obviating the need to differentiate between the formulations for simple and complex terrain (as

required with previous regulatory models) .

The general concentration equation, which applies in stable or convective conditions is

given by

where

C x y zis the total concentration, is the contribution from theT r r r{ , , }C x y z c,s r r r{ , , }horizontal plume state (subscripts

candsrefer to convective and stable conditions, respectively),

C x y zis the contribution from terrain-following state,fis the plume state weightingc,s r r p{ , , }function, {

x,y,z} is the coordinate representation of a receptor (withzrdefined relative tor r rstack base elevation),

z z zis the height of a receptor above local ground, andztis thep r t= −terrain height at a receptor. Note that in flat terrain,

z, , and the concentrationt= 0z z p r=(eq. (48)) reduces to the form for a single horizontal plume. It is important to note that for any

The formulation of the weighting factor requires the computation of

Hc. Using the receptorspecific terrain height scale (

hc) from AERMAP,Hcis calculated from the same algorithmsfound in CTDMPLUS as:

where

u{Hc} is the wind speed at heightHc, andNis the Brunt-Vaisala frequency.The height scale,

hc, characterizes the height of the surrounding terrain that most dominates theflow in the vicinity of the receptor.

The weighting between the two states of the plume depends on the relationship between

Hcand the vertical concentration distribution at the receptor location. Assuming that the wind

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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