AMS/EPA Regulatory Model (AERMOD)


AERMOD is an air dispersion model used for estimating the impact of new and existing sources of pollution on ambient levels at source-receptor distances of less than 50 km.


AERMOD is a steady-state plume model that incorporates air dispersion based on planetary boundary layer (PBL) turbulence structure and scaling concepts, including treatment of both surface and elevated sources, and both simple and complex terrain.

The complete AERMOD modeling system consists of two pre-processors and the dispersion model itself. The AERMOD meteorological preprocessor (AERMET) is a stand-alone program which provides AERMOD with the information it needs to characterize the state of the surface and mixed layer, and the vertical structure of the PBL. The AERMOD mapping program (AERMAP) is a stand-alone terrain pre-processor, which is used to both characterize terrain and generate receptor grids for AERMOD.

Using a relatively simple approach, AERMOD incorporates current concepts about flow and dispersion in complex terrain. Where appropriate the plume is modeled as either impacting and/or following the terrain. This approach has been designed to be physically realistic and simple to implement while avoiding the need to distinguish among simple, intermediate and complex terrain, as required by other regulatory models. Unlike existing regulatory models, AERMOD accounts for the vertical inhomogeneity of the PBL in its dispersion calculations. This is accomplished by "averaging" the parameters of the actual PBL into "effective" parameters of an equivalent homogeneous PBL.

One of the major improvements that AERMOD brings to applied dispersion modeling is its ability to characterize the PBL through both surface and mixed layer scaling. AERMOD constructs vertical profiles of required meteorological variables based on measurements and extrapolations of those measurements using similarity (scaling) relationships. Vertical profiles of wind speed, wind direction, turbulence, temperature, and temperature gradient are estimated using all available meteorological observations. AERMOD is designed to run with a minimum of observed meteorological parameters.

The minimum inputs to AERMET are 1) wind at one level, 2) temperature at one level, 3) cloud cover, and 4) an early morning upper air sounding. In addition, AERMET requires and information on surface roughness, albedo, and Bowen ratio.

AERMOD is a more advanced gaussian-plume model suited for use where complex terrain is an issues. AUSPLUME was an earlier less complex gaussian-plume modeland the Victorian EPA (Australia) had previously used AUSPLUME V6 for thier requlartory purposed. However this is now no longer supported by them and they use AERMOD as their regulatory model for air pollution modelling.

Latest Version V18081
State of Development Released and updated

Development Contact

U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emissions Monitoring and Analysis Division
Research Triangle Park, NC 27711


Outcome Areas Environmental
Management Domains Air Quality
Subdomains Air Quality Modelling, Air Quality Monitoring
Intended End Users
  • Regional Council Scientist
  • Researcher
Steady State or Dynamic Dynamic
Level of Integration Environmental

Input & Output Data

Key Input Data Meterological data, Terrain data (DEM), pollution discharge


Open/Closed Source Open Source
Licence Type No Licence

User Information

Operating Systems MS Windows
User Interface No user interface Command-prompt
Ease of Use Moderate No User Interface has been designed to run on Windows PCs within a Command-prompt using command-line arguments to initiate a model run.
But commercial GUI option appear to be available (
Use in Policy Process Plan (Policy Formulation), Review (Issue Identification)

An Introduction to AERMOD

User's Guide for the AMS/EPA Regulatory Model (AERMOD) (2018)

Technical Considerations

Analytical Techniques Input/output
Model Structure


Keywords Air Quality, Dispersion Modelling
Linkages to other Models

MFE - Good Practice Guide to Dispersion Modelling

Gardner, T., et. al (2015): AERMOD and AUSPLUME: Understanding the similarities and difference. Conference Paper, CASANZ2015 Conference, Melbourne, 20-23 September 2015.

USEPA Support Center for Regulatory Atmospheric Modeling (SCRAM) - Air Quality Dispersion Modeling - Preferred and Recommended Models

AERMOD - Wikipedia

You Tube Videos on AERMOD: Introduction-

How to Set Up and Run AERMOD -

How to Download & Run EPA's AERMOD Sample Run -

Air Pollution Modelling -

Key References

Alan J. Cimorelli,et. al.(2004): AERMOD: A Dispersion Model for Industrial Source Applications. Part I: General Model Formulation and Boundary Layer Characterization. Journal of Applied Meterology, Vol 44, 682-693.

Steven G. Perry, et. al.(2004): AERMOD: A Dispersion Model for Industrial Source Applications. Part II: Model Performance against 17 field study databases. Journal of Applied Meterology, Vol 44, 694-708.

Proposed updates to AERMOD Modelling System (2015) - US EPA 11th Conference on Air Quality Modelling

See other resources at the Support Center for Regulatory Atmospheric Modeling (SCRAM) website

Associated Case Studies

AERMOD - AEE for Industrial Consent

AERMOD, a key tool in this assessment, is a steady-state dispersion model designed for short-range dispersion of air pollutant emissions from stationary industrial sources.