Photochemical model representation of ozone and precursors during the 2017 Lake Michigan ozone study (LMOS)
Chicago, Lake Michigan, LMOS, O 3
Several areas in the Lake Michigan region are violating the human health-based ozone (O3) National Ambient Air Quality Standard. Land-water meteorology driven build-up of precursor pollutants (NOX and VOC) from mobile and stationary sources undergo photochemical O3 production and result in seasonal high O3 episodes during the spring and summertime. Routine and specialized surface measurements coupled with airborne and remotely sensed measurements from the 2017 Lake Michigan Ozone Study (LMOS) provide an opportunity to evaluate photochemical grid model representation of these processes. The Community Multiscale Air Quality Model (CMAQ) was applied at a 4-km grid resolution for the Lake Michigan region and compared against routine and field study measurements to determine how well the modeling system captures emissions, meteorology, and chemical production during O3 episodes. The model captured day to day and diurnal variability in observed O3 along Lake Michigan but often missed peak O3. Surface level NO2 was generally well characterized, but the model seemed to be missing a significant source of VOC, likely both regional and local (not necessarily the same source sector) based on model sensitivities. On June 2, 2017, the model captured the timing of the lake to land breeze but underestimated near-surface wind speed which coincided with peak O3. The underestimation of surface O3 north of Chicago at Zion, Illinois, on this afternoon may be related to over-water vertical mixing, the modeled lake breeze being too weak to transport ozone and precursors back onshore, regional and aloft underprediction of O3, or some combination of each of these factors. Despite underpredictions of peak O3 at some monitors on certain days, the modeling system is useful for developing control scenarios for this region. Model-predicted O3 sensitivity to precursors matched other assessments and suggests both NOX and VOC anthropogenic emissions are important to reduce O3 in the Chicago area.
Department of Earth and Environmental Sciences
Original Publication Date
DOI of published version
Baker, Kirk R.; Liljegren, Jennifer; Valin, Lukas; Judd, Laura; Szykman, Jim; Millet, Dylan B.; Czarnetzki, Alan; Whitehill, Andrew; Murphy, Ben; and Stanier, Charles, "Photochemical model representation of ozone and precursors during the 2017 Lake Michigan ozone study (LMOS)" (2023). Faculty Publications. 5356.