Laboratory measurements of turbulence and coherent structures on both sides of a wind-driven air-water interface

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The exchange across the air-sea interface of heat, moisture, momentum and gases like O2 or CO2 are critically important for many phenomena including weather and climate. In recent years, considerable progress has been made in quantifying air-sea fluxes. However, the fundamental processes involved rely on small scale turbulence at the air-sea interface. These processes are poorly resolved and air-sea fluxes are generally parametrized using readily available, bulk variables such as wind speed. This study will make detailed laboratory experiments which will simultaneously measure the flows on both sides of the air-sea interface to investigate the coherent flow structures and and whether and how turbulence on either side of the interface is coupled. Ultimately the primary societal benefits of this research will be in improved models of weather and climate and the economic and social impacts of improved forecasts including on fisheries, the energy industry, commodity markets, insurance, and disaster/threat preparedness. At the local level, the project will help improve both undergraduate and graduate opportunities including summer fellowships in Research Education for Undergraduates (REU) programs. New knowledge generated by this research will be introduced into undergraduate and graduate classes, and disseminated more broadly through the PI’s web site. Laboratory visits for schoolchildren and other groups and open houses are conducted at the PI’s laboratory. These occasions provide an opportunity to inform the general public of the scientific issues that affect them and to inform school children about careers in the ocean scienceThis project builds upon extensive experience in measuring wavy turbulent flows in one of the fluids (air or water) and extends it by resolving both sides simultaneously. Specifically, the aims of this research are to: 1) Perform controlled laboratory experiments to measure the flow on both sides of the air-water interface simultaneously, 2) Evaluate the coupling and potential causality between the turbulent coherent structures on both sides on the interface, 3) Assess the contribution and influence of a wavy interface on the turbulent fluxes, and 4) Compare these results with established turbulent boundary layer results. It is expected that the findings will lead to a more fundamental understanding of the role of short surface waves, turbulence, Langmuir circulations, microbreaking and separation in air-sea fluxes.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.