Experimental investigation of Doppler spectra of microwave signals backscattered by sea slicks

Doppler spectra obtained using an X-band radar have been used to study artificial slicks. The radar was deployed on a platform in the Black Sea to image slicks which were artificially laid in the sea nearby. The radar viewed the slicks at about an angle of 20/spl deg/ incidence. The Doppler spectra obtained from slick covered regions showed strong shifts of the mean Doppler return towards higher frequencies compared with that obtained from non-slick areas. The change in Doppler spectra can be explained if the relative contributions to the radar backscatter from Bragg and specular scatterers changes in the slick covered areas compared with that in non-slick areas. The experimental results are found to be in good agreement with theoretical predictions.