Development of coherent structures in complex terrain

Modern wind farms typically span a large domain, 10-km or more, are submerged in the atmospheric boundary layer, and can face distorted flow created by the heterogeneity of the surface topography. Satellite measurements measure the bulk mean flow and the spatial variability of very large scales motion whereas met-masts provide temporal variability at a fixed location. Alternatively, lidar technology provides a measurement system in terms of spatial variability and temporal variability relevant to wind farm scales. A scanning lidar is used to measure the spatial variability of the wind field close to ground with a temporal frequency of 2 Hz. Measurements at a fixed direction aligned with the mean wind flow are employed to track the evolution of the atmospheric flow in complex terrain. Observations are designed specifically to take into consideration the impact of topography in coherence of wind field and different turbulent length-scales. Different coherence models are considered to evaluate the change in wind coherence by the topography, and the change in energy of different length-scales along the mean wind direction is done with spectral analysis.