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

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 (������������) 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 (������������); a parameterization scheme is proposed for ������������as a function of ������������. This scheme indicates that ������������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.

Automated summary

The study investigates the turbulent Reynolds stress in the ocean surface boundary layer (OSBL) in the coastal region of the northern South China Sea. It is found that the turbulent Reynolds stress in the OSBL is mainly determined by surface waves rather than wind and ocean currents under swell-dominated conditions. A parameterization scheme is proposed for the Stokes drift velocity, which has a high correlation with the observed stress.