Coupled Discrete Models

Abstract

All three CD models considered in this study—bmo, sail, and dns—use a linear-feedback input source function S _in = BF, with reduced values of Miles’ factor B relative to first-generation DP models, in accordance with the measurements of Snyder et al. (1981). (The bmo model also includes a Phillips forcing term, S _in= A + BF, but A is small and is relevant only for triggering growth in an initially calm ocean.) All models also invoke some form of limiting saturation spectrum which depends on the stage of development of the windsea. The models differ primarily in the details of the parameterization of the nonlinear transfer in the forward face and peak regions of the windsea spectrum and in the swell-windsea transition regime. As pointed out in Chapter 2, the limitations of presently available parameterizations of the nonlinear transfer restrict the effective number of degrees of freedom of CD models in the representation of the windsea spectrum. Thus the techniques used to simulate these processes, although containing a few more degrees of freedom, do not differ qualitatively from the methods described for CH models. The principal features of the models are listed in Table 6.1.