An Investigation to the Interaction between Typhoon-induced Near Inertial Wave and Tide in the South China Sea

Zhao Xu, Ocean University of China, Physical Oceanography Laboratory, Qingdao, China, Jie Shi, Ocean University of China, Qingdao, China, Jiwei Tian, Ocean university of China, Qingdao, China and Shoude Guan, Institute of Oceanology, Chinese Academy of Sciences, Key Laboratory of Ocean Circulation and Waves (KLOCAW), Qingdao, China
Abstract:
South China Sea (SCS), a semi-closed marginal sea in the tropics, is affected by Tropical Cyclones (TCs) significantly, as TCs excite great amount of Near Inertial Waves (NIWs) and induce excessive turbulence mixing in the ocean interior. However, unlike many other tropical areas, SCS is also under the influence of strong internal tides and internal solitary waves. So it is possible that the oceanic response to TCs show some very unique features in SCS. In this study, the interaction between the internal tides and NIWs is investigated through a set of numerical experiments with the Regional Ocean Modeling System (ROMS). The ocean model is forced by a synthetic surface wind field of Typhoon Megi (October 2012) by blend NCEP wind with a pseudo surface wind based on the Best Track data. The typhoon-induced oceanic anomalies are then examined. The model reproduced the response reasonably well and some interesting differences were found by comparing the results of experiments with/without tides. A peak in the power spectrum appears in the tide experiment, probably due to the interactions between the NIWs and diurnal and semi-diurnal internal tides. In other word, energy in the inertial frequency band is transferred to other frequencies. Such energy transfer in the inertial frequency decreases the turbulence. Therefore the temperature drop after the tropical cyclone passing by is 0.5~1 degree lower in the experiment without tide.
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