Intercomparison trials: Near-surface current measurements over the norwegian continental shelf

The results of two intercomparison trials are presented. The first trial compares currents measured by satellite-positioned drifting buoys with those measured with 3-component Simrad ultrasonic current meters (UCM) mounted at 2m depth on a surface-following mooring. The second trial compares the UCM with the E.G.&G. VMCM-630 mechanical vector measuring current meter. In the drifter - current meter comparison, the drifter showed a greater response to the wind than the current meter, both at low frequencies (< 1 cpd) and at around the inertial frequency. The comparison of the two current meters was prompted by an apparent zero-point shift in the VMCM-630 measurements: the effect may be due either to a current shear between the levels of the two rotors or to an intermittent electronic fault.