where the subscripts

yandzare deleted from F

bbecause Fybis assumed equal to Fzb. With theexception of the CBL’s penetrated source the form of eq. (75) applies to all source dispersion in

both the CBL and SBL such that F

y,zbecomes Fys,zsand Fyjs,zjand Fya,zabecomes Fyas,zasand Fyajs,zajfor the SBL and CBL, respectively. For the penetrated source, the total dispersion is assumed to

include ambient and buoyancy induced turbulence only; building wakes are assumed to have little

influence. For the injected source, the total dispersion is calculated as if the source were in the

SBL.

(77)

A comment on notation: eq. (75) applies for both lateral and vertical dispersion in the SBL

and CBL. In references to the SBL, F

zappears as Fzsin the dispersion equation; Fzaappears asF

zas. In reference to the CBL, F

zappears as Fzjfor the dispersion expression applicable to thedirect and indirect sources and F

zaappears as Faj; for the penetrated source F

zappears as Fzpin thedispersion expression.

5.5.1 DISPERSION FROM AMBIENT TURBULENCE

5.5.1.1

Lateral Dispersion from Ambient TurbulenceIn general terms, the ambient component of the lateral dispersion is based upon Taylor (1921)

such that:

where

p= 0.5,uis the wind speed, Fv is the root-mean-square lateral turbulence velocity, andTLyis the Lagrangian integral time for the lateral turbulence. Application of eq. (76) in a preliminary

version of AERMOD yielded poor concentration estimates in comparison to those found in the

Prairie Grass field experiments (Barad 1958). Specifically, the lateral spread was not well

matched. Therefore, the lateral dispersion expression was reformulated to allow for an empirical

fit to the Prairie Grass data.

Using an approach similar to that of Venkatram et al. (1984)

TLyis found to bel/F

vwherelisan appropriate length scale for lateral turbulence. Equation (76) can be written in terms of the

non-dimensional downwind distance

Xand a non-dimensional height scale " as:

n951 - n952 - n953 - n954 - n955 - n956 - n957 - n958 - n959 - n960 - n961 - n962 - n963 - n964 - n965 - n966 - n967 - n968 - n969 - n970 - n971 - n972 - n973 - n974 - n975 - n976 - n977 - n978 - n979 - n980 - n881 - n982 - n983 - n984 - n985 - n986 - n987 - n988 - n989 - n990 - n991 - n992 - n993 - n994 - n995 - n996 - n997 - n998 - n999 - n1000

castellano: DISPER CUSTIC DESCAR RADIA italiano:

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

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