Physical and Chemical Properties of Aerosols in the Marine Boundary Layer

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9619984 Covert This project focuqes on the hygroscopic properties of marine aerosol particles in order to understand and to determine the physical, optical and cloud nucleating properties of marine boundary layer aerosol particles. The hygroscopic properties of aerosol are related to atmospheric relative humidity f(RH) . These properties are key factors that influence the spatial and temporal variability of the aerosol physical and optical properties during transport. The project is part of the North Atlantic Regional Aerosol Characterization Experiment (ACE-2) which will be conducted in June and July, 1997, over the subtropical Northeastern Atlantic Ocean as an international collaborative effort. The main objectives of ACE-2 are to study the properties of atmospheric aerosols that are relevant to radiative forcing and climate change using aircraft, ship-board, and ground-based measurements. The measurements will involve use of a tandem differential mobility analyzer (RH-TDMA) that is capable of measuring the hygroscopic growth properties of marine boundary layer aerosol particles. The PI will compare the hygroscopic behavior of ambient particles with those of synthetic aerosol prepared in the laboratory and having chemical compositions of artificial seawater, aerosol derived from sea water solutions, internal mixtures of acid sulfate and seasalt and internal mixtures of acid sulfate, nitrate and organic acids. The laboratory studies will be used to interpret the growth of marine boundary layer aerosols and anthropogenic aerosols measured during the large-scale ACE-2 field experiment. The project will develop information needed to evaluate with what certainty light scattering and numbers of cloud condensation nuclei can be predicted from measurements of particle size distributions and hygroscopicity in the marine boundary layer. Improving the linkage between aerosol physical and optical properties is a necessary step for quantifying the direct and indirect radiative effects of a erosol particles within the atmosphere. ATM-9619984