北南海内波波动模拟

北南海內波波動模擬陳冠宇、吳瑞中、王玉懷國立中山大學海下科技暨應用海洋物理研究所SouthChinaSea(SCS)isfamousforlargeamplitudeinternalwavesLiuandHsu,2004FieldmeasurementbyProf.Y.H.WangA#01116.55.053E20.43.974N環礁

直徑25公里環礁內最深約16公尺東沙島長3公里寬1公里面積1.74平方公里實測觀測資料顯示，當內波通過東沙環礁時，海水溫度下降約有6~8度，且湧昇上來的冷水時間約有4小時之久。但南海的內波時間尺度大約是15分鐘(AccordingtoA.K.Liuetal.,2004,internalsolitarywaveinwestSCShaswidth1.6kmandwavespeed1.8m/s;InternalsolitarywaveineastSCShaswidth3kmandwavespeed3m/s)其時間尺度比東沙冷水事件的過程短許多，因此為更進一步了解其物理過程，有必要進行詳細的數值模擬。

2DBoussinesqtypemodelisnotapplicableModelSetupforPOMDomain:116.875°E~117.025°E20.65°N~20.8°NGridsize:100m150*150*30SimulationPeriod:2daysOutput:every30secondsThein-situstratificationmeasuredat300mdepthintheeastofDongsha

isusedastheinitialstate.ThemodelisdrivenbytheflowboundaryconditionintheeastSynolakisfoundhydrostaticmodelissuitablefortherun-upoftsunamiPOMishydrostaticandissuitablefortherun-upproblem120BathymetryisprovidedbytheTaiwanOceanResearchInstitute1.Thein-situstratificationisusedtogetthebuoyancyfrequencyN

2.distributionofNisusedtoobtaintheeigenmodeforw

3.VerticaldistributionofuisusedastheboundaryconditionVariationintimeisdeterminedbytheKdVsolitonsolutionFlowBoundaryConditionsforISWstheKdVtheoryisbasedontheinviscidassumptionwhichisnotcompatiblewithPOM.Besides,theISWpropagateswithanetmasstransport,buttheeigenmodeassumeszeronetfluxTheverticalflowboundaryconditionneedstobemodifiedbyartificiallyshiftingthealtitudeofzero-flow.Afteranumberofexperimentsontheshiftingaltitude,ISWscanbegeneratedwithsomerippleslagbehind.NearDongsha,acoupleofsuccessiveinternalwavesareobserved在東沙東方製造三個波OriginallytherearethreeISWs原本三個波Threewavesmergeintoone

結合成一個波由於環礁外海淺水處的台階地形使冷水停留在台階上Aftertherunupofthesurge,itrecedeoffshorepromptlyiftheshelfdoesnotexist環礁外海淺水處的台階地形使冷水停留在台階上，更進一步延長冷水事件的時間Discussionsonthewaveform當內波進入大陸斜坡時，波形變成非對稱的前陡後緩波形內波若以湧波