Interpretation of a SAR (Synthetic Aperture Radar) Image of the Bay of Biscay

摘要

On August 20, 1978, the Synthetic Aperture Radar (SAR) on board the satellite SEASAT, gave evidence of high energy internal oceanic activity at the shelfbreak in the northern part of the Bay of Biscay. Quantitive spatial measurements of internal wave patterns were correlated with conventional, quasi-synoptic in situ data and yielded phase speeds of 0.55M/S for high frequency, nonlinear internal waves, generated in groups at the canyons indenting the shelfbreak and at the time of low tide in Brest. Their periods were found to be of 70MIN and their amplitudes estimated to be 15M. Ocean swell refraction, observed on the SAR image, together with a localized significant increase in wave height detected by the SEASAT altimeter, was related to the shear of a northwestward geostrophic jet (ca. 0.5M/S) at the break. Possible operational consequences of these features are summarized as an assessment of a SAR's capability to give tactical as well as scientific real-time information on the internal ocean. (Author)