Observation and WRF Simulation of a Lake Breeze Related Summer Ozone Event in the Salt Lake Valley

Poor air quality on the afternoon of 18 June 2015 resulted from lake breeze transport of high ozone concentrations from over the Great Salt Lake into the Salt Lake Valley. An extensive network of near-surface ozone observations were available at this time as a result of the 2015 Great Salt Lake Summer Ozone Study (GSLSO3S). Ozone observations in northern Utah were available from sensors at a dozen state air quality measuring sites, additional fixed locations, vehicles, a light rail car, unmanned aerial vehicles, tethered and free-flying sondes, and a news helicopter. Meteorological conditions were monitored from nearly a hundred automated weather stations as well as surface-based remote sensors (ceilometers, sodars, lidar, TDWR) at several locations.

Simulations of the atmospheric conditions during this day were completed using the WRF model at 1 km horizontal resolution over northern Utah. The model was initialized using hourly analyses at 3 km resolution from the NCEP High Resolution Rapid Refresh (HRRR) model. Our effort is the first one to use this state-of-the-art data assimilation system as a means to initialize the WRF for research simulations of an air pollution episode. Passive tracers initialized at several locations in the model domain help visualize the dispersion and transport of pollutants around the Great Salt Lake and in the Salt Lake Valley. Results from these model simulations are compared to the available observations of the lake breeze event and the ability of the WRF model to simulate the strength and timing of the lake breeze is investigated.