Measurements of momentum flux in the boundary layer by RASS

Abstract

Ground-based remote measurements of the turbulent vertical flux of horizontal momentum in the atmospheric boundary layer are described. For this experiment a wind profiler was operated in the radio acoustic sounding system mode, which uses the scattering at artificially generated sound waves rather that at natural microturbulent refractive-index variations as in the case of conventional clear-air radar. The method used to derive the momentum flux from sound velocities measured parallel to different radar beams is explained. The accuracy and resolution is apparently high enough to obtain useful measurements at least under conditions with moderate winds. The height range is limited to a few hundred metres in this first experiment due to the advection and adsorption of the scattering sound waves. -Authors