上层海流对台风的反应

上层海流对台风的反应演示文稿当前1页，总共30页。Contents1.Introduction2.Reviewofobservations3.Amodeloftheupperoceanresponse4.SpecificationoftheEB-10/Eloisecase5.Overviewoftheresponse6.ComparisonofthemodelsolutionwiththeEB-10data7Numericalexperiments8.Conclusion当前2页，总共30页。1.IntroductionQuestionWhatisthereasonforSSTresponsetoahurricaneandrightwardbias?2.Howdoestheresponsedependuponsuchfactorsasthehurricanetranslationspeed,theoceaninitialcondition,etc.?3.Whatroledononlocaldynamicsplayintheupperoceanresponse4.Isthereevidencethatair-seatransfercoefficientsincreasesignificantlyunderhurricaneconditions?当前3页，总共30页。2.Reviewofobservationsa.HydrographicsurveysTable1HydrographicstudiesoftheseasurfacetemperatureresponsetohurricaneFig.1ResponseofSSTacrossthetrackofhurricaneElla&ResponseofsubsurfacetemperatureacrossthetrackofhurricaneElla当前4页，总共30页。Fig2SSTaroundthetrackofhurricaneTess&TemperaturesectionABmadeacrossthetrackofTessb.Buoy/hurricaneencountersa.HydrographicsurveysFig.3NationalHurricaneCenterstormtracksofhurricanesEloise(1975)andBelle(1976)当前5页，总共30页。1)EB-10/EloiseFig4MeteorologicalmeasurementsformEB-10duringthepassageofhurricaneEloise当前6页，总共30页。Fig5.OceantemperaturefromEB-10duringandafterthepassageofHurricaneEloise当前7页，总共30页。2)EB-04/EloiseFig6.Air-seameasurement(upper/lowerpanels)fromEB-04duringthepassageofEloise2)EB-15/EloiseFig7Air-seameasurement(upper/lowerpanels)fromEB-15duringthepassageofBelle当前8页，总共30页。3.Amodeloftheupperoceanresponsea.ScalesandphysicalapproximationsFig8.Schematicplanviewofthenumericalmodel当前9页，总共30页。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当前10页，总共30页。b.BudgetsLayerthickness:EntrainmentvelocityWe≥0

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

当前11页，总共30页。HeatandsaltbalanceintheML:isunderstoodtobeverticalgradientofTwithinlayer2Momentumbalancesforthelayers:WherefistheCoriolisparametertimestheverticalunitvector,τiswindstress,Pisthehydrostaticpressureperturbation当前12页，总共30页。Thepressuregradients:ThehorizontaldensitygradientintheML:Andinthelowerlayers

当前13页，总共30页。C.Turbulent-fluxparameterizationsSensibleheatfluxLatentheatfluxDensityofairdividedbydensityofseawaterBulktransfercoefficient,=1.3*10-3Windspeedat10mheightBheatcapacityofairdividedbyheatcapacityofseaweaterq10,ssspecifichumidityat10mheight,andattheseasurfaceassumingsatuationattheseasurfacetemperatureKlatentheatofvaporationdividedbytheheatcapacityofseawaterC.Turbulent-fluxparameterizations当前14页，总共30页。C.Turbulent-fluxparameterizationsWindstress:Wherethedragcoefficient0,ifRv>1,IfRv≤1isabulkRichardsonnumberParameterizeentrainment当前15页，总共30页。Fig9Schematicplanviewofthenumericalmodeld.Implementation当前16页，总共30页。Thetimestep△t=△x/mUH,WheremisthesmallestIntegerthatgives△t≤2*103sTheoceanismoveddownthegridonerowaftereverymstepsandthefirstrowofthegridpointsisupdatedwiththeoceaninitialcondition.Spacederivativeareestimatedwithasecond-ordercenteredForm,andtime-steppingiscarriedoutusingthethree-time-level,two-step,leapfrogtrapezoidalmethod.

当前17页，总共30页。Fig10Upwellingcomputedbythenumericalmodel(leftside)andGeisler’sanalyticalsolution(rightside)AcheckoftheentrainmentcalculationsComparingwiththequasi-steadyentrainmentWheren=1/2foralinearlystraitifiedfluid,andn=1foratwo-layerstratifiedfluid,WhereRτ=(ghδρ)/(p0τ)istheexternalRichardsonNumber。当前18页，总共30页。Table4EB-10/EloiseoceaninitialconditionSpecificationontheEB-10/Eloisecasea.Oceaninitialconditionb.ModelhurricaneFig12Radialandtangentialwind-speedradialprofilecomputedfromtheEB-10winddata(points),andthemodelofthehurricaneusedinthesimulationoftheEB-10/Eloise(Solidline)当前19页，总共30页。Fig13.MLtransportV1h1computedfromthedirectlyobservedwindsofEloise(solidline)andfromthemodelhurricane(dashedline)theMLtransportscomputedfromalocalmomentumbalance:当前20页，总共30页。Fig15Planviewofthemodel-predictedycomponentofMLvelocity&TheSSTresponseshownasthechangeinseasurfacetemperaturefromtheinitialconditionRightwardbiasFig16Aschematicthatshowstherotationofawind-stressvector&thecosineoftheanglebetweenthewindstressandtheMLvelocity(ameasureofhowefficientlythewindstressisworkingtoincreasetheMLkineticenergy)5.Overviewoftheresponse当前21页，总共30页。b.HorizontaladvectionofSSTFig15bTheSSTresponseshownasthechangeinseasurfacetemperatureFig23aObservedandpredictedseasurfacetemperaturefortheEB-10/EloiseReason:they-componentofvelocityintheMLcombinedwiththestrongy-gradientsin△C.Upwelling,pressuregradientsandvelocityresponseintheinteriorFig18bPumping&Fig19bUpwellingbelowthebaseoftheML当前22页，总共30页。Twodynamicalconsequencesoftheupwelling1)ThefirsthalfoftheupwellingcycleisupwardandthustendstocausetheMLthicknesstodecrease.2)Upwellingsetsupatime-dependentpressuregradientwhichcouplestheMLwiththeinteriorandcausestheMLvelocitytorotate~5%fasterthanthatinafreeinertialmotiond.ThesubsurfaceresponseoftemperatureFig21Predictedsubsurfacetemperatureresponseshownasacross-tracksectionfortheEB-10Eloisecase&Initial(solid)andfinal(dashed)temperatureprofilesaty=-100,0,+100km当前23页，总共30页。6.ComparisonofthemodelsolutionwiththeEB-10dataa.UpwellingFig22Observed(solid)andpredicted(dashed)upwellingbelowthebaseoftheMLduringtheEB-10/EloiseeventT(t)isthecorrectedtemperature,T0istheinitialtime-averagedtemperature,Islocaltemperaturegradient当前24页，总共30页。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.当前25页，总共30页。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.当前26页，总共30页。Numericalexperimentsa.ParametricdependenceHurricane:strengthU10max,translationspeedandsize(theradiusatwhichthewindspeedeaquals1/2U10max)Ocean:initialMLdepth,the