COMPARISON OF EXTRAPOLATION METHODS FOR ESTIMATING EXTREME METOCEAN CONDITIONS

Abstract

Accurate prediction of extreme wave heights is of great importance to the design of reliable offshore structures. This study compares the performance between several commonly used extreme value distributions as well as the upcrossing rate approach. Furthermore, a new method is presented in the study that searches for an “optimal block size” to account for the correlation between adjacent sea states. This block size is optimized to account for the correlation effectively and to preserve as much data as possible. The accuracy of statistical models is assessed using a “self-checking” procedure from which the estimates can be examined by the limited data. This study also accounts for intra-period trends in the extreme wave climate due to climate change using a non-stationary extreme value model. Finally, this study proposes a new method to estimate the 5, 50, and 500-year return values based on the provided data.