where the buoyancy flux (Fb) is calculated from eq. (57).

For Fb = 0 the distance to final rise is calculated from the ISCST3 ((U.S.Environmental

Protection Agency 1995)) expression


where up is the wind speed at source height, rs is the stack radius, and ws is the stack exit gas


Beyond plume stabilization ( x>xf ), Hp varies linearly between the stabilized plume height

(H{xf}) and the mid-point of the mixed layer (zi /2). This interpolation is performed over the

distance range xf to xm, where xm is the distance at which pollutants first become uniformity

mixed throughout the boundary layer.

The distance xm is taken to be the product of the average mixed layer wind speed and the

mixing time scale, z . That is,

where the averaging of u and FwT are taken over the depth of the boundary layer.

For distances beyond xf , Hp is assumed to vary linearly between the plume's stabilized

height, H {xf }, and zi /2 such that:


Note that in the CBL, both the direct and indirect source will have the same " (effective

parameter) values. In eq. (43) F

z is the average of the updraft F

z and the downdraft F

z , the

maximum value of ht is zi , and when hb $ zi , " = " {zi}.

As discussed previously, when multiple vertical measurements of wind direction are

available a profile is constructed by linearly interpolating between measurements and persisting

the highest and lowest measurements up and down, respectively. The approach taken for

selecting a transport wind direction from the profile is different from the above. The transport

wind direction is selected as the mid point of the range between stack height and the stabilized

plume height.



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