Turbulent Diffusion of Heavy Particles in the Atmosphere

Abstract

This paper discusses the likely differences between the diffusion of gaseous and particulate matter in the atmosphere, as would be observed by fixed point instruments (“absolute” diffusion). The potential complicating factor of an “inertia effect” (which would cause a heavy particle not to participate in the higher-frequency oscillations of its fluid-particle neighborhood) is shown to be negligible in the atmosphere. Two interrelated effects termed here the “effect of crossing trajectories” and the “continuity effect,” could be, on the other hand, of great practical importance. Both are caused by the relatively rapid travel of heavy particles across the atmospheric eddies and both could result in an appreciable reduction of dispersion rates. Some estimates of the likely magnitude of these effects are given in the paper.