Determination of ocean environmental parameters from a Ka-band scatterometer

A 3-beam Ka-band radar was used as a vector slope gauge with scale like that of a pitch-and-roll buoy. The direction of dominant wave travel, the variance in wave slopes, and the directional spectra of waves are discussed. The slope distribution of ocean waves at this scale is nearly normal, and thus the authors used the moments of a bivariate normal distribution to fit an ellipse to the wave slopes. The orientation of the major axis of the ellipse indicates the direction of dominant wave travel, with 180° ambiguity. In addition, statistics of the slope distribution are readily obtainable from the fitted ellipse. The wave-direction ambiguity is then resolved by fitting an ellipse to the directional histogram of the slope distribution using the least-square method. Due to the asymmetry of the waves, the center of the ellipse is shifted from the origin in the direction from which the dominant waves are traveling. The authors´ method of calculating wave slopes and determining the direction of waves is then compared with the standard method used with pitch-and-roll buoys. The authors then compare these with those obtained by F. Ziemer of GKSS, Geesthacht, Germany