简介:BasedontheCMAtropicalcyclone(TC)besttrackdataaswellasthereanalysisdatasetsfromtheNCEP/NCARandNOAA,thevariationcharacteristicsofTCnumberfrom1949to2013overthewesternNorthPacific(includingtheSouthChinaSea)areexamined.Notably,thetimeseriesofTCnumberexhibitsasignificantabruptchangefrommoretolessaround1995.ComparativeanalysisindicatesthattheenvironmentalfactorsnecessarytoTCformationalsochangesignificantlyaroundthemid-1990s.After1995,accompanyingwithanomalouswarmseasurfacetemperature(SST)inwesternequatorialPacific,aLaNia-likepatternintropicalPacificappearsobviously.However,comparedwiththeperiodbefore1995,theverticalupwardmovementdecreases,verticalshearoftroposphericzonalwindincreases,andsealevelpressure(SLP)rises,allofwhichareunfavorabletoTCformationandworktogethertomakeTCnumberreducemarkedlyafter1995.Furthermore,whenthetypicalinterannualmoreandlessTCsyearsareselectedinthetwoseparatestagesbeforeandafter1995,therelativeimportanceofoceanicandatmosphericenvironmentsininterannualTCgenerationisalsoinvestigatedrespectively.TheresultsimplythattheSSToverthetropicalPacificexertsrelativelyimportantinfluenceonTCformationbefore1995whereastheatmosphericcirculationplaysamoreprominentroleinthegenerationofTCafter1995.
简介:Asthestrongestsubseasonalatmosphericvariabilityduringborealwinter,threeremarkablesuddenstratosphericmajorwarming(SSW)eventsinthe2000sareinvestigatedintermsoftheBrewer–Dobsoncirculation(BDC)response.Ourstudyshowsthatthechangesofcross-isentropicvelocityduringtheSSWsarenotonlyconfinedtothepolarregion,butalsoextendtothewholeNorthernHemisphere:enhanceddescentinthepolarregion,aswellasenhancedascentinthetropics.WhentheaccelerationofthedeepbranchoftheBDCdescendstothemiddlestratosphere,itsstrengthrapidlydecreasesoveraperiodofonetotwoweeks.TheaccelerationofthedeepbranchoftheBDCisdrivenbytheenhancedplanetarywaveactivityinthemid-to-high-latitudestratosphere.DifferentfromtherapidresponseofthedeepbranchoftheBDC,tropicalupwellinginthelowerstratosphereacceleratesupto20%–40%comparedwiththeclimatology,20–30daysaftertheonsetoftheSSWs,andtheaccelerationlastsforonetothreemonths.Theenhancementoftropicalupwellingisassociatedwiththelarge-scalewave-breakinginthesubtropicsinteractingwiththemidlatitudeandtropicalQuasi-BiennialOscillation–relatedmeanflow.
简介:Inthepaperthe5°×10°latitude-longitudegridpointdataofdaily500hPageopotentialheightovertheNorthernHemisphere(NH)insummer(June—August)during1980sareused.Thebasepoint(20°N,120°E)isselectedtocalcu-latepointcorrelationbetweenthebasepointandothergridpoints.WefindthatthesummerheatsourceanomalyofthetropicalwesternPacificcausesanomalyofsummergeneralcirculationoverNHandteleconnectionofgeneralcircula-tionsimilartoPNApatternformsfromEastAsiatoNorthAmerica.Theteleconnectionsshowgreatinterannualchanges.
简介:Thesecond-generationGlobalOceanDataAssimilationSystemoftheBeijingClimateCenter(BCC_GODAS2.0)hasbeenrundailyinapre-operationalmode.Itspanstheperiod1990tothepresentday.ThegoalofthispaperistointroducethemaincomponentsandtoevaluateBCC_GODAS2.0fortheusercommunity.BCC_GODAS2.0consistsofanobservationaldatapreprocess,oceandataqualitycontrolsystem,athree-dimensionalvariational(3DVAR)dataassimilation,andglobaloceancirculationmodel[ModularOceanModel4(MOM4)].MOM4isdrivenbysix-hourlyfluxesfromtheNationalCentersforEnvironmentalPrediction.Satellitealtimetrydata,SST,andin-situtemperatureandsalinitydataareassimilatedinrealtime.ThemonthlyresultsfromtheBCC_GODAS2.0reanalysisarecomparedandassessedwithobservationsfor1990-2011.TheclimatologyofthemixedlayerdepthofBCC-GODAS2.0isgenerallyinagreementwiththatofWorldOceanAtlas2001.ThemodeledsealevelvariationsinthetropicalPacificareconsistentwithobservationsfromsatellitealtimetryoninterannualtodecadaltimescales.PerformancesinpredictingvariationsintheSSTusingBCC_GODAS2.0areevaluated.ThestandarddeviationoftheSSTinBCC-GODAS2.0agreeswellwithobservationsinthetropicalPacific.BCC-GODAS2.0isabletocapturethemainfeaturesofE1NinoModokiIandModokiⅡ,whichhavedifferentimpactsonrainfallinsouthernChina.Inaddition,therelationshipsbetweentheIndianOceanandthetwotypesofE1NinoModokiarealsoreproduced.
简介:以前的研究建议在北热带大西洋(NTA)上的春天SST异例影响热带气旋(TC)在在下列夏天和秋天的西方的诺思太平洋(WNP)上的活动。现在的学习表明在春天NTASST和后面的夏天秋天WNPTC开始频率之间的连接不是静止的。后面的夏天秋天WNPTC开始频率上的春天NTASST的影响是在前弱、不足道,却在以后强壮、重要,1980年代末。在1980年代末前,在热带中央太平洋的NTASST导致异例的SST异例是弱的,并且在WNP上的大气的循环的反应不是强壮的。作为结果,在春天NTASST和后面的夏天秋天WNPTC开始频率之间的连接在以前的时期是不足道的。在1980年代末以后,相反,NTASST异例通过大西洋和平的teleconnection导致显著热带中央和平的SST异例。热带中央和平的SST异例进一步为WNPTC开始导致有利条件,包括垂直运动,中间水平的相对湿度,和垂直的带的风砍。因此,在NTASST之间的连接和WNPTC开始频率在最近的时期是重要的。进一步的分析证明interdecadal在在春天NTASST之间的连接变化,后面的夏天秋天WNPTC开始频率可能与在NTA区域上的climatologicalSST变化有关。
简介:TheprojectionofChina'snear-andlong-termfutureclimateisrevisitedwithanew-generationstatisticallydownscaleddataset,NEX-GDDP(NASAEarthExchangeGlobalDailyDownscaledProjections).Thisdatasetpresentsahigh-resolutionseamlessclimateprojectionfrom1950to2100bycombiningobservationsandGCMresults,andremarkablyimprovesCMIP5hindcastsandprojectionsfromlargescaletoregional-to-localscaleswithanunchangedlong-termtrend.Threeaspectsaresignificantlyimproved:(1)theclimatologyinthepastascomparedagainsttheobservations;(2)morereliablenear-andlong-termprojections,withamodifiedrangeofabsolutevalueandreducedinter-modelspreadascomparedtoCMIP5GCMs;and(3)muchaddedvalueatregional-to-localscalescomparedtoGCMoutputs.NEX-GDDPhasgreatpotentialtobecomeawidely-usedhigh-resolutiondatasetandabenchmarkofmodernclimatechangefordiverseearthsciencecommunities.
简介:Netprimaryproduction(NPP)ofcroprepresentsthecapacityofsequestratingatmosphericCO_2inagro-ecosystem,anditplaysanimportantroleinterrestrialcarboncycling.BylinkingtheCrop-CmodelwithclimatechangescenarioprojectedbyacoupledGCMFGOALSviageographicalinformationsystem(GIS)techniques,cropNPPinChinawassimulatedfrom2000to2050.ThenationalaveragedsurfaceairtemperaturefromFGOALSisprojectedtoincreaseby1.0℃overthisperiodandthecorrespondingatmosphericCO_2concentrationis535ppmby2050undertheIPCCAIBscenario.Withaspatialresolutionof10×10km~2,modelsimulationindicatedthatanannualaverageincreaseof0.6TgCyr~(-1)(Tg=10~(12)g)wouldbepossibleundertheAIBscenario.TheNPPinthelate2040swouldincreaseby5%(30TgC)withinthe98×10~6hm~2croplandareaincontrastwiththatintheearly2000s.AfurtherinvestigationsuggestedthatchangesintheNPPwouldnotbeevenlydistributedinChina.AhigherincreasewouldoccurinamajorityofregionslocatedineasternandnorthwesternChina,whileaslightreductionwouldappearinHebeiandTianjininnorthernChina.ThespatialcharacteristicsofthecropNPPchangeareattributedprimarilytotheunevendistributionoftemperaturechange.