Derivation of eddy diffusivities from an unsteady turbulence spectrum

A general formulation for eddy diffusivities has been derived for use in atmospheric dispersion models. Expressions of eddy diffusivities for inhomogeneous turbulence are proposed, which are calculated directly with the Batchelor theory and can consider nonstationary spectrum important in turbulence decay. A statistical evaluation shows that the results of an air pollution model, with the K-parameterisation included, produces a good fit of the measured ground-level concentration data in the experimental conditions considered.