A new in situ reference data set for ocean tides

The Ocean Tides sub-group of the Topex/Poseidon Scientific Working Team (SWT) has selected a new set of tide-gauge stations to help evaluate new ocean tide models.

It comprises 103 stations in the global ocean: 23 in the North Atlantic, 19 in the South Atlantic, 18 in the Indian Ocean, 26 in the North Pacific and 17 in the South Pacific. The site figure includes reference data-sparse areas, such as the southern Pacific.

The 103 reference stations.

Several families of in situ measurements were used to produce the new list:

• All 80 tide-gauges selected by D.E. Cartwright and R.D. Ray [1991] for validating the altimeter solution deduced from Geosat, referred to as CR91 in this article, were reanalyzed. The M2 component of these in situ measurements was compared with the CR91 solution and with that of Le Provost et al.'s finite-state hydrodynamic model [1994], referred to as LPal94 in this article. Stations with vector differences from the models greater than 10 cm were rejected and, where possible, replaced by neighboring in situ measurements more consistent with CR91 and LPal94.
  Five stations were replaced and a sixth (Campbell) eliminated.
• Among the tide-gauges surveyed by IAPSO [Smithson, 1992], 14 were selected after detailed comparison with CR91 and LPal94.
• More multi-year time series from the Woce sea level measurement array were analyzed [Molines, 1994]. Several of the stations were already part of the data set selected by Cartwright and Ray for validating their altimeter solution deduced from Geosat. The new analyses led to fairly similar results, but were used to complement the spectrum analyzed and estimate the noise level in the tide-gauge records.
• Eleven more stations were selected from other records in the Woce array to more evenly space the geographical distribution.

All the data is available as ASCII files using procedure "ftp anonymous" (on machine meolipc.img.fr, number IP 130.190.38.36):

• general information: pub/ST103/README103.MEOM (ASCII)
• list of data values: pub/ST103/LIST103.MEOM,
• harmonic constants: pub/ST103/ST103.MEOM,
• station sites and codes: pub/ST103/ST103.ps. (Postscript graphics)

For more information, please contact Florent Lyard by e-mail.

The new reference data set for evaluating present and future ocean tide data was generated with major contributions from P.L. Woodworth, D.E. Cartwright, R.D. Ray, F. Lyard, J.M. Molines and M.L. Genco.

References :

• Cartwright R.E. and R.D. Ray, J. Geophys. Res., 96, 16897-16912, 1991.
• Le Provost C., M.L. Genco, F. Lyard, P. Vincent and P. Canceill, J. Geophys Res, 1994.
• Molines J.M., MEOM/LEGI/IMG technical report, Grenoble, 1994.
• Smithson M.J., IAPSO scientific publication # 35, 1992.