Understanding the processes that control the evolution of the ocean surface boundary layer (OSBL) is a prerequisite for obtaining accurate simulations of the effects of air-sea interaction on the ocean.
Observations of the rate of dissipation of turbulent kinetic energy (ɛ), temperature, salinity, current structure and wave-field over a period of 9.5 days in the NE Atlantic during the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS), are presented. The focus of this study is a storm which passed over the observational area during this period.
The profiles of ɛ in the OSBL are consistent with profiles from large eddy simulation (LES) of Langmuir turbulence. In the transition layer (TL), at the base of the OSBL, ɛ was found to vary periodically at the local inertial frequency.
A simple bulk model of the OSBL, and a parametrisation of shear driven turbulence in the TL, are developed. The parametrisation of ɛ is based on assumptions about the momentum balance of the OSBL and shear across the TL.
The predicted rate of deepening, heat budget and the inertial currents in the OSBL were in good agreement with the observations, as is the agreement between ɛ from the parametrisation, and the observed dissipation rate in the TL.
A previous study reports spikes of elevated dissipation related to enhanced shear at the base of the OSBL after this storm. These spikes are not predicted by this new parametrisation suggesting that they are generated through a different mechanism which will be discussed.