Secondary Aerosol Formation Potential and Transportation of Air Pollution off the Coast of Southern California

MINGHAO HAN, Bradley Ries, Dongli Wang, Alexander B. MacDonald, Roya Bahreini, Andrew Metcalf, Don Collins, University of California, Riverside

     Abstract Number: 507
     Working Group: Aerosols, Clouds and Climate

Abstract
The California Bight region of the Pacific Ocean, extending from Point Conception in California to Punta Colonet in Baja California, Mexico, is characterized by its consistent and expansive stratocumulus cloud coverage. Airborne pollutants from the Los Angeles/Long Beach (LA/LB) area can be transported offshore, where they interact with this cloud layer and are also transported southward towards the San Diego area by prevailing winds. This geographic setting is particularly conducive to the study of aerosol-cloud interactions (ACI) involving marine stratocumulus clouds and a diverse mix of pollution-derived and natural aerosols. During the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) campaign, which took place in La Jolla, CA, the Naval Postgraduate School Twin Otter aircraft was utilized for an intensive 4-week, 90-flight-hour campaign off the Southern California coast in June 2023. These flights were aimed at providing a regional perspective for the EPCAPE measurements and included comprehensive below-cloud, in-cloud, and above-cloud data collection across a range of meteorological and aerosol conditions. As part of the Southern California Interactions of Low Cloud and Land Aerosol (SCILLA) experiment, the project team operated an array of instruments on the aircraft, including an Oxidation Flow Reactor (OFR) system specifically designed for airborne measurements, a Cloud Condensation Nuclei Counter, an mini Aerosol Mass Spectrometer (mAMS), and various trace gas analyzers. Here we focus on the secondary aerosol formation potential in air affected by emissions from LA/LB, as well as by atmospheric gas and cloud processing over the Bight. This study explores transformation processes, spatial distribution, and the SOA formation contribution of pollution off the coast of Southern California.