The Application of a Joint Distribution of Significant Wave Heights and Peak Wave Periods in the Northwestern South China Sea

A joint distribution of significant wave heights (Hs) and peak wave periods (Tp) in the northwestern South China Sea is created using a conditional distribution model in this work. An unstructured triangular mesh wave model covering the northwestern South China Sea is established based on the third-generation spectral wave model SWAN. This wave model has been extensively validated against field data and was run from 1979 to 2020 to generate long enough one-hourly Hs and Tp. Four probability density functions including Normal, Lognormal, Gamma and 3P Weibull distributions are adopted to construct the marginal independent distribution of Hs. The results show that the 3P Weibull distribution is more suitable in fitting the marginal distribution of Hs compared to the other three distributions. Three combinations of dependence functions (μ and σ), namely, power3 and exp3, insquare2 and asymdecrease3, and logistics4 and alpha3, are used to create the Normal and Lognormal distributions for Tp. The estimations of dependence functions and corresponding fitted Tp demonstrate that the μ and σ using power3 and exp3 perform best in producing the conditional distribution of Tp. In addition, the environmental contours derived by an IFORM are used to generate the extreme sea states with return periods of 1, 5, 10, 25, 50 and 100 years.