A Quick Report on a Dynamical Downscaling Simulation over China Using the Nested Model

A Quick Report on a Dynamical Downscaling Simulation over China Using the Nested Model A Quick Report on a Dynamical Downscaling Simulation over China Using the Nested Model ATMOSPHERICANDOCEANICSCIENCELETTERS,2010,VOL.3,NO.6,325—329 AQuickReportonaDynamicalDownscalingSimulationoverChinaUsing theNestedModel YUEn—Tao,,WANGHui.Jun,andSUNJian.Qi 1 . Nansen— ZhuInternationalResearchCentre,InstituteofAtmosphericPhysics.ChineseAcademyofSciences.Beijing100029,China ClimateChangeResearchCenter,ChineseAcademyofSciences,Bei]ing100029,China GraduateUniversityoftheChineseAcademyofSciences,Beijing100049,China Received15October2010;revised8November2010;accepted8November2010;published16November2010 AbstractThisPaperdescribesadynamicaldownscaling simulationoverChinausingthenestedmode1system. whichconsistsof坊emoditied舱atherResearchand ForecastingModel(WRY)nestedwiththeNCARCom— munityAtmosphereModelrCAM).Resultsshowthat dynamica1downscalingisofgreatvalueinimprovingthe mode1simulationofregionalclimaticcharacteristics. WRFsimulatesregionaldetailedtemperaturefeatures betterthanCAM.Withthespatialcorrelationcoemcient betweentheobservationandthesimulationincreasing from0.54forCAMto0.79forWRF,theimprovementin precipitationsimulationismoreperceptiblewithWRF Furthermore.theWRFsimulationcorrectsthespatialbias oftheprecipitationintheCAMsimulation. Keywords:dynamicaldownscaling.WRF.CAM Citation:Yu,E..T.H.一J.Wang,andJ.-Q.Sun,2010:A quickreportonadynamicaldownscalingsimulationover Chinausingthenestedmode1.Atmos.Oceanic&f.Lett.. 3,325-329. 1IntrOductiOn Duetocoarseresolution.theperformanceofglobal circulationmodelsfGCMs)is1imitedinsimulatingre— giona1climatevariability,especiallyforcomplexterrain. Therefore.statistica1anddynamicalmethodshavebeen developedtoimproveregionalclimatesimulations.Dy. namicaldownscaling.animportantdynamicalmethod (Castroeta1.,2005;Murphy,1999),istheapproachin whichregionalclimatemodels(RCMs,areforcedby lateralboundaryconditionsfromGCMorglobaldata reanalysisatregulartimeintervals.BecausetheRCMs usefinersurfaceparametersandmorecomplicated parameterizationschemes,dynamicaldownscalingcan significantlyimprovethesimulationabilityforregiona1 climatesovervariousareasoftheworld(DeSalesand Xue,2006;Dickinsoneta1.,1989;FennessyandShukla. 2000;GiorgiandMearns,1991:Joneseta1.,1995,l997; Misraetal一2003:WalshandMcGregor,l995).OverEast Asia.dynamicaldownscalingalsoshowspredominance comparedtoGCMsimulations(Fu2003:Gaoeta1.. 2002,2008;JuandWan2006;Jueta1.,2007;Parketa1., 2008;Waneta1.2003). Althoughmostpreviousdynamicaldownscalingstud. Correspondingauthor:YUEn-Tap,yetsyu@mail.iap.ac.ca iesoverChinautilizeRegCM.weusetheWeatherRe— searchandForecastingModel(WRF,.TheWRFwasini. tiallydevelopedandtestedforsimulationandforecasting ofweather,ithasrecentlybeenadaptedtosimulatecli. mate.ThisWRFmodelhasbeenusedforshort.termre. gionalclimatevariability(Loeta1.,2008;Qianeta1., 2010,:however,theperformanceoftheWRFasady. namicaldownscalingmethodinlong—termsimulations overChinaremainstobedetermined.Toaddressthisis. sue,wedevelopedanewnestedclimatemodelandevalu. ateditssimulations. 2Modelsanddata 2.1Atmosphericglobalcirculationmodel TheGCMmodelusedinthisstudyisthecoupled CommunityAtmosphereModelversion3(CAM3)一 CommunityLandModelversion3(CLM3)model (Collinseta1.,2004;Olesoneta1.,2004),whichconsists oftheCAM3andCLM3.ForCAM,weemploythefinite volumedynamicalcorewithahorizonta1resolutionof2. latitudeby2.5.longitudeand26levelsinthevertical direction.CLMhas10unevenlyspacedverticalsoillay— ers.uptofivesnow1ayers,andonevegetationlayer.The CAMsimulationconsistsofAtmosphericModdInter— comparisonProject(AMIP)-typeintegrations(Phillips, 1996)forcedbyobservedglobalSSTs.Theintegration periodisfrom1September1977to31December2002 withoutputintervalofsixhours.Theflrstfouryears (1977—80)areconsideredasthespin.upperiod,andthe outputoftheremainingyearsisusedasthelateralbound— aryconditionsfortheWRFmode1. 2.2Regionalclimatemodel Theregiona1climatemode1isWRFversion3.2.and theintegrationdomaincoversallofmainlandChina;the integrationdomainhas120gridsalongtheEast—West directionand90gridsalongtheNorth—Southdirection, withthecenterat35.N,105.E(Fig.1).Weused60km gridspacingand31sigmalevelswimthemode1topat50 hPa.TheparameterizationoptionsselectedfortheWRF simulationincludetheWRFSingle.Moment6classmi. crophysicsscheme.RapidRadiationTrant;ferModel (RRTM1long.waveradiationscheme,Dudhiashort-wave radiationscheme,theuntiedNoahland.surfacemodel, andtheYonseiUniversityboundarylayerscheme.Initial 326ATMOSPHERICANDoCEANICSCIENCELETTERS 50.N 40oN 30.N 20N 50.N Figure1Domainandtopography(meters)formodelsimulationand subregionsfordetailanalysisContourintervalsare400iYl,andvalues greaterthan1000mareshaded40.N conditionsandlatera1boundaryconditionsareallfrom CAMoutput.SSTdata.deepsoi1temperatureandgreen fractiondatawereupdatedeverysixhours.Thesimula— tionperiodisfrom1981to2002,withthefirsttwoyears (1981-82)asthespin—upperiod,andthefollowingresult isusedforcomparison. 2.3observatiOnaldata 30.N 20.N Thetemperaturedatausedformodelvalidationisthe50.N griddeddailytemperaturedataoftheChinaMeteorologi— calAdministration(cn05)at0.5.×0.5.resolution,The cn05dataisconstructedfromtheinterpolationof75140.N observingstationsinChinaovertheperiodof196l一2005 (Xueta1..2009).TheprecipitationdataisfromtheXie EastAsiadailygriddedrainfalldataat0.5.×0.5.resolu— tion;thisprecipitationdataisconstructedoverEastAsia from1978to2003usinggaugeobservationsatover2200 stationscollectedfromseveralindividualsourcesfXieet a1..2007). 3Results Thevalidationandcomparisonofthetwomodelre— sultsarebasedontheobservations.Giventhedifferent horizontalresolution,weinterpolatedthemodelfields ontothesamegridsasthecn05dataforcomparison. 3.1Temperature Figure2showstheannua1meantemperaturefronlob— servationandmode1simulations.TheobservationsfFig. 2a)indicatehighertemperaturesoverSouthChinaand 1owertemperaturesovertheTibetanPlateauandnorthern China.Ingeneral,thetemperaturegraduallydecreases northwardandwestward.Oneexceptionisinthe11a"m BasinandJunggarBasin.wherethetemperatureisrela— tivelyhigherduemainlytothehighalbedoofthedeserts intheseregions. TheCAMandWRFcanbothcalclturethelarge.scale characterjsticsoftemperatureoverChina(Fig.21.The 30.N 20.N V0L_3 90.El2O.E 一 9—6—30369l2l5I821 Figure2The20一yearannualmeantemperature(.C)of(a)thecn05 data,(b)theCAMsimulation(Correlation:0.937;RMSE:2992),and fc1thesimulationoftheWRFforcebyCAMoutput(Correlation:0.96; RMSE:2.857) spatialcorrelationcoefficientsbetweenobservationsand simulationsare0.94forCAMand0.96forWRF.Dueto finerresolution.theWRFcanreproducedetailedlocal featuresofChinesetemperaturedistribution,especiallyin theTibetanPlateau,SichuanBasin,andNortheastChina. Forthesimulatedtemperaturevalues.WRFalsopresents betterperformance,showinglesstemperaturebiasas comparedtotheCAMsimulation. 3.2Precipitation TheWRFsimulatesprecipitationmuchbetterthan N0.6YUETAL.:DYNAMICALDOWNSCALINGSIMULAr10NOVERCHINA CAM.AsshowninFig.3.WRFcanmoreaccuratelyre— producetheobservedprecipitationdistributionfeatures; maximumprecipitationmainlyOccursoverSouthChina, andtheprecipitationdecreasesnorthwestward.withthe minimumvalueoverNorthwestChina,particularlyover theTarimBasin(Fig.3a).Conversely,theCAMsimulates themaximumprecipitationoverCentralChina,which disagreeswiththeobservations.Thespatialcorrelation coe艏cientsbetweentheobservationsandsimulationsare 0.54forCAMand0.79forWRF.Valuecomparison 90oEl20.E 25501002505007501000125015002000 Figure3The20一yearannualmeanprecipitation(mm)of(a)theXie data,fb)theCAMsimulation(Correlation:0.542;RMSE:1.403mm d),and(c)thesimulationoftheWRFforcebyCAMoutput(Correla- tion:0.791:RMSE:O.9831Tund,. 327 showsthatthesimulatedbiasoftheWRFismuchless thanthatoftheCAM(Fig.3. TheabovecomparisonsshowtheWRFtobesuperior toCAMandthatdynamicaldownscalingisofvaluein regionalclimatesimulation. Itiswel1knownthatthe precipitationisquitepoor; abilityofGCMstosimulate However,thenested—model dynamicaldownscalingmethodcanimprovethemodel simulationofprecipitation.Toinvestigatethesimulation ofthetemporalfeatureofprecipitation,thetimeseriesof annualmeanprecipitationaveragedoverallthesub..re.. gionswithinMainlandChinaarecalculated(Fig.4,.In general,theimprovementissignificantoveralmostall sub—regions.AsshowninFig.4,theWRFsimulatedpre— cipitationvaluesareclosertotheobservationsforalmost everyyea5especiallyinNortheastChina.theeasternarid region,NorthChinaandthe regions,wheretheRMSEs Northwestaridandsemiarid fortheCAM(WRF)were 0.57(0.24),1.43(0.32),1.32(0.46),and0.57r0.161mm d,.respectively.Forothersub—regions.suchasSouth ChinaandtheTibetanPlateau,theamountofprecipitation simulatedbyWRFisbetweenobservedvaluesandthe CAMvalues;theseresultsindicatethattheWRFcanim— provethesimulationofprecipitationintheseareas. 4Summary Inthisstudy,thenewnestedmode1isdevelopedusing theWRFandtheCAM.Comparisonbetweentheobser— vationsandmodelsimulationsshowsthattheWRFcan improvetheabilityofregionalclimatesimulation.The regionaldetailsoftemperatureproducedbytheWRFare muchbetterthanthoseproducedbytheCAM.Theim— provementofprecipitationsimulationismoreapparent thantemperature;thespatialcorrelationtoefficientin— creasesfrom0.54fortheCAMto0.79fortheWRF.and thedisplacementofprecipitationcellscanbecorrectedin theWRFsimulation.OverdifferentsubregionsofChina, theWRFalsoshowsimprovementovertheCAM. Inanattempttoinvestigatethedynamicaldownscaling abilityoftheWRFnestedwiththeCAM.thispaperad— dressedseveralissues.TheWRFcanreducetheRMSEof precipitationoverChina.butitshows1ittleabilityin simulatingtheinter—annua1variationofprecipitationiust asCAMdoes.Thisweaknessisbecausetheinter—annual variationsimulatedbytheWRFisdrivenbytheboundary conditionsthatareexclusivelyfromtheCAMmode1.An importantremainingissueistoillustratehowwellthe nestedmodelsystemcanrepresentthesummermonsoon systemofChina.Furtheranalysisofthesimulationofthe summermonsoonsystemshouldbeconductedinthefu— ture. Acknowledgements.ThisresearchwassupportedbytheSpecial FundforPublicWelfareIndustry(meteorology)(GrantNo. GYHY200906018),theNationa1BasicResearchProgramofChina (973Program)fGrantNo.2009CB421406).andtheNationalNatu— ralScienceFoundationofChinafGrantNos.40875048and 40821092). 328 NortheastC'hina ATM0SPHERICANDoCEANICSCIENCELETTERS NorthChina SouthChina Refefences 1984l988l992l9962000 TibetanPlateau 3.O 2.5 2.O 15 lO O5 O 42 39 36 33 30 2.7 2.4 1.5 I.2 0.9 O6 03 Easternaridregion CentfalChina Northwestaridandsemi-aridregion l984l988l992l9962000 19841988l992l9962000 Observation—O—CAM-?一CAM.WRF Figure4Timeseriesofannualmeanprecipitation(? d-)averagedoversubregions,whichareindicatedinFig.1 Castro.C.L..R.A.PielkeSr..andGLeoncini2005:Dynamical downscaling:Assessmentofvalueretainedandaddedusingthe RegionalAtmosphericModelingSystem(RAMS),|,Geophys. Res..110.DO5108.doi:10.1029/2004JD004721. Collins,wD.,P.J.Rasch,B.A.Boville,eta1.2004:Descriptionof theNCARCommunityAtmosphereModel(CAM3.O).NCAR Tech.NoteNCAR/TN一464+STR.Nat1.Cent.forAtmos.Res.. Boulder.Colorado,226pp. DeSales.F.,andY.Xue.2006:Investigationofseasona1prediction oftheSouthAmericanregiona1climateusingthenestedmode1 systemGeophys.Res.,111,D20l07,doi:10.1029/2005JD 006989. Dickinson,R.E.,R.M.Errico,F.Giorgi,eta1.,l989:Aregional climatemode1forthewesternUnitedStatesCIimaticChange, 15.383-422. Fennessy,M.J.,andJ.Shukla,2000:Seasona1predictionover NorthAmericawitharegionalmodelnestedinaglobalmode1. CIimate13,2605-2627. Fu.C..2003:Potentia1impactsofhuman—inducedlandcoverchange onEastAsiamonsoon.Glo.Planet.Change.37.219-229. GaoX..YShi,R.Song,eta1.2008:Reductionoffuturemonsoon precipitationoverChina:Comparisonbetweenahighresolution RCMsimulationandthedrivingGCM.Meteor.Atmos.Phys.. 100.73-86. V0L_3 Gao,X.Z.ZhaoandF.Giorgi2002:Changesofextremeeventsin regiona1climatesimulationsoverEastAsia.Adv.Atmos.Sci..19. 927-942. Giorgi,F.andL.0.Mearns1991:Approachestothesimulationof regionalclimatechange:Areview,Rev.Geophys.,29,191—216. Jones.R.G.J.M.Murphy,andM.Noguer,1995:Simulationof climatechangeoverEuropeusinganestedregional—climate mode1.I:Assessmentofcontro1climate.includingsensitivityto locationoflateralboundariespuart.Roy.Meteor.Soc.,121, 1413—1449. Jones.R.G.J.M.Murphy,M.Noguer,eta1.l997:Simulationof climatechangeoverEuropeusinganestedregiona1.climate mode1.II:Comparisonofdrivingandregionalmodelresponses toadoublingofcarbondioxide.puartRoy.Meteor.Soc123 265—292. Ju.L..andH.Wang.2006:ModemclimateoverEastAsiasimulated byaregionalclimatemodelnestedinaglobalgridpointgeneral circulationmode1.ChineseGeophys.,49.52-60. Ju,L.,H.Wang,andD.Jiang,2007:Simulationofthelastglacial maximumclimateoverEastAsiawitharegiona1climatemodel nestedinageneralcirculationmodel,Palaeogeogr.,Palaeo— climatoL.laeoeco1.248.376-390. LoJ.C.一F,Z.一L.Yang.andR.A.PielkeSr..2008:Assessmentof threedynamicalclimatedownscalingmethodsusingtheWeather ResearchandForecasting(WRF1model,Gcophys.Res.,113, DO9l12.doi:1O.1029/2007JD009216. N0.6YUETAL.:DYNAMICALDOWNSCALINGSIMULATION0VERCHn,丁A Misra.V.PA.Dirmeyer,andB.P.Kirtman2003:Dynamic downscalingofseasonalsimulationsoverSouthAmerica. CIimate.16.103-l17. Murphy,J..1999:Anevaluationofstatisticalanddynamical techniquesfordownscalinglocalclimate.CIimate,12, 2256-2284. OlesonKDaiGBonan?etal2004:TechnicalDescription 0厂theCommunityLandModel(eLM).T_ech.NoteNCAR/TN一 461+STR.Nat1.Cent.forAtmos.Res.,Boulder,Colorado, 174pp. Park,E.一H.,S.一YHong,andH.一S.Kang,2008:Characteristicsofan East-Asiansummermonsoonclimatologysimulatedbythe RegCM3,Meteor.Atmos.P.,100,l39-158. Phillips.J..1996:DocumentationoftheAMIPmodelsonthe WOrldwideweb,B11.Amer.Meteor.Soc.,77.119l一1196. Qian,Y,S.J.Ghan,andL.R.Leung,2010:Downscaling 329 hydroclimaticchangesoverthewesternUSbasedonCAM subgridschemeandWRFregionalclimatesimulations./nt CIimato1..3O.675-693. Walsh.K—andJ.L.McGregor,1995:JanuaryandJulyclimate simulationsovertheAustralianregionusingalimited—area mode1.CIimate.8.2387—24O3. Wang,Y.,O.L.Sen,andB.Wang,2003:AHighlyResolved RegionalClimateModelfIPRC.RegCM)anditssimulationof the1998severeprecipitationeventoverCbina.PartI:Mode1 descriptionandverificationofsimulationClimate,16. 1721—1738. Xie,P,M.Chert,S.Yang,eta1.,2007:Agauge—basedanalysisof dailyprecipitationoverEastAsia,Hydrometeor.,8.607-626. Xu.Y,X.Gao,YShen.eta1.,2009:Adailytemperaturedataset overChinaanditsapplicationinvalidatingaRCMsimulation. AAtmosSci..26.763-772.