OBSERVATIONS OF RADAR BACKSCATTER AT KU AND C-BANDS IN THE PRESENCE OF LARGE WAVES DURING THE SURFACE-WAVE DYNAMICS EXPERIMENT

Ocean radar backscatter in the presence of large waves is investigated using data acquired with the Jet Propulsion Laboratory NUSCAT radar a t Ku band for horizontal and vertical polarizations and the University of Massachusetts CSCAT radar at C band for vertical polarization duri ng the Surface Wave Dynamics Experiment, off-nadir backscatter data of ocean surfaces were obtained in the presence of large waves with sign ificant wave height up to 5.6 m. In moderate-wind cases, effects of la rge waves are not detectable within the measurement uncertainty and no noticeable correlation between backscatter coefficients and wave heig ht is found. Under high-wave light-wind conditions, backscatter is enh anced significantly at large incidence angles with a weaker effect at small incidence angles. Backscatter coefficients in the wind speed ran ge under consideration are compared with SASS-II (Ku band), CMOD3-H1 ( C band), and Plant's model results which confirm the experimental obse rvations, Variations of the friction velocity, which can give rise to the observed backscatter behaviors in the presence of large waves, are presented.