TABLE OF CONTENTS In Section 3.2 we discussed how a breaking wave criterion can be applied to a Gaussian model of the sea surface. For this we assume that regions of the Gaussian random field where the down ward vertical acceleration of the surface is greater than g/2( g is the acceleration due to gravity) are subject to breaking. This breaking area model [12]provides a simple means to calculate the proportion of the sea surface that is breaking, andsince it is derived directly from the wave spectrum, it can be related to sea state, wind speed and fetch. More detailed features of the breaking area, such as the properties of the local and global maxima and the supports of above threshold excursions, may be derived from the underlying Gaussian model. These are described in Reference [12].
In the mean time we will concentrate on the contribution the breaking waves make to the clutter RCS. As shown in Figure 3.4, as a wave approaches breaking it sharpens at the top and flattens at the bottom. The sharp crest then steepens rapidly andcurls over, before the water tumbles down the front wave slope.
Using the numerically derived waveshapes of Figure 3.4, scattering calculations have been performedby Forward-Back at a grazing angle of 6 [33]. The results are shown in Figure 3.26. The first wave profile is at T = 0 s and the wave breaks at T = 1.36 s. The wave...
