On the long-term joint distribution of characteristic wave height and period and its application

By analysing the scatter diagrams of characteristic the wave height H and the period T on the basis of instrumental data from various ocean wave stations, we found that the conditional expectation and standard deviation of wave period for a given wave height can be better predicted by using the equations of normal linear regression rather than by those based on the lognormal law.The latter was implied in Ochi's bivariate log-normal model (Ochi.1978) for the long-term joint distribution of H and T.With the expectation and standard deviation predicted by the normal linear regression equations and applying proper types of distribution, we have obtained the conditional distribution of T for given H.Then combining this conditional P (T/H) with long-term marginal distribution of the wave height P (H) we establish a new parameterized model for the long-term joint distribution P (H, T).As an example of the application of the new model we give a method for estimating wave period associated with an extreme wave height.