Impacts of Langmuir Turbulence on upper ocean under Tropical Cyclones

Evolution of a tropical cyclone (TC) is strongly affected by the sea surface temperature (SST) cooling, which is caused by deepening of the ocean mixed layer and entrainment of colder water from below the thermocline. This SST cooling process is significantly modified by surface waves through the action of their Stokes drift (Langmuir turbulence). The Langmuir turbulence produces more rapid mixing, stronger cooling, as well as modified horizontal advection and upwelling. The growth or decay of surface waves can also modify the momentum input to the upper ocean to balance the air-sea momentum flux budget. In this study, the impacts of Langmuir turbulence and other surface wave effects on upper ocean responses in several historical TCs in the western Pacific ocean are simulated using a wave model (WAVEWATCH III) and an ocean model (Modular Ocean Model 6, or MOM6, configured for regional application). Vertical mixing is parameterized using with KPP mixing schemes that are modified to represent Langmuir turbulence. The results are compared with the observations of upper ocean currents, temperature, and turbulence. Our preliminary results show that Langmuir turbulence and other surface wave effects can make significant impacts on upper ocean turbulence, mean currents, mixed layer deepening, and SST cooling.