The 2015 Great Salt Lake Summer Ozone Study

Researchers from Utah universities and the Utah Division of Air Quality examined the distribution of boundary-layer ozone during summer 2015 in the vicinity of Utah's Great Salt Lake. The study is the first to provide a detailed examination of the complex temporal and spatial variations in boundary-layer ozone in the region extending from Utah's Great Salt Lake into the urbanized Wasatch Front and adjacent Wasatch Mountains, and the impacts of thermally-driven Great Salt Lake breezes on summertime pollution transport into the Salt Lake Valley. Ridging episodes over the western United States during summer 2015 led to ozone concentrations in excess of the current EPA standard at official reporting sites on many days. To supplement those official readings, ozone sensors were deployed at additional fixed locations for the entire summer as well as during scheduled and opportunistic observing periods on vehicles, a light rail car, unmanned aerial vehicles, tethered and free-flying sondes, a paraglider, and a traffic helicopter. To identify and study high ozone concentrations as they transpired, data from as many of the ozone sensors as possible were collected in real-time and displayed on the web (see http://meso2.chpc.utah.edu/gslso3s/). The Lake and surrounding terrain help to control thermally-driven flows in the surrounding areas, often driving urban and biogenic emissions of precursor chemicals towards the lake at night. The drop in recent years in the level of the Great Salt Lake has led to exposure of highly reflective playas surrounding the Lake that may lead to enhanced photochemical reactions over those surfaces. 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 is relevant to understanding the potential impact of the more stringent ozone standards proposed by the EPA throughout the western United States.