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The Lagrangian model then calculates the air pollution dispersion by computing the statistics of the trajectories of a large number of the pollution plume parcels. A Lagrangian model uses a moving frame of reference [6] as the parcels move from their initial location. It is said that an observer of a Lagrangian model follows along with the plume.
DISPLAY-2 (Greece) – A vapour cloud dispersion model for neutral or denser-than-air pollution plumes over irregular, obstructed terrain on a local scale. It accommodates jet releases as well as two-phase (i.e., liquid-vapor mixtures) releases. This model was also developed at the National Centre of Scientific Research "DEMOKRITOS" of Greece.
In 1970, a private company in the U.S. developed the regional Urban Airshed Model (UAM), which was used to forecast the effects of air pollution and acid rain. In the mid- to late-1970s, the United States Environmental Protection Agency took over the development of the UAM and then used the results from a regional air pollution study to improve it.
A great many computer programs for calculating the dispersion of air pollutant emissions were developed during that period of time and they were called "air dispersion models". The basis for most of those models was the Complete Equation For Gaussian Dispersion Modeling Of Continuous, Buoyant Air Pollution Plumes shown below: [4] [5]
The rising air creates a low pressure zone near the equator. As the air moves poleward, it cools, becomes denser, and descends at about the 30th parallel, creating a high-pressure area. The descended air then travels toward the equator along the surface, replacing the air that rose from the equatorial zone, closing the loop of the Hadley cell. [3]
A reference atmospheric model describes how the ideal gas properties (namely: pressure, temperature, density, and molecular weight) of an atmosphere change, primarily as a function of altitude, and sometimes also as a function of latitude, day of year, etc. A static atmospheric model has a more limited domain
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
The CALPUFF model is designed to simulate the dispersion of buoyant, puff or continuous point and area pollution sources as well as the dispersion of buoyant, continuous line sources. The model also includes algorithms for handling the effect of downwash by nearby buildings in the path of the pollution plumes.