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h2. The Effects of Seasonality on the Calculation of Environmental Extremes in the North Sea Wind & Wave Extremes
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The Dutch Water Defenses are designed and maintained according to hydraulic load&nbsp;
estimates determined from extreme value analysis of wind and wave data from the&nbsp;
North Sea. Commonly, this analysis involves selection of extremes via peaks-over-threshold which are then fit to a generalized Pareto distribution. This process&nbsp;
assumes the data are independent and identically distributed (iid). The first can be&nbsp;
achieved through declustering, but the second is more difficult to confirm and may&nbsp;
be violated by seasonal variation and other temporal trends.
In this study, the importance of this violation will be investigated by applying a time-stratified (seasonal) model and a time-varying model (here a non-homogeneous&nbsp;
Poisson process) for full-year return value estimates which can be compared to the&nbsp;
results of current, non-seasonal methods. In addition, an effort will be made to&nbsp;
estimate seasonal return values (eg. Separate summer and winter estimates), since&nbsp;
the critical failure modes may be different in different seasons.
The Dutch Water Defenses are designed and maintained according to hydraulic load&nbsp;estimates determined from extreme value analysis of wind and wave data from the&nbsp;

North Sea. Commonly, this analysis involves selection of extremes via peaks-over-threshold which are then fit to a generalized Pareto distribution. This process&nbsp;

assumes the data are independent and identically distributed (iid). The first can be&nbsp;achieved through declustering, but the second is more difficult to confirm and may&nbsp;

be violated by seasonal variation and other temporal trends.

In this study, the importance of this violation will be investigated by applying a time-stratified (seasonal) model and a time-varying model (here a non-homogeneous&nbsp;

Poisson process) for full-year return value estimates which can be compared to the&nbsp;results of current, non-seasonal methods. In addition, an effort will be made to&nbsp;

estimate seasonal return values (eg. Separate summer and winter estimates), since&nbsp;the critical failure modes may be different in different seasons.
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