This document provides an overview of the AERMOD air dispersion modeling system. AERMOD is a steady-state Gaussian plume model preferred by the EPA for assessing near-field pollutant impacts within 50km of emission sources. It uses meteorological and site data to predict downwind pollutant concentrations based on source emissions. AERMOD requires meteorological pre-processing with AERMET and terrain data processing with AERMAP. It can model point, area, line and building sources to evaluate impacts on receptors.

1. GEOL4346-Air Pollution
Meteorology Lab.
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AERMOD
10/27/2020

2.  Steady-state Gaussian plume air dispersion model
 Preferred air quality model for near-field (<50km) impacts
 Predict downwind pollutant concentrations based on source
emissions, meteorological field, and site parameters (land use,
terrain features etc.)
 Developed and published by the U.S. EPA
AERMOD, What it Does?
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3. Applications and Regulatory Uses
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Applications
• Design of Stacks
• Design of Air Pollution Control Equipment
• Emergency Planning for Accidental Chemical Releases
Regulatory uses
• Evaluate Impact of a new pollution source(s)
• Evaluation Impact of “Major Modifications” at Existing Stationary
Sources

4. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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5. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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6. AERMET
 AERMET: The AERMOD meteorological pre-processor
 Uses meteorological information and surface characteristics to
calculate the boundary layer parameters for use by AERMOD
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7. Surface Data and On-Site Data
Minimum required parameters
 Wind Speed
 Wind Direction
 Temperature
 Cloud Cover
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8. Upper Air Data
Minimum required parameters
 Wind Speed
 Wind Direction
 Pressure
 Temperature
 Height
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9. Surface Characteristics
Albedo (r): Fraction of solar energy reflected (0 to 1), “Bigger the
Brighter”
Bowen Ratio (B0): Ratio of the sensible to latent heat fluxes. A
measure of the dryness at the surface, “The Higher the Drier”
Surface Roughness (z0): The height at which wind speed become
zero. For example: sea (0.0002 m), grass prairie or farm fields
(0.03 m).
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10. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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11. Source Types
Point: A single identifiable source of air pollutant emissions,
either elevated or ground level. Example: Stacks
Area: A two-dimensional source of diffuse air pollutant emissions.
Example: Forest fire
Line: A line of air pollutant emissions. Example: Highways
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12. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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13. AERMAP Terrain Processing
AERMAP: AERMOD mapping program
Calculates terrain Elevations for sources and receptors
The effects of terrain on concentrations
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14. Complex Terrain
Flat Terrain: Terrain Heights < Stack Base
Elevated Terrain: Stack Base < Terrain Heights < Stack Height
Complex Terrain: Terrain Heights > Stack Height
Terrain Types
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15. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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16. BPIP- Building Profile Input Program
Calculates building downwash
Effects of buildings on pollutant
concentrations
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17. Overview
Met Data: Surface,
Upper Air, On-site
Surface
Characteristics
Terrain Data
Building Data
AERMET
Source Location
and Emission Data
AERMAP
BPIP
Receptor Location
AERMOD Output
Application Site
Information
Control
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18. Input (aermod.inp)
CO - for specifying overall job COntrol options;
SO - for specifying SOurce information;
RE - for specifying REceptor information;
ME - for specifying MEteorology information;
EV - for specifiying EVent processing;
OU - for specifying OUtput options.
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19. Limitations
AERMOD is not free. It costs around $2000.
AERMOD is a Steady-State, Straight-Line Plume Model
– Assumes uniform atmosphere across modeling domain for each hour
– Limited to near-field (< 50 km) impact assessments
 AERMOD can be used to estimate emissions from continuous releases
– Not valid for emergency release episodes
– Limited methods to simulate start-up and shutdown events
AERMOD should not be used to evaluate instantaneous concentrations in
space and time
– AERMOD most accurate for annual pollutant concentration estimates
– AERMOD least accurate for 1-hr pollutant concentration estimates
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https://www.epa.gov/scram

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24. Your TASK
Last disit of PSID
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QS (emission rate)
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2
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HS (stack height)
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3
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TS (stack exit temperature)
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4
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VS (exit velocity)
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5
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DS (stack diameter)
0