Comparison of current meters in a coastal environment

Abstract

As part of an in-house assessment of the quality of data collected by 3 different types of current meters routinely used at the National Water Research Institute (NWRI), a comparison deployment was undertaken. During the fall and winter of 2001-2002, two single-point current meters (a Nobska MAVS-3SL and a Sontek Hydra) and an acoustic Doppler current meter (RD Instruments 1200 kHz Workhorse ADCP Waves Array) were deployed in the southwest end of Lake Ontario. All 3 units were deployed on bottom mounted support frames within 100 metres of each other in 12 metres of water. The single-point devices measured approximately one metre off the bottom and the lowest bin of the ADCP was 0.5 metres higher in elevation. Ambient water temperatures ranged from approximately 2.5 to 11 /spl deg/C over the deployment period. Mean currents for each system compared favourably. Analysis of the individual components of velocity indicated a good comparison between the single-point current meters but the agreement with the two lowest ADCP bins was not as good. Short-term (single burst) velocity spectra from the MAVS and the Hydra showed good agreement during significant events. However, during quiet periods, the Hydra spectra had a fairly high noise floor, probably due to the reduced number of reflecting particles in the water. Comparison of directional wave data between the three sensor types showed good agreement of the characteristic wave height and fair to good agreement of the peak period and the peak direction.