Authors
Lindsey D. Anderson (CIRES,Department of Chemistry), Drew Blauth (CIRES,Department of Chemistry), Seonsik Yun (CIRES,Department of Chemistry), Doug Day (CIRES,Department of Chemistry), Erick Mattson (Colorado Department of Public Health and Environment), Barbara Dix (CIRES), Anne Handschy (CIRES,Department of Chemistry), Jose L. Jimenez (CIRES,Department of Chemistry), Alma Hodzic (NCAR/UCAR), Joost de Gouw (CIRES,Department of Chemistry)

Abstract

Ground-level ozone is a toxic air pollutant that is formed from reactions of NOx (= NO + NO2) and volatile organic compounds (VOCs) in the presence of sunlight. Ozone chemistry is complex and nonlinear with respect to its precursors, complicating emissions regulations aimed at reducing ozone. It is common to use a careful analysis of NOx and VOCs to probe the ozone production regime in a city, which requires the measurement of many VOCs that are not routinely monitored. In contrast, space-based remote sensing allows us to monitor species relevant to ozone formation globally, which is especially important in regions where airborne and ground-based measurements are sparse or non-existent. Previous studies have shown that satellite remote sensing can be used to interpret local ozone chemistry by utilizing the ratio between HCHO, as a proxy for VOCs, and NO2, as a proxy for NOx. The recently launched Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument measures hourly HCHO, NO2, and other air pollutants at an unprecedented spatial resolution (~2km x 4.5km) across the United States. In this study, we investigate the relationship between satellite HCHO and NO2 and ground-level oxidation chemistry. This past summer, we collected six weeks of real-time VOC measurements using a high resolution proton-transfer reaction time-of-flight mass spectrometer (PTR ToF-MS) and HCHO measurements using a cavity ring down spectrometer at a long-term air quality monitoring site in Denver, managed by the Colorado Department of Public Health and Environment and the Atmospheric Science and Chemistry mEasurement NeTwork (ASCENT) team. The measurement site hosts a suite of instrumentation, including in-situ observations of NOx, ozone, and aerosols. Our goal is to connect the satellite observations of HCHO and NO2 with measurements of atmospheric composition at the surface. Ongoing data analysis will investigate connections between satellite-derived ratios of HCHO to NO2 and ground-based observations of hydrocarbon oxidation, OH exposure, photochemical age, and the formation of secondary products, examining how these relationships change throughout the day. Ultimately, we hope to provide a framework for how to use satellite observations to better understand ground-level oxidation chemistry.