An Empirical Evaluation of Turbulence Closure Models in the Coastal Ocean

A comprehensive in situ data set was obtained for the purpose of testing upper ocean turbulence models. The data set was collected in 38 m deep water over the North Carolina shelf. Available time series of surface meteorological forcing, including waves, winds, and heat fluxes, as well as underwater profiles of temperature, salinity, and horizontal velocity, were found suitable for constraining and testing numerical models in realistic environmental scenarios of the coastal ocean. The Navy Coastal Ocean Model was tested in a vertical 1-D mode with a suite of previously incorporated subgrid turbulence closure models. Modeled output of turbulent quantities, such as the turbulent kinetic energy and its dissipation rate, were evaluated against comparable turbulence observations from a bottom mounted acoustic velocity profiler and a glider mounted turbulent shear probe. The results demonstrate a steady incremental skill increase among available turbulence closure models over several decades of their development, however the correlation with observed turbulence remains weak. The analysis of remaining model errors identified a need to add wave-dependence to the air-sea momentum flux formulation to account for waves that are out of balance or misaligned with the wind.