... threshold, the rate of exceedance of which is described using a Poisson process. The size of threshold exceedances is described by a generalised Pareto model. The characteristics of the threshold, rate and size models are all non-stationary with respect to directional and spatial covariates, parameterised...

... with periods of more than 50 years remain unusual. In addition, metocean criteria are often stratified by covariate - seasonality or directionality are common examples. Further, specification of joint occurrence of parameters at long return periods is necessary to avoid excessive conservatism...