Abstract:

This paper presents the results of acoustic measurements of the ocean surface and near-surface features using a conventional broadband acoustic Doppler current profiler (ADCP). An analysis of the trade offs and error sources associated with surface detection reveals how transducer beam geometry and signal processing can affect surface measurement. Configurations are considered for the measurement of mean-surface height, ambient sound, wind speed, wind direction, surface currents, directional wave spectra, tidal flow, and entrained air. Observations of the sea surface conditions at Scripps Pier are compared with acoustic data collected using upward facing ADCPs of different beam geometries and a pressure sensor. Comparisons are made with previous studies [Zedel, Deep ocean wave measurements using a vertically oriented sonar, J. Atmos. Oceanic Tech. 11, 182--191 (1994) and Terray et al., Measuring wave height and direction using upward-looking ADCPs, to be presented at Oceans '97].