AERMOD Tech Guide

Gaussian Plume Air Dispersion Model

Table of Contents (TOC)

Please note that links to the main sections are available on the left-hand side and as tabs along the top.

Within each main section, links to subsections will be listed on the right-hand side if needed.



1. Introduction

1.1 Background

1.2 The AERMIC Focus: A Replacement for the ISC Model

1.3 Model Development Process

1.4 Purpose of Document


2. Model Overview


3. Meteorological Preprocessor (AERMET)

3.1 Derived Parameters in the CBL

3.1.1 Sensible Heat Flux(H) in the CBL

3.1.2 Friction Velocity(u) & Monin Obukhov Length(L) in the CBL 15*

3.1.3 Convective Mixing Height(z)

3.1.4 Convective Velocity Scale(w)

3.1.5 Mechanical Mixing Height(z) in the CBL

3.2 Derived Parameters in the SBL

3.2.1 Friction Velocity(u) in the SBL

3.2.2 Sensible Heat Flux(H) in the SBL

3.2.3 Monin Obukhov Length(L) in the SBL

3.2.4 Mechanical Mixing Height(z) in the SBL


4. AERMOD's Meteorological Interface

4.1 General Profiling Equations

4.1.1 Wind Speed Profiling in the Interface

4.1.2 Wind Direction Profiles in the Interface

4.1.3 Profiles of the Potential Temperature Gradient in the Interface

4.1.4 Potential Temperature Profiling in the Interface

4.1.5 Vertical Turbulence Calculated by the Interface

4.1.6 Lateral Turbulence Calculated by the Interface

4.2 Vertical Inhomogeneity in the Boundary Layer as Treated by the Interface


5. Terrain Preprocessor (AERMAP)


6. The AMS/EPA Regulatory Model (AERMOD)

6.1 General Structure of AERMOD including Terrain

6.2 AERMOD Concentration Predictions in the CBL

6.2.1 Direct Source Contribution to Concentration Calculations in the CBL

6.2.2 Indirect Source Contribution to Concentration Calculations in the CBL

6.2.3 Penetrated Source Contribution to Concentration Calculations in the CBL

6.3 Concentrations in the SBL Calculated by AERMOD

6.4 Estimation of Dispersion Coefficients

6.4.1 Ambient Turbulence for Use in Calculating Dispersion

6.4.2 Buoyancy Induced Dispersion(BID) Component of Sigma & Sigmayz

6.4.3 Component of Dispersion Coefficients due to Downwash

6.5 Plume Rise Calculations in AERMOD

6.5.1 Plume Rise in the CBL

6.5.2 Plume Rise in the SBL

6.6 Source Characterization

6.7 Adjustments for the Urban Boundary Layer


7. List of Symbols

Page 1

Page 2

Page 3

Page 4

Page 5

Page 6


8. Appendix: Input/Output Needs & Data Usage

8.1 AERMET Input Data Needs

8.1.1 Meteorology

8.1.2 Directionally and/or Monthly Varying Surface Characteristics

8.1.3 Other

8.1.4 Optional

8.2 Estimation of Solar Insolation for Small Solar Elevation Angles

8.3 Selection & Use of Measured Winds, Temperature & Turbulence in AERMET

8.3.1 Threshold Wind Speed

8.3.2 Reference Temperature & Height

8.3.3 Reference Wind Speed & Height

8.3.4 Calculating the Potential Temperature Gradient above the Mixing Height from Sounding Data

8.3.5 Measured Turbulence

8.3.6 Data Substitution for Missing On-site Data

8.4 Information passed by AERMET to AERMOD

8.5 Restrictions on the Growth of PBL Height

8.6 Initializing the Mechanical Mixing Height Smoothing Procedure

8.7 Determining the Mixing Height when the Sounding is too Shallow

8.8 Input Data Needs for AERMAP

8.9 Information passed by AERMAP to AERMOD

8.10 Wind Speed & Turbulence Limits used in Model Calculations

8.11 Using Profiles for Interpolating between Observations

8.12 Using Measured Mixing Heights


9. References