Investigation of Secondary Aerosol Formation Potential of Air off the Coast of Southern California

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

     Abstract Number: 579
     Working Group: Aerosols, Clouds and Climate

Abstract
The area of the Pacific Ocean within the California Bight that extends from Point Conception in California to Punta Colonet in Baja California is notable for its substantial and enduring stratocumulus cloud layer. Polluted air from Los Angeles/Long Beach (LA/LB) can be drawn offshore and interact with the cloud layer over the Bight. Prevailing winds typical in late spring and early summer, commonly carry pollution from LA/LB to the south and towards the San Diego area. This area is ideal for studying aerosol-cloud interactions (ACI) between marine stratocumulus and a mixture of pollution and natural aerosol spinning a wide range in concentration. Since early 2023, the chemical and radiative properties of the aerosol in La Jolla, CA have been characterized as part of the DOE Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE). To complement and leverage EPCAPE, the Naval Postgraduate School Twin Otter research aircraft was deployed during the June 2023 Southern California Interactions of Low Cloud and Land Aerosol (SCILLA) experiment. The flights provided a regional context for the point measurements in La Jolla and captured the spatial variability relevant to models. The analysis presented here uses a subset of the measurements from SCILLA with a focus on those from an oxidation flow reactor (OFR), that was specifically designed and constructed to comply with aircraft physical and sampling constraints. We describe secondary aerosol formation potential of air influenced to varying extent by LA/LB emissions and to varying extent by gas- and cloud-processing over the Bight. These measurements provide valuable insights into the relationship between cloud properties and the temporally and spatially variable aerosol field between LA and SD.