A dispersion-optics model for calculating visibility impairment and comparisons of model estimates with field measurements

Abstract This paper describes a computerized dispersion-optics model developed for the U.S. Army which calculates the impairment of visibility caused by the presence of suspended particulates and other obscurants. The dispersion model, which is applicable to point or volume sources is used to calculate plume dispersion and other plume properties including the integrated concentration along any line of sight. The optics model utilizes the output from the dispersion-model calculations and single Mie scattering to calculate light transmittance through the plume, the contrast of objects or the plume against the horizon sky and the probability that an object is visible. A partial test of the model performance was made by comparing model calculations with measurements taken during 57 smoke trials conducted at the U.S. Army Dugway Proving Ground, Utah. The results of this comparison indicate that the model adequately calculates line-of-sight integrated concentrations measured during these trials. Additional tests of the optics portion of the computer program are planned.