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The Role of Stokes drift in Dynamics of Bohai Sea, China under Typhoon Condition
  • Zengan Deng,
  • Menghan Wang,
  • Yu Cao
Zengan Deng
Tianjin University

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Menghan Wang
Tianjin University
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Yu Cao
Tianjin University
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Abstract

The role of Stokes drift production (SDP), including Coriolis-Stokes forcing, small scale Langmuir circulation and resolved-scale Craik-Leibovich vortex forcing, in ocean dynamics of Bohai Sea (BS), China under typhoon condition is systematically investigated for the first time, utilizing a coupled wave-current modeling system, which is verified to be capable of well simulating the ocean dynamical processes. The effects of SDP on the turbulent mixing and further the dynamics during the entire typhoon period, including the pre-typhoon, during-typhoon, and after-typhoon stages, are comprehensively detected and discussed. Experimental results show that SDP greatly enhances the turbulent mixing at all depths in BS under typhoon condition, the increase can be up to 7 times that of the normal weather. At the same time, SDP generally strengthens the sea surface cooling by more than 0.4℃, with the maximum SST decrease exceeding 2℃ at the during-typhoon stage, about 7 times that in normal weather. SDP-induced current speed decrease can be over 0.2m/s, and change in current direction is generally opposite to the wind direction, suggesting that to a certain extent Stokes drift depresses the impact of high wind speed on current by intensifying the turbulent mixing. MLD is distinctly increased by ~O(1) during typhoon due to SDP, in deep water region the deepening is greater than 5m, and the maxima can be ~7.5m. In addition, the continuous impacts of SDP on SST, current and MLD at the after-typhoon stage present a hysteretic response between SDP and typhoon action.