The Impact of Diferent Vertical Difusion Schemes in a Three-Dimensional Oil Spill Model in the Bohai Sea

Vertical transport is critical to the movement of oil spills in seawater.Breaking waves play an important role by developing a well-defined mixing layer in the upper part of the water column.A three-dimensional(3-D)Lagrangian random walk oil spill model was used here to study the influence of sea surface waves on the vertical turbulence movement of oil particles.Three vertical difusion schemes were utilized in the model to compare their impact on oil dispersion and transportation.The first scheme calculated the vertical eddy viscosity semi-empirically.In the second scheme,the vertical difusion coefcient was obtained directly from an Eulerian hydrodynamic model(Princeton Ocean Model,POM2k)while considering wavecaused turbulence.The third scheme was formulated by solving the Langevin equation.The trajectories,percentages of oil particles intruding into water,and the vertical distribution structures of oil particles were analyzed for a series of numerical experiments with diferent wind magnitudes.The results showed that the diferent vertical difusion schemes could generate diferent horizontal trajectories and spatial distributions of oil spills on the sea surface.The vertical difusion schemes caused diferent water-intruding and resurfacing oil particle behaviors,leading to diferent horizontal transport of oil particles at the surface and subsurface of the ocean.The vertical difusion schemes were also applied to a realistic oil spill simulation,and these results were compared to satellite observations.All three schemes yielded acceptable results,and those of the third scheme most closely simulated the observed data.