VOCALS: Measurements of Organic Aerosol Composition to Improve Aerosol-Cloud Characterization

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Measurements of the organic fraction of aerosol will be made on the R/V Ron Brown during the VOCALS (VAMOS Ocean-Cloud-Atmosphere-Land Study) experiment with the overall goal of reducing uncertainty in aerosol/climate interactions. The compounds that constitute the organic fraction in the atmosphere span a wide range of chemical, thermodynamic, and optical properties, none of which are known sufficiently well to be described in global climate models. The data will represent some of the first measurements of organic functional groups in aerosols in the Southern Hemisphere, and will be used to quantify the amount and types of organic compounds and assess the microphysical and optical roles of organic particles in clouds. Fourier Transform Infrared (FTIR) and X-Ray Fluorescence (XRF) spectroscopy, Aerosol Mass Spectrometry (AMS), and Near-Edge X-Ray Absorption Fine Structure Scanning Transmission X-Ray Microscopy (NEXAFS/STXM) will be used to measure aerosol concentrations of elements, organic functional groups, and organic mass. The following aerosol properties will be measured: organic mass and organic-mass-to-organic-carbon ratios (OM/OC) by FTIR and AMS; organic functional groups by FTIR and organic mass fragments by AMS; and single-particle organic composition and morphology by NEXAFS/STXM. The measured organic composition will be analyzed with microphysical and thermodynamic models.This project provides the opportunity for a graduate student and a postdoctoral researcher to participate in the multinational scientific team for VOCALS. The collaboration will strengthen international ties and contribute to the advancement of science in a developing country. The investigators and students will participate in and contribute to outreach and K-12 educational programs developed for VOCALS. The broader scientific impacts of this work will be an improved understanding of the climate-related effects of organic aerosols.