AMS/EPA Regulatory Model (AERMOD)

Purpose

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.

Description

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

Scope

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

Accessibility

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 (https://www.pdsconsultancy.com.au/aermod-ciou?gclid=EAIaIQobChMI-JCStYWi2wIVASQrCh1DAQ8AEAAYASAAEgJGzfD_BwE)
Use in Policy Process	Plan (Policy Formulation), Review (Issue Identification)
Documentation	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	CALPUFF (CALPUFF)
Links	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. https://www.slideshare.net/BREEZESoftware/aermod-and-ausplume-understanding-the-similarities-and-differences-53996015 USEPA Support Center for Regulatory Atmospheric Modeling (SCRAM) - Air Quality Dispersion Modeling - Preferred and Recommended Models AERMOD - Wikipedia You Tube Videos on AERMOD: AERMODtraining.com Introduction- https://www.youtube.com/watch?v=xup3QQ422ko How to Set Up and Run AERMOD - https://www.youtube.com/watch?v=0dLAwGHzZ7o How to Download & Run EPA's AERMOD Sample Run - https://www.youtube.com/watch?v=oC_aBvvBXKw Air Pollution Modelling - https://www.youtube.com/watch?v=kdcMy_3d_co
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