Reconstruction of aeolian saltation enabled by measurements of particle accelerations

Aeolian saltation critically affects geo-morphological processes and Earth's climate, but our understanding of it is incomplete. The dynamics close to the bed are challenging to characterize experimentally, due to the combination of rapid small-scale processes happening at relatively dense concentrations. The process is also difficult to model numerically, due to the vast range of scales at play in the two-way coupling between the turbulent boundary layer and the microscopic particles. In this study, imaging experiments on size-selected glass microspheres are conducted in a large atmospheric wind tunnel, obtaining extensive data sets at high spatio-temporal resolution. Particle tracking velocimetry is applied to measure the saltating particle kinematics, including accelerations, in the millimetres above the bed. Assuming established drag formulations, the data is used to estimate the mean fluid velocity, recovering a logarithmic profile. Also, assuming a quasi-ballistic motion in the vertical direction, constraints on the vertical energy distribution are derived and the trajectory shape for a given ejection energy is reconstructed. This allows evaluating the statistical distribution of the saltation length and height, which are crucial for the modelling of the process.