First Results from Coastal Cloud Chemistry at Mt. Soledad during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE)

LYNN RUSSELL, Abigail Williams, Jeramy Dedrick, Christian Pelayo, Nattamon (Jeep) Maneenoi, Sourita Saha, Sanghee Han, Elavarasi Ravichandran, Markus Petters, Catherine Banach, Veronica Berta, Suzanne E. Paulson, Rachel Chang, Laura-Helena Rivellini, Jonathan Abbatt, Alex K.Y. Lee, Jeremy Wentzell, Michael Wheeler, John Liggio, EPCAPE Science Team, Scripps/UCSD

     Abstract Number: 595
     Working Group: Aerosols, Clouds and Climate

Abstract
Coastal cities provide the opportunity to characterize marine clouds and the substantial effects of manmade particles on cloud properties and processes. La Jolla lies to the north of San Diego, CA, but it is often about a day directly downwind of the major pollution sources located in the ports of Los Angeles and Long Beach. The large dynamic range of aerosol particle concentrations combined with the multi-hour to multi-day persistence of stratocumulus cloud layers makes the site ideal for investigating the seasonal changes in cloud and aerosol properties as well as quantifying the relationships between cloud and aerosol properties. The Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) is taking advantage of the coastal location of La Jolla to characterize the extent, radiative properties, aerosol interactions, and precipitation characteristics of stratocumulus clouds in the Eastern Pacific across all four seasons at the Scripps Pier and the Mt. Soledad. In collaboration with the DOE Atmospheric Radiation Measurement (ARM) deployment of the first Atmospheric Measurement Facility (AMF1) cloud, aerosol, and precipitation instrumentation at the Scripps Pier in La Jolla from February 2023 to February 2024, our multi-institution, international collaboration is collecting physical and chemical measurements at Mt. Soledad (~250 m above and 3 km to the southeast of the Scripps pier) of aerosol particles, gases, and droplet residuals. Sampling from an isokinetic aerosol inlet in clear air and a counterflow virtual impactor in cloud provides characterization of the activated and aerosol phases associated with cloud chemical processing and microphysics. Measurements include cloud condensation nuclei (CCN) properties, chemical contributions to CCN, oxidation of components, and production of gas-phase species. Here we report some of the first results of aerosol-cloud interactions measured during the record-breaking precipitation events of 2023. The observations show size-resolved changes in the droplet residual distribution tracks the drop distribution, with some expected changes in chemical composition between aerosols and droplets. Comparison of aerosol size distribution during and after precipitation events provides an approach for quantifying wet scavenging. In addition, we report aerosol population types from the single-particle mode of the aerosol mass spectrometer (AMS) collected by event-based triggering for the characterization of the activated fraction.