An observational climatology of anomalous wind events at offshore meteomast IJmuiden (North Sea)

- Analysis of high quality offshore wind observations up to 315 m as far as 85 km off the coast.
- New methods to systematically analyse anomalous wind profiles is presented.
- Extensive climatological description of wind ramp events, for wind speed and direction.

Uncertainty reduction in offshore wind systems heavily relies on meteorological advances. A detailed characterization of the wind climate at a given site is indispensable for site assessment, and its accurate representation in load assessment models can reduce costs of turbine design and the risk of failure. While regular wind conditions are reasonably described by established methods, some atypical wind conditions are poorly understood and represented, although they contribute substantially to load on turbines. In this study, 4 years of high-quality observations gathered up to 300 m are analyzed to characterize the wind climate at the IJmuiden tower, focusing on these ill-defined conditions. Following a systematic approach, six 'anomalous wind events' are identified and described: low-level jets, extreme wind speeds, shear, veer, turbulence and wind ramps. In addition, we identify typical weather conditions that favour their formation. Stable stratification in spring and summer leads to low-level jets (up to 12% of the time) for moderate wind conditions, and to extreme wind shear for stronger wind regimes. Typical wind ramps lead to a change in wind speed of 2 m s−1 in one hour. The applicability of turbulence intensity as a measure of turbulence and gusts is found to be questionable.