Long‐term tropospheric ozone concentrations and associated meteorological and emissions variables at a suburban monitoring station in Dallas‐Fort Worth, Texas

Abstract

AbstractThis study portrayed and analyzed long‐term tropospheric (ground‐level) ozone concentrations and associated meteorological and emissions variables at a predominantly downwind suburban monitoring location in the Dallas‐Fort Worth, Texas, USA metropolitan area. Maximum daily 8‐h average ozone concentrations (MDA8), number of days with MDA8 ozone exceeding 70 ppb, maximum outside air temperature, noon relative humidity and wind speed, noon vapor pressure deficit, and average oxides of nitrogen (NOx) were compiled for each day in July and August from 1998 to 2021. MDA8 ozone had an overall downward trend with less variability through time. Each meteorological and emissions variable significantly correlated with MDA8 ozone. MDA8 ozone most strongly correlated with noon relative humidity (negative association), followed by vapor pressure deficit (positive association), average NOx (positive association), maximum temperature (positive association), and noon wind speed (negative association). MDA8 ozone trended downward despite substantial increases in population and vehicle miles traveled in the 10‐county study area over the past 24 years. Decreasing ozone concentrations reflect decreased NOx emissions, which also trended downward over the period of study, whereas meteorological variables showed no clear temporal trend. Results show positive emission reductions outcomes, key ozone associations, and baseline tendencies despite regional decreases in NOx emissions.