A hybrid plume model for local-scale atmospheric dispersion

This paper presents a local-scale dispersion model, based on atmospheric bo undary layer scaling theory. In the vicinity of the source, Gaussian equati ons are used in both the horizontal and vertical directions. After a specif ied transition distance, gradient transfer theory is applied in the vertica l direction, while the horizontal dispersion is still assumed to be Gaussia n. The dispersion parameters and eddy diffusivity are modelled in a form, w hich facilitates the use of a meteorological pre-processor. We present a no vel model of the vertical eddy diffusivity (K-z), which is a continuous fun ction of height in various atmospheric scaling regions. The model also incl udes a treatment of the dry deposition of gases and particulate matter. The accuracy of the numerical model was analysed by comparing the model predic tions with two analytical solutions; the numerical deviations from these so lutions were less than 2% for the computational regime. The model has been tested against the Kincaid experimental field data. The agreement of the pr edictions and the data is good on the average, although the internal variat ion of the predictions versus data scatter plot is substantial. (C) 1999 El sevier Science Ltd. All rights reserved.