Measurements of ocean surface turbulence and wave-turbulence interactions

Abstract

The uppermost layers of the ocean, along with the lower atmospheric boundary layer, play a crucial role in the air-sea fluxes of momentum, heat, and mass, thereby providing important boundary conditions for both the atmosphere and the ocean that control the evolution of weather and climate. In particular, the fluxes of heat and gas rely on exchange processes through the molecular layers, which are usually located within the viscous layer, which is in turn modulated by the waves and the turbulence at the free surface. The understanding of the multiple interactions between molecular layers, viscous layers, waves, and turbulence is, therefore, paramount for an adequate parameterization of these fluxes. In this paper, the authors present evidence of a clear coupling between the surface waves and the surface turbulence. When averaged over time scales longer than the wave period, this coupling yields a spatial relationship between surface temperature, divergence, and vorticity fields that is consistent with spatial patterns of Langmuir turbulence. The resulting surface velocity field is hyperbolic, suggesting that significant stretching takes place in the surface layers. On time scales for which the surface wave field is resolved, the authors show that the surface turbulence is modulated by the waves in a manner that is qualitatively consistent with the rapid distortion theory. © 2009 American Meteorological Society.