SHIPBOARD ACTIVE AND PASSIVE MICROWAVE MEASUREMENT OF OCEAN SURFACE SLICKS OFF THE SOUTHERN CALIFORNIA COAST

Ship-based radar scatterometer measurements at L band (20 cm) and X band (3.2 cm), radiometer measurements at C band (5.5 cm) and K(a) band (0.86 cm), and microlayer chlorophyll fluorescence measurements on the southern California continental shelf were acquired across several surface slicks during October 1989. These measurements allowed the simultaneous extraction of both the short wave damping at Bragg wavelengths 24 cm and 4 cm and the chlorophyll a biological concentration with sufficient spatial resolution to observe features within individual slick bands. The measurements show that (1) the largest peaks in fluorescence, a measure of the peak chlorophyll a concentration, are colocated with the short wave damping at 24-cm and 4-cm wavelengths, (2) the maximum damping ratio, between the 24-cm and 4-cm waves is at least 16 for wind speeds of 3-4 m s-1, and (3) the radar roughness signatures at these short Bragg gravity wavelengths suggest that the slicks are caused by organic surface film damping rather than straining of these waves. The radar roughness changes in synthetic aperture radar imagery have usually been interpreted in terms of wave straining. The limited radiometer signatures are uncorrelated with the other microlayer measurements. Additional shipboard measurements are needed to further quantify these preliminary results.