Summer Seasonal Variation of Baseline Ozone and Source Analysis for California

Recent studies have shown that, since the 1980s, baseline ozone throughout the troposphere has been increasing over California even though ozone precursor emissions in California have been decreasing with progressively stricter regulations from the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). Because of ozone's direct impacts on air quality, health, and global climate, the EPA and CARB have continued to lower the exceedance value for ozone. Therefore, several air quality regions have remained in non-attainment for both the 8-h ozone national standard, 75 ppb, and the stricter California 8-h ozone standard, 70 ppb.

This study is aiming to provide an updated summertime (JJA) ozone climatology by combining all available ozone data in California from 2004 to 2014. Data used for this study include ozonesonde launches from the Trinidad Head site and the CalNex 2010 experiment, CARB and EPA ozone ground monitoring stations across the state, as well as satellite observations. Summer trends and the inter-annual variability of tropospheric and surface baseline ozone affecting California from long-range Pacific Ocean transport will be evaluated. Detailed comparisons of the ozonesondes and the ground ozone station data will be performed and analyzed to distinguish baseline ozone from inland anthropogenic sources. Additionally, a summertime climatology of back-trajectory analyses will be performed for the Trinidad Head ozonesonde location.