What is Air Dispersion Modeling?

Air dispersion modeling provides a visual mathematical simulation of how air pollutants disperse in the ambient atmosphere. Based on emissions source and meteorological data as well as topography information, a dispersion model calculates an estimate of the downwind concentration of pollutants as they travel away from emissions sources.

How are dispersion models used?

Dispersion models can be used to determine whether a new source will adversely impact an area or to predict whether the control of an individual source will have a beneficial effect. For example, these models are used to determine compliance with National Ambient Air Quality Standards (NAAQS) and other regulatory requirements, such as New Source Review (NSR) and Prevention of Significant Deterioration (PSD) regulations.

ADEQ Modeling Guidance for Permits 

ADEQ has developed a guidance document to help applicants understand air quality modeling procedures with regard to Air Quality Permit applications for sources located in Arizona under ADEQ jurisdiction | See Guidance >

ADEQ Modeling Checklist for Minor NSR Permits

This checklist provides assistance to the Permittee required to perform modeling analyses for a minor NSR permit. It is recommended but not required that the Permittee attach a completed modeling checklist to a modeling report when submitting a permit application | See Checklist >

ADEQ AERMET Pre-processed Meteorological Data 

ADEQ processed the meteorological data using AERMET version 24142, AERMINUTE version 15272, and AERSURFACE version 24142.  Five years of meteorological data were compiled for 11 Arizona stations and one California station (2020 – 2024 for 10 stations, 2019 – 2023 for one, and 2017 – 2021 for one). The ADJ_U* option was used to process all meteorological data | View AERMET Data >

EPA's 2013 – 2015 Prognostic Meteorological Data

The EPA has generated a nationwide prognostic meteorological dataset for 2013 – 2015 (12km WRF simulations for CONUS and MMIF processed data for each 12km grid cell). The dataset has approximately 2,000 data points (a point is the center of a grid cell) within the State of Arizona. A full listing of these points is shown in the following KMZ file. The Permittee may open the KMZ file in Google Earth and find the points of interest for a particular project. To request the meteorological data for specific points, please email ADEQ | Email > | View Google Earth Map for Locations of Data Points >

1-Hour NO₂ Modeling Data

ADEQ has compiled five-years of hourly ozone ambient air quality monitoring data (2020 – 2024) for 13 ozone monitors across Arizona. These hourly ozone data, concurrent with ADEQ's pre-processed meteorological data, may be used in Tier 3 modeling (PVMRM or OLM) for one-hour NO₂. ADEQ also processed hourly NO2 monitoring data from seven active monitors in Arizona to generate background NO₂ concentrations based on season and hour-of-day | View NO₂ Data >