Exploring the role of wave-driven turbulence at the air-sea interface through measurements of TKE dissipation rates across the air-sea interface

Abstract

This work serves as an observation-based exploration into the role of wave-driven turbulence at the air-sea interface by measuring Turbulent Kinetic Energy (TKE) dissipation rates above and below the sea surface. Subsurface ocean measurements confirm a TKE dissipation rate enhancement relative to the predicted law-of-the-wall (εobs > εp), which appears to be fully supported by wave breaking highlighting the role of the transport terms in balancing the subsurface TKE budget. Simultaneous measurements of TKE dissipation rates on the atmospheric side capture a deficit relative to the law-of-the-wall (εobs < εp). This deficit is explained in terms of wave-induced perturbations, with observed convergence to the law-of-the-wall at 14 m above mean sea level. The deficit on the atmospheric side provides an estimate of the energy flux divergence in the wave boundary layer. An exponential function is used to integrate in the vertical and provide novel estimates of the amount of energy going into the wave field. These estimates correlate well with classic spectral input parameterizations and can be used to derive an effective wave-scale, capturing wind-wave coupling purely from atmospheric observations intimately tied to wave-induced perturbations of the air-flow. These atmospheric and oceanic observations corroborate the commonly assumed input-dissipation balance for waves at wind speeds in the 8-14 ms−1 range in the presence of developed to young seas. At wind speeds above 14 ms−1 under young seas (U10/cp > 1.2)observations suggest a deviation from the TKE input-dissipation balance in the wave field.