Improved form of wind wave frequency spectrum

The lower frequency part of the theoretical wind wave spectrum proposed by the authors (Wen et al., 1988a, b, c) has been improved and the form of spectrum is appreciably simplified.In addition to the field data collected in the Bohai Sea region and used in the previous papers, those obtained in the Huanghai Sea, the East China Sea and the South China Sea have been employed so that the improved spectra can be verified on a more extensive observational basis.Computed results agree with the observations well.Further comparisons have been made between the proposed spectra and the JONSWAP spectrum.Though the two types of spectrum are close to each other in form, the former shows, as a whole, better agreement with the observation than the latter.By introducing an improved relation between the peakness factor and significant wave steepness, the spectrum contains only significant wave height and period as parameters.For spectra given in this form, the computed peak frequencies coincide approximately with observed values and the compuled peak magnitudes of spectra agree basically with observations, but, because of the statistic variability inherent in the measurements of significant wave heights and periods, there ate certain discrepancies between computed and measured spectrum peak magnitudes.