FY 1989 Use of the geostrophic approximation to estimate time-varying zonal currents at the equator Picaut, J., S.P. Hayes, and M.J. McPhaden J. Geophys. Res., 94(C3), 3228–3236, doi: 10.1029/JC094iC03p03228 (1989) |

Moored thermistor chains at 2°N and 2°S and current-temperature moorings at 0° are used to examine the accuracy of geostrophically estimated zonal velocity on the equator in the eastern (110°W) and western (165°E) Pacific. The meridionally differentiated form of the geostrophic balance is used to eliminate large errors due to wind-balanced cross-equatorial pressure gradients. Statistical analyses indicate that for time scales longer than 30–50 days, the observed and geostrophically estimated zonal velocities are similar (correlation coefficients of 0.6–0.9 and comparable amplitudes). Thus low-frequency equatorial current oscillations are reasonably well represented by the geostrophic approximation. However, the mean currents are poorly resolved with the available array. In the eastern Pacific the mean zonal speed difference over the 10-month comparison period is 25 cm s |

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