简介:综合利用辽宁省及周边区域9部多普勒天气雷达组网拼图资料与地面加密自动气象站降水观测资料,通过最优化法,建立适合辽宁本地区的动态Z-I关系,实时得到高时空分辨率雷达定量降水反演资料。结果表明:对2011年台风"米雷"和2012年台风"达维"降水反演表明,动态Z-I关系法可以反演地面降水的主要空间分布特征,但反演的强降水中心存在较大偏差;动态Z-I关系法定量降水反演能力整体优于固定Z-I关系法,但存在高估小雨强度和抑制大雨强度的系统性偏差,特别是对于20.0mm·h^-1以上量级的强降水,平均误差达-10.0mm以上,平均相对误差超过70.0%;各量级降水样本所占比例的差异与地理区域气候条件的差异,是动态Z-I关系法反演降水产生误差的两个主要原因。
简介:Ensembleforecastingoftropicalcyclone(TC)motionwasstudiedusingaprimitiveequationbarotropicmodelbyperturbinginitialpositionandstructurefor1979-1993TC.TheresultsshowthatTCinitialpositionperturbationaffectsitstrack,buttheensemblemeanisclosetocontrolforecast.ExperimentswasalsoperformedbyperturbingTCinitialparameterswhichwereusedtogenerateTCinitialfield,andmoreimprovementcanbeobtainedbytakingensemblemeanofselectivememberthanselectingmembersrandomly.Theskillof60%-70%ofallcasesisimprovedinselectiveensemblemean.Whentheambientsteeringcurrentisweak,moreimprovementcanbeobtainedoverthecontrolforecast.
简介:Thethirdalgorithmintercomparisonproject(AIP-3)involvedrainestimatesfrommorethan50satelliterainfallalgorithmsandgroundradarmeasurementswithintheIntensiveFluxArray(IFA)overtheequatorialwesternPacificwarmpoolregionduringtheTropicalOceanGlobalAtmospherecoupledOcean-AtmosphereResponseExperiment(TOGACOARE).Earlyresultsindicatedthattherewasasystematicbiasbetweenrainratesfromsatellitepassivemicrowaveandgroundradarmeasurements.Themeanrainratefromradarmeasurementsisabout50%underestimatedcomparedtothatfrompassivemicrowave-basedretrievalalgorithms.ThispaperisdesignedtoanalyzerainpatternsfromtheFloridaStateUniversityrainretrievalalgorithmandradarmeasurementstounderstandphysicallytheraindiscrepancies.Resultsshowthatthereisaclearrange-dependentbiasassociatedwiththeradarmeasurements.However,thisrange-dependentsystematicalbiasisalmosteliminatedwiththecorrectedradarrainrates.Resultssuggestthattheeffectsfromradarattenuationcorrection,calibrationandbeamfillingarethemajorsourcesofraindiscrepancies.ThisstudydemonstratesthatrainretrievalsbasedonsatellitemeasurementsfrompassivemicrowaveradiometerssuchastheSpecialSensorofMicrowaveImager(SSM/I)arereliable,whilerainestimatesfromgroundradarmeasurementsarecorrectable.
简介:与REOF(旋转实验直角的功能)的方法,从43的夏天降水在东方中国上驻扎为1901-2000时期被检验。结果显示出那个华南和西南中国,中间和Changjiang河的更低的活动范围,诺思中国并且东北中国西南是夏天降雨的三个主要区域异例。而且,关联分析主要在三的三个次系列被使用夏天降雨模式和四季节的和平的SSTA(海表面温度异例),并且结果建议显著地在东方中国上引起夏天降雨异例的和平的SSTA是在西北太平洋,的自台湾东面的菲律宾海流向日本的暖流区域上的前面的冬季的SSTA在东方、中央的赤道的太平洋的前面的春天的SSTA,并且在中间的纬度的中央区域的当前的夏天的SSTA。在在和平的关键区域的东方中国和SSTA上的夏天降水之间的关系被SVD(单个价值分解)进一步验证分析。合成分析被用来在积极、否定的降水异例的年里分析大气的一般循环的特征。它的结果被用来用作数字模拟分析的底。
简介:基于从threedimensional的方程推出的垂直涡度的Lagrangian变化方程旋涡的Ertel潜在的涡度(PVe),发展和运动从潜在的涡度并且diabatic加热(PV-Q)的看法被调查。在在垂直、水平的罐头加热的不一致的diabatic的旋涡的不对称的分发导致旋涡发展和运动,这被表明。理论结果被用来分析旋涡(TPV)出现在TP上,然后滑动了在下面并且移动的一个西藏的高原(TP)的发展和运动在2008年7月下旬东方,在四川省并且沿着长江的中间、更低的活动范围导致重降雨。对TPV的垂直涡度发展的相对贡献被分解成三部分:加热的diabatic,在PVe的水平部件的变化(定义为PV2),并且在静态的稳定性z的变化。结果证明在大多数情况中,加热的diabatic起主要作用,当当空气变得更稳定,并且当空气接近中立层化时,有积极贡献时,z的变化通常在稳定的气氛有否定影响时,在PV2由变化列在后面。当它在四川盆的东北边的起来斜坡上高举了时,从2008年7月主要由于diabatic加热的0600~1200UTC22的TPV的增强在TPV的东方方面上与降水联系了。加热的diabatic的垂直坡度成为积极(否定)PVe产生在下面(在上面)加热的diabatic的最大值;积极PVe产生不仅加强低级旋涡而且提高它高举的旋涡的垂直程度。在PVe的变化由于加热的diabatic的水平坡度取决于垂直通过加热的diabatic的中心的水平风砍。加热的diabatic的水平坡度成为积极(否定)在右(左)的PVe产生方面垂直水平风砍。右边上的积极PVe产生垂直水平风砍不仅加强本地垂直涡度而且影响TPV的运动的方向。这些诊断结果在对从PV-Q看法开发的理论上的结果的好同意。
简介:FourobservedblockinganticyclonesindifferentregionsoftheNorthernHemispherearein-vestigated.Analysesshowthatthereexistdistinctdifferencesinthemaintenanceofthetime-meanquasi-geostrophicpotentialvorticity(PV)lowin300hPawithinblockingareas.IntwoPacificblockingcases,thePVadvectionbytime-meanflowtendstoflowthePVlowtonorthwesternpartoftheblockinghighs,andthusisbeneficialtothemaintenanceoftheblockings’strength.Thetransferbytransienteddiesactstobalancetheeffectofthetime-meanflow.IntheAtlanticandAlaskablockingcases,however,theadvectionofmeanflowtendstoflowthePVloweastward.ThePVtransferbytransienteddiesactstoflowpotentialvorticitylowtothewesternpartoftheblockingridgesandalsotobalancethetime-meanflow’seffect.Thus,inthelattertwocases,itisthetransferbythetransienteddiesthatactstomaintaintheblockings.
简介:Discussionsarecarriedoutontheverticaldiscretizationofcurrentatmosphericmodels.Itispointedoutthatthereexistproblemsintheintegrationofthehydrostaticequationandthecomputationofverticaladvection,verticaldiffusionandsoon.Thensomepossiblewaysforsolvingoralleviatingthemaresuggested.Finally,thechoiceofverticalcoordinateandbasisfunctionsisdiscussed.
简介:ALandSurfaceModel(IAP94)forClimateStudiesPartI:FormulationandValidationinOf-lineExperiments①DaiYongjiu(戴永久)andZengQingcun(曾庆存...
简介:以西南澳类季风环流为出发点,考察了IPCC第四次评估报告AMIP提供的12个大气环流模式对于澳大利亚西南部(SWWA)地区降水的季节演化特征,西南澳类季风环流(SWAC)的季节特征、季节演化、对应的异常环流型及其年际变率的模拟性能进行了评估。结果表明,除了NCAR—CAM3模式以外,其余模式均能较好的再现SWWA地区近地层盛行风向季节性反转及副热带高压脊线的季节性跳跃特征。对副热带高压脊线的季节演化特征,虽然大部分模式可以模拟出其季节移动特征,但是对于副热带高压脊线的北跳、南撤时间、到达位置和年内振幅均不能很好模拟。其次,除了NCARCAM3,其余模式基本能刻画出与SWAC相联系的异常环流型结构;而对于SWAC的年际变率,基本所有模式均不能较好模拟。整体权衡,GISSMODELER在模拟SWAC环流的年际变率方面表现出较其它模式稍好的性能,大致可以模拟出与观测SWAC相似的特征,对SWWA地区的冬季降水显示出了与观测相似的显著影响。
简介:UsingaregionalclimatemodelMM5nestedtoanatmosphericglobalclimatemodelCCM3,aseriesofsimulationsandsensitivityexperimentshavebeenperformedtoinvestigatetherelativeLastGlacialMaximum(LGM)climateresponsetodifferentmechanismsoverChina.Modelsimulationsofthepresentday(PD)climateandtheLGMclimatechangeareingoodagreementwiththeobservationdataandgeologicalrecords,especiallyinthesimulationofprecipitationchange.UnderthePDandLGMclimate,changesofearthorbitalparametershaveasmallinfluenceontheannualmeantemperatureoverChina.However,themagnitudeoftheeffectshowsaseasonalpattern,withasignificantresponseinwinter.Thus,thisinfluencecannotbeneglected.DuringtheLGM,CO_2concentrationreacheditslowestpointto200ppmv.ThisresultsinatemperaturedecreaseoverChina.TheinfluencesofCO_2concentrationonclimateshowseasonalandregionalpatternsaswell,withasignificantinfluenceinwinter.Onthecontrary,CO_2concentrationhaslessimpactinsummerseason.Insomecases,temperatureevenincreaseswithdecreasinginCO_2concentration.Thistemperatureincreaseistheoutcomeofdecreaseincloudamount;henceincreasethesolarradiationthatreachedtheearth'ssurface.Thisresultsuggeststhatcloudamountplaysaveryimportantroleinclimatechangeandcoulddirecttheresponsepatternsofsomeclimatevariablessuchastemperatureduringcertainperiodsandovercertainregions.IntheTibetanPlateau,thetemperatureresponsestochangesoftheabovetwofactorsaregenerallyweakerthanthoseinotherregionsbecausethecloudamountinthisareaisgenerallymorethanintheotherareas.Relativetothecurrentclimate,changesinorbitalparametershavelessimpactontheLGMclimatethanchangesinCO_2concentration.However,bothfactorshaveratherlesscontributionstotheclimatechangeintheLGM.About3%-10%changesintheannualmeantemperaturearecontributedbyCO_2.
简介:这份报纸调查与轨道预报了使用全球/地区性的吸收和预言系统(葡萄)的热带气旋(TC)联系的错误的可能的来源。葡萄预报在2008和2009个季节期间在西方的诺思太平洋盆为16landfallingTC被做,与72个小时的预报长度,并且使用缺省起始的条件(initials,此后),它从NCEP-FNL数据集,以及ECMWFinitials。预报与ECMWF预报相比。当与缺省initials相比使用ECMWFinitials时,结果证明在大多数TC,GRAPES预报被改进。与ECMWFinitials相比,缺省initials生产更低的紧张TC和更低的紧张副热带的高度,而是更高的紧张南亚高度和季风马槽,以及更高的温度但是在TC中心的更低的特定的湿度。有ECMWFinitials在并且在在起始的时间的TC中心附近的geopotential高度和风地的代替被发现是改进预报的最有效的方法。另外,在预报精确性显示出最大的改进的TC通常在TC紧张有最大的起始的无常并且通常在加强的阶段。结果为用葡萄做的TC轨道预报表明起始的紧张的重要性,并且显示模型在比TC的腐烂的阶段描述加强的阶段更好。最后,改进的限制显示与葡萄预报联系的模型错误可以是landfallingTC的差的预报的主要原因。因此,模型错误的进一步的考试被要求。
简介:In2005,significantrainfallreinforcementandseveredisasterwasinducedbytropicalcyclone(TC)TalimafteritmadelandfallontheeastofChina.Observationalanalysesshowthatithasrelationshipwithcoldairintrusion.Forinvestigatingtheimpactofcoldairintensity,wemakeuseofWeatherResearchandForecasting(WRF)model,thesynthesizerofNCEP/NCARreanalysisdataandJapanregionalspectralmodeldata,tocarryoutnumericalexperiments.Resultsshowthatrainfallreinforcementoccursinallexperiments.Differentintensityofcoldaircanmodifytherainfalldistributionandintensitysignificantly.Intherainfallcenter,theincrementmaximumofrainfallistwiceaslargeasthatoftheminimum.Moderatecoldairintrusionmayresultinthestrongestrainfallreinforcement.Differentcoldairintensitycanleadtodifferentmotionoflow-levelconvergencelinesandfronts.Thereisagoodrelationshipbetweentherainfallregionandtheeasternpartofthefront.Ononehand,strongcoldairweakenstheTCintensitybyitsintrusionintotheTCcenterandresultsinweakconvergenceandaconvergentzoneandarainbandshiftedsouthward.Ontheotherhand,weakcoldairreducestheconvergenceandmovestheconvergentzoneandrainbandnorthward.Moderatecoldairintrusionmaintainsstronglow-levelconvergenceandhigh-leveldivergence,keepingstrongupwardmotionovercertainregions.Consequently,therainbandbeginstostagnateandrainfallreinforcesabruptlytherein.
简介:利用多种常规和非常规高时空分辨率的观测资料,对2015年通榆县两次龙卷过程(5月31日和6月8日,分别简称为“531”龙卷和“608”龙卷)形成机制进行详细对比分析。结果表明:直接影响系统均为东北冷涡前部的次天气尺度短波槽或切变线,强对流层中层偏西急流使700—500hPa温差大值区东移,低空西南急流使低层湿区显著北伸,叠加在温差大值区之下,龙卷发生在湿舌边缘多尺度系统叠加区附近;但“531”龙卷急流风速、700—500hPa温差及925hPa露点温度均明显高于“608”龙卷,且850hPa切变线和负变压区的存在导致辐合上升运动更强,龙卷强度更强。两次龙卷过程发生前对流有效位能均超过1500J·kg-1,低层存在逆温,抬升凝结高度较低,但湿层较薄,辐合切变线或冷锋是龙卷直接触发机制,且“531”龙卷辐合线两侧有明显风速辐合,为对流风暴发展提供了强入流。两次过程中“531”龙卷过程为强水平风垂直切变下的超级单体龙卷,“608”龙卷过程为弱水平风垂直切变下的非超级单体龙卷。
简介:Basedontheexistingland-surfaceschemesandmodels,animprovedLand-surfaceProcessModel(LPM-ZD)hasbeendeveloped.Ithasthefollowingmajorcharacteristics:(1)Thecombinationofphysicalequationsandempiricalanalyticalformulaeareusedtoconstructthegoverningequationsofsoiltemperatureandmoisture.Higherresolutionofmodellevelandphysicalequationsareadoptedfortheuppersoillayers,andforthelowersoillayers,lowerresolutionofmodellevelisadoptedandempiricalanalyticalformulaeareused.(2)Inlandsurfacehydrologicalprocess,thesub-griddistributionofrainfallanditseffectsaretakenintoaccount.(3)Asimplesnowcoversubmodelhasbeenused,whichincludeseffectsofsnowcoveronsoilthermodynamicsandhydrology,aswellasalbedo.Byuseofthismodelandthreegroupsofpointobservationdata,aseriesof“off-line”testshavebeencarriedout.Thesimulationresultsindicatethatland-surfaceprocessmodelhasgoodperformanceandcanwellsimulatediurnalandseasonalvariationoflandsurfaceprocessesformanykindsoflandsurfacecovers(forest,grass,cropsanddesert)indifferentclimatezone.Theresultssimulatedbythemodelareconsistentwiththeobservations.Later,byuseofonegroupofobservationdataandthemodel,aseriesofsensitivityexperimentshavebeendone.Itisshownthatthemodelismuchsensitivetosomeparameters,suchasinitialsoilmoisture,vegetationphysicalparametersaswellastheproportionofthegridcoveredwithrain.Thereforeitismuchimportantforland-surfaceprocessmodeltodefinetheseparametersasaccuratelyaspossible.