and velocity deficit. In general, these building induced effects act to restrict the rise that the

plume would have in the absence of the building.

PRIME was originally designed (Schulman et al., 2000) to enhance plume growth using

Pasquill Gifford (PG) dispersion (Pasquill 1961; Gifford 1961). AERMOD’s estimate of plume

growth is based on dispersion parameters derived from profiles of turbulence (see Section 4), not

from radiation base turbulence surrogates as is done in the PG approach. A basic design tenet for

incorporating PRIME into AERMOD was to be as faithful as possible to the PRIME formulation

while ensuring that 1) AERMOD’s ambient dispersion was used in place of PG dispersion and 2)

far beyond the wake region, where building influences should be insignificant, concentrations

approach the AERMOD estimate. Therefore, within the wake, PRIME algorithms are use

exclusively to calculate concentration with AERMOD-derived ambient turbulent intensities as

input. To insure a smooth transition between concentrations estimated by PRIME, within the

wake, and AERMOD estimates in the far field, concentrations beyond the wake are estimated as

the weighted sum of the two calculations. That is, beyond the wake the total concentration (Ctotal)

is calculated as follows:

where Cprime is the concentration estimated using the PRIME algorithms with AERMOD-derived

meteorological inputs, CAERMOD is the concentration estimated using AERMOD without

considering building wake effects, and ( the weighting parameter. The weighting parameter, (, is

designed such that the contribution from the PRIME calculation decreases exponentially with

vertical, lateral and downwind distance from the wake. It is calculated as follows:

where x is the downwind distance from the upwind edge of the building to the receptor, y is the

lateral (crosswind) distance from the building centerline to the receptor, z is the receptor height

above ground, Fxg is longitudinal dimension of the wake, Fyg is the distance from the building

centerline to lateral edge of the wake, and Fzg is the height of the wake at the receptor location.

5.6 Plume Rise Calculations in AERMOD

5.6.1 PLUME RISE IN THE CBL

The plume rise for the direct source is given by the superposition of source momentum and

buoyancy effects following Briggs (1984).

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