DRIFTER OBSERVATIONS OF A COLD FILAMENT OFF POINT ARENA, CALIFORNIA, IN JULY 1988

We use the position fixes and temperature readings from 56 Tristar-II mixed-layer drifters, in conjunction with advanced very high resolution radiometer images, to provide a description of the mesoscale variability of the flows associated with cold-water filaments in the California Current system off nor-them California in July 1988. We find that the northern, offshore temperature front of the filament is convergent and is closely associated with the core of a high-speed (> 100 cm/s) jet that has a broader spatial scale than the cold-water filament. Mesoscale features are observed to be related to all developments of the cold-water filament on a variety of time scales (1-30 days). In one well-observed feature, estimates of vertical velocity (w) based on a vorticity budget are -20 m/d over an area of 150 km2 and are associated with a gain of vorticity. Estimates of w based on a local heat budget following a drifter are about 3 times larger over an area of 60 km2. These intense downwelling features are also places where horizontal stirring occurs.