Observation and parameterization of turbulent Reynolds stress in the ocean surface boundary layer under swell-dominated conditions

Abstract

The turbulent Reynolds stress in the ocean surface boundary layer (OSBL) is investigated using two sets of turbulence measurements conducted on an offshore tower-based platform in the coastal region of the northern South China Sea. Observations reveal that the turbulent Reynolds stress in the OSBL (τw) is mainly determined by surface waves rather than by wind and ocean currents under swell-dominated conditions. This stress is closely related to the Stokes drift velocity (us); a parameterization scheme is proposed for τw as a function of us. This scheme indicates that τw increases with wave amplitude, and decays exponentially with water depth. Further analysis shows that the turbulent stress estimated using this scheme has a high correlation with the observed stress, evidenced by a correlation coefficient of 0.92 during our two measurement periods.