Investigation of the Sources of High Ozone in California's San Joaquin Valley Using Lidar, Aircraft, and Balloon-Borne Observations from the 2016 California Baseline Ozone Transport Study

Despite dramatic improvements in California's air quality, many areas in California struggle to meet the 8-hour National Ambient Air Quality Standard (NAAQS) for ozone. This is in large part due to local emissions, but long-range transport of ozone (e.g. from Asia) and ozone from natural sources, such as stratosphere-to-troposphere transport and wildfires, contribute to California’s ozone burden. Understanding these different sources of ozone, their transport mechanisms, and their relative contribution to high-ozone episodes in California is becoming increasingly important as the state strives to meet the new, stricter ozone NAAQS of 70 ppbv. To help address these questions, the National Oceanic and Atmospheric Administration deployed its truck-based, scanning Tunable Optical Profiler of Aerosol and oZone (TOPAZ) lidar in California’s San Joaquin Valley during the California Baseline Ozone Transport Study (CABOTS) in spring and summer 2016. More than 400 hours of ozone and aerosol backscatter profiles collected with the TOPAZ lidar, together with near-daily ozone sonde launches at two sites along the Central California Coast, and observations from two instrumented aircraft yielded a rich data set to examine the mix of ozone sources that contribute to high ground-level ozone often observed in the San Joaquin Valley (SJV). First results from the CABOTS study will be discussed with an emphasis on the influence of transported ozone on SJV air quality.