Surface equatorial flow anomalies in the Pacific ocean during the 1986-87 ENSO using GEOSAT altimeter data | Western Pacific international meeting and workshop on Toga Coare : proceedings
1989
Picaut, Joël | Camusat, Bruno | Delcroix, Thierry | McPhaden, M.J. | Busalacchi, A.J.
Estimates of surface geostrophic zonal flow in the equatorial Pacific are deduced from the 17-day exact repeat orbit GEOSAT measurements for the period november 1986-november 1987. This period coincides with the height of the 1986-87 ENSO. Along-track altimeter height anomalies are first smoothed using a combination of linear and non linear filters. By combining several tracks in the zonal direction and filtering in time, we are able to obtain low frequency sea surface height at any point of the tropical Pacific. Currents are calculated from the differentiated form of the meridional momentum equation at the equator and from the classical first derivative of the meridional pressure field away from the equator. Comparisons of low frequency near-surface zonal current directly measured from equatorial moorings at 165°E, 140°W and 110°W yield a correlation of 0.83, 0.84 and 0.50 respectively with a mean rms difference of 0.23 m.s-1. Sea level and zonal velocity solutions from a tropical Pacific numerical model are used as proxy data sets in order to quantify errors induced to quantify the geostrophic calculation by the GEOSAT space-time sampling.
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