An overview of the SEA Spray and Whitecap (SEASAW) field study

The Sea Spray and Whitecap study (SEASAW) is a UK SOLAS project aimed at advancing our understanding of the physical processes controlling the air-sea exchange of trace gases – primarily CO2 – and the generation of sea salt aerosol. A major objective was to obtain measurements under high wind conditions – amply achieved with mean wind speeds up to 20 m/s. The measurement program consisted of two research cruises in the North East Atlantic in the late autumn of 2006 and the spring of 2007. Two separate flux systems were installed on the foremast of the RRS Discovery: the AUTOFLUX system from the National Oceanography Centre in Southampton measured wind stress, heat, water vapor, and CO2 fluxes; a system from the University of Leeds also measured size segregated aerosol particle fluxes in 16 channels between radii of 0.15 and 3.5 micrometres, and ozone flux. Photographic images of the sea surface were recorded throughout daylight hours in order to assess the surface whitecap fraction. For limited periods of time two buoy systems were deployed. A free-floating spar buoy instrumented with wave wires, digital video and stills cameras, and an acoustic bubble measurement system made detailed measurements of surface waves, whitecapping, and bubble properties; a smaller tethered buoy instrumented with two compact aerosol probes, a bubble imaging camera, and a motion pack examined the bubble population and near-surface aerosol production from individual wave and whitecap events. Here we present a brief overview of the measurement campaign, science objectives, and some of the highlights of the data set. A series of other contributions will examine different aspects of the data set in detail.