Measurements of relative σy up to 1800 km from a single source

• Published in: Atmospheric environment 1988, Vol.22 (6), p.1061-1069
• Main Authors: Carras, J.N., Williams, D.J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Exact sciences and technology; Long-range diffusion; plume dispersion; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; σy measurements
• ISSN: 0004-6981
• DOI: 10.1016/0004-6981(88)90336-8

Measurements of the relative dispersion of plume material, σ y , have been made up to distances of 1800 km from a single source. These distances correspond to ages or travel times up to 67 h. The data were obtained from an aircraft over remote parts of Australia and from plumes emanating from sulphide smelters at Mount Isa and Kalgoorlie. Plume trajectories were calculated from pilot balloon data obtained from a meteorological network across the continent and values of the plume age or travel time were obtained. A phenomenological model shows how the crosswind distribution of plume material is related to the turbulence present in the atmospheric boundary layer. In general, the crosswind distribution of plume material is non-Gaussian in shape. The often-used equation for long-range plume modelling, σ y = 0.5 t, is shown to provide, overall, a poor fit to the experimental data. The data provide evidence for the existence of a region of accelerating diffusion of the form σ 2 y ∝ t 3 for values of t such that t > ∼3 h as predicted by Gifford (1984, Boundary Layer Met. 30, 159–175). At the largest values of plume age measured in the study the data do not unambiguously distinguish between a t 3 2 , t 1 2 or the exponential dependence of σ 2 y characteristic of two-dimensional turbulence.