Quoted from: Perry, S.G., 1992. CTDMPLUS: A dispersion model for sources near complex topography. Part I: Technical Formulations. Journal of Applied Meteorology, 31(7), pp.633-645. https://doi.org/10.1175/1520-0450(1992)031<0633:CADMFS>2.0.CO;2 

The Complex Terrain Dispersion Model (CTDMPLUS), a point-source, steady-state model for complex-terrain applications, is described. The model simulates the flow and plume distortion near user-selected, three-dimensional terrain features, yet retains simplicity by applying flow-distortion corrections to flat-terrain, Gaussian, and bi-Gaussian pollutant distributions.

The algorithms for stable and near-neutral conditions are based on the demonstrated concept of a dividing streamline. These algorithms were developed using data from three major plume-impaction field studies and a number of fluid-modeling studies. The algorithms for plumes released into convective layers are based on recent understanding of the convective boundary layer through fluid modeling, numerical modeling, and field studies. The non-Gaussian nature of vertical dispersion is accounted for; lateral dispersion is modeled with the aid of convective scaling concepts.

A terrain preprocessor and a meteorological preprocessor, which provide input specifically for the CTDMPLUS model, are described. The model requires a fully three-dimensional description of individual terrain features in order to estimate flow (and plume) distortions. Estimates of surface-layer parameters (friction velocity and Monin-Obukhov length) and depth of the mixed layer are required to define the state of the boundary layer.