Consider the two receptors depicted in Figure 10. Both receptors are located at the same

distance

xrfrom the source but at different heights above ground, i.e.,zr1andzr2. An exampleprofile of some parameter " is shown at the far left of the figure. The value of the effective

parameter used by AERMOD to represent transport and diffusion from source to receptor

depends on the location of the receptor. For receptor 1 the effective parameter value ~α

1

(shown in the figure as "

eff1) is determined by averaging the values of " {z} betweenHp{xr} and

zr1. Therefore, the layer over which this average is taken is smaller than the plume’s half-depth.Whereas, (shown in the figure as "

eff2) is determined by averaging " {z} over the full layer ~α2

from

Hp{xr} down through a depth of 2.15Fz{xr} since the receptor is located below the definedlower extent of the plume.

Since F

z{xr}depends on the effective values of FwTandu,the plume size is estimated byfirst using the plume height values of F

wT{Hp} andu{Hp} to calculate F

z{xr}.As illustrated incalculated. Once the averaging layer for a given plume and receptor is established the effective

values, , are computed as simple averages: ~α

where

hbandhtare the bottom and top, respectively, of the layer of importance such that:For all plumes, both limits are bounded by either the

zrorHp.For both the direct and indirectsources

ht, in eq. (43) is not allowed to exceedziand ifhb$zithen α~ = α {z} .iFor plumes in stable conditions and for the penetrated source in the CBL,

Hpis always setequal to the plume centerline height (Δ

h h) , wherehsis the stack height corrected for stacks s+tip downwash and )

hsis the stable source plume rise. The stable source plume rise )hsiscalculated from expressions found in Section 5.6.2.

In the CBL, the specification of

Hpis somewhat more complicated. Because of limitedmixing in the CBL the center of mass of the plume will be the plume height close to the source

and the mid-point of the PBL at the distance where it becomes well mixed. Beyond final plume

rise,

Hpis varied linearly between these limits.Prior to plume stabilization, i.e.,

x < xf(distance to plume stabilization),

H h h, where )hdis the plume rise for the direct source (estimated from eq. (91)),p s dp= + Δ,and )

hp(=hep - hs) is the plume rise for the penetrated source, wherehep(penetrated sourceplume height) is calculated from eq. (94).

The distance to plume stabilization,

xf, is determined following Briggs (Briggs 1975; Briggs1971) as

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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