Shallow current measurements

The dynamics of mixed layers and the variability of coastal current systems are two important problems that require the measurement of near-surface currents. Near the surface, the wave field generates currents of higher frequency than the current field of interest, leading to the requirements for a current meter which properly averages motion at frequencies higher than the sampling frequency. A mechanical meter, dubbed the vector-measuring current meter (VMCM), which measures two orthogonal components of the current, has been developed, tested and compared with other current meters. Results show the meter to perform well under conditions in which it is expected to be used. Two versions have been developed-- one for use in shallow water, on a mooring which does not rotate with respect to the bottom; another for deep oceanic measurements, in which mooring rotation is accounted for in the averaging scheme.