I am an atmospheric chemist with broad interests in air quality, climate, and atmosphere-biosphere interactions. My research group makes measurements at the Earth’s surface and from onboard aircraft in diverse locations, including polluted cities, agricultural areas, and within forest canopies. Our focus is on the role of reactive nitrogen in chemical oxidation mechanisms and emissions of the greenhouse gas nitrous oxide. We utilize spatial and temporal variability in our datasets to derive mechanistic insight into processes taking place in urban and human-influenced environments. We work to find solutions to atmospheric problems that adversely affect human health and ecosystems.