Online Chemical Composition of Submicron Aerosol Particles and Cloud Residuals at Mt. Soledad during EPCAPE 2023-24. In Aerosol Microphysics and Chemical Measurements at Mt. Soledad and Scripps Pier during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) from February 2023 to February 2024

As part of EPCAPE, a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS; Aerodyne Inc., Billerica MA) was deployed on Mt. Soledad in La Jolla, CA between February 2023 and February 2024. The HR-ToF-AMS provides measurements of the chemical composition and size of non-refractory aerosol particles and was operated on a menu-switching cycle for the duration of the campaign. A complete cycle totals to 5 minutes, with 2 minutes of mass spectra (MS) and particle time of flight (PToF) collections under V-mode, 2 minutes of event trigger (ET) single particle collections under V-mode, and 1 minute of MS collections under W-mode. During non-cloudy periods, the HR-ToF-AMS sampled submicron ambient aerosol particles behind a PM1 cyclone on an isokinetic aerosol inlet. During in-cloud events, the HR-ToF-AMS sampled cloud droplet residuals behind a Counterflow Virtual Impactor (CVI). Available measurements include a raw form of MS, PToF, and ET (intended for more in-depth analysis) and a processed form of corrected mass concentrations, size distributions, and single-particle composition clusters of sulfate, nitrate, ammonium, chloride, and organics (intended for ready use in comparisons with other instrument measurements). Users of these measurements are encouraged to consult with the authors about appropriate interpretation before submitting for publication, offering co authorship where appropriate.