An investigation of offshore circulation using satellite data and feature tracking techniques.

Abstract

Satellite-derived sea surface motion vectors are obtained for an area 100 to 300 kilometers from the central California coast south of Point Arena. These vectors are compared with hydrographic data acquired during the OPTOMA 21 cruise. Three AVHRR images, with 24 hour spacing between images, are used to create two sets of sea surface flow vectors. The vectors obtained show only limited agreement with geostrophic velocities computed relative to 750 meters. There is good agreement when the geostrophic flow is strong and persistent submesoscale features are advected by the flow. Unfortunately this technique is only able to identify some of the strong flows and its utility for identifying weak ( < 10 cm/ sec) flows is questionable. There are numerous eddies and perturbations in the surface flow in this area that cannot be resolved by this technique when the images are 24 hours apart. Cloud contamination in the second image emphasizes the dependence of this technique on an unobstructed view of the ocean. Nevertheless, when used with an understanding of its limitations, the feature tracking technique can be a useful method of interpreting satellite oceanographic data.