Monte Carlo simulation of buoyant dispersion

Transport and diffusion of dust and nonbuoyant smoke are simulated in a realistic manner by the particle model originally developed by Ohmstede and Stenmark (1980, 1981). However, many pollutants are buoyant, such as burning trash, oil, or other flammable or explosive material. The resultant buoyant cloud is taken into account by a new simple algorithm included in the particle model. For the model discussed in this paper, a particle represents a small parcel of air plus pollutant. The method uses the difference in temperature between an individual particle and the ambient atmosphere to generate a vertical acceleration. It also considers entrainment and ingestion of unheated material on, or loss of heat by contact with, the ground during initial release and subsequent ground contact. A series of computer runs suggests that the particle model with the new buoyancy algorithm realistically simulates transport and diffusion of buoyant material.