Assessing the uncertainties of using land-based wind observations for determining extreme open-water winds

For the assessment of the Hydraulic Boundary Conditions (HBC), information is required on wind conditions over open water areas, pertaining to return periods up to thousands of years. In earlier assessments of the HBC, a wind modelling concept was developed to provide adequate estimates of the required information. About 5 years ago however, it was noticed that the observed variation in shape (curvature) of the extreme wind statistics at the KNMI stations does not fit within the
developed wind modelling concept. This disagreement between the data and the modelling concept has become known as the curvature problem. It was clear that the curvature problem needed to be solved in order to derive reliable estimates for the required wind information (for the assessment of the HBC). The aim of the present study was to gain more insight in the curvature problem by means of brief analyses into some physical and statistical
assumptions in the wind modelling concept that is applied in the determination of potential wind series and in the earlier assessments of the HBC.