A proposed directional function and wind-wave directional spectrum

A directional function for frequencies equal to and larger than the peak frequency of a wind-wave frequency spectrum is constructed by fitting the angular spreading based on the analytically derived directional spectrum of Wen et al. (1993, Journal of Oceanography, 49 (2), 131-147, 149-172).For frequencies smaller than the peak frequency, the directional function is obtained by comparing and analyzing existing formulas.The nondimensional wind-wave frequency spectrum of Wen et al. (1994, Progress in Natural Seience, 4 (4), 407-427;4 (5), 586-596) has been used together with the directional function just mentioned to obtain the directional spectrum for easier application.