Plant Scherer AERMET Surface Characteristics Comparison

November 24, 2015

Since no on-site meteorological data was available, the surface and upper air observations from 

the Middle Georgia Regional Airport located in Macon, GA (surface) and the Peachtree City, 

GA (upper) NWS stations for the period of 2012-2014 were used in this modeling. 

AERMOD modeling for Georgia Power’s Plant Scherer facility was performed with two sets of 

surface characteristics (albedo, Bowen ratio, and surface roughness). One set of surface 

characteristics was based on the Macon Middle Georgia Regional Airport NWS surface 

meteorological station (Macon NWS station) while the other set was based on the surface 

characteristics surrounding the Plant Scherer facility site. Both sets used AERSURFACE (13016) 

derived for twelve 30-degree sectors out to 1 km at a seasonal temporal resolution for average 

surface moisture conditions. A comparison of the surface characteristics between the Macon 

NWS station and the facility site is shown in Table 1. No significant differences in the albedo 

and Bowen ratio were found. However, significant differences in the surface roughness were 

observed.

Figure 1 contains the 4th highest modeled maximum 1-hour SO2 concentration averaged over 

3-years using the surface characteristics at the Macon NWS station. The maximum value was 

located at approximately 4.4 kilometers southwest of Plant Scherer. Figure 2 contains the 4th

highest modeled maximum 1-hour SO2 concentration averaged over 3-years using the surface 

characteristics at facility site. The maximum value was located at approximately 3.5 kilometers 

west of Plant Scherer. Figure 3 shows a three year wind rose at the Macon NWS station for 

2012-2014.

Table 2 contains the AERMOD modeling results (g/m3) using the surface characteristics at the 

Macon NWS station and the surface characteristics at the Plant Scherer facility site. Table 3 

contains the AERMOD modeling results (ppb) using the surface characteristics at the Macon 

NWS station and the surface characteristics at the Plant Scherer facility site. The results from 

both model runs indicate that SO2 emissions from Plant Scherer do not cause or contribute to any 

violations of the 1-hour SO2 NAAQS.
Table1. Comparisons of albedo, Bowen ratio, and surface roughness at the Macon NWS station 

and the Plant Scherer facility site.

Macon NWS Station Plant Scherer Facility Site

Albedo Bowen 

Ratio

Surface

Roughness

Albedo Bowen 

Ratio

Surface

Roughness

 Surface

Roughness

% Surface

Roughness

Time 

Frequency

Wind 

Sector

0.16 0.58 0.018 0.15 0.64 0.204 -0.19 -91.2 Winter 1 of 12

0.16 0.58 0.016 0.15 0.64 0.107 -0.09 -85.0 Winter 2 of 12

0.16 0.58 0.026 0.15 0.64 0.027 0.00 -3.7 Winter 3 of 12

0.16 0.58 0.030 0.15 0.64 0.040 -0.01 -25.0 Winter 4 of 12

0.16 0.58 0.041 0.15 0.64 0.187 -0.15 -78.1 Winter 5 of 12

0.16 0.58 0.036 0.15 0.64 0.028 0.01 28.6 Winter 6 of 12

0.16 0.58 0.024 0.15 0.64 0.029 -0.01 -17.2 Winter 7 of 12

0.16 0.58 0.039 0.15 0.64 0.109 -0.07 -64.2 Winter 8 of 12

0.16 0.58 0.016 0.15 0.64 0.167 -0.15 -90.4 Winter 9 of 12

0.16 0.58 0.036 0.15 0.64 0.223 -0.19 -83.9 Winter 10 of 12

0.16 0.58 0.062 0.15 0.64 0.143 -0.08 -56.6 Winter 11 of 12

0.16 0.58 0.042 0.15 0.64 0.179 -0.14 -76.5 Winter 12 of 12

0.15 0.39 0.025 0.14 0.50 0.238 -0.21 -89.5 Spring 1 of 12

0.15 0.39 0.023 0.14 0.50 0.127 -0.10 -81.9 Spring 2 of 12

0.15 0.39 0.036 0.14 0.50 0.032 0.00 12.5 Spring 3 of 12

0.15 0.39 0.042 0.14 0.50 0.047 -0.01 -10.6 Spring 4 of 12

0.15 0.39 0.055 0.14 0.50 0.254 -0.20 -78.3 Spring 5 of 12

0.15 0.39 0.045 0.14 0.50 0.031 0.01 45.2 Spring 6 of 12

0.15 0.39 0.030 0.14 0.50 0.032 0.00 -6.3 Spring 7 of 12

0.15 0.39 0.050 0.14 0.50 0.135 -0.09 -63.0 Spring 8 of 12

0.15 0.39 0.023 0.14 0.50 0.208 -0.19 -88.9 Spring 9 of 12

0.15 0.39 0.050 0.14 0.50 0.263 -0.21 -81.0 Spring 10 of 12

0.15 0.39 0.085 0.14 0.50 0.178 -0.09 -52.2 Spring 11 of 12

0.15 0.39 0.057 0.14 0.50 0.207 -0.15 -72.5 Spring 12 of 12

0.17 0.40 0.034 0.14 0.27 0.350 -0.32 -90.3 Summer 1 of 12

0.17 0.40 0.039 0.14 0.27 0.162 -0.12 -75.9 Summer 2 of 12

0.17 0.40 0.104 0.14 0.27 0.039 0.07 166.7 Summer 3 of 12

0.17 0.40 0.187 0.14 0.27 0.060 0.13 211.7 Summer 4 of 12

0.17 0.40 0.182 0.14 0.27 0.420 -0.24 -56.7 Summer 5 of 12

0.17 0.40 0.098 0.14 0.27 0.039 0.06 151.3 Summer 6 of 12

0.17 0.40 0.063 0.14 0.27 0.039 0.02 61.5 Summer 7 of 12

0.17 0.40 0.087 0.14 0.27 0.185 -0.10 -53.0 Summer 8 of 12

0.17 0.40 0.055 0.14 0.27 0.250 -0.20 -78.0 Summer 9 of 12

0.17 0.40 0.108 0.14 0.27 0.315 -0.21 -65.7 Summer 10 of 12

0.17 0.40 0.117 0.14 0.27 0.253 -0.14 -53.8 Summer 11 of 12

0.17 0.40 0.082 0.14 0.27 0.287 -0.21 -71.4 Summer 12 of 12

0.17 0.58 0.029 0.14 0.64 0.350 -0.32 -91.7 Fall 1 of 12

0.17 0.58 0.032 0.14 0.64 0.162 -0.13 -80.2 Fall 2 of 12

0.17 0.58 0.095 0.14 0.64 0.039 0.06 143.6 Fall 3 of 12

0.17 0.58 0.186 0.14 0.64 0.060 0.13 210.0 Fall 4 of 12

0.17 0.58 0.180 0.14 0.64 0.420 -0.24 -57.1 Fall 5 of 12

0.17 0.58 0.097 0.14 0.64 0.039 0.06 148.7 Fall 6 of 12

0.17 0.58 0.062 0.14 0.64 0.039 0.02 59.0 Fall 7 of 12

0.17 0.58 0.083 0.14 0.64 0.185 -0.10 -55.1 Fall 8 of 12

0.17 0.58 0.047 0.14 0.64 0.250 -0.20 -81.2 Fall 9 of 12

0.17 0.58 0.097 0.14 0.64 0.315 -0.22 -69.2 Fall 10 of 12

0.17 0.58 0.104 0.14 0.64 0.253 -0.15 -58.9 Fall 11 of 12

0.17 0.58 0.072 0.14 0.64 0.287 -0.22 -74.9 Fall 12 of 12
Figure 1. Plot of the 4th highest maximum daily 1-hour SO2 (ppb) averaged over 3 years using 

surface roughness at the Macon NWS station.

Figure 2. Plot of the 4th highest maximum daily 1-hour SO2 (ppb) averaged over 3 years using 

surface roughness at the Plant Scherer facility site.
Figure 3. Three year wind rose at the Macon NWS station for 2012-2014.

Table 2. Summary of 1-hour SO2 NAAQS (g/m3) analysis using the surface roughness at the 

Macon NWS station and the Plant Scherer facility site.

Surface 

Roughness

Location

SO2

Averaged 

Period 

SO2 Model Design 

Concentration 

(g/m3)

SO2 Background 

Concentration 

(g/m3)

SO2 Total 

Concentration 

(g/m3)

SO2

NAAQS 

(g/m3)

Below SO2

NAAQS 

(Y/N)

Macon NWS 

Station 1-hour 98.24 30.3 128.54 196 Y

Facility Site 1-hour 94.66 30.3 124.97 196 Y

Table 3. Summary of 1-hour SO2 NAAQS (ppb) analysis using the surface roughness at the 

Macon NWS station and the Plant Scherer facility site.

Surface 

Roughness

Location 

SO2

Averaged 

Period 

SO2 Model Design 

Concentration 

(ppb)

SO2 Background 

Concentration 

(ppb)

SO2 Total 

Concentration 

(ppb)

SO2

NAAQS 

(ppb)

Below SO2

NAAQS 

(Y/N)

Macon NWS 

Station 1-hour 37.5 11.6 49.1 75 Y

Facility Site 1-hour 36.1 11.6 47.7 75 Y