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Ozone Modeling



To aid in evaluating the impact of emissions control strategies as well as developing Attainment Demonstrations in accordance with State Implementation Plan (SIP) requirements, the RAQC engages in photochemical modeling efforts. Photochemical modeling is a grid based computer model used to simulate air pollution episodes. It is the most effective tool for determining how serious air pollution problems are and how they occur. Photochemical modeling allows for the assessment of:

    • How sensitive pollutants are to varying parameters such as meteorological conditions and emission rates
    • How sensitive pollutants are to control scenarios
    • Efficacy of proposed control strategies

Photochemal modeling is completed using EPA approved modeling platforms and methodologies. A detailed modeling protocol is developed which outlines the technical details of the modeling being performed. The protocol documents the approach, procedures, participants and other requirements need to conduct photochemical grid model modeling. This page provides references, tools, and reports that have been developed to support the RAQC’s ongoing modeling efforts.

Modeling Reports and Dashboards for Current Planning Efforts

The RAQC is conducting modeling efforts to aid in planning and SIP development efforts under the 2008 and 2015 8-hour ozone Standards. Below are currently available reports and tools developed in support of this effort.

Presentation of Draft SIP Elements – Attainment Demonstration (RAQC – May 2022)

Modeling Protocol for 2008 and 2015 Ozone Standards (Ramboll – May 2022)

Preliminary 2026 Future Year Modeling Results (RAQC – March 2022)

Modeling Protocol for 2008 and 2015 Ozone Standards  (Ramboll – April 2019)

2023 Emissions Dashboard (Ramboll/Alpine – April 2021)

2023 NOx/VOC Sensitivity Analysis – Daily (Ramboll/Alpine – April 2021)

2023 NOx/VOC Sensitivity Analysis – Hourly (Ramboll/Alpine – April 2021)

2023 Local Source Apportionment Analysis (Ramboll/Alpine – April 2021)

2023 Transport Analysis (Ramboll/Alpine – April 2021)

Archived Reports and Presentations from Previous Planning Efforts

Reports and tools developed in support of prior modeling efforts are detailed below:

NOx/VOC Sensitivity Analysis (Ramboll/Alpine Geophysics – March 2018)

Source Apportionment Modeling Report (Ramboll – April 2017)

2017 Photochemical Grid Modeling – Model Performance Evaluation (Ramboll – September 2017)

2017 Photochemical Grid Modeling – Attainment Demonstration (Ramboll – September 2016)

Source Apportionment Modeling Analysis for the Denver Early Action Ozone Compact (Environ/Alpine Geophysics, May 2004)

Modeling Forums

Forums are dedicated RAQC meetings where modeling methodologies, analyses, and results are discussed in-depth. They cover a wide range of topics, from how the model is selected to how the model demonstrates the effects of local, regional, and international sources on ozone. Below are references to forums previously conducted by the RAQC.

May 12, 2023 Forum

Topics Covered:

  • Methodology Outline: Denver Metro/North Front Range Oil and Gas Emission Inventory, May 10, 2023
  • Revised Oil and Gas Emission Inventory Results
      • 2017 Oil and Gas Emission Inventory Spreadsheets, April 28,2023
      • 2026 Oil and Gas Emission Inventory Spreadsheets, May 10, 2023
  • Severe SIP Modeling Plan


May 18, 2022 Forum

Topics Covered:

    • 2016 Modeling Platform Update since April 2021
    • Analysis of 2020 and 2021 Meteorology
    • 2023 and 2026 Design Value Projections
    • Planned and Potential Sensitivity Analyses


April 14, 2021 Forum 

Topics Covered:

    • 2016 Modeling Platform Update
    • 2023 NOx/VOC Sensitivity Analysis
    • 2023 Local Source Modeling
    • 2023 International and Interstate Transport Analysis


June 4, 2020 Forum

Topics Covered:

    • Development of 2016 Base Case Modeling,
    • 2020 and 2023 Future Year Modeling Projections


November 2, 2017 Forum

Topics Covered:

    • Overview of Modeling Sensitivities
    • 2017 Local Source Apportionment Modeling
    • Contribution of International Emissions on 2011 Base Case
    • 2023 Ozone Projections and NOx/VOC Sensitivity
    • FRAPPE and DISCOVER-AQ 2014 Regional Source Impacts
    • Comparison of Oil and Gas Inventories with Monitored Ambient VOC Precursors


August 9, 2012 Forum

Topics Covered:

    • Development of 2008 Base Case Model
    • Ozone Model Evaluation for the Denver 2008 Episode
Guidance Documents

Guidance documents from the EPA recommend steps to conduct modeling for ozone nonattainment areas. Generally, the guidance comes in two parts. The first part includes how to set up and apply a photochemical modeling platform, which includes meteorology, emissions, and air quality modeling. The second part describes how to use the modeling platform to project future year concentrations and demonstrate whether attainment of the standard is likely.

Modeling Guidance – Final (Nov. 2018) 

Requests for Proposals

The RAQC puts out requests for services from a consulting firm to aid in completing the modeling recommended under EPA guidance.

2018 Request for Proposal

2011 Request for Proposal (RFP)