1.1.5.4

Procedures Used to Account forBuoyancy‑Induced Dispersion.The method of Pasquill (1976) is used to account for the initial dispersion of plumes caused by turbulent motion of the plume and turbulent entrainment of ambient air. With this method, the effective vertical dispersion σ

_{ze}is calculated as follows:where σ

_{z}is the vertical dispersion due to ambient turbulence and Δh is the plume rise due to momentum and/or buoyancy. The lateral plume spread is parameterized using a similar expression:where σ

_{y}is the lateral dispersion due to ambient turbulence. It should be noted that Δh is the distance‑dependent plume rise if the receptor is located between the source and the distance to final rise, and final plume rise if the receptor is located beyond the distance to final rise. Thus, if the user elects to use final plume rise at all receptors the distance‑dependent plume rise is used in the calculation of buoyancy‑induced dispersion and the final plume rise is used in the concentration equations. It should also be noted that buoyancy‑induced dispersion is not used when the Schulman‑Scire downwash option is in effect.

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APLICACIONES castellano: DIS CUS DES RAD english: DIS CUS DES RAD

português: DIS CUS DES RAD italiano: DIS CUS DES RAD