An evaluation of the aanderaa RCM4 current meter in the wave zone

As part of a project to evaluate the performance of current meters in the near-surface coastal environment, a single point sub-surface mooring was deployed in 40m of water over the period May to September 1983. This mooring was located on a flat bank 40Km in width in Hecate Strait, near53\deg11'N131\deg17'W. Together at approximately 14m depth were three current meters, a Marsh McBirney 585 and two Aanderaa RCM4's, one with Savonius-like rotor and one with an experimental paddle-wheel rotor supplied by Aanderaa. Wind data was recorded on a nearby surface mooring and the low frequency surface wave field was sampled with burst measurements of bottom pressure. Time series and statistical analyses strongly confirmed the unsuitability of the standard Aanderaa RCM4 for use in the wave zone where, in moderate winds, errors of 100% and more were not uncommon. The RCM4 fitted with the experimental rotor performed very well compared to the standard unit, although large errors were still present at times.