Rapid Mixed Layer Deepening by the Combination of Langmuir and Shear Instabilities: A Case Study

摘要: Langmuir circulation (LC) is a turbulent upper-ocean process driven by wind and surface waves that contributes significantly to the transport of momentum, heat, mass in oceanic layer. The authors have previously performed direct comparison large-eddy simulationsandobservationsof response event with rapid mixed layer deepening. evolution simulated crosswind velocity varianceandspatialscales,aswellasmixedlayerdeepening,wasonlyconsistentwithobservationsifLCeffects are included model. Based on an analysis these validated simulations, this study fundamental differences mixing between purely shear-driven turbulence LC identified. In former case, kinetic energy (TKE) production due shear instabilities largest near surface, gradually decreasing zero base This stands contrast case which at middepth range TKE can be dominated Stokes drift shear. Furthermore, Eulerian mean vertical peaks so flow elevated there. transports horizontal momentum efficiently downward leading along-wind jet below downwelling regions Locally enhanced as result erode thermocline. turn, breaking internal inject cold deep water into layer, where currents temperature perturbation advectively. Thus, locally generated work intimately together facilitate strongly deepening process.