UC Irvine

Air quality simulations are performed to determine the impact of changes in future climate and emissions on regional air quality in the South Coast Air Basin (SoCAB) of California. The perturbation parameters considered in this study include (1) increased temperatures, (2) increased absolute humidity, (3) increased biogenic VOC emissions due to increased temperatures, and (4) increased pollutant concentrations at the western inflow boundary. All parameters are first perturbed individually. In addition, the impact of simultaneously perturbing more than one parameter is analyzed. Air quality is simulated over a three-day period with meteorology representative of a summertime ozone pollution episode using both a baseline 2005 emissions inventory and a future emissions projection for the year 2023. Different locations within the modeling domain exhibit varying degrees of sensitivity to the perturbations considered. Afternoon domain wide average ozone concentrations are projected to increase by 13-18% as a result of changes in future climate and emissions. Afternoon increases at individual locations range from 10-36%. The change in afternoon PM levels is a strong function of location in the basin, ranging from -7.1% to +4.7% when using 2005 emissions and -8.6% to +1.7% when using 2023 emissions. Afternoon SOA concentrations for the entire domain are projected to decrease by over 15%, and the change in SOA levels is not a strong function of the emissions inventory utilized. Temperature increases play the dominant role in determining the overall impact on ground-level ozone, PM, and SOA concentrations in both the individual and combined perturbation scenarios.