简介:Consideringtheimportanceofblackcarbon(BC),thisstudybeganbycomparingthe20thcenturysimulationofSouthAsiansummerclimateinIPCCCMIP3,basedonthescenarioofmodelswithandwithoutBC.Generally,themulti-modelmeanofthemodelsthatincludeBCreproducedtheobservedclimaterelativelybetterthanthosethatdidnot.Then,the21stcenturySouthAsiansummerprecipitationwasprojectedbasedontheIPCCCMIP3projectionsimulations.Theprojectedprecipitationinthepresentapproachexhibitedaconsiderabledifferencefromthemultimodelensemblemean(MME)ofIPCCAR4projectionsimulations,andalsofromtheMMEofthemodelsthatignoretheeffectofBC.Inparticular,thepresentprojectionexhibitedadryanomalyoverthecentralIndianPeninsula,sandwichedbetweenwetconditionsonthesouthernandnorthernsidesofPakistanandIndia,ratherthanhomogeneouswetconditionsasseenintheMMEofIPCCAR4.Thus,thespatialpatternofSouthAsiansummerrainfallinthefuturemaybemorecomplicatedthanpreviouslythought.
简介:摘要:随着技术深化发展, HXD3D型电力机车应运而生,具备多样化优势特征,但在运用中呈现一些问题。因此,本文多层次客观分析了 HXD3D型电力机车及其运用问题,提出了一些行之有效的改进措施,在改进、优化的基础上促使 HXD3D型电力机车在实际运用中安全、稳定以及经济运行。
简介:3D地震波走时计算是偏移、反偏移、层析等诸多地震勘探技术中的重要中间步骤。快速推进法计算3D地震波走时具有高效率、稳定性及适应能力强的特点,但快速推进法在震源附近区域的计算精度不高,降低了整个走时算法的计算精度。本文提出了一种联合3D走时计算方法来解决这一问题。该方法在震源附近小范围内使用计算精度较高的波前构建法计算走时,在剩余区域使用快速推进法计算走时,由于模型中绝大多数网格节点走时是通过快速推进法计算的,故新方法保留了快速推进法高效的特点,同时由于震源附近网格节点走时精度的提高,整个新算法的计算精度相对于快速推进法而言有了较大的改善。文中通过数值分析对上述结论进行了验证并使用三维岩丘模型验证了新方法的稳定性和适应能力。
简介:NonhydrostaticmesoscaleWRFandits3D-Varsystemareusedtostudyadensefogeventoccurringin13-14January2006.ThreedifferentobservationdatasetsincludingGTS(GlobalTelecommunicationSystem),AMDAR(AircraftMeteorologicalDataRelay)data,and9210dataareassimilatedintotheinitialanalysisfieldsinexperiments.Experimentswiththreedifferentassimilationtimeintervals(1,3,and6h)arealsocarriedout.Threeexperimentswithdifferentdatasetshaveallmodifiedthetemperatureandhumidityfieldofinitialfields,andthereforeshowanobviouspositiveeffectonfogsimulation.Furtherstudyindicatesthatthehumidityandstabilityofboundarylayerareimprovedobviouslyinassimilationexperiments,althoughdifferentdatasetsmakedifferentcontributiontotheanalysisfields.Themulti-timeassimilationcycleexperimentsshowthattheanalysisincrementinexperimentwith1-hintervalismorerealisticthanthatwith3-and6-hintervals.
简介:BasedonthefirstarrivalPandSdataof4625regionalearthquakesrecordedat174stationsdispersedintheYunnanandSichuanProvinces,the3-Dvelocitystructureofcrustanduppermantleintheregionisdetermined,incorporatingwithpreviousdeepgeophysicaldata.Intheuppercrust,apositiveanomalyvelocityzoneexistsintheSichuanbasin,whereasanegativeanomalyvelocityzoneexistsinthewesternSichuanplateau.TheboundarybetweenthepositiveandnegativeanomalyzonesistheLongmenshanfaultzone.TheimagesoflowercrustanduppermantleintheLongmenshanfault,Xianshuihefault,Honghefaultandothersshowthecharacteristicoftectonicboundary,indicatingthatthefaultslikelypenetratetheMohodiscontinuity.Thenegativevelocityanomaliesatthedepthof50kmintheTengchongvolcanicareaandthePanxitectoniczoneappeartobeassociatedwiththetemperatureandcompositionvariationsintheuppermantle.TheoverallfeaturesofthecrustalandtheuppermantlestructuresintheSichuan-Yunnanregionaretheloweraveragevelocityinbothcrustanduppermostmantle,thelargecrustalthicknessvariations,andtheexistenceofhighconductivitylayerinthecrustor/anduppermantle,andhighergeothermalvalue.AllthesefeaturesarecloselyrelatedtothecollisionbetweentheIndiaandtheAsiaplates.ThecrustalvelocityintheSichuan-Yunnanrhombicblockgenerallyshowsnormalvalueorpositiveanomaly,whilethenegativeanomalyexistsintheareaalongthelargestrike-slipfaultsastheblockboundary.Itisconducivetothecrustalblockside-pressingoutalongthefaults.Inthemajorseismiczones,theseismicityisrelativetothenegativeanomalyvelocity.Moststrongearthquakesoccurredintheupper-midcrustwithpositiveanomalyornormalvelocity,wherethenegativeanomalyzonegenerallyexistsbelow.
简介:Atime-domainmethodisappliedtosimulatenonlinearwavediffractionaroundasurfacepiercing3-Darbitrarybody.ThemethodinvolvestheapplicationofTaylorseriesexpansionsandtheuseofperturbationproceduretoestablishthecorrespondingboundaryvalueproblemswithrespecttoatime-independentfluiddomain.AboundaryelementmethodbasedonB-splineexpansionisusedtocalculatethewavefieldateachtimestep,andthefreesurfaceboundaryconditionissatisfiedtothesecondorderofwavesteepnessbyanumericalintegrationintime.Anartificialdampinglayerisadoptedonthefreesurfacefortheremovalofwavereflectionfromtheouterboundary.Asanillustration,themethodisusedtocomputethesecond-orderwaveforcesandrun-uponasurface-piercingcircularcylinder.Thepresentmethodisfoundtobeaccurate,computationallyefficient,andnumericallystable.