Results of airborne backscatter measurements during the Surface Wave Dynamics Experiment

Ocean backscatter data over a wide variety of oceanic and atmospheric conditions were obtained by the Jet Propulsion Laboratory NUSCAT K_u-band scatterometer during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia. A sea surface temperature front at the Gulf Stream boundary existed in the SWADE measurement area. Swells up to 6 m in significant wave height and a large range of wind speeds were encountered. Large differences in backscatter between cold and warm sides of the Gulf Stream were observed. Relations of backscatter with friction velocity are derived from the NUSCAT-SWADE data set. The increasing trend observed in the backscatter with younger wave age agrees with a rougher surface condition for a younger wave field. The results show that backscatter is more sensitive to friction velocity with smaller deviation factors compared to the backscatter functions of wave age. NUSCAT data indicate that the azimuth direction, at which the backscatter is maximum, is in between the wind direction and the dominant wave direction at light wind conditions. Excluding cases of large swells, there is no systematic trend between backscatter and significant wave height