The Fires, Asian, and Stratospheric Transport-Las Vegas Ozone Study (FAST-LVOS)
Résumé
Abstract. The Fires, Asian, and Stratospheric Transport-Las Vegas Ozone Study (FAST-LVOS) was conducted in May and June of 2017 to study the transport of ozone (O3) to Clark County, Nevada, a marginal non-attainment area in the Southwestern U.S. (SWUS). This 6-week (20 May–30 June 2017) field campaign used lidar, ozonesonde, aircraft, and in-situ measurements in conjunction with a variety of models to characterize the distribution of O3 and related species above southern Nevada and neighbouring California, and to probe the influence of stratospheric intrusions, wildfires, and local, regional, and Asian pollution on surface O3 concentrations in Las Vegas and the surrounding area. In this paper, we describe the FAST-LVOS campaign and present case studies illustrating the influence of different transport processes on background O3 and air quality attainment in the SWUS. The measurements found elevated O3 layers above Las Vegas on more than 75 % (35 of 45) of the sample days, and show that entrainment of these layers contributed to mean 8-h average background O3 concentrations of 50–55 parts-per-billion by volume (ppbv) across southern Nevada. These background concentrations constitute 70–80 % of the current U.S. National Ambient Air Quality Standard (NAAQS) of 70 ppbv, and illustrate some of the challenges facing air quality managers tasked with O3 attainment in the SWUS during late spring and early summer. The companion paper by Zhang et al. (2020) describes the use of the AM4 and GEOS-Chem global models to estimate the impacts of transported O3 on surface air quality in the Southwestern U.S. and Intermountain West during the FAST-LVOS campaign.