The document evaluates surface roughness using three methods - AERSURFACE modeling, on-site surveys, and meteorological monitoring - at four example sites. AERSURFACE uses land use data that may not accurately represent specific sites. Surveys and monitoring provide site-specific surface roughness values but require time and equipment. Results varied between methods. Using the most up-to-date, site-specific data improves uncertainty in air quality modeling.

1. Surface Roughness
Evaluation Methods
Guideline on Air Quality Models: The Path Forward
Meghan Barber and Dan Dix
mbarber@all4inc.com | ddix@all4inc.com
610.933.5246
March 21, 2013
www.all4inc.com
Kimberton, PA | 610.933.5246
Columbus, GA | 706.221.7688

2. Agenda


Why evaluate surface roughness?
Which evaluation methods were used?
• AERSURFACE (13016)
• Site Survey
• Meteorological Monitoring

Why are these evaluation methods important?
• Impact on modeling results.
• Data representativeness considerations.
• Results and Conclusions.

3. Surface Roughness and AERMET


Surface roughness is used in estimating planetary
boundary layer parameters.
Surface roughness should be:
• Evaluated within 1 kilometer of the measurement site.
• Evaluated within 30-degree arcs (if land use is
variable).

3
AERMOD is particularly sensitive to variations in
surface roughness.
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4. Four Example Sites Evaluated
Eastern Pennsylvania Site
4
Central Pennsylvania Site
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5. Four Example Sites Evaluated
Eastern Virginia Site
5
Western North Carolina Site
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6. AERSURFACE



6
Uses 12 30-meter segments USGS 1992 Land Use
Land Cover (LULC) data to estimate surface
roughness.
21 land use categories, each with an assigned
seasonal surface roughness.
For each sector, surface roughness is calculated as
an inverse distance-weighted geometric mean.
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7. USGS Land Use Patterns
Eastern Pennsylvania Site
7
Central Pennsylvania Site
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8. USGS Land Use Patterns
Eastern Virginia Site
8
Western North Carolina Site
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9. AERSURFACE Results
Virginia
Eastern Pennsylvania
Central Pennsylvania
North Carolina
Wind Direction Sector
Average AERSURFACE Surface Roughness
(meters)
0° - 30°
0.118
0.217
0.474
30° - 60°
0.132
0.101
0.185
0.419
60° - 90°
0.344
0.133
0.186
0.523
90° - 120°
0.226
0.142
0.375
0.494
120° - 150°
0.162
0.189
0.227
0.448
150° - 180°
0.218
0.191
0.177
0.432
180° - 210°
0.161
0.273
0.229
0.439
210° - 240°
0.204
0.269
0.345
0.885
240° - 270°
0.154
0.204
0.297
0.838
270° - 300°
0.126
0.198
0.226
0.452
300° - 330°
0.169
0.185
0.302
0.188
330° - 360°
9
0.124
0.113
0.118
0.219
0.321
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10. Overhead Photo/Survey



10
Site visit to assess actual land use patterns and
height of surface elements.
Calculate an inverse distance weighted geometric
mean surface roughness for actual land use
patterns.
Calculation is similar to that performed by
AERSURFACE using LULC data.
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11. Overhead Photo Approach
11
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12. Site Survey Land Use Patterns
Eastern Pennsylvania Site
12
Central Pennsylvania Site
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13. Site Survey Land Use Patterns
Eastern Virginia Site
13
Western North Carolina Site
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14. Overhead Photo Results
Virginia
Wind Direction
Sector
Eastern Pennsylvania
Central Pennsylvania
North Carolina
Average Site Survey Surface Roughness
(meters)
0° - 30°
0.083
0.099
0.354
30° - 60°
0.213
0.058
0.150
0.410
60° - 90°
0.304
0.059
0.258
0.294
90° - 120°
0.240
0.042
0.402
0.220
120° - 150°
0.236
0.069
0.191
0.214
150° - 180°
0.210
0.084
0.079
0.379
180° - 210°
0.157
0.226
0.075
0.338
210° - 240°
0.184
0.121
0.218
0.621
240° - 270°
0.170
0.136
0.599
0.485
270° - 300°
0.158
0.412
0.423
0.613
300° - 330°
0.148
0.187
0.134
0.483
330° - 360°
14
0.217
0.204
0.069
0.138
0.757
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15. Overhead Photo Advantages/Limitations

Surface roughness is based on site-specific data
(potentially more defensible):
• More direct correlation to actual land use patterns.
• Potential to avoid dependence on generic surface
roughness values.


15
Time considerations for site visit and surface
roughness calculations.
Human biases.
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16. Meteorological Monitoring
16
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17. Meteorological Monitoring Results
Virginia - 10m
Average
Wind Direction
Gustiness
Sector
Equation Surface
Roughness
(meters)
Eastern Pennsylvania - 10m
Central Pennsylvania - 10m
Count
Average Gustiness
Equation Surface
Roughness
(meters)
Count
Average Gustiness
Equation Surface
Roughness
(meters)
North Carolina - 10m
Average Gustiness
Equation Surface
Count
Count
Roughness
(meters)
0° - 30°
0.330
17
0.198
1,135
0.105
346
0.189
1
30° - 60°
0.204
11
0.187
679
0.099
520
0.269
5
60° - 90°
0.354
1
0.254
424
0.097
434
0.186
65
0
0.305
160
0.058
35
0.245
47
90° - 120°
120° - 150°
194
0.329
60
0.223
46
0.344
124
150° - 180°
0.231
448
0.250
218
0.166
85
0.323
7
180° - 210°
0.315
388
0.203
609
0.126
325
0
210° - 240°
0.311
231
0.185
503
0.160
769
0
240° - 270°
0.274
974
0.230
3,758
0.117
4,092
0.367
57
270° - 300°
0.265
1,256
0.268
7,372
0.102
5,985
0.250
1,131
300° - 330°
0.220
1,836
0.296
2,488
0.110
1,970
0.255
1,487
330° - 360°
17
0.211
0.225
1,087
0.258
1,561
0.140
313
0.343
38
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18. Meteorological Monitoring
Advantages/Limitations




18
Surface roughness values are based on
monitored, quality assured meteorological data
that are continuously recorded.
Equation can be added to datalogger software
and continuously calculated.
Requires operation of a meteorological
monitoring station.
5-minute wind speeds must be great than 5m/s,
leading to data gaps.
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19. Comparison of Results
Gust
AERSURFACE
Site Survey
0.500
Surface Roughness (meters)
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
Eastern Pennsylvania Site
19
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20. Comparison of Results
Gust
AERSURFACE
Site Survey
0.700
Surface Roughness (meters)
0.600
0.500
0.400
0.300
0.200
0.100
0.000
Central Pennsylvania Site
20
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21. Comparison of Results
Gust
AERSURFACE
Site Survey
0.800
Surface Roughness (meters)
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
Eastern Virginia Site
21
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22. Comparison of Results
AERSURFACE
Site Survey
Surface Roughness (meters)
Gust 10m
Western North Carolina Site
22
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23. Conclusions


Surface roughness evaluation should be based
upon the most recent land use patterns and
available information.
Overhead photo evaluations and meteorological
analyses are based on site-specific data:
• Diminishes the uncertainty associated with the use of
default land use information.
23
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24. Contact Information
Meghan Barber and Dan Dix
mbarber@all4inc.com | ddix@all4inc.com
610.933.5246 ext. 18
www.all4inc.com
Kimberton, PA | 610.933.5246
Columbus, GA | 706.221.7688