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Past studies have leveraged distinct observed weekly patterns in emissions of two ozone precursors, volatile organic compounds (VOCs) and nitrogen oxides (NOX = NO + NO2), to better understand ozone chemistry. These studies evaluated day-of-week (DOW) patterns in ozone concentrations to characterize whether ozone formation in certain locations occurs in VOC-limited or NOX-limited chemical regimes. In this work, we analyze 18 years (2002–2019) of Community Multi-scale Air Quality (CMAQ) model data from EPA’s Air QUAlity TimE Series Project (EQUATES) in combination with measured data to evaluate the CMAQ model’s ability to capture changes in ozone formation chemistry in nonattainment areas across the U.S. Statistically significant ozone DOW patterns are quantified using the Welsch t-test. Multi-year trends in DOW patterns were determined using Theil-Sen regression with the Mann–Kendall test for significance. The trends analysis is demonstrated using data from the Phoenix, Arizona and Amador County, California nonattainment areas. In Phoenix, observed and modeled ozone weekend-weekday differences started out positive (VOC-limited) and became negative over the analysis period indicating a trend towards NOX-limited conditions. In Amador County, observed and modeled ozone weekend-weekday differences were negative indicating NOx-limited conditions but diminished over time potentially indicating a reduced role of local weekly varying NOx sources on ozone production in this area. Overall, the model captures DOW ozone trends well across 51 U.S. nonattainment areas.

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Comparison of 18 years of Modeled and Observed day-Of-Week Ozone Patterns

  • 会议论文

  • 发表日期：

    2025年

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  • Heather Simon,
  • Wyat Appel,
  • Kristen Foley,
  • Barron Henderson,
  • Christian Hogrefe,
  • Shannon Koplitz,
  • Norm Possiel,
  • Gail Tonnesen,
  • Luke Valin,
  • Benjamin Wells,
  • Andrew Whitehill

摘要

Past studies have leveraged distinct observed weekly patterns in emissions of two ozone precursors, volatile organic compounds (VOCs) and nitrogen oxides (NOX = NO + NO2), to better understand ozone chemistry. These studies evaluated day-of-week (DOW) patterns in ozone concentrations to characterize whether ozone formation in certain locations occurs in VOC-limited or NOX-limited chemical regimes. In this work, we analyze 18 years (2002–2019) of Community Multi-scale Air Quality (CMAQ) model data from EPA’s Air QUAlity TimE Series Project (EQUATES) in combination with measured data to evaluate the CMAQ model’s ability to capture changes in ozone formation chemistry in nonattainment areas across the U.S. Statistically significant ozone DOW patterns are quantified using the Welsch t-test. Multi-year trends in DOW patterns were determined using Theil-Sen regression with the Mann–Kendall test for significance. The trends analysis is demonstrated using data from the Phoenix, Arizona and Amador County, California nonattainment areas. In Phoenix, observed and modeled ozone weekend-weekday differences started out positive (VOC-limited) and became negative over the analysis period indicating a trend towards NOX-limited conditions. In Amador County, observed and modeled ozone weekend-weekday differences were negative indicating NOx-limited conditions but diminished over time potentially indicating a reduced role of local weekly varying NOx sources on ozone production in this area. Overall, the model captures DOW ozone trends well across 51 U.S. nonattainment areas.