Influence of Thermally- and Terrain-Driven Flows on Summer Ozone Concentrations

The Great Salt Lake Ozone Study was conducted during the 2015 summer. The study was the first to provide a detailed examination of the distribution of boundary-layer ozone over Utah's Great Salt Lake as well as the nearby urbanized Wasatch Front and Wasatch Mountains. Ridging aloft over the western United States led to ozone concentrations in excess of the current EPA standard at official reporting sites on many days during the summer. In addition to a network of 27 ozone sensors in rural and urban locations continuously monitoring ozone concentrations, extensive data were collected from sensors mounted on a novel mix of vehicles, a light rail car, traffic helicopter, tethered sonde, and unmanned aerial vehicle.

Thermally-driven wind systems including slope, valley, and land/lake breezes modulated the transport and exchange of background ozone and ozone precursors between the Lake, urban environments, and nearby mountains. Lake breeze fronts during some afternoons led to the transport of high levels of ozone back into the metropolitan Wasatch Front. The data collected as part of this study are relevant to understanding the potential impact of the more stringent ozone standards proposed by the EPA throughout the complex terrain of the western United States.