Observing air pollution variability with climate change and environmental injustice

Tropospheric ozone (O3) and nitrogen dioxide (NO2) are U.S. Environmental Protection Agency-designated criteria air pollutants regulated to protect human health and public welfare. While air pollution levels have decreased across the U.S., and in many cities around the world, there are still major uncertainties in the sources, the processes affecting their spatiotemporal variability, and their impacts. Climate change will alter many controls over the abundance and distribution of these pollutants, especially for O3, such that air quality may vary differently in the future than the past. Primary pollutants such as NO2 are very highly spatially heterogeneous, and their impacts are unequally distributed, with communities of color and low-income communities disproportionately affected in U.S. cities. In this dissertation, I present a landscape-scale analysis of severe drought impacts on O3 chemistry in California; an evaluation of measurements of the recently-launched satellite sensor, the TROPospheric Ozone Monitoring Instrument (TROPOMI), to resolve NO2 spatiotemporal variability between neighborhoods in Houston, Texas; and observational constraints on the contribution of diesel engine emissions to NO2 inequalities in 52 U.S. cities. I found prolonged severe drought conditions impacted O3 pollution in California by shifting O3 production to become more NOx suppressed and decreasing O3 loss through dry deposition. I show relative NO2 inequalities measured by TROPOMI combined with a physics-based oversampling algorithm are comparable to those from higher resolution aircraft sensor GCAS. Finally, I find diesel emissions are a large driver of NO2 inequality in U.S. cities but decreasing these emissions completely would not eliminate air pollution inequality.