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DFE World: Design & the Global Environment
Photograph of Nature
Air Pollution

Atmospheric Stability

Dispersion Coefficients

Coordinate System




Central Campus Map


Model Output


Central Campus Air Quality Model (CCAQM) Instructions


Gaussian Model Coordinate System

The location of the source is important in determining the pollution concentration at a receptor.  Pollutants from a smoke stack are assumed to spread according to the figure below.  Emissions from vehicles traveling along a road will behave similarly, except the height of the source is located at ground level, and the stack can be thought of as extended in the y-direction according the length of the road.  Thus, the location of the source relative to the location of the chosen receptors will partially determine the pollution concentration at those receptors.  The pollution concentration is also dependent on emission rate, stability class, wind direction, and wind speed. 

In this orientation, the positive x-direction is downwind, and x is the distance downwind.  The positive y-direction is normal to the x-direction so that y is the lateral distance from the plume centerline.  The z-direction indicates the elevation of the pollutant; therefore, the z distance is the vertical distance to the centerline of the plume.


Coordinate System for Gaussian Model