上层海流对台风的反应

上层海流对台风的反应演示文稿现在是1页\一共有30页\编辑于星期六Contents1.Introduction2.Reviewofobservations3.Amodeloftheupperoceanresponse4.SpecificationoftheEB-10/Eloisecase5.Overviewoftheresponse6.ComparisonofthemodelsolutionwiththeEB-10data7Numericalexperiments8.Conclusion现在是2页\一共有30页\编辑于星期六1.IntroductionQuestionWhatisthereasonforSSTresponsetoahurricaneandrightwardbias?2.Howdoestheresponsedependuponsuchfactorsasthehurricanetranslationspeed,theoceaninitialcondition,etc.?3.Whatroledononlocaldynamicsplayintheupperoceanresponse4.Isthereevidencethatair-seatransfercoefficientsincreasesignificantlyunderhurricaneconditions?现在是3页\一共有30页\编辑于星期六2.Reviewofobservationsa.HydrographicsurveysTable1HydrographicstudiesoftheseasurfacetemperatureresponsetohurricaneFig.1ResponseofSSTacrossthetrackofhurricaneElla&ResponseofsubsurfacetemperatureacrossthetrackofhurricaneElla现在是4页\一共有30页\编辑于星期六Fig2SSTaroundthetrackofhurricaneTess&TemperaturesectionABmadeacrossthetrackofTessb.Buoy/hurricaneencountersa.HydrographicsurveysFig.3NationalHurricaneCenterstormtracksofhurricanesEloise(1975)andBelle(1976)现在是5页\一共有30页\编辑于星期六1)EB-10/EloiseFig4MeteorologicalmeasurementsformEB-10duringthepassageofhurricaneEloise现在是6页\一共有30页\编辑于星期六Fig5.OceantemperaturefromEB-10duringandafterthepassageofHurricaneEloise现在是7页\一共有30页\编辑于星期六2)EB-04/EloiseFig6.Air-seameasurement(upper/lowerpanels)fromEB-04duringthepassageofEloise2)EB-15/EloiseFig7Air-seameasurement(upper/lowerpanels)fromEB-15duringthepassageofBelle现在是8页\一共有30页\编辑于星期六3.Amodeloftheupperoceanresponsea.ScalesandphysicalapproximationsFig8.Schematicplanviewofthenumericalmodel现在是9页\一共有30页\编辑于星期六Physicalapproximationsareasfollows:1)TheCoriolisparameterfisconstant,pressureishydrostatic,theBoussinespapproximationanddiffusiveprocessesareexcluded2)Density:Whereα=-3.3*10-4andβ=7.6*10-4aretheappropriatethermalandhalineexpansioncoefficientsandρ0=1.0235*103

kgm-3isthereferencedensity3)Theseasurfaceistreatedasarigidlid(excludesthebarotropicmode).4)Thesubthermoclineoceanistakenasinfinitydeepandunabletosustainapressuregradient。5）Thetemperatureandsalinityinlayer2areassumedtohavedepthdependence。Thevelocitywithinlayer2isassumedconstant.Theinitialthicknessoflayerischosensothatafterthehurricanepassage,h2≈h16)Verticaldensitygradientsinlayer2and3areheldconstantsincethestretchingissmall现在是10页\一共有30页\编辑于星期六b.BudgetsLayerthickness:EntrainmentvelocityWe≥0

HeatandsaltbalanceintheML:TheheatfluxQ=Qs+QL+Risthesumofsensible,latentandradiativeHeatexchangeacrosstheseasurfaceFisthemassflux,equaltoevaporationminusprecipitationThetermδTWeiscalledtheentrainmentheatfluxandisthebulkRepresentationoftheturbulentheatflux

现在是11页\一共有30页\编辑于星期六HeatandsaltbalanceintheML:isunderstoodtobeverticalgradientofTwithinlayer2Momentumbalancesforthelayers:WherefistheCoriolisparametertimestheverticalunitvector,τiswindstress,Pisthehydrostaticpressureperturbation现在是12页\一共有30页\编辑于星期六Thepressuregradients:ThehorizontaldensitygradientintheML:Andinthelowerlayers

现在是13页\一共有30页\编辑于星期六C.Turbulent-fluxparameterizationsSensibleheatfluxLatentheatfluxDensityofairdividedbydensityofseawaterBulktransfercoefficient,=1.3*10-3Windspeedat10mheightBheatcapacityofairdividedbyheatcapacityofseaweaterq10,ssspecifichumidityat10mheight,andattheseasurfaceassumingsatuationattheseasurfacetemperatureKlatentheatofvaporationdividedbytheheatcapacityofseawaterC.Turbulent-fluxparameterizations现在是14页\一共有30页\编辑于星期六C.Turbulent-fluxparameterizationsWindstress:Wherethedragcoefficient0,ifRv>1,IfRv≤1isabulkRichardsonnumberParameterizeentrainment现在是15页\一共有30页\编辑于星期六Fig9Schematicplanviewofthenumericalmodeld.Implementation现在是16页\一共有30页\编辑于星期六Thetimestep△t=△x/mUH,WheremisthesmallestIntegerthatgives△t≤2*103sTheoceanismoveddownthegridonerowaftereverymstepsandthefirstrowofthegridpointsisupdatedwiththeoceaninitialcondition.Spacederivativeareestimatedwithasecond-ordercenteredForm,andtime-steppingiscarriedoutusingthethree-time-level,two-step,leapfrogtrapezoidalmethod.

现在是17页\一共有30页\编辑于星期六Fig10Upwellingcomputedbythenumericalmodel(leftside)andGeisler’sanalyticalsolution(rightside)AcheckoftheentrainmentcalculationsComparingwiththequasi-steadyentrainmentWheren=1/2foralinearlystraitifiedfluid,andn=1foratwo-layerstratifiedfluid,WhereRτ=(ghδρ)/(p0τ)istheexternalRichardsonNumber。现在是18页\一共有30页\编辑于星期六Table4EB-10/EloiseoceaninitialconditionSpecificationontheEB-10/Eloisecasea.Oceaninitialconditionb.ModelhurricaneFig12Radialandtangentialwind-speedradialprofilecomputedfromtheEB-10winddata(points),andthemodelofthehurricaneusedinthesimulationoftheEB-10/Eloise(Solidline)现在是19页\一共有30页\编辑于星期六Fig13.MLtransportV1h1computedfromthedirectlyobservedwindsofEloise(solidline)andfromthemodelhurricane(dashedline)theMLtransportscomputedfromalocalmomentumbalance:现在是20页\一共有30页\编辑于星期六Fig15Planviewofthemodel-predictedycomponentofMLvelocity&TheSSTresponseshownasthechangeinseasurfacetemperaturefromtheinitialconditionRightwardbiasFig16Aschematicthatshowstherotationofawind-stressvector&thecosineoftheanglebetweenthewindstressandtheMLvelocity(ameasureofhowefficientlythewindstressisworkingtoincreasetheMLkineticenergy)5.Overviewoftheresponse现在是21页\一共有30页\编辑于星期六b.HorizontaladvectionofSSTFig15bTheSSTresponseshownasthechangeinseasurfacetemperatureFig23aObservedandpredictedseasurfacetemperaturefortheEB-10/EloiseReason:they-componentofvelocityintheMLcombinedwiththestrongy-gradientsin△C.Upwelling,pressuregradientsandvelocityresponseintheinteriorFig18bPumping&Fig19bUpwellingbelowthebaseoftheML现在是22页\一共有30页\编辑于星期六Twodynamicalconsequencesoftheupwelling1)ThefirsthalfoftheupwellingcycleisupwardandthustendstocausetheMLthicknesstodecrease.2)Upwellingsetsupatime-dependentpressuregradientwhichcouplestheMLwiththeinteriorandcausestheMLvelocitytorotate~5%fasterthanthatinafreeinertialmotiond.ThesubsurfaceresponseoftemperatureFig21Predictedsubsurfacetemperatureresponseshownasacross-tracksectionfortheEB-10Eloisecase&Initial(solid)andfinal(dashed)temperatureprofilesaty=-100,0,+100km现在是23页\一共有30页\编辑于星期六6.ComparisonofthemodelsolutionwiththeEB-10dataa.UpwellingFig22Observed(solid)andpredicted(dashed)upwellingbelowthebaseoftheMLduringtheEB-10/EloiseeventT(t)isthecorrectedtemperature,T0istheinitialtime-averagedtemperature,Islocaltemperaturegradient现在是24页\一共有30页\编辑于星期六b.SeasurfacetemperatureFig23Observed(solid)andpredicted(dashed)seasurfacetemperaturefortheEB-10/Eloiseevent&TheMLheatbalanceforthesimulationoftheEB-10/Eloiseeventb.SeasurfacetemperatureAlongthetrack,thenetair-seaexchangeis0.2*102℃m(~2Kcalcm-2);thenetentrainmentheatfluxis1.3*102℃m(~13Kcalcm-2),or~85%ofthetotalirreversiblefluxintotheML.EntrainmentisimportantintheMLmomentumbalance.Becauselayer2isquiescentduringtheentrainmentprocess,entrainmentactstoincreasetheMLthicknessanddecreaseVl.TheincreaseinMLdepthbyentrainmentiscrucialindeterminingthemaximumMLvelocity.CQisdifficulttoinferfromsimulationsbecausetheair-seaexchangeissmall.AconstantdragcoefficientCD=1.5*10-3givesgreatlyreducedentrainmentandanSSTresponse~40%belowthatobserved.现在是25页\一共有30页\编辑于星期六b.SeasurfacetemperatureAlongthetrack,thenetair-seaexchangeis0.2*102℃m(~2Kcalcm-2);thenetentrainmentheatfluxis1.3*102℃m(~13Kcalcm-2),or~85%ofthetotalirreversiblefluxintotheML.EntrainmentisimportantintheMLmomentumbalance.Becauselayer2isquiescentduringtheentrainmentprocess,entrainmentactstoincreasetheMLthicknessanddecreaseVl.TheincreaseinMLdepthbyentrainmentiscrucialindeterminingthemaximumMLvelocity.CQisdifficulttoinferfromsimulationsbecausetheair-seaexchangeissmall.AconstantdragcoefficientCD=1.5*10-3givesgreatlyreducedentrainmentandanSSTresponse~40%belowthatobserved.现在是26页\一共有30页\编辑于星期六Numericalexperimentsa.ParametricdependenceHurricane:strengthU10max,translationspeedandsize(theradiusatwhichthewindspeedeaquals1/2U10max)Ocean:initialMLdepth,thetempera