ECMWF 数值预报模式简介ppt课件

,ECMWF数值预报模式简介,1,气象预报的四个方面问题,当前的天气或气候信息完备的综合观测系统完善的观测系统；资料信息识别；资料的综合处理（同化）天气或气候的演变规律从资料得到新认识从资料得到新认识；反映大气运动数学物理规律的微分方程组。外力和强迫的变化地形和边界强迫；太阳常数；引力等从已知预报未来的手段完备的数值模式；承载数值模式计算、显示和通讯平台驾驭观测、资料分析和数值模式发展和应用的人才队伍,2,大气圈,水圈,冰晶圈/冰冻圈,生物圈,岩石圈,人类圈,3,纷繁多样数值预报产品-什么会有差别？,4,分辨率不同模式的表述的物理过程有差异计算方案、网格、变量分布等再分析资料分析的初值能代表大气实况吗？,5,OrographyandResolutions,GSMT213(60km),RSM(20km),MSM(10km),Orographiceffectsarebettercapturedbyhigherresolutionmodels.ThesurfaceparameterssuchasTsurfmightbepredictedmorerealisticallybythosemodels.,6,ECMWF致力于2016-2025数值预报发展战略：利用集合预报方法提前2周预报高影响天气事件提前4周，无缝隙地预报大尺度系统形势和系统移动提前1年预测全球范围的异常状况,7,研究和更丰富的知识基于集合预报的分析和预报技术如何实现目标：ObservationsHighresolutionensembleEarth-systemScalabilityFundingPeople（引自ErlandKlln，“Earthsystemmodellingforseamlessprediction”ECMWFAnnualSeminar2016）,8,FutureEarthSystemmodelandassimilationdevelopmentsErlandKlln,ECMWF,9,10,Oceanmodel(NEMO),Wavemodel(ECWAM),Atmosphericmodel(IFS),Airdensity,Gustiness,Neutralwind,Roughness,Currents,Seasurfacetemperature,Allconfigurations,EnsembleFC,Solarandnonsolarfluxes,E-P,Towardsafullycoupledsystem(currentlyonlyoperationalinEPS),ORCA1_Z42,TCo1279/TCo639,14km/28km,9km/18km,Ensemblesystemsonly:-Mediumrangeforecast-Monthlyforecast-Seasonalforecast,EveryIFStimestep,Everycouplingtimestep(1or3hours),Singleexecutable,11,Oceanmodel(NEMO),Wavemodel(ECWAM),Atmosphericmodel(IFS),Airdensity,Gustiness,Neutralwind,Roughness,Turbulentenergy,Stokesdrift,Currents,Seasurfacetemperature,Allconfigurations,Stress,EnsembleFC,Solarandnonsolarfluxes,E-P,Towardsacoupledsystem,ORCA1_Z42,TCo1279/TCo639,14km/28km,9km/18km,Singleexecutable,Operationalfromday0since2013,12,Oceanmodel(NEMO),Iceconcentration,Wavemodel(ECWAM),Atmosphericmodel(IFS),Airdensity,Gustiness,Neutralwind,Roughness,Turbulentenergy,Stokesdrift,Currents,Icemodel(LIM),Seasurfacetemperature,Iceconcentration,Allconfigurations,Stress,EnsembleFC,futureoperational,Solarandnonsolarfluxes,E-P,Towardsacoupledsystem,ORCA0.25_Z75,Addingactiveseaicemodel,Implementation:End2016.,Singleexecutable,13,Callingsequenceofthesingleexecutable,14,Simplifiedflowchartofthecoupledmodel,heretwotimestepsareshown.Inreality,IFS/WAMcouplingeveryIFStimestep,butCalltoNEMOeveryhour(or3hours)withaveragedaccumulatedfluxes.,ImpactofResolutionontropicalcycloneforecast,ForinstanceTyphoonHaiyan:forecastsfrom4th,5thand6thNovember2013,0UTCallfromoperationalanalysis.,Black:estimatedfromobservationsRed:oldoperationalEnsembleresolution(32km)Blue:oldoperationalHRESconfiguration(16km)Green:experimental:newHRESconfiguration(10km),TyphoonHaiyanatpeakintensityonNovember7,2013,15,ImpactofCouplingontropicalcycloneforecast,ForinstanceTyphoonNeoguri:forecastsfrom6July2014,0UTC,Black:estimatedfromobservationsGreen:oldoperationalHRESconfiguration(uncoupled)(16km)Red:experimental:16kmcoupledtoNEMO(ORCA025_Z75)Blue:16kmcoupledtoNEMO+newphysics,minMSLP(hPa),900,950,NeoguriaffectingOkinawaonJuly8,2014,16,Climatereanalysesforthecoupledearthmodel,ECMWFcoupledEarthmodelformedium-rangeweatherforecasting,Newcoupledassimilationsystem(CERA)forthecoupledEarthmodel:atmosphericandoceanobservationsassimilatedsimultaneouslyoceanobservationscanimpactatmosphericestimateandconverselyCERA-20Creanalysisinproduction(1900-2010),KarlandTrenberth2003,Coupledassimilationsystem(CERA),EDAvariationalapproachwitha24-hourwindowthatassimilatessimultaneouslyatmosphericandoceanobservations,coupledmodelcomputesobservationmisfitsineachouteriteration,atmosphericandoceanincrementsarecomputedinparalleltocorrecttheinitialstate,SSTcomputedinNEMOandconstrainedbyrelaxation,analysisdynamicallyconsistentwithrespecttothecoupledmodel,Conclusions:,ECMWFhasacoupledatmosphere-wave-oceancirculationforecastingsystem,currentlyoperationalintheEnsemblePredictionSystem.Workisongoingonusingahigherresolutionoceancomponents(ORCA025z75)plannedforendof2016intheEnsembleforecastsandlaterintheHighresolutionsystem.Thereisaclearbenefitincouplingthedifferentmodels,butitcreatesnewchallengesindeterminingwhatphysicalparametersneedtobeexchanged.Furthermore,modelparameterisationsmightneedrevisiting.,19,EC模式动力框架,垂直采用坐标，U=ucos；V=vcos,20,21,22,对比球坐标系中的基本方程组,曲率项,23,重力不是指向地心，等位势面也不是球面。,24,非静力学模式静力学模式,静力学平衡：运动的垂直尺度远小于水平尺度的情况下成立,模式的分类,25,基于连续方程的模式分类,非静力学模式根据模式中是否包含声波，分为：滞（非）弹性（anelastic)模式假定大气不可压，滤掉声波弹性(elastic)模式大气可压、由散度预报气压的变化，但声波需要特殊的处理,26,根据连续方程的近似程度，滞弹性和弹性模式又可进行不同的分类：,滞弹性模式,不可压缩模式,滞弹性模式,弹性模式,准可压模式,完全可压模式,27,数值计算方案,大气运动方程组是一套复杂的非线性方程组，目前，还没有理论解存在，只能借助数值方法求解。数值方法有很多，目前气象上用的主要用的是差分方法、谱方法、有限元法等。差分方法：就是在离散的网格点上，以差商代替微商，求解微分方程的方法。,28,关于有限差分与谱方法的图例,有限差分,谱方法,29,30,|n-1nn+1,从物理上考虑，差分的精度还与采样点密即网格，与要素在采样区的变化分布有关。即采样数据是否能有代表性。,中央差,精确值,采样值,混淆误差,31,离散网格所能表示的最短波长上表中当L/x=2时，即两倍格距波，R=0，误差100%，因此，离散网柜完全不能表示两倍格距以下的短波。如格距为100km，则你只能预报出200km以上的天气系统。,1.5倍格距波,3倍格距波,最短的波，2倍格距波,1.5倍格距波被当成3倍格距的波混淆误差会把小于2倍格距的波歪曲为2倍格距以上的波。因此混淆误差主要集中在24倍格距间。预报员会在什么情况下遇到“混淆误差”？,32,拉格朗日和半拉格朗日方法,拉格朗日和半拉格朗日方法是从另外一个角度来求取平流方程的解。有解析解：不失一般性，考虑情况下平流方程的解。,可以证明下述两个式子是成立