SYNTHETIC APERTURE RADAR IMAGING OF UPPER OCEAN CIRCULATION FEATURES AND WIND FRONTS

Airborne C band synthetic aperture radar (SAR) data were collected during the Norwegian Continental Shelf Experiment (NORCSEX) carried out in March 1988. Unique signature variations in the SAR backscatter due to upper ocean circulation features and wind fronts were found. It is documented that a current jet of 0.3 m s-1 with a shear of about 0.3 x 10(-3) s-1 is correlated with a narrow, bright curved line in the backscatter. In comparison a rapid wind shift of 9 m s-1 resulted in a sharp transition from dark to brighter backscatter regions. The corresponding profiles of backscatter modulation across these features are expressed by a peak of about 2 dB in contrast to a steplike increase of 5-8 dB. This suggests that SAR image expressions of upper ocean circulation features and wind fronts can be distinguished and classified. On the basis of this classification, we attempt to quantify the dominating marine geophysical variables. This method for systematic interpretation of SAR images should be further validated with the use of airborne or satellite data such as from the first European Space Agency remote sensing satellite, ERS 1.