Diffusion in the diabatic surface layer

Abstract

Diffusion from point and line sources in an adiabatic surface layer were briefly discussed using a similarity method by Ellison, following a suggestion made at the 1958 Oxford Symposium by Batchelor. The chief result is that the ground concentration at a downwind distance x, from a point source at ground level, is found to be proportional to xm, where m lies in the range −1.85 to −1.9. Assuming that Lagrangian similarity of the surface layer turbulence obtains also in the diabatic case, the power index, m, of the downwind ground level concentration is shown, in the present work, to vary from about −1.35 in very stable conditions to −3.0 in superadiabatic conditions. This result is in good agreement with recent detailed concentration measurements.