Evaluation Of Models For The Vertical Extrapolation Of Wind Speed Measurements At Offshore Sites

Monin-Obukhov theory predicts the well-known log-linear form of the vertical wind speed profile. Two parameters, namely the aerodynamic surface roughness length and the Monin-Obukhov-length, are needed to predict the vertical wind speed profile from a measurement at one height. Different models to estimate these parameters for conditions important for offshore wind energy utilisation are discussed and tested: Four models for the surface roughness and three methods to derive the Monin-Obukov-length from measurements are compared. They have been tested with data from the offshore field measurement Rdsand by extrapolating the measured 10 m wind speed to 50 m height and comparing it with the measured 50 m wind speed. The mea