Comparison of Profiling Current Meter and Shipboard ADCP Measurements in the Western Equatorial Pacific

Profiling current meter (PCM) measurements under a drifting buoy are compared with concurrent shipboard acoustic Doppler current profiler (ADCP) measurements carried out in the western equatorial Pacific in March 1991, from 10°S to 7°N along the 165°E meridian. The mean (ADCP minus PCM)±rms differences between zonal and meridional velocity components are 5.7±11.2 cm s−1 and 0.0±8.8 cm s−1, respectively, when PCM measurements are relative to 600 m. The mean±rms differences decrease to 2.3±7.8 cm s−1 and 0.0±6.3 cm s−1 when the PCM and ADCP data are both referenced to the same layer (on a mean, 16–240 m). As compared with ADCP, it is found that PCM underestimates velocities of less than 20 cm s−1 by about 25%.