Scales of Langmuir circulation generated using a large-eddy simulation model

Sensitivity experiments were performed using a large-eddy simulation (LES) turbulence model of the ocean surface boundary layer. Parameters defining w ind and wave forcing were varied to help understand how different forcing a ffects the formation and dispersive qualities of Langmuir circulation (LC). Comparison of the model with observed surface velocity variance shows a co nsistent linear increase in velocity scale with increasing wave Stokes drif t, however, the model systematically under predicts the velocity scale for large Stokes drift. Results using particle trajectories show that in open-o cean conditions, wave forcing dominates the structure of near surface turbu lence causing organized LC cells that actively collect surface material. Wi th weak waves, surface particles display a more random pattern in compariso n to strong wave cases. Analysis of the turbulence kinetic energy budget sh ows that the reduction in wave forcing is offset by shear production, which produces less organized patterns in surface material in comparison to LC, (C) 2001 Elsevier Science Ltd. All rights reserved.