation. The annual 
                         and interannual variability study was done by use of the TG data, 
                         which was shown to be consistent with our altimeter data described 
                         in another work in this Symposium. The study shows that while the 
                         annual cycle may be absent south of 4S, which is dominated by a 
                         biennial cycle, but it is present north of 4S, with a interannual 
                         modulation. This is interpreted as a consequence of the fact that 
                         the NBC-NBUC south of 4S has a negligible annual cycle, while the 
                         C-SEC has a strong one. It is also shown that large phase 
                         differences (time scale of a week)between the annual cycle on 
                         sites at relative distances of 200 km may be a consequence of 
                         interference patterns of incident and scattered 
                         equatorially-trapped Rossby waves by the NE coast.",
  conference-location = "S{\~a}o Paulo",
      conference-year = "26-30 ago. 2002",
                label = "11377",
             language = "Pt",
        urlaccessdate = "03 maio 2024"
}