| Abstract: | A joint probability density funelion (PDF) for surface slopes in two arbitrary directions is de-rived on the basis of Longuel-Higgins s linear model for three-dimensional (3-D) random wave field, and the correlation moments of surface slopes, as parameters in the PDF. are expressed in terms of direclional spectrum of ocean waves. So long as the directional spectrum model is given, these parameters are deter mined. Since the directional spectrum models proposed so tar are mostly parameterized by Ihc wind speed and fetch, this allows for substituting these parameters with the wind speed and letch. As an example, the wind speed and fetch are taken to he 14 m sand 200km. and the Hasselmann and Donelan directional spectra are respcctively. used to compute these parameters. Some novel results are obtained. One of the interesting results is that the variances of surface slope in downwind and cross-w ind directions determined by the Donelan directional spectra are close to those measured by Cox and Munk (1954). Some discussions are made on these results. |
