Evaluating Monin-Obukhov Scaling for the Turbulent Ocean Surface Layer

Zhihua Zheng, Ramsey R Harcourt and Eric A D'Asaro, Applied Physics Laboratory, University of Washington, Seattle, WA, United States
Turbulent flow in surface layer, the top few meters in the ocean, tends to exhibit consistent and repeatable characteristics, and useful empirical laws can be formed to shed light on turbulence parameterization. Here, Monin-Obukhov similarity theory (MOST), developed for the atmospheric surface layer, is examined for the ocean surface layer. Using data collected from several moored surface flux buoys, we consider the relationship between surface fluxes and subsurface temperature gradients under a wide range of stability conditions. Large deviations from MOST predictions are found in our analysis, with smaller observed temperature gradients under both stable and unstable forcing. We hypothesize that these are attributed to the presence of Langmuir structures through interaction of Eulerian current with Stokes drift, which is not included in traditional Monin-Obukhov formulation. We examine the ability of recent Langmuir turbulence closure models to predict the observed differences.