Validation of the geostrophic method for estimating zonal currents at the Equator from Geosat altimeter data

Abstract

The applicability of satellite altimeter data for estimating zonal current variability at the equator is assessed using the meridionally differenced form of the geostrophic balance. Estimates of geostrophic zonal flow anomalies in the Equatorial Pacific have been deduced from 17-day collinear altimeter data during the first year of the Geosat exact repeat mission, November 1986 to November 1987. Altimeter-derived geostrophic estimates agree well with in situ zonal current variability. Comparison of low-frequency, near surface zonal current observed from equatorial moorings at 165°E, 140°W, and 110°W yield correlations of 0.83, 0.85 and O.51, respectively, with a mean rms difference of 23 cm s-