Tuesday 23 August 2005

GP2

PT0082
Analysis of the mean sea level from a 50 years tide gauge record and GPS observations at Cananéia (São Paulo, Brazil)
Mesquita, Afrānio², França, Carlos², Ducarme, Bernard⁴, Venedikov, Angel^1,2, Costa, Daniel¹, Vieira, Ricardo⁶, Blitzkow, Denizar¹, Freitas, Silvio³
1 Escola Politecnica da Universidade de São Paulo, Brazil
2 Instituto Oceanografico - da Universidade de São Paulo, Brazil
3 CPGCG - Universidade Federal do Parana, Brazil
4 Observatoire Royal de Belgique, Bruxelles, Belgium
5 Geophysical Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria
6 Instituto de Astronomia y Geodesia (CSIC-UCM) Facultad de Matematicas, Madrid, Spain
Author email: dblitzko@usp.br
A homogeneous tide gauge record covering the period 1954-2004 was obtained at Cananéia (φ = 25°01'12"S, λ = 47°45'29"W). The series offers rather good possibilities for the study of the mean sea level (MSL). A previous analysis of a 36 years data set has shown many interesting features, especially a seasonally variable trend. The re-analysis benefits from the longer time series and a powerful tidal analysis program. Moreover GPS data, available since 2002 with the installation of a continuous station, are being processed. The analysis of the tide gauge data has been made by our computer program VAV for tidal analysis and POLAR for regression analysis of such data. Through VAV a residual curve or "drift of the record" is determined, free of all low and high frequency tidal constituents. Further the drift is submitted to a sophisticated regression analysis, using various models, including annual and other low frequency periodic constituents, e.g. 11 years period, related with solar activity, as well as polynomial terms. The programs allow the detection and elimination of discontinuities in the data, eventually due to instrumental manipulations, as well as of some strongly perturbed data. The final result consists in a smoothed MSL. The GPS data are being processed and the results, although for the shorter period, will be compared with tide gauge and meteorological data.

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