Estimating the turbulence length scales from cross-correlation measurements in the atmospheric surface layer

Abstract

Dynamic wind effects on small physical structures have been shown to be dependent on the spatial distribution and three-dimensional structure of highly sheared and elongated eddies embedded in anisotropic turbulence due to the presence of the ground. The turbulence length scales in the lowest 10 m of a low-roughness atmospheric surface layer (ASL) during different stability conditions were analysed from the cross-correlation of velocity measurements obtained from field experiments in the Utah desert. Turbulence length scales of the vertical velocity component are largest in magnitude in the convective ASL from the sporadic bursting of turbulence due to buoyancy forces, whereas the spanwise length scales are similar in magnitude to the longitudinal length scales during stable conditions. During neutral conditions, the longitudinal length scales in the low-roughness ASL were not consistent with semi-empirical models and other field measurements, however the ratios of the lateral and vertical length scales with the longitudinal length scales showed good agreement.