A semiempirical model to estimate vertical dispersion of elevated releases in the stable boundary layer

Abstract An analysis of estimates of σz obtained from data collected during a field study sponsored by the U.S. EPA suggests the following model of vertical dispersion of elevated releases in the stable boundary layer. σz = σwpost|staggered|t/(1+ t 2T L ) 1 2 The dispersion time scale TL is given by TL = l/sigma;w, where the mixing length l is 1 l = 1 l n + 1 l s and the neutral length scale ln and the stable length scale ls are given by ln= αzr; l s = γ 2 σ w N . The variance of the vertical velocity fluctuations σ2w and the Brunt-Vaisala frequency N are evaluated at the release height zr. The constants γ2 and α are obtained from surface layer flux-gradient relationships in the limits of z-less stratification and zero heat flux, respectively. Our analysis does not support the new theory of Pearson et al. (1983) that suggests that γ depends upon molecular mixing processes.