Subfilter scale fluxes in the marine surface layer: Results from the Ocean Horizontal Array Turbulence Study (OHATS)

A long term objective of our research is to identify and quantify the fundamental coupling mechanisms that occur between the marine boundary layers and surface waves using both observational data and numerical simulations. Wind generated waves influence the dynamics of the marine surface layer and the air-sea fluxes of momentum and scalars which has implications for both climate and weather predictions. Large eddy simulation (LES) plays a prominent role in our investigation of air-sea coupling but LES predictions and, in particular, its subfilter-scale (SFS) parameterization require validation against and guidance from observations for this complex flow. In 2004 we conducted the Ocean Horizontal Array Turbulence Study (OHATS) field campaign specifically directed at the measurement of SFS variables in the marine surface layer. OHATS was carried out at the recently constructed air-sea interaction tower (ASIT) located off the coast of Martha's Vineyard. The ASIT and the Martha's Vineyard Coastal Observatory are operated by Woods Hole Oceanographic Institute. The experimental configuration for OHATS employed 14 sonic anemometers in a two-level setup similar to the Horizontal Array Turbulence Study (HATS) (Sullivan, JFM 2003) and included wave measurements obtained from 3 downward pointing laser altimeters. SFS velocity and temperature fluxes were constructed by spatially filtering the measured total 3-D velocity and temperature fields from these point measurements.

We found 350 30-minute periods in the OHATS database that simultaneously satisfy our stationarity and angular orientation criteria. A range of unstable, neutral, and slightly stable conditions $-1