Lagrangian stochastic models for turbulent dispersion in the atmospheric boundary layer

A one-particle three-dimensional stochastic Lagrangian model for transport of particles in a horizontally-homogeneous atmospheric surface layer with arbitrary one-point probability density function of Eulerian velocity fluctuations is suggested. A uniquely defined Lagrangian stochastic model in the class of well-mixed models is constructed from physically plausible assumptions. These assumptions are: (i) in the neutrally stratified horizontally homogeneous surface layer, the vertical motion is mainly controlled by eddies whose size is of order of the current height; and (ii), the streamwise drift term is independent of the crosswind velocity. Numerical simulations for neutral stratification have shown a good agreement of our model with the well-known Thomson's model, with Flesch and Wilson's model, and with experimental measurements as well. However there is a discrepancy of these results with the results obtained by Reynolds' model.