简介:ApossiblemechanismisputforwardinthispaperforElNinoeventsfromtheviewpointofplatetec-tonicsandoceanicgeology.Anumberofthedataarecitedtoillustratetheviewsthatsea-bottomvolcanicac-tivitiesandhotspringsmaycauseElNinoevents.
简介:ElNinoaswellastheSouthernOscillationisoneofthestrongestsignalsknownsofaroverclimaticnoiseininterannualvariationsoftheatmosphereandoceans.Agreatnumberofstudieshaveshowndefinitelyrelationshipsbe-tweentheeventsandclimaticanomaliesinChina.Inthisreview,observationalresultsobtainedintherecentseveralyearsarefirstsummarized.ThenthepossiblephysicalmechanismsontheinfluenceofElNinoarepresentedand,finally,theassociatedproblemsarediscussed.
简介:Inthispaper,byusingspectralmethod,themonthly-andseasonal-scaleatmosphericdiabaticheatflow(ADHF)departurefieldsarediagnosedintheperiodof1964—1985with6ElNinoyearsand6anti-ElNinoyearsovertheNorthernhemisphere(NH).TheresultsshowthatElNinophenomenahavepronouncedinfluenceontheADHFdepar-turefields.Theresponseofatmosphereexhibitsapreferredarrangementoforganizingpositiveandnegativedeparturecentersatlow,middleandhighlatitudes.Inanti-ElNinoyears,theresponsehasthesameformsasinElNinoyears,butdeparturecentersareoppositeinphase.Furthermore,ADHFdepartureshowslow-frequencyoscillationinElNinoyearsandanti-ElNinoyears.ThecenterofdifferenceindeparturebetweenElNinoandanti-ElNinoyearsdisplaysabi-monthlyoscillation.Finally,throughair-seacorrelationanalysis,itispointedoutthattheSSTanomalyisthemostimportantcauseforADHFanomaly.
简介:OnthebasisofNOAA/CPCdataofseasurfacetemperatureanomalyintheNinoregionsduringJan.1950-Dec.2003,thewaveletpowerspectrumofSSTwerestudiedwithsignificanceandconfidencetestingatdifferentscalesinthispaper.ItshowsthattheSSTareprovidedwithmulti-timescalesstructurenestedoneanother,andvaryonscalesof2-7years,8-20yearsand>30years.Themostsignificantvariationofthewarmandcoldepisodesisinthe4-yearbandofperiod.Thepower,frequencystructureandconfidenceofthesameepisodearedifferentindifferentNinoregions.TheintensityofoscillationsisincreasingatlowfrequencybandsanddecreasingathighfrequencybandsfromeasttowestintheNinoregions,especiallyafter1970.
简介:IthaslongbeenacknowledgedthattherearetwotypesofElNioevents,i.e.,theeasternPacificElNio(EE)andthecentralPacificElNio(CE),accordingtotheinitialpositionoftheanomalouswarmwateranditspropagationdirection.Inthispaper,theoceanicandatmosphericevolutionsandthepossiblemechanismsofthetwotypesofElNioeventswereexamined.ItisfoundthatalltheElNioevents,CEorEE,couldbeattributedtothejointimpactsoftheeastwardadvectionofwarmwaterfromthewesternPacificwarmpool(WPWP)andthelocalwarmingintheequatorialeasternPacific.BeforetheoccurrenceofCEevents,WPWPhadlongbeeninastateofbeinganomalouswarm,sothestrengthofeastwardadvectionofwarmwaterwasmuchstrongerthanthatofEE,whichplayedamajorroleintheformationofCE.WhilefortheEEevents,mostcontributioncamefromthelocalwarmingoftheequatorialeasternPacific.ItisfurtheridentifiedthattheimmediatecauseleadingtothedifferenceofthetwotypesofElNioeventswastheasynchronousvariationsoftheSouthernOscillation(SO)andtheNorthernOscillation(NO)asdefinedbyChenin1984.WhenthetransitionfromthepositivephaseoftheNO(NO+)toNO-waspriortothatfromSO+toSO-,therewouldbeeastwardpropagationofwesterlyanomaliesfromthetropicalwesternPacificinducedbyNOandhencethegrowthofwarmseasurfacetemperatureanomaliesinWPWPanditseastwardpropagation.ThiswasfollowedbylaggedSO-inducedweakeningofsoutheasttradewindsandlocalwarmingintheequatorialeasternPacific.ThesewereconducivetotheoccurrenceoftheCE.Onthecontrary,thetransitionfromSO+toSO-leadingthetransitionofNOwouldfavortheoccurrenceofEEtypeevents.
简介:WestatisticallyanalyzethetropicaltyphoonformingintheSouthChinaSeaanduseTC(TropicalCyclone)forshortinthefollowing)bytyphoonyearbook.Thetyphoonquantityisverydifferentindifferentmonthsandyears.TCappearsinallmonthsexceptMarch,andthemostTCquantityinayearis11,theleastis1and6.2onaverage.ThemostTCquantityinamonthis5andtheleastis0.TClandsmostinAugustandnoTClandsonChinesecontinentfromDecembertothefollowingApril.TheprimarylandingareaisbetweenShantouandHainanIsland.ThesustainingperiodofTCisusuallybetween4daysto7days,andthelongestis19days.Only15%oftheTCformingintheSouthChinaSeacanintensifytotyphoon,andtheyallformintheoceanareadeeperthan150m.TheSouthChinaSeaistheoceanareaoverwhichtheTCoccursfrequently.
简介:Basedonaseriesofdataanalyses,theintimaterelationsbetweenanomalouswintermonsooninEastAsiaandElNinoarcstudiedinthispaper.AnomalisticcirculationintheNorthernHemispherecausedbyElNinoeventcanleadtoenhancingtheFerre!cellandthewesterliesinthemid-latitudesastheHadleycellandresultinthelocationofthefrontzoneinEastAsiatothenorth.TheseareunfavourableforthecoldwavebreakingoutsouthwardinEastAsia.Therefore,thereatewarmerweatherandweakerwintermonsooninEastAsiainElNinowinter.TherearestrongerandfrequentcoldwavesinEastAsiaduringthewintertimepriortotheoccurrenceofElNinoevent.TheywillinducestrongerwintermonsooninEastAsia.Thus,theweakenedtradewindandenhancedcumulusconvectionintheequatorialmiddle-westernPacificareacausedbythestrongerwintermonsoonwillplayanimportantroleintheoccurrenceofElNinoevent.Therefore,theanomalouslystrongwintermonsooninEastAsiaduringwinter
简介:Acoupledmodel,whichisemployedtostudythedominatingfactorandkeyareaofElNinocycleformation,consistsofadynamicaloceanmodelandastatisticalatmosphericmodel.ThecoupledmodelwithseasonalforcingsuccessfullyreproducestheElNinoeventcyclewhichexhibitsquasi-regularoscillationswithapreferredperiodofabout4years.Theresultsshowthattheheatcontent(HC)istransportedbetweentheeasternandthewesterntropicalPacificareas.ThespatialdistributionofHCanomaliesforfourphasesofthewholecycleclearlyshowsapossibleformationmechanismofElNino.ExperimentsfurthersuggestthatseasurfacetemperatureinthetropicalPacificandHCinthecentraltropicalPacificarethemostimportantfactorsandthecentraltropicalPacificisthemostimportantareafordeterminingformationofElNinocycle.
简介:Byusingtheupper-winddatafromJuly1980toJune1983,thevariationsofthelow-frequencyoscillation(LFO)intheatmospherebeforeandduring1982ElNinohavebeeninvestigated.BeforetheElNino,theLFOpropagatesfromwesttoeastovertheequatoroftheEasternHemisphereandfromeasttowestover20°N.TheeastwardpropagatingLFOovertheequatorconsistsofzonalwavenumber1propagatingeastwardandzonalwavenumber2withacharacterofstationarywave.Theoscillationofzonalwavenumber2canmodulatetheoscillationstrength.AftertheonsetoftheElNino,thepropagatingdirectionsoftheLFOovertheequatorand20°NoftheEasternHemispherechangetobewestwardandeastward,respectively.TheLFOoverthewesternPacificweakensrapidlyandonecomingfrommiddleandhighlatitudespropagatestotheequator.Fromthephasecompositionsofstreamlinefieldsforthezonalwavenumber1ofequatorialwestwardpropa-gatirgLFO,itisfoundthattheatmosphericheatsourceintheequatoroftheeasternPacific(EEP)excitesaseriesoftheequatorialcyclonesandanticycloneswhichmovenorthwardandwestwardandformthewestwardpropagatingLFOovertheequator.Withthewavelengthof20000km,thiskindofequatorialwaveissimilartothemixingRossby-gravitywave.Initswestwardandnorthwardmovement,thecirculationinEastAsiaismodified.ThismaybethemechanismoftheinfluenceofElNinoontheclimateofChina.
简介:利用1961~2014年春季宁夏20个气象站的降水及NCEP再分析等资料,重点分析了不同分布型ElNino事件次年宁夏春季降水的差异。结果表明:由于ElNino事件在1990年代以后主要转为中部型,宁夏春季降水对ElNino的响应也发生了变化,由之前在ElNino发生次年春季降水偏多,转为次年春季降水偏少。东部型和混合型ElNino事件次年春季,500hPa高度距平场上欧亚中高纬地区环流分布及700hPa水汽输送条件,均有利于宁夏出现降水;而中部型ElNino事件次年春季,青藏高原南侧以偏西风为主,青藏高原东南侧相对湿度较低,不利于宁夏春季出现降水。
简介:
简介:DuringthedevelopingphaseofcentralPacificElNio(CPEN),morefrequentTCgenesisoverthenorthwestquadrantofthewesternNorthPacific(WNP)isattributedtothehorizontalshiftofenvironmentalvorticityfield.SuchanorthwestwardshiftresemblestheLaNiacomposite,eventhoughfactorsthatcausetheshiftdiffer(intheLaNiacasetherelativehumidityeffectiscrucial).GreaterreductionofTCfrequencyoverWNPhappenedduringthedecayingphaseofeasternPacificElNio(EPEN)thanCPEN,duetothedifferenceoftheanomalousPhilippineSeaanticyclonestrength.TheTCgenesisexhibitsanupward(downward)trendoverthenorthern(southern)partoftheWNP,whichislinkedtoSSTandassociatedcirculationchangesthroughlocalandremoteeffects.
简介:ThenormalmodemethodisadoptedtodecomposethedifferencesbetweensimulationswithSST(seasurfacetemperature)anomahesovercentra-easternPacificandnormalSSTbyuseofanine-layerglobalspec-tralmodelinordertoinvestigateshort-rangeclimaticoscillationwithvarioustimescalesforcedbyElNinoduringthenorthernsummer.InvestigationshowsthatElNinomayhavethefollowinginfluenceonatmosphereonvariousspace-timescales.Extra-longwavecomponentsofRossbymodeforcedbyconvectiveanomalyoverequatorialwesternPacificresultingfromElNinoproduceclimaticoscillationonmonthly(sea-sonal)timescaleinmiddle-highlatitudesofSouthernandNorthernHemispheres;extra-longwavecomponentsofKelvinmodeforcedbySSTanomaliespropagatealongtheequator,resultingin30—60dayoscillationoftropicalandsubtropicalatmosphere;anditslongwavesmoveeastwardwithwesterly,resultinginquasi-biweekoscillation.
简介:A6-layer,4°×5°horizontalresolutionglobaloceanmodelhasbeendesignedandimproved.Aftera100-yearin-tegration,anequilibriumstatehasbeenreachedfromtheuppertolowerlayers.Bytakingthemeanstateoflastl0mod-elyearsasclimaticstate,weanalyzedthecharacteristicsoftheseasonalvariationinourmodelintegration.Theresultsshowthatthesimulatedseasonalvariationissimilartotheobserved.Sothedesignofourmodelissuccessful.Then,us-ingthesimulatedclimaticstateoftheseasonalvariationastheinitialstate,andtheobservedstressandthermalstateastheatmosphericforcing,wesimulatedtheprocessofElNinoin1972—1973successfully.Thesimulatedresultsofsea-sonalvariationusingourmodelwillbepresentedinpartI.