synoptic systems interacting with the rocky mountain barrier observations and theories clemens spensberger资料.pdf

该【synoptic systems interacting with the rocky mountain barrier observations and theories clemens spensberger资料 】是由【小舍儿】上传分享，beplayapp体育下载一共【35】页，该beplayapp体育下载可以免费在线阅读，需要了解更多关于【synoptic systems interacting with the rocky mountain barrier observations and theories clemens spensberger资料 】的内容，可以使用beplayapp体育下载的站内搜索功能，选择自己适合的beplayapp体育下载，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此beplayapp体育下载到您的设备，方便您编辑和打印。:..AMERICANMETEOROLOGICALSOCIETYMonthlyWeatherReviewEARLYONLINERELEASEThisisapreliminaryPDFoftheauthor-producedmanuscriptthathasbeenpeer-,ithasnotyetbeencopyedited,formatted,,distributed,andcited,:-D-16-,pleaseusethefollowingfullcitation:Spensberger,C.,,,2016:SynopticSystemsinteractingwiththeRockyMountainBarrier::-D-16-,inpress.?2016AmericanMeteorologicalSociety:..LaTeXFile(.tex,.sty,.cls,.bst,.bib)ClickheretodownloadLaTeXFile(.tex,.sty,.cls,.bst,.bib)cialAMSLATEXtemplate1SynopticSystemsinteractingwiththeRockyMountainBarrier:2ObservationsandTheories3ClemensSpensbergerGeophysicalInstitute,UniversityofBergen,andBjerknesCentreforClimateResearch,Bergen,Norway4JosephEggerMeteorologicalInstitute,UniversityofMunich,Germany5ThomasSpenglerGeophysicalInstitute,UniversityofBergen,andBjerknesCentreforClimateResearch,Bergen,NorwayCorrespondingauthoraddress:,GeophysicalInstitute,UniversityofBergen,,5007Bergen,-mail:clemens.******@:..6ABSTRACTpositeanalysisforstrongsea-levelpressureperturbationsotheWestCoast8ofNorthAmerica,theevolutionoflarge- ned10byavoidingmultiplecountingofeventsandextendedbyincludingpotentialvorticity,vertical11motion,,,,theseanomaliescontributetothesea-,potentialvorticityexhibitsabipolarstructure17withlobesoverthereferencepointandovertheCordillera, ndingsdi,thesefeaturescanberecoveredifasix-dayhigh-pass24 :..-28ingeastwardthroughtheNorthPaci cstormtrackregion,leadingtoamaximumofcy-29clolysisupstreamofNorthAmericanWestCoast,inparticularintheGulfofAlaska,anda30distinctminimuminsurfacecyclonefrequencyovertheRockyMountains(.,Wernliand31Schwierz2006,andreferencestherein).Casestudiesaswellasnumericalhindcastssuggest32thatimpingingcyclonescansplit,wherepartsofthesystemremainwestofthebarrier(.,33SteenburghandMass1994).Otheranalysesindicatethattheupperpartoflowpressuresys-34temsisdeformedwhencrossingthebarrier(PalmenandNewton1969;Davis1997).Several35studiesalsopinpointmaximaofcyclogenesisfrequencyeastoftheRockyMountainslinked36tocyclonescrossingthebarrier(HessandWagner1948;McClain1960;Steenburghand37Mass1994;Davis1997;).However,thesituationattheWestCoasthas38mainlybeeninvestigatedwithanemphasisonmesoscalephenomenalikesurgesofmarine39airaectingtheweatheralongthecoast(;MassandBond1996).40Usinghigh-pass ltereddata,Wallaceetal.(1988,hereafterWLB)-,44lowpressuresystemscrosstheCordilleraandappeartomovesouthwardforlagslargerthan45+1dayandexhibitasouthwestwardtiltwithheight().Incontrastto46laterstudies(.,SteenburghandMass1994),,(1989)-levelpressure,butdid51notincludeothervariablessuchaspotentialvorticity(PV),however,hasbeendiscussedintensivelyforthe2:..53Alps(.,PichlerandSteinacker1987),but,toourknowledge,,SpensbergerandSpengler(2014)showedthatow55diversionaroundblockingorographyisassociatedwithacharacteristicdeformationpattern,,,(Smith1979;HoltonandHakim2013,theory65T0,seealsoTable1).Muchofthelessconceptualworkonthecrossingisbasedonthe66quasi-geostrophic(QG)framework,,.(1987,1993)(strengthening)ofacyclone(anticyclone)overthe72topofthemountainandacorrespondingstrengthening(weakening)ontheupstreamand73downstreamside,providedthestationarywaveissymmetricwithrespecttothemountain74ridge(T1).Davis(1997,T2),Bannon(1992)andDavisandStoelinga(1999)re nedthelowerboundarycon-77ditionforQGtheorysothattheperturbationscanalsointeractdirectlywiththemountain,78wherebyupslope(downslope)owcreatesanticyclonic(cyclonic)vorticity(T3).Davisand79Stoelinga(1999)alsodiscusssecondordereectsinanexpansionwithrespecttomountain3:..80height(T4).BuzziandTosi(1989)studiedlinearnormalmodesofbaroclinicowsover81meridionallyelongatedmountainmassifsandfoundgoodcorrespondencewithpointcorre-82lationmapsanchoredattheAmericanWestCoast(T5).Theyusedaselectioncriterion83thatrestrictsthe500hPageostrophicowtonear-(1995,T6)introduced84atwo-dimensionalthree-,a85positiveupper--88tionalstudiesanddiscussthevalidityofthetheoriesintroducedabove(Table1).WhileWLB89onlycorrelatedgeopotentialheightperturbations,wealsorelatetemperature,PV,deforma-90tion,(2005,seealsofurtherreferencestherein),whoinvestigatedstrongcyclone92eventsintheWestPaci candWirthandEichhorn(2014),,-trains96andcyclogenesis,-hourlyERA-Interimdataat0:5resolutionforthetimeperiod1001979{2014obtainedfromtheEuropeanCentreforMediumRangeWeatherForecasting101(ECMWF;).FollowingChang(2005)andWirthandEichhorn(2014),we102selectvaluesofsea-levelpressurepatareferencepoint(45N,127W)suchthatpisss103within5%ofthelowest(highest)valuesobservedinwinter(December-February,DJF).The104correspondingindextimeseriesCforcyclonic(Aforanticyclonic)=1(An=1)at4:..105thetimestepofminimum(maximum)sea-levelpressurewithinaperiodofconsecutivetime106stepsexceedingthethreshold.=0(An=0).Thesubscriptn107denotesthediscretetimeswithintervalt=6hoursonwhichtheERA-(maximum)procedureratherthanmerelyapplyinga109thresholdtoavoidincludingmultipletimesofoneeventarounditspeakintensity.(C;S;),com(A;S;)ofCandA,respectively,withS111representingtheanomalyorthefullvalueofaselectedvariableatlag=m(C;S;)=CnSn+m;(1)NCn= ,=190cycloniceventsandNA=,positeselectioncriteriato6-day116high-pass lteredsea-levelpressure,inthefollowingcalledthe paredtotheun lteredones,we119considerthesenumberstobeinthesameoverallrange, cationofacycloneorananticyclonerequirestolook122atthetotalsea-,positivesea-levelpressureanomaliesarerarelycoincidentwithasurfacehighnear124theWestCoast,becausetheAleutianlowissodominantinthemeansea-levelpressure eld125().Thus,weareratherstudyinganomaliesthatpropagatethroughamean Nand49N,respectively,-129thermore,werepeatedouranalysisusinggeopotentialon300hPa,500hPa,and1000hPaas130wellaspotentialvorticityon315Kand330Kinsteadofsea-levelpressureasbasisforthe5:..positesbasedonsea-levelpressure132ortheaforementionedmid-andupper-troposphericvariablesisthattheanomalyattheref-133erencepointispartofawavetrainforthemid-andupper-erence,ourdiscussionandconclusionsarenota,werepeatedtheanalysisfordi.(2013,2015),weusedtherespectivepositiveandnegativephasesofthe137Paci c-NorthAmericapattern(PNA)andtheWestPaci cpattern(WP)+case(notshown),positesdonotdi-levelpressure,temperature,geopotentialheight,PV,144deformation,-meansea--meansea-levelpressureinthenorthernPaci cisdominated147bytheAleutianlowandthesubtropicalhighpressurebeltfurthersouth,({8)is149locatednearthelow'ssou