Analysis of wind speed observations over the North Sea

Wind speed observations of three offshore platforms over the period 1985–1992 have been analysed. These platforms located in the southern North Sea off the Dutch coast, are: K13 Platform (K13), Euro Platform (EPF) and Measuring Post Noordwijk (MPN). First, a statistical analysis of the data was performed, including calculation of mean wind speeds, availability of data, annual and diurnal variations, the Weibull parameters and the distribution by wind direction. Then, in order to compare the wind speeds of the platforms measured at different heights, Monin-Obukhov similarity theory was applied. Therefore, air and seawater temperature data were used from observations on the platforms (if available) or from Voluntary Observing Ships. The seawater temperatures were fitted to a sine function. Although, on a yearly average, (very) unstable conditions prevail, the calculated wind profiles showed hardly any difference between the logarithmic and the diabatic wind profile. On a seasonal basis, however, the logarithmic and diabatic wind profile differ significantly, for the spring season in particular. Wind speeds increased with increasing distance from the coast.