Detection and characterization of very-large-scale motions in the atmospheric surface layer through wind LiDAR measurements

Coherent turbulent structures with dimensions larger than the height of the atmospheric surface layer (ASL), h, denoted as very-large-scale motions (VLSMs) or superstructures, have been investigated through scanning Doppler wind LiDARs. Measurements were performed at two sites: one very flat and homogeneous at the SLTEST facility, Utah, and a second site in Celina, Texas, which is characterized by a certain level of heterogeneity and an aerodynamic roughness length of two orders of magnitude larger than for the first site. LiDAR measurements were performed using a probe-volume with a length of 18 m, which leads to a vertical resolution smaller than 1 m. Pre-multiplied velocity spectra of the LiDAR data singled out the presence of an energy peak at an altitude about 0.15 h associated with wavelengths about 4-10 h. Integral length scales, aspect ratio and inclinations of VLSMs are estimated as well, which are in good agreement with previous experiments. The results indicate that current wind LiDAR technology is a valuable measurement technique to investigate VLSMs, while providing easier deployments than traditional towers and allowing for custom scanning strategies to probe the entire ASL height.