High Resolution Air-Sea Interaction DRI
The practical objectives motivating the establishment of the High Resolution Air-Sea Interaction DRI (Hi-Res DRI) are the determination of how well ship-based radars can measure the phase-resolved surface wave field (PRSWF), testing the skill of highly-nonlinear numerical surface wave models to predict the evolution of the PRSWF, and the incorporation of ocean wave effects into models of the Marine Atmospheric Boundary Layer (MABL). Together, enhanced skills in these areas would lead to the goal of improved predictions of the PRSWF around surface vessels and contribute to the safety and effectiveness of naval operations and sea keeping in moderate to high winds and sea states. While these are practical objectives and goals, their achievement will stretch the scientific limits of wind and wave measurements, theory and modeling, and our understanding of microwave (radar) scattering at grazing incidence.

The current generation of wind and wave models are largely based on a statistical description of the wind and wave fields and do not resolve the phase of the waves nor that of the winds that are modulated by the waves. The growth, evolution, propagation and dissipation of the surface wave field depend on wind input due to pressure and viscous forces at the surface, nonlinear wave-wave interactions, refraction by currents, and dissipation, the last being due mainly to breaking. The waves in turn modify the marine atmospheric boundary layer, affecting the momentum flux (drag), energy and mass fluxes between the atmosphere and the ocean.

Radar measurements of the waves, depend on microwave scattering by the small-scale surface roughness (short waves) phase-resolved on the longer waves, and its inversion to give the description of the longer surface waves. While measurements of small-scale roughness of waves are a necessary element of the field program, this DRI is not designed to investigate in any fundamental way microwave scattering, but rather has the more practical objective of using empirically-based techniques to calibrate radar measurements of the surface wave field over a range of wind and wave conditions.

The ultimate goal of the program is to develop the basis for the next generation of large eddy simulation/direct numerical simulation (LES/DNS) models of the coupling between the ocean-wave-atmosphere systems, which will need to have wave-resolved dynamics and kinematics. In order to achieve its goals the DRI will include field measurements, theory and numerical modeling of the wind-wave interaction problem.