Estimating Plume Dispersion-A Comparison of Several Sigma Schemes

Abstract The lateral and vertical Gaussian plume dispersion parameters are estimated and compared with fieldtracer data collected at II sites. The dispersion parameter schemes used in this analysis include Cramer'sscheme, suggested for tall stack dispersion estimates, Draxier's scheme, suggested for elevated and surfacereleases, Pasquill's scheme, suggested for interim use in dispersion estimates, and the Pasquill-Gifford schemeusing Turner's technique for assigning stability categories. The schemes suggested by Cramer, Draxler andPasquil estimate the dispersion parameters using onsite measurements of the vertical and lateral windvelocity variances at the effective release height. The performances of these schemes in estimating the dispersion parameters are compared with that of the Pasquill-GitFord scheme, using the Prairie Grass andKarlsruhe data. For these two experiments, the estimates of the dispersion parameters using Draxier's schemecorrelate better with the measurements than did estimates using th...