OVERVIEW

1. A study of the effect of surface ocean waves on total transport Abstract: A coupled current-wave model is used to study the net effect of surface ocean waves on total transport during extreme weather events. PIs: V. Kamenkovich and D. Nechaev (USM) By V.Kamenkovich (USM), D.Nechaev (USM)), J. Wallmark (NAVO), J. Veeramony (NRL) • OVERVIEW • The interaction between ocean waves and currents has long been recognized as an important aspect of ocean dynamics, particularly in near shore environments. Until recently, these interactions have been modeled using depth-integrated wave models coupled one way with circulation models. In 2006, Mellor et al introduced a three-dimensional wave model with two-way coupling to the Princeton Ocean Model (POM), to more realistically simulate both three-dimensional circulation and surface waves. Such a model promises to more accurately simulate the vertical transport of energy from the surface into the water column, with corresponding improvements in predictions od current structure and net transport. The purpose of this investigation is to determine whether this coupled model yields results sufficiently different from the standard POM model to justify its use. The coupled wave model was developed by George Mellor and Mark Donelan, and is described the paper “A Surface Wave Model for Coupling with Numerical Ocean Circulation Models”, Mellor and Donelan, 2006. The initial stage of this experiment involved comparing the Mellor-Donelan coupled POM/wave model against the standard POM model to determine whether integrating a depth-dependent wave model with circulation yields significantly different results to justify its employment. Particular attention was focused on the difference in the vertical transport of turbulent energy, the difference in vertical distribution of velocity and transport, and the difference in the overall geostrophic balance. Results thus far indicate that by accounting for depth-dependent surface wave activity yields a significant difference in all these parameters. The tests were run on a simple enclosed shallow basin, with constant westerly winds. The grid parameters were: Grid configuration: 41 cells long by 41 cells wide, 25 cells deep. Constant depth of 20m Grid cell size: 8000m long by 8000m wide, vertical cell width logarithmically distributed from top and bottom The basin was closed on all four boundaries. Displayed results are for fully-developed seas. The vertical distribution of turbulent energy is also seen to be significantly different between the two models. Much more energy is being transported downward from the surface, an effect which is also more pronounced as wind speed increases. The difference in the vertical transport of energy between the two models results in two distinct results for the vertical distribution of velocity, and thus transport. While the standard POM model yields a smoothly changing vertical velocity profile, while the coupled model yield a distinct two-layer system. A significant difference in km is seen between the standard POM model and the coupled POM/Wave model. This difference increases with wind speed, increasing the vertical transport of turbulent energy in the coupled model.