A stochastic model for the motion of a particle initially at rest on a surface is explored. Fluid and adhesive forces are quantified based on first principles, and turbulent fluctuations are addressed probabilistically from probability distribution functions. A Monte Carlo process yields the distributions of particle position and velocity under a wide range of wind conditions and soil sizes. Results indicate that particle size and friction velocity are the most important factors in determining if a particle will resuspend and in predicting its subsequent motion. Larger wind speeds produce more violent fluctuations, which have a greater effect on small particles than on large particles. A theoretical analysis of the threshold friction velocity supports earlier experimental findings. The aerodynamic lift force cannot be neglected, and the torque exerted on a particle can be important in some cases. Applying the results of this work may contribute to reducing uncertainty in large-scale aerosol models.

This article describes a stochastic model for resuspension that combines both aerodynamic entrainment and momentum transfer from saltating particles. Two case studies are performed based on soil conditions for the topmost layer of soil in Los Angeles County, CA, and Allegheny County, PA. Wind friction velocity, u * , and soil size distribution were found to be the most important factors in predicting mass and number flux. Under a broad range of wind conditions mass and number fluxes agree to within an order of magnitude with the empirical models of Marticorena and Bergametti (1995) and Ginoux et al. (2001) at u * ≤0.4 m/s. For u * ≤0.60 m s −1 and u * ≥ 0.85 m s −1 aerodynamic forces and splash were the dominant resuspension mechanisms, respectively. Flux was sensitive to wind speed but was not proportional to u * 3 . The mass and number distributions with height peaked at heights corresponding to the maximum concentration of saltating particles and the maximum concentration of suspended particles, respectively. Particles that are most likely to resuspend in the absence of saltation are <10 µm or >100 µm in diameter. The average particle diameter increases with height but is consistently less than the average particle diameter of the parent soil. Simulations reached steady state in approximately 0.01 seconds, and an alternative method of predicting the reduction in near-surface wind speed as a result of saltation is presented as a component of the model.

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