Comparing Wind Speeds on the North Sea Coast and Offshore

As part of the objective to describe the wind climate of the North Sea and the coastal zone, specifically with regard to wind energy applications, we study the observations of two meteorological stations on the North Sea coast: Hoek van Holland (HVH) and Umuiden (UM). Statistical analysis of the 8-year datasets shows that the mean wind speeds are 7.8 m/s (at 18.5 m height) for UM, and 7.6 m/s (at 15.0 m height) for HVH, respectively. The coastal observations are compared to the observations of three offshore platforms in the North Sea analysed in earlier work. It is found that diurnal variations are very similar in autumn and winter, but differ in spring and summer. Furthermore, wind speeds with fetch over sea do behave very similarly at the coastal stations and offshore platforms. It is shown that the effects of thermal circulation leading to the sea breeze are distinctly present, at least up to 30 km offshore. These effects can be attributed to relatively low wind speeds (less than 7 m/s at 10 m height), and manifest themselves as a shift, on average, of wind directions from easterly to westerly directions during the day. Higher wind speeds (more than 7 m/s), most relevant for wind energy applications, compare well at coastal stations and offshore platforms.