osterild: A natural laboratory for atmospheric turbulence

Understanding atmospheric turbulence is without a doubt one of the most complex subjects in meteorology. However, its behavior can be more easily investigated by analysis of high-quality measurements of the velocity and temperature fluctuations. Here, we show that at the large test station of wind turbines in osterild, northern Denmark, measurements from a 250-m lightning mast provide unique insights into the behavior of atmospheric turbulence within the range of heights where modern large wind turbines operate. We illustrate that for the predominant westerly winds at the site, the flow can be assumed to be close to homogeneous. This allows the analysis of the behavior with atmospheric stability and height of the wind speed and direction and of different turbulence measures, i.a., velocity variances and covariances, as well as turbulence spectra and their characteristics. It is shown, e.g., that for a wide range of atmospheric stability conditions, turbulence parameters up to 241 m are directly related to mean flow characteristics, which will aid in improving the simulation of turbulence in, i.a., aeroelastic simulations. These measurements can be used for the evaluation of a wide range of models describing the meteorological conditions and the atmospheric flow and its turbulent behavior.