Intercomparison of ADCP Measurements at 0°, 140°W

Abstract

Three sets of horizontal velocity measurements obtained within 3 miles of each other at 0°, 140°W are compared. Measurements were taken by acoustic Doppler current Profilers (ADCPs) on different platforms, with different tracking filter configurations, and were processed by three different groups. A veraged over more than 12 days, mean velocity measurements differ by less than 1 cm s?1 at most depths. This discrepancy is about the same as the skew error of ADCP measurements. The rms value of residual velocity components for measurements averaged over 5?6 min is 0(5 cm s?1). These residuals are due to the combined effects of navigational errors and spatial variability in the oceanic velocity field. The estimated navigational error has an rms value of 2?3 cm s?1 for each velocity component. Meridional gradients of the Equatorial Undercurrent estimated from transient velocity differences and ship-buoy separations agree with those estimated from meridional transect data.