Investigation of aeolian streamers in an atmospheric wind tunnel

Aeolian saltation critically affects geo-morphological processes and Earth's climate, but our understanding of it is incomplete. An apparent but elusive phenomenon is represented by aeolian streamers, elongated regions of seemingly large concentration of dust and sand that are believed to significantly modulate the transport. Their systematic investigation in the field is difficult as the conditions are not well controlled, thus any connection between the streamers and flow structures in the turbulent boundary layer remains unclear. In this study, we conduct experiments in a large atmospheric wind tunnel using monodisperse microspheres. Using high-speed laser imaging, the concentration and velocity of the saltating particles are measured by particle tracking velocimetry along a wall-parallel plane, while the airflow is simultaneously characterized by time-resolved particle image velocimetry along a spanwise wall-normal plane. This extensive dataset allows us to characterize the spatio-temporal distribution of particle concentration and velocity in a cross-section of the saltation layer, and gives us insight in the correlation between the particle motion in the saltation layer and the airflow above. We investigate the length and time scale of particle streamers in the saltation layer, and gain further understanding of how this mode of particle transport is coupled with the dynamics of the turbulent boundary layer.