CAREER: Revitalizing aerosol-cloud-chemistry research at Whiteface Mountain

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A new measurement strategy is proposed at the Whiteface Mountain (WFM) summit research observatory in New York State that will enable a more complete characterization of the chemical processes occurring within the clouds. Multiphase chemical observations have been made at WFM since the mid-1970s, when there was particular interest in the conversion of gas-phase sulfur dioxide emissions to aerosol sulfate resulting in acidic rain. Subsequent to the implementation of federal and regional air quality standards, the chemistry occurring within the clouds at this location has changed substantially. These changes suggest the emergence of a new chemical regime dominated by organics and ammonium. This project is investigating this changing chemical regime.The central hypothesis of the proposed work is that cloud processing continues to alter the chemical composition of ambient aerosols in the northeastern U.S., in ways that fundamentally differ from the dominant inorganic processes in previous decades. More specifically, cloud processing increases secondary organic aerosol mass via condensation of soluble organic gases and subsequent aqueous reactions, yielding less volatile organic compounds that remain in the condensed phase upon droplet evaporation. The proposed research will investigate the following science questions: (1) What is driving the increasing trend in water soluble organic carbon (WSOC) at WFM? (2) What happens to the excess ammonia and WSOC vapor when the cloud droplets evaporate? and (3) Will increases in excess ammonia lead to increased WSOC in the future? The proposed research will build upon past and ongoing research at WFM and lead to a better understanding of multiphase chemical processes occurring within clouds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.