A new formulation of #sigma# _y and #sigma# _z for air quality dispersion models

摘要

A general formulation for estimating dispersion parameters #sigma# _y and #sigma# _z in the Planetary Boundary Layer (PBL) is proposed. These parmeterizations can be utilised in Gaussian air quality dispersion models for regulatory applications. They are based on the classical Taylor's statistical diffusion theory and on the modelled turbulent kinetic energy spectra and represents an extension of previous models (Degrazia et al.~(1,2)) which were mainly focused on dispersion in a purely convective or in a purely mechanic boundary layer. The sigmas proposed here allow to treat the dispersion in a boundary layer where both buoyancy and shear are important forcing mechanisms. The improved parameterization, inserted in a Gaussian model, has been validated using SF_6 tracer data taken from dispersion experiments.