The Coupled Boundary Layers Air-Sea Transfer Defense Research Initiative (CBLAST-DRI) focuses on processes that occur in the oceanic and atmospheric wave boundary layers, which are regions influenced by ocean surface waves. This Office of Naval Research (ONR) program combines observational and modeling components in all of its investigations. These investigations will focus on processes that couple the turbulent atmospheric and oceanic boundary layers across the interface through the exchange of momentum, mass, and heat. Understanding the influence of surface waves and determining the 3-D structure of these boundary layers is one of the main objectives of this program. Two regimes will be emphasized: a low wind, convectively (heating/ cooling) dominated regime, typically less than 5 m/s, with investigations of the transitions from stable to unstable flows where the buoyant forcing changes sign and from smooth to fully rough seas where wave-induced processes begin to dominate; and a very high wind regime with wind speeds greater than 20 m/s up to hurricane strength where in situ and remote observations are desperately needed to improve and evaluate forecast models. 
     The observational components include in situ investigations of ocean-atmospheric turbulence and mean flow from fixed towers and moorings, remote sensing of 2- and 3-D structure of the boundary layers and ocean surface, appropriate surface wave measurements with particular emphasis on small-scale and breaking waves, and Autonomous Underwater Vehicle (AUV) and aircraft-based measurements. The program will work toward quantifying the TKE budget and the momentum, mass, and heat budgets in the oceanic mixed-layer and atmospheric boundary layer. Novel instrumentation development efforts will be included, particularly for very high winds. 
     The modeling and simulation (e.g., LES and DNS) components are expected to develop improved, physics-based parameterizations of the fluxes (momentum, energy, heat, mass) and/or the coupled nature of the wave boundary layer.  We are also interested in physics-based parameterizations of the direct coupling of the surface wave field with particular emphasis on small scale and breaking waves. An important product of this program will be parameterizations useful in larger scale, coupled ocean-air models.