A new formualtion of the probability density function n random walk models for atmospheric dispersion

摘要

Simulation of atmospheric diffusion in vertifcally nhomogeneous skewed turbulene,which is typical for the daytime boundary layer,is investigated.Particle trajectories are simulated by using the Langevin equationThe main objecitve is to introduce a fformualtion of the probability density funcitn (PDF) of the vertical velocity fluctuation based on a fourth order expansion after Hermite ploynomials (Gram-Charlier expansion).The statistics of the turbulence are introduced by forcing the moments of the Gram-Charlier expansion to equal the parameterzed moments of atmospheric turbulence.