Aerosol Chemical Composition and Cloud Interactions: Findings from the SCILLA Campaign

BRADLEY RIES, Alexander B. MacDonald, Dongli Wang, Minghao Han, Sierra Bollinger, Mason Leandro, Lisa Welp-Smith, Patrick Chuang, Mikael Witte, Andrew Metcalf, Don Collins, Roya Bahreini, University of California, Riverside

     Abstract Number: 415
     Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality

Abstract
The SCILLA (Southern California Interactions of Low cloud and Land Aerosol) campaign was a comprehensive airborne research project aimed at investigating aerosol-cloud interactions and their impact on regional climate and air quality. In June 2023, we conducted 21 research flights onboard a Navy Twin Otter aircraft, equipped with a suite of instruments including a mini Aerosol Mass Spectrometer (mAMS), a Single Particle Soot Photometer (SP2), a scanning Electrical Mobility Spectrometer (SEMS), and cloud droplet counters, among others. Our flights sampled diverse air masses in locations near the coastal pollution sources of Los Angeles Basin (which often are transported out over the water) and off of the coast of San Diego, including nearshore and offshore areas, San Clemente Island, and various cloud regimes (in-cloud, below-cloud, above-cloud and in the cloud wake of the island).

The mAMS alternated sampling through an isokinetic inlet in cloud-free air, a Counter-flow Virtual Impactor (CVI) in clouds, and an oxidation flow reactor. This investigation focuses on a subset of flights to investigate how atmospheric aging and cloud interactions in the marine environment affect aerosol composition. For this, we analyzed compositional data collected from the "missed-approach" flight patterns at Santa Monica, Long Beach and Torrance Airports and contrasted them with our observations of cloud residuals and aerosols in cloud-free air masses off of the coast of San Diego. Our results and their significance in understanding pollution-cloud interactions will be discussed.