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.
简介:将有限区域流函数、速度势求解中常用的两种张驰法(即理查逊法和加速利布曼法)与调和一余弦谱展开法(H—C法)进行了比较,理论研究表明:H-C法单独考虑边界影响分量,物理意义明确,且不会丢失边界上的天气系统;从计算上看,H-C法重建的风场能精确还原原始风场,且计算效率明显高于两种张驰法,即收敛更快。通过在台风Bilis(0604)暴雨增幅过程诊断中的应用发现,常用的两种张驰迭代方法在求解有限区域流函数和速度势的问题上效果都不是很好,即:用理查逊法和加速利布曼法计算的流函数和速度势重建的风场与原始风场差别较大,不能准确还原原始风场;用H—C法不仅计算效率高,还原的风场与原始风场差异极小,且不受南边界较强的西南季风涌影响,在暴雨增幅前期能较好地反映与暴雨增幅相关的强辐合信号。因此,可用H—C法计算得到的无辐散风和无旋风对有限区域的天气系统进行更深入的动力结构分析。