Understanding the Impact of Pollution Aerosol From Los Angeles/Long Beach on Clouds and Radiation in and Upwind of the EPCAPE Study Domain

Abstract

The atmosphere over the northeastern Pacific off the coast of Southern California serves as a natural laboratory where a large and persistent blanket of low-level clouds interacts with a dynamic mixture of clean marine air and highly polluted air originating from the emissions-rich Los Angeles/Long Beach (LA/LB) region.  Between February 2023 and January 2024, the Department of Energy (DOE) will lead the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE), during which an extensive array of sensors will be used to characterize the chemical and radiative properties of the atmosphere just north of San Diego in La Jolla, CA.  To complement and leverage EPCAPE, the Office of Naval Research (ONR) will support a 90-flight hour deployment of the Naval Postgraduate School’s Twin Otter research aircraft during the May/June 2023 Southern California Interactions of Low cloud and Land Aerosol (SCILLA) experiment. Those research flights will provide a regional context for the point measurements in La Jolla and will add extensive below-, in-, and above-cloud measurements spanning an area encompassing a wide range of meteorological and, especially, aerosol conditions.  Our collaborative team from the University of California Riverside and Clemson University will be supported by the DOE Atmospheric System Research (ASR) program to significantly augment the aerosol measurement capabilities on the Twin Otter in order to provide a much more comprehensive description of the sources, processing, chemistry, radiative and cloud-altering properties, and spatial distribution of the aerosol upwind of the San Diego area in general, and the EPCAPE study sites in particular.  The instruments our team will provide and operate will characterize the size distribution, composition, light absorption efficiency, and cloud droplet formation properties of the aerosol particles and the concentrations and aerosol formation potential of important trace gases.  The greatly expanded aerosol measurement payload that will result will provide details of the aerosol that are needed to connect the atmosphere offshore with that at the surface sites and to provide the detailed characterization that can be used to understand the connection between the aerosol and the cloud properties measured on the Twin Otter by other researchers.