California Air Resources Board

Principal Investigator/Author: Laura Iraci

Contractor: National Aeronautics and Space Administration (NASA)

Contract number: 17RD004

Project Status: Completed

Relevant CARB programs: California State Implementation Plans, Ozone Transport

Topic areas:  Climate Change, Ozone, State Implementation Plans (SIPs)

Research Summary:

Because health effects research has consistently led to more stringent ambient air quality standards for ozone (O3), California must continue to achieve reductions in O3 precursor emissions. However, background O3 from other sources outside the State's control can also affect California's air quality. Due to increasing baseline O3, the atmospheric transport mechanisms have the potential to make attainment of the stringent O3 National Ambient Air Quality Standards (NAAQS) increasingly more difficult in regions like the San Joaquin Valley (SJV). To better understand the ground-level O3 contributions from the transport and the atmospheric processes in the SJV, the California Baseline Ozone Transport Study (CABOTS) produced a three-month dataset of aloft O3 data collected with ozonesondes and an O3 lidar during May - August 2016. The National Aeronautics and Space Administration (NASA) Alpha Jet Atmospheric eXperiment (AJAX) group, an unfunded collaborator, conducted eight flights designed to investigate the incoming air, the variability of free-tropospheric O3, and the atmospheric transport of O3 across the State during the CABOTS field campaign. AJAX flights linked ozonesonde launches at the coast to lidar measurements in Visalia. This project will finalize and complete the analysis of the data collected by the NASA AJAX group during CABOTS, which will provide additional insight into baseline O3 transport mechanisms from the Pacific and into the SJV. The results will help CARB determine if and how atmospheric O3 transport impacts ground-level O3, especially on days when the O3 concentrations exceed the NAAQS in the SJV. The information can also help evaluate and improve the representation of the horizontal transport and downward mixing processes of O3 aloft in the regional air quality and meteorological models needed for the development of the State Implementation Plans.

Keywords: ozone (O3), national air quality ambient standards (NAAQS), emissions, transport, atmosphere, atmospheric

Final Report: Please email research@arb.ca.gov to request the final report generated by this research contract.