| abstract | - Atmospheric dispersion models are computer programs that use mathematical algorithms to simulate how pollutants in the ambient atmosphere disperse and, in some cases, how they react in the atmosphere. The dispersion models are used to estimate or to predict the downwind concentration of air pollutants emitted from sources such as industrial plants and and vehicular traffic. Such models are important to governmental agencies tasked with protecting and managing the ambient air quality. The models are typically used to determine whether existing or proposed new industrial facilites are or will be in compliance with national ambient air quality standards. The models may also be used assist in the design of effective control strategies to reduce emissions of harmful air pollutants. The dispersion models require the input of data which includes:
* Meteorological conditions such as wind speed and direction, the amount of atmospheric turbulence (as characterized by what is called the "stability class"), the ambient air temperature and the height to the bottom of any inversion aloft that may be present.
* Emissions parameters, such as source location and height, source vent stack diameter and exit velocity, exit temperature and mass flow rate.
* Terrain elevations at the source location and at the receptor location.
* The location, height and width of any obstructions (such as buildings or other structures) in the path of the emitted gaseous plume The atmospheric dispersion models are also known as atmospheric diffusion models, air dispersion models, air quality models, and air pollution dispersion models. This compilation of atmospheric dispersion models lists and, where possible, very briefly describes the models currently in use by the U.S. EPA.
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