Derivation of a decorrelation timescale depending on source distance for inhomogeneous turbulence in a shear dominated planetary boundary layer

Abstract

In the literature there exists a variety of pollution of dispersion models and in general, Lagrangian stochastic models are efficient and fundamentals tools in the investigation and study of turbulent diffusion phenomenon in the planetary boundary layer. The LAMBDA model is one of them. In this study, the influence of decorrelation time scales in the LAMBDA model under neutral conditions is evaluated. To this end a new parameterization of decorrelation time scales is proposed and validated. This method is based on the Eulerian velocity spectra and a formulation of the evolution of the Lagrangian decorrelation timescales. A spectral distribution of an Eulerian velocity profile and a formulation of the evolution of Lagrangian decorrelation timescales under neutral conditions is used as the forcing mechanisms (shear-dominated boundary layer) for the turbulent dispersion. The model performance was established by comparing the levels of ground-level concentrations of the tracer gas with experimental results from the classical Prarie Grass experiment.