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Simulation of Precipitation in Monsoon Regions of China by CMIP3 Models

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Simulation of Precipitation in Monsoon Regions of China by CMIP3 Modelsof,in,by,China,CMIP3

    Simulation of Precipitation in Monsoon

    Regions of China by CMIP3 Models ATMOSPHERICANDOCEANICSCIENCELETTERS,2009,VOL.2,NO.4,194200

    SimulationofPrecipitationinMonsoonRegionsofChinabyCMIP3 Models

    TUKai,,YANZhongWei,ZHANGXueBin3,

    andDONGWenJie4

    RCE-TEA,InstituteofAtmosphericPhysics,ChineseAcademyofSciences,Beijing100029,China

    2GraduateUniversityoftheChineseAcademyofSciences.Beij'ing100049,China 3ClimateDataandAnalysisSection.

    EnvironmentCanada,Toronto.Ontario.Canada

    StateKeyLaboratoryforEarthS.rfaceProcessandResourceEcology,BeijingNormalUniversity,Beijing100875,China

    Received22April2009;revised9June2009;accepted18June2009;published16July2009 AbstractTheoutput0f25modelsusedintheCoupled

    ModelIntercomparisonProjectphase3(CMIP3)were

    evaluated,withafoCUSonsummerprecipitationineastern

    Chinaforthelast40yearsofthe20thcentury.Mostrood.

    elsfailedtoreproducerainfa11associatedwiththeEast

    Asiansummermonsoon(EASM).andhencetheseasonal

    cycleineasternChina.butprovidedreasonableresultsin

    SouthwestfSW1andNortheastChinaE).Thesimula

    tionsproducedreasonableresultsfortheYangtzeHuai

    fYH1Basinarea,althoughtheMeiyuphenomenonwas

    underestimatedingenera1.Onetypicalregionalphe

    nomenon,aseasonalnorthwardshiftintherainbeltfrom

    earlytolatesummer,wascompletelymissedbymost models.Thelongtermclimatetrendsinrainfal1over easternChinawerelargelyunderestimated.andtheob. servedgeographicalpaRemofrainfal1changeswasnot reproducedbymostmodels.Precipitationextremeswere evaluatedviaparametersoftiffedGEVrGeneralizedEx

    tremeValues)distributions.Theannualextremeswere grosslyunderestimatedinthemonsoon.dominatedYH andSWregions,butreasonablevalueswerecalculated fortheNorthChinafNC)andNEregions.Theseresults suggestageneralfailuretocapturethedynamicsOfthe EASMincurrentcoupledclimatemodels.Nonetheless. modelswithhigherresolutiontendtoreproducelarger decadaltrendsandannualextremesofprecipitationinthe regionsstudied.

    Keywords:precipitation,EastAsianMonsoon,IPCC AR4,coupledmodels,generalizedextremevalues Citation:Tu,K..Z.w.Yan,X..B.Zhang,eta1.,2009:

    SimulationofpreciFIit~ioninmonsoonregionsofChina byCMIP3models,Atmos.Oceanic&.Lett.,2,194-200. 1Intr0ducti0n

    Thedevelopmentofcoupledmodelsforclimate changestudyhasmadenotableprogressessinceIPCC TAR(theIntergovernmentalPanelonClimateChange ThirdAssessmentReport).Toimprovethemodelinter. comparisonsundertheWorldClimateResearchPro. gramme's(weRP's1CMIP3(phase3oftheCoupled ModelIntercomparisonProject),apilotprojectcalled '20thCenturyClimateinCoupledModels'(20C3M)was carriedout.Inthisproject,observedforcingsincluding

Correspondingauthor:YANZhongWei,yzw@tea.ac.cn

    solarradiation,greenhousegases,aerosols,ozone,etc., wereincorporatedintomodelstofacilitatecomparison withtheobservationalclimateduringpastdecades.Sofar. 25modelgroupshavesubmittedtheirresults.and23of themhavebeensummarizedbyIPCCAR4(theFourth AssessmentReport)(Randalleta1..2007).Ataglobal scale.thoroughevaluationsandintercomparisonsofthese modelshavebeenconductedfortemperature(Zhouand Yu,2006),precipitation(Suneta1.,2006),andforex. tremeclimateconditions(Kharineta1..2007).Atare. gionalscale,precipitationinmonsoondominatedareas

    hasgeneratedsignificantattentionandconcern.bothfor globalconfinentsfPhillipsandGleckler,2006),EastAsia (Xueta1..2007;Zhangeta1.,2008),SouthAsia(Anna

    malaieta1.,2007),andwesternAfrica(CookandVizy, 2006).Nevertheless,detailedcomparisonsbetweensimu

    1ationsandobservationsinregionssuchaseasternChina arestil1neededandmaybeusefu1forevaluatingcurrent models'abilitVtosimulateregionalmonsoondominated

    climatesandthechangestheymayundergoinresponseto globalclimatechange.

    TheEarth'sclimatehasbeenundergoingconsiderable changessincethelate20thcentury.Thesechangesin. eludenaturalinterdecadalvariationsandincreasingevi

    dencehasalsobeenfoundforanthropogenicinflHenceon globalclimatepatterns(LeTreuteta1..2007).Anycom parisonbet,veendirectobservationsandclimatesimula. tionsspanningafewdecadesorlessmaybemisleading, duetothelargenaturalvariabilityinobservationsover

    suchtimeperiods.Howevercomparisonsofthegeo graphica1patternsoflong.termclimatetrendscanbe helpfu1forobtaininginsightsintocurrentmodels'ability toreproduceandpredictlargescaleclimatevariability.

    Anotherdifhcultaspectofmodelevaluationdealswith climateextremes.whichareofgreatinterestbecause theseextremeshavesubstantialimpactsonsociety.From aglobalperspective.Kharineta1.(2007)foundthat simulatedpresent.dayprecipitationextremesareplausible intheextratropics.However.themodels'abilitytore. producerainfallextremesinmonsoondominatedregions

    suchaseasternChinaremainsquestionableandhasyetto beexamined.AtypicalfeatureoftheEastAsiansummer monsoonASMineasternChinaisthenorthward

    movementoftherainbeltfromearlytolatesummer.in concertwiththeseasonalnorthwardshiftorexpansionof NO.4TUETAL.:SIMULAT10N0FPRECIPI1'ATIONINCHINABYCMIP3MODELS thenorthwesternPacificSubtropicalHigh(NWPSH)cir

    culation.Thistrendhassignificantimplicationsinthe contextofclimatechange.asithasgivenrisetoaphe. nomenonofseasonaldryinginNorthChinaandwetting inthesouthoverthepastfiftyyears(GongandHe.2002; Zhoueta1.,2008).

    Thepresentworkseekstoillustratecurrentclimate models'performanceinsimulatingsummerprecipitation, particularlyinareasofeasternChinadominatedbyre. gionalmonsoons.

    2Dataandmethods

    CMIP3's25multi.modeldailyandmonthlyprecipita. tiondataset,coveringthelastfortyyearsofthe20thcon.

tury.wasusedasthebasisforthiswork.The2.5.×2.5.

    griddeddatasetofglobalmonthlyprecipitationC?IAP

    (theCPCMergedAnalysisofPrecipitation)f1979-99) (XieandArkin.1997)wasusedasasetofobservational dataonlargescaleprecipitationpatternsforcomparison tosimulationoutputs.Theobserveddailyprecipitation datausedherewerechosenfromthedatasetof740 weatherstationsinmainlandChinacompiledattheNa

    tionalMeteorologyInformationCenteroftheChinese MeteorologicalAdministration.Multimodelmeanvalues

    werecalculatedfrommodelsforwhichresolutionhad beennormalizedto2.5.x2.5..Observationswerenot gridded,anddirectcomparisonswereavoidedinour study.

    Inordertocapturethelarge.scalefeaturesofsummer precipitation,fourregionsofChina'slandareawerese. 1ected:theNorthChinafNC1(33.542oN,l10124.E1

    Yangtze-Huai(YH)basin(2533.50N,110124.E1,north

    eastChina(mE)(4254~N,l18-I35~E).andsouthwest

    China(SW)(2230oN,97.5110.E1,asoutlinedinFig.1. NotethattheNEregionisusedasareferencetoNC.a1. thoughitisnotconsideredaregionthatisheavilyjnflu. encedbyEASMingenera1.

    AnnualprecipitationexemeswerefittedtotheGen

    eralizedExtremeValues(GEV)distribution,whichwas determinedusingthreetimedependentparameters:the

    1ocationparameterthescaleparametero-,andincreas. ingshapeparameter

    50.N

    40.N

30.N

    20.N

    1O.N

    CMAP

    50.N

    40.N

    3ON

    2O0N

    10.N

    /(;?,,):

    exp

    ex

    p{

    195

    e

    Xp(=.

    +

    (]>.

    TheGEVdistributionhasaheavytail,wherethePDF (probabilitydensityfunction)decreasesgraduallywith Asincreases,theuppertailelongates.ietherateat

    whichthePDFdecreaseswillbesloweratthetail.The GEVdistributionhasafiniteuppertailfor<0. measuresthevariabilityoftheextremes."isthemean valueofthePDF.GEVanalyseshavebeenappliedpre. viouslytoevaluateclimatesimulationsinrecentyears, e.g.,KharinandZwiers(2005),althoughnot.tothebest ofourknowledge.inthecontextoftheEASM. 3Results

    3.1Totalrainfa11

    PreliminaryresultsbasedontheIPCCAR4data showedthatmodelseffectivelyreproducedreasonable spatialpaaemofannualprecipitationovertheno~hwest

    ernPacific(Randalleta1.,2007).ButfortheEASMsea. soninChina.theresultsworelessoptimistic.Figure1 presentsthesummer(JJA_June,July,andAugust)rain.

    faIIpatternbasedonobserved(CMAP)andcalculated multimodelmeanvalues.Observationsshowedrelatively strongrainfaIlcentersfromeasternChinatothesouthwest ofJapan,partlyduetothewel1.knowntheEastAsian rainyseason(MeiyuinChinese)intheseregions. Multi.mode1meanvaluesdidnotrefloctthispattem.a1. thoughabroadrainbeltdidextendtotheSOUthofJapan. Accordingtosimulations.therainfal1centerintheSouth ChinaSeaappearedtorarelyreachthecoastalregionof southemChina,andtoberatherweak.Despitetheweak treatmentofEASMsinsimulations.simulatedrainfallin NCwascomparablewithobservations.implying(incor. rectly)thatintenseprecipitationinthisregionmaybe Multimodelmean

    90.EI10.EI30.EI50.E170.E90.EI10.E130~EI50OE170~E Figure1TheJJArainfallofCMAPandMulti

    modelmeanovernorthwestPacificandEastAsia, Units:mm.

    196ATM0SPHERICANDOCEANICSCIENCELETTERS

    broughtbythewesterliescirculatingaroundthenorthern sideoftheTibetanPlateau.Thisdiscrepancywasattrib. utedtothecoarseresolutionofcurrentGCMs(Gaoeta1.. 2006).

    Intropica1zones.theseasonalprecipitationcenters

    aroundl5N(extendingfromtheBavofBengaltothe easternPhilippines)werereproducedfairlywellbythe models,althoughtheirstrengthwassignificantlyunderes. timated.suggestingthatthelarge.scaleITCZisreason. able.Itisnoticeablethatanerroneoussimulatedrainfa11 beltextendsdeepintotheSWregion,indicatingthat modelsaccountfortheIndianmonsoon,butprojectit furthernorthwardthantheregionsinwhichitisgenerally observed,whiletheEASMremainsachallengeforcur

    rentglobalmodels.

    V0L.2

    modelsconsidered.FortheSWregion.whichisinflu

    encedbytheIndianmonsoon,manymodelsreproduced theseasonalcyclequitewell,althoughestimatedslightly heavierprecipitationfromJunethroughtheendofwinter thanwasobserved.Theaveragingusedinthemulti. modelmeanseasonalcyclesmoothedsomeofthebiases observedinindividualmodels.resultingincalculations atmatchedobservationsforeNCandNEregions duringtherainymonths.fortheYHregionbenveen AprilMayandforSWfromApril-June.

    Inshort,thesimulationsofseasonalcyclesofprecipi

    tationsuggestedagainthatmostofthepresentmodels failedtosimulatetheEASM.whiletheyreproducedthe Indianmonsoonsuccessfully,althoughperhapsfactored itseffectstooheavilyintheSWregion.

    3.2Seasonalcycle3.3Seasonalshiftsintherainbelt TheseasonalcycleisoneofthemostbasicpaRernsin climatologyformonsoon.dominatedregions.Figure2 showstheaverageseasonalcycleofprecipitationinevery

modeloverthefourmonsoonaffectedregionsinChina.

    Generallyspeaking,thesimulatedseasonalstructuresfor NCandNEdidnotmatchobservations.Withtheexcep

    tionoftherainyseason(JulyandAugustforNCandNE), simulatedprecipitationsignificantlyexceededobserved valuesthroughouttheyear.Thesegentlesimulatedcycles couldbetheresultsofexcessivefrequencyof1ightrain (1essthan10mmday-,duringthenon.rainyseasonin GCMs(Sunetal2006).FortheYHregion.mostmodels

    fafledtoreproducetheprominentMeiyuphenomenonin June.However.thesimulationsforApri1-MayandSep

    tember-Octoberappearedtheleastdivergentamongthe Therapidnorthwardadvanceoftherainbeltineastern ChinafromMaytoAugustisaremarkablefeatureofthe EASM.Zhangeta1.(2008)havediscussedrelevantre. suitsinthetwodecadesfron)1979-99.basedonmonthly measurementsrecordedalongasinglelineof1ongitude r1l5E1.Herewecomparedthedailymodeloutputand observedvaluesinordertoundertakeamoredetailed treatmentoftheproblem.AccordingtoFig.3,theob. servedprecipitationcenterexpandswithtimefromthe lowlatitudes(southemChina)inMavJunetothehigher

    latitudes(northernChina1inJulvAugust.Insimulations,

    thosemodelsthatwereabletoreproduceareasonable seasonalcyclebothintheNCandYHregionstendedto displaytheadvancementoftheprecipitationcenterfrom thesouthtothenorth(e.g.,theBCCR.BCM2.0(Bierknes Figure2Theaverageseasonalcycleofprecipitationoverfourregionsstudied.Thicklineisthe

    observedcycle,(a)NC,(b)NE,(c)YH,and

    (d)SW.

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