Investigating The Relative Importance Of Voc And Nox Emissions On Observed Ozone Exceedances In Arizona
Presenter: Seyed Mohammad Amin Mirrezaei1
Co-Author(s): Amin Mirrezaei, Yafang Guo, Chayan Roychoudhury, Avelino Arellano, Armin Sorooshian, Grace Betito
Advisor(s): Dr. Avelino F. Arellano
1Department of Hydrology and Atmospheric Sciences, University of Arizona
An improved understanding of the drivers of ozone in Arizona is important to aid in designing mitigation strategies of ozone pollution in the region. Here, we analyze satellite retrievals of the atmospheric abundance of select ozone precursors (nitrogen oxides or NOX and anthropogenic and biogenic volatile organic compounds or VOCs) to gain insights on the sensitivity of O3 to changes in these precursors. In particular we use retrievals of carbon monoxide (CO), NO2, and formaldehyde (HCHO) from Tropospheric Monitoring Instrument (TROPOMI) for our analysis. TROPOMI provides retrievals at kilometer-scale (3.5km x 5.5km) and daily resolution of these precursors. Due to the short lifetime of NOX, as well as the scarcity of VOCs observations, we use NO2 and HCHO column abundance as proxies for VOC and NOx reactivity. We especially analyze the spatial and temporal distribution of the ratio of HCHO to NO2 tropospheric columns (FNR) across counties (e.g., Gila, Maricopa, Pima, Pinal, and Yuma) experiencing prevalent ozone pollution. During 2019–2021, we find that FNR in Phoenix is relatively lower (less than 2) across the season than Pima and Yuma suggesting that ozone in Maricopa is more sensitive to VOC than NOX, while Pima, Pinal, Gila, and Yuma are still sensitive to NOX emissions. This is supported by land use/land cover regression analysis to determine the relationships of these inferred regimes to anthropogenic and biogenic emissions. Such analysis is also complemented by direct comparisons of these space-based ratios to modeled ratios from the Weather Research and Forecasting model coupled with chemistry (WRF-Chem).