Large-scale coherent structures in the atmosphere over a flat terrain

Large-scale coherent motions in the atmospheric boundary layer are investigated from field measurements made with two scanning wind lidars over a two-dimensional domain covering approximately 50 km(2). The size, isotropy and two-point statistics of the coherent structures, show their influence on wind field homogeneity and local conditions that wind turbines might experience within a wind farm. For neutral atmospheric stability and high wind conditions, most of these structures are observed to be narrow streaks of low streamwise momentum having positive vertical velocity component (ejections), extending several kilometers. The results shown here are consistent with numerical simulations of atmospheric flows under similar conditions, and scale experiments made in laboratories.