9529808 Melville Funding is provided to the Marine Physical Laboratory at Scripps Institution of Oceanography to develop and test instrumentation for measuring entrained air and bubble size distributions in the ocean surface layer beneath breaking waves. Bubbles in the ocean surface layer play an important role in air-gas transfer, in the generation of aerosols, in biological processes, and in the acoustics of the surface layer. Laboratory data and preliminary field data suggest that air entrained by breaking waves may be dynamically significant through the work done against buoyant forces. The instrument will be a broad band (2kHz -200kHz) system for in situ measurements of the bubble size distribution in the surface layer by inverting direct measurements of sound speed and attenuation over path lengths of 0.1 - 1m. The research will be split into two phases, a laboratory development and testing phase, followed by a field instrument and testing phase.