台风Oliwa对北日本海岸上升流模拟研究

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TheeffectofTyphoononcoastalupwellingintheNorthernJapanesecoastalusingathree-dimensionalprimitiveequationnumericalmodel

Athree-dimensionalprimitiveequationmodel(thePrincetonoceanModel,oftencalledPOM)hasbeenimplementedforsimulatingTyphoonOliwatoexaminedthecoastalupwelling.Asuddentemperaturedecrease(SenjyuandWatanabe,1999)alongthesan’incoastwasobservedafterthepassageofTyphoonoliwa.ThemodelreproduceswelltheprominentfeaturesobtainedintheobservationsuchaswindandatmosphericpressureespeciallySSTdecrease(-6to-7℃),andreasonablyexplainsittobeinducedbycoastalupwellinginaclassicaltheory.Whatismore,typhoonsimulationwasimplementedunderseveraldifferentcondition:track,movingspeed,minimalcentralpressureandgridinterval.ModelresultssuggestthatTheSSTcoolingisalivelyfunctionoftrack,movingspeedandcentralpressure,aweakfunctionofgridsize.

1.Introduction

Duringthelasttwocenturies,tropicalcyclones(typhoon)havebeenresponsibleforthedeathsofabout1.9

millionpeopleworldwide.Itisestimatedthat10,000

peopleperyearperishduetotropicalcyclones.ManytropicalcyclonesfrequentlyoccurinthePacificOceanandmovenorthwardinthesummer,affectingtheoceanicconditionsinthenorthwesternPacificOcean(Figure1),aswellascausingcasualtiesandterribledamagetopropertyinthenearshorecountries.Aprimaryresponsetotropicalcyclones(hereaftertyphoons)istocoolseasurfacewater.Manyauthorshavereportedthisseasurfacecooling(SSC)associatedwithphysicalandbiogeochemicalresponse,especiallyintheopenoceanofthewesternNorthPacific.Mostrecently,numericalmodelhasbeenimplementedtoexaminethebehaviorsoftyphoons.SenjuandWatanabe[1999]observedasuddentemperaturedecreasealongtheSan’incoastwhenthetyphoonwasapproachingandthesuddentemperaturedecreasewasattributedtoanupwelling.Wada[2003]implementednumericalsimulationstoelucidatethe3CSSTcoolingbyTyphoonRex,andHoonandYoon[2003]simulatedTyphoonHollyusingathree-dimensionalnumericalmodel

However,itseemsthattherehavebeengotacoupleofreportstheSSC,especiallyinthecoastalregionsoftheNorthPacific,despitethefactthatmanytyphoonsveryoftenlandonthecontinentsinthisregion.IftheSSCwithtyphoonpassageisfoundinthecoastalregion,itshouldbeinducedbycoastalupwellinginaclassicalEkmandynamics(Yoshida,1955).

SenjyuandWatanabe(1999;hereafterSW)firstlyobservedarapidSSTdecreasealongthenorthernJapanesecoastintheEast/JapanSea(hereaftertheEastSea)withthepassageofTyphoonOliwa(1997)(Figure1).Duringthetyphoonpassage,thefivestations(Figure1b)includingIslandMishimarecordedalltheSSTdecreaserangingfrom-6to-8C(Figure1c).AmeasurementinIslandMishima(dottedlines)wasperformedbybyaferryboatbeforeandafterOliwa.Infact,coastalupwellingcanoccurwheneverthewindblowsinparallelwithacoast.DuringtheTyphoonOliwa,thewindatHamada(Figure1d)wasbasicallynorth-easterlyalongthenorthernJapanesecoast,thusmostpreferableheretocoastalupwellingaspointedoutbySW.Thegoalofthispaperistofindoutwhatroledothecondition(track,movingspeed,centralpressureandgridinterval)playintheSST.

NumericalModel

2.1GoverningEquation

ThePrincetonoceanmodel(POM)isacommunitygeneral

\o"Numericalmodel"

numericalmodel

for

\o"Oceancirculation"

oceancirculation

thatcanbeusedtosimulateandpredictoceaniccurrents,temperatures,

\o"Salinity"

salinities

andotherwaterproperties.Themodelincorporatesthe

\o"Mellor–Yamadaturbulencescheme(pagedoesnotexist)"

Mellor–Yamadaturbulencescheme

developedintheearly1970sbyGeorgeMellorandTedYamada;thisturbulencesub-modeliswidelyusedbyoceanicandatmosphericmodels.Atthetime,earlycomputeroceanmodelssuchastheBryan–Coxmodel(developedinthelate1960satthe

\o"GeophysicalFluidDynamicsLaboratory"

GeophysicalFluidDynamicsLaboratory

,GFDL,andlaterbecamethe

\o"Modularoceanmodel"

modularoceanmodel

,MOM)),wereaimedmostlyatcoarse-resolutionsimulationsofthelarge-scaleoceancirculation,sotherewasaneedforanumericalmodelthatcanhandlehigh-resolutioncoastaloceanprocesses.TheBlumberg–Mellor

[1987]

model(whichlaterbecamePOM)thusincludednewfeaturessuchasfreesurfacetohandletides,sigmaverticalcoordinates(i.e.,terrain-following)tohandlecomplextopographiesandshallowregions,acurvilineargridtobetterhandlecoastlines,andaturbulenceschemetohandleverticalmixing.ThemodelformulatedbyaCartesiancoordinatesolvesthefollowingtraditionalhydrodynamicsequationsforconservationofmass,momentum,temperature,andsalinitycoupledwiththeequationofstate,

(1)

(2)

(3)

(4)

(5)

(6)

(7)

WhereKMistheverticaleddyviscosity,KHistheverticaleddydiffusivity,F(X,Y)thehorizontaleddyfrictionterms,andF(T,S)thehorizontaleddydiffusionterms.TheBoussinesqandhydrostaticapproximationareassumed,andKnudsen’sequationisutilizedtosolveequation(7).TheKMandKHarecalculatedusingtheMellorandYamadalevel2.5turbulenceclosuremodel[Galpernetal.,1988].HorizontalfrictionanddiffusiontermsaretreatedbytheLaplacianformswiththecoefficientsAMandAHwiththeSmagorinskyscheme.ThemodelisformulatedbyaCartesiancoordinatewithbottom-following,sigma-coordinatesystemб=(z-η)/(H+η),whereηandHaretheseasurfaceelevationandwaterdepth,respectively.Themodelhas26verticalsigmalevels.Themodelgeometry(Figure7upper)obtainedfromtheNOAANationalDataCenterhasopenboundariesintheeastandsouthandhasaresolutionof10km,20kmrespectively.ThusthemodeldomaincoversmostofthenorthwesternPacificOceanincludingthemarginalseaandTaiwan.Thebottomtopographywiththemaximumdepthof3600mhasbeensmoothedsothatthesigmalcoordinatesystemdoesnotcausespuriouscurrentintheregionofsteeptopographicgradients.Intheinitialconditions,verticaltemperatureislinearlygivenfrom27Catthesurface,andsalinityisassumedtobeequaleverywhereto34.5psutoconsiderherethermodynamicsinthisresearch.Atopenboundaries(dashedlineinFigure1),theinternalnormalvelocityisgovernedbyaSommerfeldradiationcondition;anelevationisspecifiedastheexternalopenboundarycondition;aslipperyconditionisemployedfortemperature.AnextendedmaparoundtheKorean/TsushimaStraitsisshownasFigure2(bottom)toinvestigateseawatervariationswithcoastalupwellingmoreindetail.Themodelresultsobtainedfromeachstation(A~DinFigure2,bottom)whichcorrespondstoKJ,KY,HA,andIslandMishima,respectively,willbecomparedwiththeobservedSST.

Intherealistictopography,2openingBDintheNorthandwestand2closingboundaryinthesouthandeast.Themodelhasahorizontalresolutionof20kminbothxandydirections.Gridsize162*186.Themodelhas26verticalsigmalevels.TheForceiscausedbywindandairpressure.Intheinitialconditions,verticaltemperatureislinearlygivenbyfrom27℃atthesurface,andsalinityisassumedtobeequal34.5psu.Theinitialsealevelandvelocitiesaresettobezero,u=v=w=η=0。Atopenboundaries,theinternalnormalisgovernbyaSommerfieldradiationcondition.Thetangentialcomponentsofvariablesaresubjecttothefreeslipconditions.Forsimplified,noair-seaheatexchangesandnobasiccurrentsareconsidered.

2.2AtmosphericConditions

Inthisstudy,atmosphericconditionswithairpressureandwindarealmostthesameasthatofHongandYong[1992],whosimulatedTyphoonHollyusingashallowwaterequationmodel.Brieflyrepeatingsomesalientpoints,theairpressureP(x,y)at(x,y)thatoriginatedfromthecenterofTyphoonHollyisgivenas[Fujita,1952]

(8)

WhereP∞istheambientairpressure,δPisadepressionofairtemperatureatthecenterofTyphoon,rtheradiusfromthecenterofthetyphoon,andr0adistanceinwhichthedepressionoftheairtemperaturebecomeshavingthemaximumgradientwind;thatis,itcorrespondingtoaradiusofthetyphoon’score.Hereweobtainedr0fromthefollowingequation,i.e.,similartoaleastsquaremethos,

(9)

WherePcisanairpressure,P(x,y)calculatedfromequation(8)atanytime,andP0anairpressureobtainedfromaweatherreportchartatthattime.

Anisostaticelevation(inversebarometricelevation)isobtainedfromthehydrostaticequationwithsecondtermintheright-handsideofequation(8),andisincoporatedintothepressuregradienttermsinequation(2)and(3).

ThewindWisgivenas[Miyazakietal.,1961]

(10)

WhereWgisagradientwind,Wbisawindproportionaltothemovingspeedofthetyphoon,Cg(=0.8)andCb(=0.5)areparametersforfittingintheobservation,andαacoefficientgivenbyatr=500kmfortheexponentiallydecreasedamountofWbfromthecenteroftyphoon.WindStressiscalculatedby

WhereCdisthedragcoefficientofthewind,istheatmospheredensity,andwxandwythecomponentsofWinxandydirections,respectively.Cdischangedbywindspeed[DenmanandMiyake,1973]andalsobyseasurfacestatewithsurfacewave[MasudaandKusaba,1987],largelyrangingfrom[heap,1967]to[Platsman,1963].HereCdisusedasaconstantvalue(=),frequentlyhavebeenusedforsimulatingstormsurges[e.g.,Unokietal.,1964]

Modelresults

3.1CoastalupwellingwithTyphoonOliwa

Intheinitialcondition,themodeldomainisboundedby24030’N,52000’Eand117025’N,143000’E.Themodelresultsobtainedfromeachstation(A~DinFigure2,bottom)whichcorrespondingtoKJ,KY,HA,andIslandMishima,respectively,willbecomparedwiththeobservedSST.Earlytime,TyphoonOliwamovedwestward,developingintoastrongtyphoonwiththelowestcentralpressureof915hpa(10:1800)(seeFigure1a).At15:0000,TyphoonOliwaislocatednortheastofTaiwanaftermovingintothecontinentalshelfintheEastChinaSea.Then,typhoonmovednortheastward,passingthroughtheKoreaStrait.Inthemodel,wesimulatethetimeseriesoftheSSTandTheSSTdecreaseateachstationisproducedateachstation(Figure3a)intermsofthetendencytorapidlydecreasetheSST,thetimetoreachtheSSTminimumandthecoolingamplitudes(4).Ontheotherhand,inthemodel,thewind(Figure3b)andtheairpressure(Figure3c)atSt.C(Hamada)alsowellsimulatetheobservation(HA.Figure1d)withrespecttovariationpatternsintimeandroughlytheiramplitude.Forinstance,themaximumwind(~18m/sec),althoughthelowestairpressure(~994hpa)ismoreintensifiedthanthatatHA(~998hpa).

TimeseriesofvelocityatSt.C(HA)(Figure3d)showsthatthesouth-westwardflowisweaklyformedfromanearliertimewhenOliwawaslocatedinlowlatitudeandisfullydeveloped(~1m/sec)withthepassageofOliwa.Seasurfaceelevation(Figure3e)herewellreflectsthisflowfieldfromtheearliertime,i.e.,negativesealeveliscausedbyEkmantransport(presentedlaterinFigure5)duetothenorth-easterlywind(Figure3b),andreachesthemaximum(~30cm)halfadayafterOliwa’spassage.On15thAugust,however,theelevationtemporarilyshowspositivesealevelsforaday.ThisiscausedbypropagationofKelvinwavesalongtheJapanesecoast(Figure4).FromearliertimeKelvinwavespropagatesat13:0900andweaklypropagatesalongthenorthernJapanesecoast(Figure4a),asnegativeamplitudeKelvinwaves.AsOliwaapproachesthesouthKyushu(Figure4b-4c),theKelvinwavesfullydevelopsandpropagates(Figure4b-4d)aspositiveamplitudeKelvinwaves,i.e.,thepositiveamplitudeKelvinwavesconsecutivelypropagatesfromthesouthernJapanesecoastintheNorthPacifictothenorthernJapanesecoastintheEastSea,asearlierpointedoutbysomeauthors(e.g.,HY).AfterthepropagationofthepositiveamplitudeKelvinwaves,theelevation(Figure3e)becomesnegativeagainduetostrongalongshorewind(Figure3b),andreachestheminimumearlieronSept.17,showingtheSSTminimum(Figure3a),whenOliwapassesaroundSt.C.Inthisperiod,itshouldbepointedoutthatcooledwaterregions(~26C)areextensivelyspreadtotheYellowSeaandtheEastSea(Figure4b-4d)fromthecentralregionofthetyphoon.

Nextconsiderthecoastalupwellinginverticalvelocityfields(Figure5).TimeevolutionsofverticalvelocityfieldonSectionA(seeFigure2,bottom)showthatverticalvelocityfield(coastalupwelling)fullydevelopsduring16:0900(Figure5b)-16:2100(Figure5c)whenTyphoonOliwaprovidesthemostpreferablewind(thenorth-easterlywind)tocoastalupwellingalongtheJapanesecoastintheEastSea(Figure3b).Thus,themodelclearlyshowsthattheobservedSSTcoolingbySWwasinducedbycoastalupwelling.

3.2InitialconditionsforTyphoon

3.2.1differenttrackofTyphoon

Inthissimulation,weusethePOMmodelsameasHYexceptfordomainareaanddifferenttrackofTyphoon(Figure6).Themodelhasahorizontalresolutionof20kminbothxandydirectionsfromitsfromitsleft-southern-mostgridpoint(200N,1170E)toitsright-northernmostgridpoint(520N,1440E),includingawholeareaofEastChinaSea,TheYellowsea,theEastSeaandTaiwan.Theleft-hideside(LHS)trackstartsfromthegridpoint(13043’N,130043’E)tothegridpoint(39059’N,120016’E),thecentraltrack(CTR)beginsfromgridpoint(13043’N,130043’E)togridpoint(38015’N,130042’E),andtheright-handsidetrackstartsfromgridpoint(13043’N,130043’E)tothegridpoint(40006’N,141007’E)(Figure7upper).Themodelresultsobtainedfromeachstation(A~DinFigure7,bottom)whichcorrespondingtoKJ,KY,HA,andIslandMishima,respectively,willbecomparedwiththeobservedSST.Theminimumpressureis970hpa;

AstyphoonapproachesthenorthernJapanesecoast(Figure10a-10b),theseawateraroundnorthernJapanesecoastdecrease.Aftertyphoonpasses(Figure10c-10d),thecoolingwaterregionsareextensivelyspreadtotheYellowSeaandtheEastSea.Thetimeseriesofverticalvelocityat16m,25mand50mrespectivelyandSSTsimulation(Figure9)issimulatedinthemodel.Themaximumverticalvelocityis(252hrs)(Figure8).Aftertyphoonpassingtime(216hrs),andtheupwellingvelocityhasbeenestimatedby.Considerthedepths(50-100m)aroundthecoastalregions,thisspeedisenoughtoraisebottomwatertothesurface.Theupwellingat16misstrongerthanthatat25m,50mdepth(Figure8).Becauseofupwelling,dense,coolerwaterrisestowardsthe

ocean

surface,replacingthewarmer

surfacewater

.TheminimumtemperatureatSt.Cis14.1Cat227hrs(Figure8),decreasingfrom26.4Cat180hrs,accompaniedbycoolingamplitude(12~12.5C).NegativeverticalvelocityiscausedbyEkmanTransport(Figure11)duetoNorth-easternwind.IntheLHSandRHStrack(Figure6),thetyphooneffectisweek,SSTcoolingissmall(1.5-2C).Verticalvelocityfields(Figure11)wassimulated,too.TimeevolutionsofverticalvelocityfieldonSectionA(seeFigure2,bottom)showthatverticalvelocityfield(coastalupwelling)fullydevelopsduring204hrs(Figure11b)-216hrs(Figure11c)whenTyphoonprovidesthemostpreferablewind(thenorth-easterlywind)tocoastalupwellingalongtheJapanesecoastintheEastSea(Figure3b),i.e.,thisperiodcoincideswithtimewhenthetyphoonisintheclosestproximityofSt.C(HA).Thus,themodelclearlyshowsthattheobservedSSTcoolingbySWwasinducedbycoastalupwelling.

TheSSTatSt.Cdecrease12~12.5Castyphoonover(216hrs)andincrease4C(Figure12b).Therewasanirregularoscillationof0.5Camplitudeafterthestormpassage.TheSSTthenstabilizedandremainedapproximatelyfortheremainderofthetime.Ontheleft-handandright-handoftrack,theTyphoonSSTatSt.Cdecrease1.5C(Figure12a,c)duringthewholesimulationtime.ThedecreaseoftheSSTthatoccurredduringthetyphoonpassageappeartobeirreversible,andwascausedbytheupwellingofcoldwatertotheseasurface..

3.2.2differentmovingspeedofTyphoon

Inthissimulation,themodelconditionisthesamewiththebeforecondition,exceptthatwechoosethecentraltrackatdifferentspeed(3m/s,6m/s,9m/s).

Thetimeseriesofverticalvelocityat3ms/(Figure13a),6m/s(Figure13b)and9m/s(Figure13c)respectivelyandSSTsimulationisperformedinthemodel.At3m/s,theSSTatSt.Cdecrease13C(Figure13a)astyphoonpassesover,whichislargerthan9Cat6m/s,and6Cat9m/srespectively.

AfterTyphoonpassing,TheSSTat3m/sincrease6Rapidity,andthengrowslowly.WhiletheSSTat6m/sand9m/sgraduallygrow,whichiscausedbyweekTyphoonEffects.Cardoneetal[1977]suggestthatabouthalfthetranslationvelocitymayaddtothe10mwindsofasymmetrichurricane,,thiscausedasubstantialasymmetryinthewind-stressmagnitudeandsomewhatenhancestheasymmetricintheSSTresponse.,SSTismoresmallontherightsideofthetrackthatonthatoftheleftside.Ontheotherhand,.surfacefrictionaldragisnearlysymmetricforslowmovingcyclones,andincreasesontherightsideofthetrackwhenthetyphoonmovesfast.Itisclear,however,thatinthismodeltheasymmetricintheSSTresponseisduemainlytotheasymmetryintheturningdirectionofthewind-stressvector

3.2.3differentminimumcentralpressureofTyphoon

Inthissimulation,themodelconditionisthesamewiththeobovecondition,exceptthatwechoosethecentraltrackatdifferentminimuncentralpressure(950hpa,970hpa,990hpa)(Figure14).

At950hpa,TheSSTatSt.Cdecrease16Castyphoonpassesoverandincrease11C(figure14a),whiletheSSTofSt.Cat970hpadecrease13Castyphoonpassesover(figure14b),andtheSSTofSt.Cat970hpadecrease6C(figure14c).Inthesamecoordinatesystem,wecanfindthatasthecentraltyphoonpressuredecrease,theSSTdecreasinginasimilarway.

Ithasbeenknownthatasthepressureincreases,thepressuregradientforceincreases,andthetyphoonbecomestronger.

3.2.4differentgridintervalofTyphoon

Inthissimulation,wewanttocompareSSTatdifferentgridinterval10kmand20km.Theinitialconditionasfollows:movingspeedis3m/susingthecentraltrackandcentralpressureis970hpa.

At10kmgridinterval,TheSSTatSt.Cdecrease13.5C(figure15a)astyphoonpassesover;whileTheSSTof20kmgridintervalatSt.Cdecrease14C(figure15b)astyphoonpassesover.ItwastruethatSSTdecreasedoesnotdependonthegridinterval(figure15c).

TherewasanirregularoscillationofCamplitudeforroughly1dayafterthestormpassage.TheSSTthenstabilizedandremainedapproximatelyfortheremainderofthetime.ThedecreaseoftheSSTwascausedbytheupwelling.ItisclearthattheSSThaslittlerelationtothegridsize.

4.Conclusionsanddiscussion

Inthispaper,athree-dimensionalprimitiveequationmodel(POM)wasimplementedtoexaminetheobservedSSTdecrease(SenjyuandWatanabe,1999)inthenorthernJapanesecoastintheEastSeaduringTyphoonOliwa.Themodelsuccessfullywellreproducedtheobserved-prominentfeatures,suchasaSSTreducingtendencyintimeandspace,andsufficientlydescribedhowtheyhappened.ThemodelconcludesthattheSSTdecreasehasbeencausedbycoastalupwellingtocomplementEkmantransport,especiallywhileOliwaprovidesapreferablewindtocoastalupwellingevolution,i.e.,thenorth-easterlywindparalleltothecoast.

SWshowedthatthemostSSTcoolingwasobservedatHamada(~-8C)(Figure1c),andthemodelwellreproducedsuchSSTcoolingatSt.C(Figure3a),correspondingtoHamada.AccordingtoOkeandMiddleton(2000),thismaybeasharpcontinentalshelfinthisregion(Figure1b;Figure2,bottom),i.e.,theyreportedthatupwellinginducedbytopographydevelopsoveranarrowcontinentalshelfbecauseofestablishingahighbottomstressregion.However,thiseffectofashelfshouldbestudiedmoreinprecisehorizontalresolutionsbecausethegridsize(20km)inthemodelmaynotbeenoughtoresolvetheshelfaroundthenorthernJapanesecoast.

Themodelwassimplifiedtocapturebasickeypoints.Forexample,air-seaheatinteractionhasbeenexcluded,andthusthemodelresultsmaymodifySSC,especiallytowardweakeningitasdiscussedbySakaidaetal.(1998).Basiccurrents,suchastheKuroshioandtheTsushimaCurrent,werealsonegligible.SincetheKuroshiowillcrossatrackofTyphoonOliwa,inparticular,themodelresultsmaybeinfluencedinmomentumflux,andtheTsushimaCurrentmayalsoaffectcoastalupwellingevolutioninthenorthernJapanesecoastalregionoftheEastSea.Inordertosimulatetyphoonsinreality,thesepointsshouldbetakenintoconsideration.Nevertheless,physicalconceptsinthemodelwillnotbesignificantlycontaminatedbytheseassumptions.

UpwellingistheprimarymechanismthatlowerstheSSTbeneathamovinghurricane,causingasignificantenhancementoftheSSTresponse.Air-seaheatexchangesplayaminorrole.TheSSTisalivelyfunctionoftrack,movingspeedandcentralpressure,aweakfunctionofgridsize.Infact,moreconditionsshouldbestudiedsuchasthemixinglayerdepth,latitude,andhurricanesize.

Acknowledgments

References

Blumberg,A.F.,andG.L.Mellor,Adescriptionofathree-dimensionalcoastaloceancirculationmodel.InThreeDimensionalCoastalOceanModels,CoastalEstuarineScience,vol.4,editedbyN.S.Heaps,AGU,Washington,D.C.,208pp,1987.

Chenetal.,2003

Colling,1989

Cushman-Roisin,B.,Introductiontogeophysicalfluiddynamics.PrenticeHall,EnglewoodCliffs,NewJersey,320pp,1994.

Fujita,T.,Pressuredistributionwithintyphoon.Geophys.Mag.,23,437-451,1952.

Gill,A.E.,Atmosphere-oceandynamics.Academicpress,NewYork,666pp.,1982.

Heaps,N.S.,Stormsurge,1967-1982.Geophys.J.Roy.Astron.Soc.,74,331-367,1983.

Hong,C.H.,andJ.H.Yoon,Athree-dimensionalnumericalsimulationofTyphoonHollyinthenorthernPacificOcean.J.Geophys.Res.,108(C8),3282,doi:10.1029/2002JC001563,2003

JAMESF.PRICE，UpperOceanResponsetoahurricane,1981

KonishiT.,andY.Tsuji,AnalysisofstormsurgesinthewesternpartoftheSetoinlandseaofJapancausedbyTyphoon9119.ContinentalShelfRes.,15,1795-1823,1995.

Leeetal.(200?)

Linetal.,2011?.

Miyazaki,M.,T.Ueno,andS.Unoki,TheoreticalinvestigationoftyphoonssurgesalongtheJapanesecoast.Oceanogr.Mag.,13,51-75,1961.

SakaidaF,H.Kawamura,andY.Toba,SeasurfacecoolingcausedbytyphoonsintheTohokuareainAugust1989.J.Geophys.Res.103,No.C1,1053-1065,1998

SenjyuT,andT.Watanabe,AsuddentemperaturedecreasealongtheSan’inCoastinducedbyatyphoon.UmitoSora,75,1-8,1999.(inJapanesewithEnglishabstract)

Siswantoetal.,2008;

Suginohara,N.,Onsetofcoastalupwellinginatwo-layeroceanbywindstresswithlongshorevariation.J.Oceanogr.Soc.Japan,30,23-33,1974.

UnokiS.I.,I.Isozake,andS.Otsuka,SimulationofstormsurgesinTokyoBay,Reportof2ndDistrictPortConstructionBureau,125pp.,1964.(inJapanesewithEnglishabstract)

WadaA.,TheprocessesofSSTcoolingbytyphoonpassageandcasestudyoftyphoonRexwithamixedlayeroceanmodel.Meteorol.Geophys.,52,31-66,2002.

Yoshida,K.,CoastalupwellingofftheCaliforniacoast.

Rec.Oceanogr.WorksJapan.2(2):1-13,1955.

ListofFigures

Figure1.(a)AtrackofTyphoonOliwa.Leftandrightnumeralsonthetrackrepresentatmosphericpressuresanddatesatevery09:00o’clock,andthedottedlinedenotesopenboundariesinthemodel.(b)TheobservedstationsinthenorthernJapanesecoast.(c)TimeseriesofSSTateachstation;dottedplotrepresentstheobservationbyaferryboatatIs.Mishimabeforeandafterthetyphoonpassage;temperaturevaluesintheordinateaxisareadjustedforvisualconvenience.(d)WindatHamada(HA)inthisperiod.(b)(c),(d)arereproducedfromSW.

Figure2.Modelbathymetry(top)(depthinmeters).Thecontourintervalis300mexceptfor20mintheYellowSeaandtheEastChinaSea.AnenlargedregionaroundtheKoreanStrait(bottom)isgiven,andtransectA(bottom)givescrosssectionalprofilesofvelocityandtemperatureintheEastSea.StationsA,B,C,andDcorrespondtoKJ,KY,HA,andIsMishimainSW’sobservation(Figure1b),respectively.

Figure3.(a)TimeseriesofSSTatStationsA~D(Figure2,bottom),correspondingtoKJ,KY,HA,andIsMishima(Figure1b).Thevaluesaregiveninthefirstlevelofthemodel.AtSt.C(correspondingtoHA),calculated(b)wind(m/sec),(c)atmosphericpressure(hpa),(d)velocity(cm/sec),and(e)seasurfaceelevation(cm)aregiven.VerticalbarinFigs.3b-3erepresentsatimewhenOliwapassedincloseproximityofSt.C.

Figure4.Timeevolutions(13:0900-16:0900)(Figure5a-5d)ofseawatervariationinelevation(contours),SST(colors),andvelocity(arrows)onedayapart.Velocitieslessthan10cm/secareeliminatedforvisualconvenience.C.I.=5cm.

Figure5.Timeevolutions(15:2100-19:0900)ofcoastalupwelling((a)-(d))onSectionA(seeFigure2,lower)halfadayapart.Notethatverticalvelocity(x10cm/sec)isexaggeratedforvisualconvenience.

Figure6. ThreetracksofTyphooninthesimulation.LHSrepresentsleft-handsideoftrackstartsfromthegridpoint(13043’N,130043’E)tothegridpoint(39059’N,120016’E),CTRrepresentsthecentraltrackstartsfromthegridpoint(13043’N,130043’E)tothegridpoint(38015’N,130042’E)andRHSrepresentstheRight-handsideofthetrackstartsfromgridpoint(13043’N,130043’E)tothegridpoint(40006’N,141007’E).

Figure7.AnewModelbathymetry(top)(depthinmeters)includingTaiwan.Thecontourintervalis300mexceptfor20mintheYellowSeaandtheEastChinaSea.AnenlargedregionaroundtheKoreanStrait(bottom)isgiven,andtransectA(bottom)givescrosssectionalprofilesofvelocityandtemperatureintheEastSea.St