Joseph HARARI & Paulo Leão CACCIARI

Instituto Oceanográfico da Universidade de São Paulo (IOUSP)

A project for observing and modelling the circulation in the coastal
area of Santos, Sao Paulo State, Brazil, has recently been approved by
the Fundação de Amparo a Pesquisa do Estado de São
Paulo, the State Foundation for scientific researches support The main
objective of the project is to determine characteristics of hydrodynamical
processes in the area shown in Figure 1, with grid limits 46º-47ºW
23º50'-24º30'S, and depths up to 60 m, approximately. The processes
of interest are:

- propagation of tidal waves and their composition into the total tidal
circulation.

- mean seasonal circulation.

- wind driven currents and the effects of meteorological fronts.

- temperature/salinity variabilities and density currents.

Instruments are planned to be moored in the positions P1 and P2 (Fig. 1), for measuring the tides and surface waves, currents and temperature (at mid-depth and bottom), together with meteorological observations of pressure, temperature and winds (at the surface). Data will be radio transmitted to a reception station at the coast (R1) and the moored instruments will be recovered for maintenance every three months, in cruises with temperature and salinity profiling sections. Additionally, continuous tidal measurements in the Port of Santos are available. The observed time series will be submitted to analyses, in order to estimate statistical parameters, significant periodicities and the tidal signals.

fig1 Coastal area of Santos (SP, Brazil), with mooring positions P1 and P2 and data reception station R1.

High resolution non linear models are being implemented for the coastal area of Santos, using finite differences in the horizontal and finite elements in the transformed (sigma) vertical coordinate (Davies, 1986). These models allow to use linear or spherical coordinates, slip or no-slip bottom boundary conditions, several formulations for the coefficient of vertical eddy viscosity - including zero order turbulence closures (Davies, 1991), and different basis functions in the vertical (such as cosines, Legendre polynomials or B-Splines).

For initial tests of tidal waves propagation, a grid of 120 x 80 points was implemented, with horizontal spacing of about 1 km, and the processings consider the system of basic equations with linear coordinates, uniform density of the sea water, quadratic law for representing the bottom friction, constant coefficient of eddy viscosity at each grid point and harmonic basis functions. Open boundary conditions are based on results of a meso-scale hydrodynamical numerical model of São Paulo State shelf (Harari, 1985), with cotidal lines given by Harari & Camargo (1994)

The measurements are planned to begin in January 1996 and preliminary results of the numerical models are being obtained, which should be validated with observations al. the end of 1996. Once implemented the models will be useful as a valuable tool to solve many problems in the area, such as navigation security, water pollution, coastal erosion and salinity intrusion.

References

Davies, A. M. 1986. A three-dimensional model of the Northwest European continental shelf, with application to the M4 tide. J. phys. Oceanogr., 16(5):797-813.

__1991. On using turbulence energy models to develop spectral viscosity
models. Continent. Shelf Res., 11(11):1313-1353.

Harari, J. 1985. Desenvolvimento de um modelo numérico hidrodinâmico
tri-dimensional linear, para a simulação e a previsão
da circulação na plataforma brasileira, entre 23º12
e 26ºS. Bolm Inst. oceanogr., S Paulo, 33(2):159-191.

__& Camargo, R. 1994. Simulação da propagação
das nove principais componentes de maré na plataforma sudeste brasileira
através de modelo numérico hidrodinâmico. Bolm Inst.
oceanogr., S Paulo, 42(1):35-54.