A description of drifter trajectories in the neighbourhood of current meters in the Southern part of the North Sea near the coast of Texel

Two methods have been used to simulate drifter trajectories out of current meter data. The results of the method using one current meter can be improved little by using data from three current meters. Errors in the simulations are made because of the existence of spatial variabilities in the velocity field which are not recognized by the current meters. The scale of these variabilities is between the tidal excursion of the drifters and the diameter of the cluster of 6 drifters. The influence of the variabilities is much greater than the influence of the velocity gradient over the current meter triangle. Divergence, vorticity, stretching and shearing deformation from drifter data have in general the same tidal character as these quantities determined from 3 current meter data sets, hut sometimes differences occur. These differences indicate also the variabilities in the velocity field.