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DISPER software: Air pollution map produced by three different stacks (XZ-plane)
Canarina software for analysis of air pollution in environment: air pollution control, environmental engineering, environmental consultancy service, environment simulation, environmental modeling and environmental impact assessment. Air dispersion software: ISC 108 dynamics
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DISPER: Air pollution dispersion ˇ DISPER - Solutions - Data - Algorithms - Emissions - Graphs - ISC3 (VOL. 2)
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1.5 ISC COMPLEX TERRAIN SCREENING ALGORITHMS
The
Short Term model uses a steady‑state, sector-averaged Gaussian plume
equation for applications in complex terrain (i.e., terrain above stack or
release height). Terrain below release
height is referred to as simple terrain;
receptors located in simple terrain are modeled with the point source
model described in Section 1.1. The
sector average approach used in complex terrain implies that the lateral
(crosswind) distribution of concentrations is uniform across a 22.5 degree
sector. The complex terrain screening
algorithms apply only to point source and volume source emissions; area source and open pit emission sources are
excluded. The complex terrain point
source model, which is based on the COMPLEX1 model, is described below. The description parallels the discussion for
the simple terrain algorithm in Section 1.1, and includes the basic Gaussian
sector-average equation, the plume rise formulas, and the formulas used for
determining dispersion parameters.
1.5.1 The Gaussian Sector Average Equation
The Short Term complex terrain screening algorithm for stacks uses the steady‑state, sector-averaged Gaussian plume equation for a continuous elevated source. As with the simple terrain algorithm described in Section 1.1, the origin of the source's coordinate system is placed at the ground surface at the base of the stack for each source and each hour. The x axis is positive in the downwind direction, the y axis is crosswind (normal) to the x axis and the z axis extends vertically. The fixed receptor locations are converted to each source's coordinate system for each hourly concentration calculation. Since the concentrations are uniform across a 22.5 degree sector, the complex terrain algorithms use the radial distance between source and receptor instead of downwind distance. The calculation of the downwind, crosswind and radial distances is described in Section 1.5.2. The hourly concentrations calculated for each source at each receptor are summed to obtain the total concentration produced at each receptor by the combined source emissions.
