Source Characterization
AERMOD gives the user the ability to characterize a source as either a point, an area, or a volume. AERMOD additionally has the capability of characterizing irregularly shaped area sources.
Point sources are characterized exactly as in the ISC3 model (USEPA, 1995). The input to the model includes the location, elevation, emission rate, stack height, stack gas temperature, stack gas exit velocity, and stack inside diameter. The temperature, exit velocity, and diameter are required for plume rise calculations.
Similarly,
volume sources require the same input as the ISC3 model. This
includes the location, elevation height (optional), height of
release, emission rate, the initial lateral plume size (
y
) and y initial vertical plume size (z
). AERMOD differs from ISC3 in
the treatment of volume sources z only in how the initial plume size is implemented. Where ISC3 uses the
virtual source technique to account for initial plume size, AERMOD
adds the square of the initial plume size to the squareof the ambient
plume size:
The area source treatment is enhanced from that available in ISC3. In addition to being input as squares or rectangles, area sources may be input as circles or polygons. A polygon may be defined by up to 20 vertices. A circle is defined by inputting its center location and radius. The AERMOD code uses this information to create an equivalent nearly-circular polygon of 20 sides, with the same area as the circle.
As with ISC3, AERMOD allows for the calculation of a simple half-life decay.
6 The AMS/EPA Regulatory Model AERMOD
6.1
General Structure of AERMOD Including Terrain
6.2
AERMOD Concentration Predictions in the CBL
6.2.1
DIRECT SOURCE CONTRIBUTION TO CONCENTRATION
CALCULATIONS
IN THE CBL
6.2.2
INDIRECT SOURCE CONTRIBUTION TO CONCENTRATION
CALCULATIONS
IN THE CBL
6.2.3
PENETRATED SOURCE CONTRIBUTION TO CONCENTRATION
CALCULATIONS
IN THE CBL
6.3
Concentrations in the SBL Calculated by AERMOD
6.4
Estimation of Dispersion Coefficients
6.4.1
AMBIENT TURBULENCE FOR USE IN CALCULATING DISPERSION
6.4.2
BUOYANCY INDUCED DISPERSION (BID) COMPONENT OF _ AND _
y z
6.4.3
COMPONENT OF DISPERSION COEFFICIENTS DUE TO
DOWNWASH
6.5
Plume Rise Calculations in AERMOD
6.5.1
PLUME RISE IN THE CBL
6.5.2
PLUME RISE IN THE SBL
6.6
Source Characterization
6.7
Adjustments for the Urban Boundary Layer
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