WAVE-CURRENT INTERACTION NEAR THE GULF-STREAM DURING THE SURFACE-WAVEDYNAMICS EXPERIMENT

This paper presents a case study on the wave-current interaction near the local curvature of a Gulf Stream meander. The wave data were obtai ned from in situ measurements by a pitch-roll discus buoy during the S urface Wave Dynamics Experiment (SWADE) conducted off Wallops Island, Virginia, from October 1990 to March 1991. Owing to the advection of t he Gulf Stream by the semidiurnal tide, the discus buoy was alternatel y located outside and inside the Gulf Stream. The directional wave mea surements from the buoy show the changes in wave direction, wave energ y, and directional spreading when waves encountered the current in the Gulf Stream meanders. A wave refraction model, using the ray-tracing method with an estimated Gulf Stream velocity field and meandering con dition, was used to simulate wave refraction patterns and to estimate wave parameters at relative locations corresponding to buoy measuremen ts. The numerical simulation shows that a focusing zone of wave rays w as formed near the boundary and behind the crest of a simulated Gulf S tream meander. The focusing of wave rays causes changes in wave direct ion, increases in wave energy, and decreases in wave directional sprea ding, which are in good agreement with the results from the buoy measu rements.