Impacts of nonbreaking wave‐stirring‐induced mixing on the upper ocean thermal structure and typhoon intensity in the South China Sea

Abstract

To investigate the effect of nonbreaking wave-induced mixing caused by surface wave stirring on the upper ocean thermal structure (UOTS) and the typhoon intensity, a simple nonbreaking wavestirring-induced mixing parameterization (WMP) scheme is incorporated into a regional coupled atmosphere-ocean model for the South China Sea (SCS), which couples the Princeton Ocean Model (POM) to the Weather Research and Forecasting (WRF) model using the OASIS3 coupler. The results of simulating two selected typhoon cases indicate that the nonbreaking wave-stirring-induced mixing has significant impacts on UOTS and the typhoon intensity, and the incorporation of the simple WMP scheme in the coupled model helps to improve the simulation of UOTS and thus the typhoon intensity. In the case that the typhoon intensity is underestimated by the atmosphere model alone, the improvement of initial UOTS by the ocean model with the WMP included can deepen the initial thermocline depth, reduce the effect of SST cooling, and prevent the typhoon intensity from undesired weakening. In the case that the typhoon intensity is overestimated (with strong winds), including the WMP in the ocean model significantly enhances the total vertical mixing rate in the upper ocean, which in turn enhances the SST cooling and thus reduces the typhoon intensity as desired. The results obtained in this study make a contribution to the ongoing efforts of improving the typhoon intensity forecast using a regional atmosphere-ocean coupled model by worldwide researchers and forecasters, especially for the typhoons in the SCS regions.

Simulated ocean response to tropical cyclones: The effect of a novel parameterization of mixing from unbroken surface waves

“…Li et al . [] tested a viscosity‐based parameterization of SWM in coupled simulations of two TC case studies and found a different pattern of wave‐induced surface temperature anomalies to what is described here. Those anomalies were an order of magnitude larger and almost entirely negative throughout the storm‐affected region.…”

“…[] provide indirect evidence that SWM can significantly deepen the mixed layer in TC conditions, with SWM suggested as the only process consistent with the timing and magnitude of the observed mixed layer deepening. Viscosity‐based parameterizations of SWM have been tested in coupled TC simulations, showing general improvement in intensity [ Li et al ., ] and track position [ Zhao et al ., ].…”

Sensitivity of typhoon modeling to surface waves and rainfall

“…The large waves in typhoon conditions could strongly enhance upper ocean vertical mixing and result in a cooling of the sea surface and ocean mixed layer, which in turn prevent a typhoon from deepening further [ Bender et al . ; Ginis , ; Li et al ., ].…”

Upper‐ocean mixing due to surface gravity waves

“…Numerical simulations, theoretical analyses, and laboratory experiments have demonstrated that nonbreaking waves can generate turbulence [i.e., Qiao et al, 2004;Babanin, 2006;Dai et al, 2010;Pleskachevsky et al, 2011;Babanin and Chalikov, 2012;Savelyev et al, 2012;Tsai et al, 2015] and that their intensity is related to the wave state [i.e., Qiao et al, 2004;Babanin, 2006;Pleskachevsky et al, 2011]. From the turbulent kinetic energy (TKE) dissipation rate induced by wave turbulence interaction, some parameterizations have been proposed and applied to improve the performance of OGCMs and coupled models [i.e., Huang and Qiao, 2010;Ghantous and Babanin, 2014;Li et al, 2014;Fan and Griffies, 2014]. As expected, parameterizations of nonbreaking-waveinduced mixing improve the performance of models when they are applied to OGCMs [i.e., Qiao et al, 2010;Hu and Wang, 2010;Huang et al, 2011].…”