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Upcoming Seminars
| Title: | Challenges in Modeling Future Tropospheric Ozone for the federal health standards in the
Denver Metro / North Front Range region
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| Speaker: |
Mr. Tom Moore
Tom joined the RAQC in February 2023 as the Planning Director, working on air quality control
strategies, coordinating development of the State Implementation Plan components, and
leading emission inventory and photochemical modeling analyses. He came to the RAQC after
serving as the Technical Services Program manager at the State of Colorado’s Air Pollution
Control Division as well as working for many years for the Western Regional Air Partnership,
coordinating air quality analysis and planning for the 15-state WRAP region. He has served as
the Vice Chair for the Air Quality Enterprise Board and chaired the Fort Collins Air Quality
Advisory Board. Tom has a B.S. degree in Physical Geography from Arizona State University.
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| Date/Time: |
Thursday, April 16, 2026 01:00 PM MDT (-0600)
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| Location: |
David Skaggs Research Center, Room GC402
Google Meet |
Abstract
The Denver Metro/North Front Range (DM/NFR) region has suffered from elevated
concentrations of ground-level ozone (O3) for decades. While progress has been made to
reduce emissions, the area continues to fall short of National Ambient Air Quality Standards
(NAAQS), leaving difficult decisions about further emissions reductions. Increasingly hot dry
summers, population growth, and wildfire smoke add to the challenge. Regional air quality
improvement plans required by the federal Clean Air Act (CAA) are formulated on statutory
timelines by the Regional Air Quality Council (RAQC), the designated lead air planning agency
for the O3 Nonattainment Area (NAA) are developed in collaboration with the Colorado
Department of Public Health and Environment’s Air Pollution Control Division (CDPHE APCD).
These NAA-focused emission control and air quality improvement plans are evaluated and
considered for approval by the RAQC Board and the Colorado Air Quality Control Commission
(AQCC) then submitted to the U.S. Environmental Protection Agency (USEPA) for review and
approval.
USEPA prescribes and RAQC/APCD develop and apply regional photochemical grid modeling
(PGM) platforms with local and regional data to evaluate a recent year as the basis of projecting
air quality improvement expected by a near-term future year. Air quality planning procedures
require use of a PGM platform to evaluate emission control strategies for nitrogen oxides (NOx)
and volatile organic compounds (VOCs) to demonstrate future O3 standard attainment via
modeled changes in air quality. Following USEPA procedures, the PGM inputs and results are
evaluated by RAQC, APCD, USEPA, and stakeholders to determine the accuracy, precision,
and representativeness of the analysis. Actual NAAQS compliance, however, is based on
measured O3. Thus far, for more than 20 years, monitored O3 concentrations in the DM/NFR
have generally exceeded repeated iterations of modeled projections and the region remains out
of attainment, posing health risks and requiring more stringent emission control programs under
the federal CAA.
PGM results and supporting analyses suggest that O3 formation potential and measured
impacts from different sources vary across the DM/NFR NAA; however, the accuracy of these
estimates depends on the underlying quality of emissions inventories and modeled
meteorology. If the amounts, spatiotemporal distributions, or chemical speciation of sources are
incorrect or incomplete, the model cannot accurately simulate true O3 formation. Evaluation and
improvement of PGM performance requires comparing modeled concentrations of O3, NOx,
and speciated VOCs to observations. Unfortunately, the availability of such observations is
limited. While APCD maintains a limited number of NOx and VOC monitoring locations, some
have only recently been implemented, NOx and VOC measurements are not often co-located,
and regional monitoring gaps remain. This makes model evaluation problematic. While
predicted O3 can be evaluated, there has been little basis to assess whether modeled
emissions of NOx and VOCs are accurate, leaving high uncertainty in projecting how O3 will
respond to control strategies.
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