Particles dispersion in a stratified turbulent Ekman boundary layer

Particle dispersion in a stratified bottom Ekman layer is studied by direct numerical simulation. Neutral, stable and unstable stratifications are considered. The stable stratification tends both to suppress the turbulence and to reduce the boundary layer thickness, while the opposite is observed for the unstable case. Therefore stable stratification inhibits vertical dispersion of particles, whereas unstable stratification gives rise to a rapid dispersion of particles in the vertical direction. We show that besides having a strong influence on the diffusion along the vertical, stratification also affects particle dispersion along the horizontal directions.