AERMOD is a steady-state Gaussian plume dispersion model used to predict pollutant concentrations from emissions sources. It uses meteorological and site data along with source specifications to calculate pollutant dispersion and concentrations at receptor locations. The model workflow involves using AERMET to process meteorological surface and upper air data along with surface characteristics. AERMAP processes terrain data. BPIP accounts for building downwash effects. The model then calculates concentrations at receptor locations specified by the user. Model output includes concentration and deposition values at receptors which can be used to assess impacts and compliance with air quality standards.

1. AERMOD
American Meteorological Society (AMS) and the
United States Environmental Protection Agency
(EPA) Regulatory Model (AERMOD)
Lakes Environmental V6.7.1

2. AERMOD, What It Does
 Steady-state Gaussian plume air
dispersion model
 Predict downwind pollutant
concentrations based on source
emissions, meteorological field, and
site parameters (land use, terrain
features etc.)
 For near-field impacts (50-km or less)

3. Gaussian Dispersion
𝐶 𝑥, 𝑦, 𝑧 =
𝑄
2𝜋𝜎 𝑦 𝜎𝑧 𝑈
exp −
𝑦2
2𝜎 𝑦
2 {exp −
𝑧 − ℎ 𝑠
2
2𝜎𝑧
2
+ exp −
𝑧 + ℎ 𝑠
2
2𝜎𝑧
2
}
𝐶 𝑥, 𝑦, 𝑧 : 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛, µ𝑔 𝑚3
, 𝑎𝑡 𝑥 𝑚𝑒𝑡𝑒𝑟𝑠 𝑑𝑜𝑤𝑛𝑤𝑖𝑛𝑑.
𝑄: 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑟𝑎𝑡𝑒, µ𝑔 𝑠
𝑈: 𝑤𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑 𝑎𝑡 𝑠𝑡𝑎𝑐𝑘 ℎ𝑒𝑖𝑔ℎ𝑡, 𝑚 𝑠
𝜎 𝑦, 𝜎𝑧 : 𝑑𝑖𝑠𝑝𝑒𝑟𝑠𝑖𝑜𝑛 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡𝑠 𝑎𝑡 ℎ𝑖𝑟𝑜𝑛𝑧𝑜𝑛𝑡𝑎𝑙 𝑎𝑛𝑑 𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑑𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛𝑠.
𝑦, 𝑧: ℎ𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑎𝑛𝑑 𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑠 𝑓𝑟𝑜𝑚 𝑝𝑙𝑢𝑚𝑒 𝑐𝑒𝑛𝑡𝑒𝑟𝑙𝑖𝑛𝑒 𝑎𝑡 𝑥 𝑚𝑒𝑡𝑒𝑟𝑠, 𝑚
ℎ 𝑠: 𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑠𝑡𝑎𝑐𝑘 ℎ𝑒𝑖𝑔ℎ𝑡 𝑠𝑡𝑎𝑐𝑘 ℎ𝑒𝑖𝑔ℎ𝑡 𝑝𝑙𝑢𝑠 𝑝𝑙𝑢𝑚𝑒 𝑟𝑖𝑠𝑒 ,

4. Dispersion Coefficients
𝜎 𝑦 = 𝑎 𝑥0.894
𝜎𝑧 = 𝑐 𝑥 𝑑
+ 𝑓

5. Why AERMOD
 1. Permitting
 2. Design of stacks
 3. “Culpability” analysis
 4. Prediction of air quality
 5. Selection of air monitoring sites
 6. Evaluation of the impact of new
pollution sources

6. Overview
AERMO
D
AERMET
Met Data:
Surface, Upper
Air, On-Site
Surface
Characteristic
s
Application
Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location
and
Emission
Data
Receptor
Location
Control
Output

7. AERMOD
AERMET
Met Data:
Surface, Upper
Air, On-Site
Surface
Characteristics
Application Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location and
Emission Data
Receptor
Location
Control
Output
Met Pathway

8. AERMET
 AERMET: The AERMOD
meteorological pre-processor
 Uses meteorological information and
surface characteristics to calculate the
boundary layer parameters for use by
AERMOD Surface
Characteristics
Application
Site

9. Surface Data
Minimum required parameters:
 1. Year, Month, Day, Hour
 2. Wind Speed
 3. Wind Direction
 4. Dry Bulb Temperature
 5. Cloud Cover (tenths)

10. Where To Get
 Five years surface data from LGA (4.1
km east from WI WWTP)
(ftp://ftp.ncdc.noaa.gov/pub/data/noaa/
)
 Data Format: NCDC TD-3505
 Time in GMT

12. Upper Air Data
Parameters
 Year, Month, Day, Hour
 Pressure
 Height
 Temperature
 Wind Direction
 Wind speed

13. Where To Get
 Five years upper air data from Upton,
NY (88 km east from WI WWTP)
(http://www.esrl.noaa.gov/raobs)
 Data format: FSL.
 Time in GMT.

14. Upper Air Data

15. On-Site Data
 Requires the same minimum
parameters as that for surface data:
◦ Wind Direction
◦ Wind Speed
◦ Temperature
◦ Sky Cover/Cloud Cover
 The file must be ASCII and must be in
a form that can be read using Fortran
FORMAT statements.

16. On-Site Data

17. Surface Characteristics
 Albedo(r): Fraction of solar energy
reflected (0 to 1), “Big & Bright”
 Bowen Ratio (Bo): A measure of the
dryness at the surface, “The Higher
the Drier”
 Surface Roughness (zo): The
height at which wind speed
approaches zero

18. AERMET Sectors
 Apply a weighted average of surface
characteristics by surface area within
each sector

19. AERSURFACE
 Calculates surface parameters from
land cover files in USGS NLCD92
format

20. AERSURFACE

21. Application Site

22. AERMET Output Files
Surface File
Profile File

23. Surface File: *.SFC
 the hourly boundary layer parameters
estimates

24. Inspecting Surface File
(*.SFC) Sensible Heat Flux: positive for convective
conditions (daytime), negative for stable
conditions (nighttime); usually ≥-64 W/m2
 Monin-Obukhov Length: negative for convective
conditions (daytime), positive for stable
conditions (nighttime)
 Surface Friction Velocity u*:5-15 times less than
Wind Speed.
 Convective Velocity Scale w*: usually < 5m/s
 Wind Speed ↑, Surface Roughness Length ↑→
Mechanical Mixing Height↑
 Dew Point Temperature < Ambient Temperature
 Zero Wind Speed → Zero Wind Direction

25. Profile File: *.PFL
 multiple levels of wind speed, wind direction,
temperature, and standard deviation of the
fluctuating wind components.

26. Met Pathway

27. Met Pathway

28. Source Pathway
AERMOD
AERMET
Met Data:
Surface, Upper
Air, On-Site
Surface
Characteristics
Application Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source Location
and Emission
Data
Receptor
Location
Control
Output

29. Source Types
 1. POINT
 2. AREA (rectangular, circular,
polygonal)
 3. VOLUME
 4. OPEN PIT

30. POINT Sources
 A single, identifiable source
of air pollutant emissions,
either elevated or at ground-
level
◦ Pollutant release rate
(mass/time)
◦ Stack location
◦ Stack height and diameter
◦ Stack gas temperature and
exit velocity
 Examples: Stacks,

31. AREA Sources
 A two-dimensional source of diffuse air
pollutant emissions, low level or
ground level releases with no plume
rise
◦ Pollutant release rate (mass/time/area)
◦ Release height
◦ Location and dimensions
 Examples: material storage piles,
forest fires, landfills, waste lagoons

32. VOLUME Sources
 A three-dimensional source of diffuse
air pollutant emissions
◦ Pollutant release rate (mass/time)
◦ Location
◦ Release height
◦ Initial lateral and vertical dimensions
 Examples: building roof monitors,
multiple vents, conveyor belts, haul
roads

33. OPEN PIT Sources
 Similar to area sources (no plume
rise)
◦ Pollutant release rate (mass/time/area)
◦ Average release height
◦ Dimensions and volume
◦ Orientation angle
 Examples: surface mines and quarries

34. Area Source Example

35. Open PIT Source Example

36. AERMOD
AERMET
Met Data:
Surface,
Upper Air,
On-Site
Surface
Characteristic
s
Application
Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location and
Emission
Data
Receptor
Location
Control
Output
Receptor Pathway

37. Need To Specify:
 1. Modeling Domain?
 2. Receptor Spacing?
 3. Number of Receptors?
 4. Type of Receptors?

38. Example of Receptors

39. Example of Receptors

40. TERRAIN
AERMOD
AERMET
Met Data:
Surface, Upper
Air, On-Site
Surface
Characteristics
Application Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location and
Emission Data
Receptor
Location
Control
Output

41. AERMAP
Terrain Processing
 AERMAP: AERMOD mapping
program
 Calculates Terrain Elevations for
Sources and Receptors
 The Effect of Terrain on Concentration
Values

42. Terrain Data Format
 United States:
◦ USGS NED GeoTIFF (~30m, ~10m,
~3m)
◦ USGS 7.5-Min DEM (~30m)
◦ USGS 1-Deg DEM (~90m)
◦ SRTM1 (~30m)
 International:
◦ SRTM3 (~ 90m)
◦ SRTM30 & GTOPO30 (~900m)

43. Where To Get

44. Building Downwash Analysis
AERMOD
AERMET
Met Data:
Surface,
Upper Air, On-
Site
Surface
Characteristics
Application
Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location and
Emission Data
Receptor
Location
Control
Output

45. BPIP- Building Profile Input
Program
 Calculates building downwash
 Effects of buildings on pollutant
concentrations
Parameters: Point sources and building
Locations/dimensions

46. Area of Influence

47. Control Pathway
AERMOD
AERMET
Met Data:
Surface, Upper
Air, On-Site
Surface
Characteristics
Application Site
Information
AERMAPTerrain Data
BPIPBuilding Data
Source
Location and
Emission Data
Receptor
Location
Control
Output

50.  Flat Terrain: Terrain Heights < Stack
Base
 Elevated Terrain: Stack Base < Terrain
Heights <Stack Height
 Complex Terrain: Terrain Heights >
Stack Height

51. Summary

52. Interpreting Results
Output Types
 1. Main Output file
 2. Plot file
 3. Post file
 4. Threshold violations
 5. Others…

53. Main Output File
 1. Automatically created
 2. Contains input and output
summaries
 3. Lists errors and warnings
 4. Contains optional output data tables

54. A Part of Main Output File

55. Highest Values Table
 Reports the nth highest
concentration at each receptor; n =
1 to 10 (specified by user)

56. PLOTFIILE
 Same data as highest values table
 Not a snapshot in time
2 ppb
335 ppb

57. Maximum Values Table
 Reports the x highest concentrations
 x (specified by user)

58. MAXIIFIILE
 Threshold Violation File
 Lists all concentrations above a user
specified threshold
 H2S regulations: 10 ppbv (New York
State, 1972) or 1 ppb (New York City,
2010; Mahin, 2001)

59. 2 ppb
120 ppb

60. POSTFIILE
 Reports all concentrations at each
hour and at every receptor
 Large Files!

61. Analysis of Results
 Check the date/time maximums occur
◦ Maximums occurring all at the same
time?
◦ Maximums at different dates, but same
time of day?
◦ Is a particular met condition to blame?
 Compare with Air Quality Standard
 Contribution from individual sources

62. Model Validation
 Inspect the Main Output File
 Compare with ambient monitoring
data

64. Resources
 Lakes Environmental:
www.webLakes.com
 RFLee Consulting: www.rflee.com/
 US EPA: www.epa.gov/scram001/

65. Acknowledgements
 CCNY
 Lakes Environmental
◦ Cristiane L. Thé, M.A.Sc.
◦ Jason M. Redman, B. Es
◦ Chamarie Perera
◦ Farida Dehghan, Ph.D.
 NOAA
◦ Patricia Miller
◦ Mark Govett
 RF Lee Consulting
◦ Russell F Lee, Meteorologist
 Odotech Inc
◦ Nicholas Leblanc