Measurements of the angle between the wind vector and wind stress vector in the surface layer over the North Sea

Measurements of surface layer turbulence, in addition to full meteorological and oceanography quantities, over the North Sea indicated that the stress vector on long time scales is often aligned with a direction slightly different from the mean wind flow. When stratifications were near neutral, the angle difference between the stress and wind exhibited a dependence on the heat and momentum fluxes. In general, the stress vector was observed to be to the left of the flow during stable stratifications, while for unstable stratifications, it was to the right. This finding was consistent using two independent sets of wind stress data, i.e., from MARSEN (1979) and the North Sea Platform Winter Exercise (1985).