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  • Author or Editor: A. D. Clarke x
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A. Clarke, V. Kapustin, S. Howell, K. Moore, B. Lienert, S. Masonis, T. Anderson, and D. Covert

Abstract

The authors' participation in the Shoreline Environment Aerosol Study (SEAS) involved measurements focused on the coastal aerosol size distribution and related optical measurements, including aerosol light scattering, visibility, and remote sensing of aerosol using lidar backscatter. Aerosol production from shoreline breaking waves and the more distant reef (∼1 km) was characterized for dry sizes between 0.01 and 10 μm for both their contribution to the marine aerosol population and their influence on near-surface lidar extinction. Thermal volatility was used to extract the refractory sea-salt particles from the other constituents volatile at 360°C. At 7 m ASL and 20 m inland from the water's edge the production of sea-salt nuclei number was often in the range of 50–100 cm−3 above the open-ocean value of ∼250 cm−3. This number peak was near 0.03-μm dry diameter, while light scattering was dominated by a few particles larger than 1 μm. This indicates that production of sea salt from breaking waves contributes not only to aerosol mass and optical effects but also to nuclei mode particle number in remote regions. Separate studies of optical closure quantified links between the size distribution and optical scattering measurements, visibility, and extinction values for both nearshore breaking waves and open-ocean conditions. These data confirmed that extinction derived from coastal lidar measurements at 0.530 μm was accurate to better than the 25% uncertainty claimed for the lidar inversion.

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P. Campuzano-Jost, C. D. Clark, H. Maring, D. S. Covert, S. Howell, V. Kapustin, K. A. Clarke, E. S. Saltzman, and A. J. Hynes

Abstract

The first deployment of an emission-based aerosol sodium detector (ASD), designed to chemically characterize marine aerosols on a near-real-time basis, is reported. Deployment occurred as part of the Shoreline Environment Aerosol Study (SEAS) from 16 April to 1 May 2000 at Bellows Air Force Base on the east side of Oahu, where the University of Hawaii's Department of Oceanography maintains a tower for aerosol measurements. The instrument was operated in size-unsegregated mode and measurements were made that included two extended continuous sampling periods, each of which lasted for 24 h. During this time, the ASD was compared with measurements that used aerosol volatility coupled with optical particle counting to infer sea-salt size distributions. A reasonable agreement was obtained between the instruments when sampling in clean air, suggesting that under these conditions both approaches can provide reliable sea-salt distributions. The combination of these measurements suggested that sea salt was the dominant constituent of aerosol particles with diameters larger than 500 nm and that sulfate was the dominant constituent at smaller diameters during clean air sampling.

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