An Analysis of the Tidal Signal in the WOCE Sea Level Dataset

Abstract

A new sea level observation network initiated by the World Ocean Circulation Experiment (WOCE) program is delivering hourly data from about 150 ocean stations worldwide. A complete analysis of these data was performed using a least squares method allowing better accuracy over time series virtually unlimited in time (up to 13 yr in this case). In addition to the classical tidal harmonic constants, the power density spectrum of the detided signal was computed. The 95% confidence intervals of the results of the analysis have been systematically estimated. The numerical and statistical methods applied to produce these numbers are presented for three stations as an illustration. One example of application of this new dataset and its error bars is the selection of a tidal constant set, which is useful for validating and comparing the long-period tide models. This selection is performed by eliminating stations where the oceanic continuum spectrum magnitude (around a given tidal frequency) is more than 25% of the corresponding tidal peak amplitude. This study intends to lead to a better exploitation of sea level observations, which contain highly valuable information in the tidal and nontidal domains. The authors conclude that the WOCE Sea Level network must be maintained, in particular for a combined use with the present and future satellite altimetry missions. Thus, the aim of this paper is to present a new analysis of the in situ sea level observations acquired within the WOCE program with a particular emphasis given to the precise determination of the tidal harmonic constants.