Comparison of the Complex Terrain Algorithms Incorporated into Two Commonly Used Local-Scale Air Pollution Dispersion Models (ADMS and AERMOD) Using a Hybrid Model

Figures & data

Figure 1. Different flow regimes above and below the dividing surface used in ADMS when Fr < 1.

Table 1. Stack parameters for the stacks in each of the cases

	Stack	Height (m)	Diameter (m)	Exit Velocity (m/sec)	Volume Flow Rate (m^3/sec)	Temperature (°C)	Emission Rate (g/sec)
Clifty Creek	Stack1	207.9	4.63	45*	—	172	2726*
	Stack2	207.9	4.63	46*	—	172	2756*
	Stack3	207.9	4.63	47*	—	172	2813*
Ribblesdale	Dry Kiln	92	2.3	—	115.8	160	168
	Wet Kiln	104	4.2	—	175	220	218.5
Notes: *This parameter varies hourly and this is the average value. In the case of Clifty Creek, plume rise was not accounted for and the exit velocities and temperatures were not used.

Figure 2. Terrain contour map and isometric projection for Clifty Creek. The stack is marked with a white star, the heights are in meters.

Figure 3. Terrain contour map and isometric projection for Ribblesdale. The stacks are marked with white stars, the heights are in meters.

Table 2. Meteorological parameters used in the Clifty Creek and Ribblesdale calculation

	Clifty Creek				Ribblesdale
Data capture		100%			99.8%
Height (m)		10			10
Roughness length at met site (m)		0.2			0.5
	Statistics
	Mean	Minimum	Maximum	Mean	Minimum	Maximum
Temperature (°C)	12.0	−17.8	34.4	9.9	−4.8	26.5
Wind speed (m/sec)	5.0	0	21.1	4.7	0	15.5
Cloud cover (oktas)	5.0	0	8	5.5	0	8

Figure 4. Wind roses of wind data used for the (a) Clifty Creek and (b) Ribblesdale model calculations.

Table 3. Maximum (and minimum) values for the average and maximum normalized concentrations for Clifty Creek

Model	Average Concentration (μsec/m^3)		Maximum Normalized Concentration (μsec/m^3)
ADMS hills	0.0464		10.40
ADMS no hills	0.0343		5.24
AERMOD hills	0.0251		5.01
AERMOD no hills	0.0265		5.21
	Minimum	Maximum	Minimum	Maximum
ADMS hills–ADMS no hills	−0.0017	0.0335	−1.25	6.21
AERMOD hills–AERMOD no hills	−0.0012	0.0052	−3.32	1.85
ADMS hills–AERMOD hills	0.0005	0.0355	−1.85	7.91
ADMS no hills–AERMOD no hills	−0.0021	0.0112	−2.41	2.52

Figure 5. Clifty Creek annual average concentrations normalized by the emission rate. Terrain elevation contours (black) are shown in the top two plots. The first four plots show concentrations calculated by the models, the second four plot differences in concentrations.

Table 4. Maximum (and minimum) values for the average and maximum normalized concentrations for the Ribblesdale case

Model	Average Concentration (μsec/m^3)		Maximum Normalized Concentration (μsec/m^3)
ADMS hills	0.0470		1.01
ADMS no hills	0.0417		0.90
AERMOD hills	0.0518		10.36
AERMOD no hills	0.0316		0.54
	Minimum	Maximum	Minimum	Maximum
ADMS hills–ADMS no hills	−0.0027	0.0063	−0.11	0.53
AERMOD hills–AERMOD no hills	−0.0017	0.0416	−0.03	9.94
ADMS hills–AERMOD hills	−0.0421	0.0164	−9.90	0.60
ADMS no hills–AERMOD no hills	−0.0008	0.0104	−0.21	0.51

Figure 6. Ribblesdale annual average concentrations normalized by the emission rate. Terrain elevation contours (black) are shown in the top two plots. The first four plots show concentrations calculated by the models, the second four plot differences in concentrations.