Quantifying Turbulence Effects on Aeolian Sand Transport
Thursday, 18 December 2014
Models of aeolian sand transport generally assume wind momentum inputs and transport rates that are homogenous in space and steady in time. In contrast, field measurements indicate broad temporal and spatial variability in wind velocities and resulting transport fluxes. Poor agreement between field-measured and model-predicted sediment fluxes may therefore result from the problematic steady-state assumption in models. Here, we offer a new approach to modeling aeolian transport in unsteady natural systems. This approach depends on two components: (1) A stochastic description of variability in downward turbulent momentum flux immediately above the layer of saltating particles and (2) Adaptation of existing models for the saltation “saturation” process (spinup of saltation following an abrupt initiation of wind shear over the sediment bed) to treat the response of saltation to time-varying momentum inputs. Development of our new model framework is aided by high-frequency simultaneous measurements of wind velocity and saltation flux during natural aeolian sand transport.