EDDIES DETECTED IN ERS-1 SAR IMAGES AND SIMULATED IN REDUCED GRAVITY MODEL

The first ERS-1 C-band SAR image of the western coast of Norway was re ceived at Tromso Satellite Station, Norway, on 21 August 1991. It depi cts clearly an eddy-like structure located in the coastal water. The e ddy has a cyclonic spiral structure with a diameter of about 5 km. The expressions of the dark lines outlining the spiral are probably cause d by the presence of natural surface slicks resulting in a damping of the Bragg scattering waves. Eddies at this particular location with th e same spatial characteristics are also detected in simulations with a nonlinear, one-layer active reduced gravity model. From the model res ults we conclude that the eddy is formed by horizontal current shear i nstability associated with variations in the larger scale coastal curr ent. A second case of an observed and simulated eddy occurred later in the Outer Oslofjord. The simultaneous observations and simulations of these eddies clearly demonstrate the potential advantage in integrate d use of weather independent SAR data and model results for the monito ring and modelling of mesoscale circulation processes.