Ambient conditions are defined by the land and atmospheric conditions in the vicinity of the pollutant emission. This Menu lists: Meteorology and Topographic lines.
Meteorology: DISPER analyses, as all mixing zone evaluations, are usually carried out under the assumption of steady-state ambient conditions. If you click this command, the next dialog box is shown:
The necessary data in the Meteorology command is:
Pasquill stability: Classification scheme that describes the degree of atmospheric turbulence. Categories range from extremely unstable (A=1) to extremely stable (F=6). Unstable conditions promote the rapid dispersion of atmospheric contaminants and result in lower air concentrations compared with stable conditions.
Wind speed at reference anemometer height (m/s): The measurement of wind speeds is usually done using a cup anemometer. The cup anemometer has a vertical axis. The number of revolutions per minute is registered electronically.
Wind angle (0 to 360 degrees): It is the horizontal angle of wind measured clockwise from the North (at the window top).
Ambient temperature (K): The temperature of the medium surrounding an object. This is the air temperature at stack location.
Mixing height (m): Mixing Height is used by meteorologists to quantify the vertical height of mixing in the atmosphere. It is the height at which vertical mixing takes place. There is a smaller volume which the pollutant can be dispersed. There is a seasonal variation of mixing height. For Summer daylight hours maximum mixing height can be a few thousand feet where as for Winter it can be a few hundred feet. It is lowest at night and increases during the day.
Anemometer height (m): This is the ambient temperature at stack location.
RURAL/URBAN option: This is the RURAL/URBAN terrain options.
Obtain K value: With this button, you can estimate the Pasquill stability category if it is unknown. If you know the K value, you don't need to use this command. You can write it directly in the Meteorology window. If you click this button, the next dialog box is shown:
Air pollution map (XY-Plane) produced by continuous discharge in time (three stacks). The red colour represents high pollutant concentrations. Wind: E (90 degrees).
Air pollution map (XY-Plane) produced by continuous discharge in time (two stacks). The red colour represents high pollutant concentrations. Wind: S (180 degrees).
Canarina Algoritmos Numéricos, S.L.
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Canary Islands, Spain
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