ON THE LONG-TERM JOINT DISTRIBUTION OF CHARACTERISTIC WAVE HEIGHT AND PERIOD AND ITS APPLICATION

By analysing the scatter diagrams of characteristic wave height H and period T on the basis of instrumental data from various ocean stations, it was established that the conditional expectation and standard deviation of wave periods for a given wave height can be better predicted by using the equations of normal linear regression rather than by those based on the log-normal 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, the authors 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) they established a new parameterised model for the long-term joint distribution (P(H.T). As an example of the application of the new model, a method for estimating wave periods associated with extreme wave height is given.