surface roughness evaluation methods - awma
DESCRIPTION
Dan Dix and Meghan Barber of All4 Inc. present "Surface Roughness Evaluation Methods." The presentation describes why surface roughness is important, evaluation methods, and what impact each evaluation method has on modeling results.TRANSCRIPT
www.all4inc.comKimberton, PA | 610.933.5246Columbus, GA | 706.221.7688
Surface Roughness Evaluation Methods
Meghan Barber and Dan [email protected] | [email protected]
610.933.5246 March 21, 2013
Guideline on Air Quality Models: The Path Forward
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.
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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). AERMOD is particularly sensitive to variations in
surface roughness.
Surface Roughness and AERMET
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Four Example Sites Evaluated
Eastern Pennsylvania Site Central Pennsylvania Site
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Four Example Sites Evaluated
Eastern Virginia Site Western North Carolina Site
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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.
AERSURFACE
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USGS Land Use Patterns
Eastern Pennsylvania Site Central Pennsylvania Site
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USGS Land Use Patterns
Eastern Virginia Site Western North Carolina Site
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AERSURFACE Results
Wind Direction Sector
Virginia Eastern Pennsylvania Central Pennsylvania North Carolina
Average AERSURFACE Surface Roughness(meters)
0° - 30° 0.124 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° 0.113 0.118 0.219 0.321
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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.
Overhead Photo/Survey
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Calculate the inverse distance weighted surface roughness:
] (
Approach developed by the State of Alaska for cases when AERSURFACE is not appropriate.
Overhead Photo Approach
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Site Survey Land Use Patterns
Eastern Pennsylvania Site Central Pennsylvania Site
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Site Survey Land Use Patterns
Eastern Virginia Site Western North Carolina Site
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Overhead Photo Results
Wind Direction Sector
Virginia Eastern Pennsylvania Central Pennsylvania North Carolina
Average Site Survey Surface Roughness(meters)
0° - 30° 0.217 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° 0.204 0.069 0.138 0.757
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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. Time considerations for site visit and surface
roughness calculations. Human biases.
Overhead Photo Advantages/Limitations
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Estimates surface roughness for each sector based on wind gustiness:
Wind data is required. 3 example sites used just 10 m wind data and 1
example site used 10 m and 60 m wind data :• Surface roughness equation added to datalogger
software.• 5-minute surface roughness values are calculated.
Meteorological Monitoring
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Meteorological Monitoring Results
Wind Direction Sector
Virginia - 10m Eastern Pennsylvania - 10m Central Pennsylvania - 10m North Carolina - 10m
Average Gustiness
Equation Surface Roughness
(meters)
Count
Average Gustiness Equation Surface
Roughness(meters)
Count
Average Gustiness Equation Surface
Roughness(meters)
Count
Average Gustiness Equation Surface
Roughness(meters)
Count
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
90° - 120° 0 0.305 160 0.058 35 0.245 47
120° - 150° 0.211 194 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° 0.225 1,087 0.258 1,561 0.140 313 0.343 38
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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.
Meteorological Monitoring Advantages/Limitations
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Comparison of Results
Eastern Pennsylvania Site
0° - 30°
30° - 60°
60° - 90°
90° - 120°
120° - 150°
150° - 180°
180° - 210°
210° - 240°
240° - 270°
270° - 300°
300° - 330°
330° - 360°
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
Gust AERSURFACE Site SurveySurf
ace R
oughness (
mete
rs)
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Comparison of Results
Central Pennsylvania Site
0° - 30°
30° - 60°
60° - 90°
90° - 120°
120° - 150°
150° - 180°
180° - 210°
210° - 240°
240° - 270°
270° - 300°
300° - 330°
330° - 360°
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
Gust AERSURFACE Site SurveySurf
ace R
oughness (
mete
rs)
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Comparison of Results
Eastern Virginia Site
0° - 30°
30° - 60°
60° - 90°
90° - 120°
120° - 150°
150° - 180°
180° - 210°
210° - 240°
240° - 270°
270° - 300°
300° - 330°
330° - 360°
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
Gust AERSURFACE Site SurveySurf
ace R
oughness (
mete
rs)
22 Your environmental compliance is clearly our business.
Comparison of Results
Western North Carolina Site
0° - 30°
30° - 60°
60° - 90°
90° - 120°
120° - 150°
150° - 180°
180° - 210°
210° - 240°
240° - 270°
270° - 300°
300° - 330°
330° - 360°
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
Gust 10m AERSURFACE Site SurveySurf
ace R
oughness (
mete
rs)
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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.
Conclusions
www.all4inc.comKimberton, PA | 610.933.5246Columbus, GA | 706.221.7688
Contact Information
Meghan Barber and Dan Dix [email protected] | [email protected]
610.933.5246 ext. 18