Analysis of a Three-Beam Radar as an Instrument for Determining Ocean Wave Heights and Vector Slopes
2006
Evans, Christopher T.
The Vector Slope Gauge (VSG) is a 35-GHz FM-CW scatterometer that has the unique capability of simultaneously (nearly) measuring the range and backscattered power to three points on the ocean surface. With three ranges and knowledge of the experimental geometry, the wave height at each footprint can be obtained. The three footprints form a plane surface which enable two orthogonal slope components to be obtained. Obtaining the slope of ocean waves is important because it is correlated with the backscattered power. By obtaining the vector slope, one does not have to make any assumptions about the linearity or long- crestedness of the ocean waves. With a time series record of ocean wave heights and slopes, one can learn a great deal about the ocean surface. Spectral analysis of the recorded time series yields information about the wave height power spectral density, the mean wave direction vs. frequency, and the directional width spectrum. The results from the VSG are similar to those obtained from a pitch-and-roll buoy. In addition, since the slope distribution of ocean waves is nearly normal, the moments of a bivariate normal distribution can be used to fit an ellipse to the wave slopes.
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