Year-round North Atlantic-European Weather Regimes in ERA5 reanalyses

RReadme.mdforZenodoDataset“Year-roundNorthAtlantic-Europeaneadme.mdforZenodoDataset“Year-roundNorthAtlantic-European WeatherRegimesinERA5reanalysis”WeatherRegimesinERA5reanalysis” IInformationnformation ddoi:10.5281/zenodo.17080146oi:10.5281/zenodo.17080146 aauthorcontact:ChristianGramsuthorcontact:ChristianGramsweatherr[email protected]weatherr[email protected] DDate:12September2025ate:12September2025 VVersion:1.0ersion:1.0 DDescriptionescription Thisdatasetcontainstheoriginalfilesforalife-cycledefinitionof7+1year-roundNorthAtlantic-Europeanweatherregimesfollowingthe definitionofGramsetal.(2017)doi:10.1038/nclimate3338,updatedtoECMWFERA5reanalysisasdescribedinHauseretal.(2024)doi:10.5194/ wcd-5-633-2024.ItissupplementarydatatothepublicationGrams(2025,ItissupplementarydatatothepublicationGrams(2025, inpreparationforWeatherClim.Dynam.inpreparationforWeatherClim.Dynam. ))whichwillcontainanin-depth technicalexplanationandanalysisofkeycharacteristicsandtrendintheseregimes.Akeynoveltyintheregimedefinitionaretheobjectively identifiedregimelifecycleswhichallowprocess-orientedpredictabilitystudies(e.g.Hauseretal.2024). Thedatasethasbeenoriginallycomputedforthedataperiod1979-2019.UsingthebackwardextensionofERA5(Societal.,2024,doi:10.1002/qj. 4803),ithasbeenextendedto1950.Usingthenear-realtimeupdateitisextendedforwarduntil20250726_21inreleaseV1.0.Forthelifetimeof ERA5itisplannedtocontinouslyupdatethedatairregularlyatleastonceperyearanduponrequest.Futureupdateswillensurefullbackward compatibility. ThisdatasetalsocontainsaJuypternotebookwithexamplesofsimpledataanalysisinpython.Thenotebookaimstofacilitateaneasystartofthe workwiththedata.ChristianthanksSeraphineHauserandDominikBüelerforhelpwithcodingthisipynbandreformattingthedataforeasier accessibility.Formoretechnicalinformation,pleaserefertotheremainderofthisReadme.md.Usersareadvisedtogetfamiliarwiththis Readme.mdpriortousingthisdata. RReferenceseferences Bell,B.,Hersbach,H.,Simmons,A.,Berrisford,P.,Dahlgren,P.,Horányi,A.,etal.:TheERA5globalreanalysis:Preliminaryextensionto1950.QJR MeteorolSoc,147(741),4186–4227,doi:10.1002/qj.4174,2021. Grams,C.M.:Alife-cycledefinitionofyear-roundweatherregimes:characteristicsandtrendsintheNorth-AtlanticEuropeanregion, in preparationforWeatherClim.Dynam. ,2025. Grams,C.M.,Beerli,R.,Pfenninger,S.,Staffell,I.,andWernli,H.:BalancingEurope’swindpoweroutputthroughspatialdeploymentinformedby weatherregimes,Nat.Clim.Change,7,557–562,doi:10.1038/nclimate3338,2017. Hauser,S.,Teubler,F.,Riemer,M.,Knippertz,P.,andGrams,C.M.:LifecycledynamicsofGreenlandblockingfromapotentialvorticityperspective, WeatherClim.Dynam.,5,633–658,doi:10.5194/wcd-5-633-2024,2024. HersbachH,BellB,BerrisfordP,etal.:TheERA5globalreanalysis.QJRMeteorolSoc,146:1999–2049.doi:10.1002/qj.3803,2020. Soci,C.,Hersbach,H.,Simmons,A.,Poli,P.,Bell,B.,Berrisford,P.,etal.:TheERA5globalreanalysisfrom1940to2022.QJRMeteorolSoc, 150(764),4014–4048,doi:10.1002/qj.4803,2024. UUSEOFTHISDATA:SEOFTHISDATA: AfullexplanationofthemethodandkeycharacteristicsoftheregimesandtrendsofregimelifecycleswillbeprovidedinGrams(2025, in preparationforWeatherClim.Dynam. ).Sofarthemethodologyhasbeendescribedanddataalreadyusedinthe#LSDPatKITteams’svarious papers.ThebestavailabledescriptionsofarcanbefoundintheinitialpaperGramsetal.2017doi:10.1038/nclimate3338(methodologysection andsupplement)andinHauseretal.2024doi:10.5194/wcd-5-633-2024.ThelatteralsoexplainstheslightmodificationswiththeupdateonERA5. PleasecitethesepaperalongwiththerepositoryversionofGrams(2025)inthemeantimeanduntilthelatterisfullypublished. Previousworkusesadistinctcolourschemeforeachoftheregimes,whichreflecttherelationbetweenregimes.Wekindlyasktousethiscolour schemeandthecorrectorderofregimesasdescribedbelow.Forconveniencethedatarecordsprovidedinthisdatasetarealreadypre-sortedin thisorder.WeprovideRGBtripletsaswell.Thisensures,thatreadersrecognizethelinkofyourstudytootherstudiesusingthisregimedefinition. Orderandcoloursarebrieflyexplainedbelow,andinmoredetailfurtherdowninthisReadme. ooriginalcolourschemeandweatherregimedataindexincorrectorderriginalcolourschemeandweatherregimedataindexincorrectorder abbreviationofregimesinpreferredorderanddatafilesabbreviationofregimesinpreferredorderanddatafiles“ATZOScTrAREuBLScBLGLno” correspondingregimeindicesincorrespondingregimeindicesin texttext filesfiles“12345670” wr_metadata_rgb_new_colors.txt LongnameNameColorRGB AtlantictroughATindigo(75,0,130) ZonalZOred(255,0,0) ScandinaviantroughScTrdarkorange(255,140,0) AtlanticridgeARgold(255,215,0) EuropeanblockingEuBLyellowgreen(154,205,50) ScandinavianblockingScBLdarkgreen(0,100,0) GreenlandblockingGLblue(0,0,255) Noregimenogrey(128,128,128)  VVersionsersions VV1.01.0 Initialreleasecontainingtheoriginalregimedefinitionandtheexpansiontotheperiod19500111_00-20250726_21. CContentofdatasetontentofdataset detailedexplanationsfollowbelow ./ Readme.mdthisreadmefile ./scripts_first_steps WR_read_example.ipynbJupyternotebookwithfiveexamplesfordatausage WR_read_example.htmlJupyternotebookasHTMLwithoutputafterrunningsuccessfully fct_wrera_db.pyfunctionforreadingregimeattributiondata,usedinJupyternotebook fct_wrlcera_db.pyfunctionforreadingregimelifecycledata,usedinJupyternotebook ./wr_data/thefullregimedata WR_LCattribution.txtweatherregimeattributiontimeseries WR_lifecycle_information_*.txtweatherregimelifecycles WRI_projections.txtweatherregimeindextimeseries WRI_std_params.txtmean&stddev.ofprojectionforweatherregimeindexIWRcalculation normweights_Z0500.txtcalendartimedependentnormalisationweightsfornormalisingZ0500anomalies EOFs_WRs.ncEOFpatternsas2DfieldsinnetCDFformatandnormalizationweights Clusters_WRs.ncnon-normalisedregimepatternsinnetCDFformatonglobaldomain Normed_Z0500-patterns_EOFdomain.ncnormalisedregimepatternsinnetCDFformatinEOFdomainneededforprojection ./example_data/additionaldatafor.ipynbexamples CLIM_Z@500_year_1979-2019.nc2DfieldofmeanZ500year-round1979-2019 Z_N161_20250601_00.ncLanczos-filteredZ500datafor20250601_00  DDatadescriptionforERA5year-round7regimelifecycledefinition.atadescriptionforERA5year-round7regimelifecycledefinition. CConfigurationonfiguration 1979-2019referenceclimatologyforZ500anomalycomputationandIWRscaling 10-daylow-passfilter(Lanczos) period19790111_00–20191231_21usedforEOFclusteringandoriginallifecycledefinition 7leadingEOFsexplaining74,4%ofvariance regimeprojection(regimeindexIWR),andlifecyclesextendedtocoverthedataperiod19500111_00-presentwithirregularupdatesat leastonceperyearduringERA5lifetime CChangestoearlierERA-Interimdefinition(Gramsetal.2017)hangestoearlierERA-Interimdefinition(Gramsetal.2017) normalizationweightsusingthe‘lat-weightedspatialmean(inEOFdomain)ofthegrid-pointbased30dtemporalstddevofZ0500’.This normalizationweightsusingthe‘lat-weightedspatialmean(inEOFdomain)ofthegrid-pointbased30dtemporalstddevofZ0500’.This improvessummerregimeidentification. EOF-clusteringperformedfor6hdata(insensitiveto6h,12,48htimeinterval) IWR(projection)computedfor3hdata Z500normweightfor3,9,15,21UTCusesnormweightof0,6,12,18UTC WWeatherregimeattributionandregimeindextimeserieseatherregimeattributionandregimeindextimeseries RRegimeAttributiontimeseriesegimeAttributiontimeseries ThefollowingTEXTfilecontainsthetimeseriesoftheunambigousattributionofeachthree-hourlytimesteptooneofthesevenregimesorno regimefollowingeithertheoriginalcontributiontotheEOFclusters(only1979-2019),themaximumstandardisedregimeprojection(regimeindex IWR),orthefulllifecycledefinition. WR_LCattribution.txtWR_LCattribution.txt WRindexafterMichelandRiviere(2011)offiltereddataN161lowpass>10days,Z0@500,normed:intersectiontimes,OVERLAPLCsallowed ----------------------------------------------------------------------------------------------------------------------------------------- ClusterClassIndex0-7:noATZOScTrAREuBLScBLGL ----------------------------------------------------------------------------------------------------------------------------------------- timeinhsince19790101_00|YYYYMMDD_HH|EOFattribution|maxWRindex|lifecycleWRindex ----------------------------------------------------------------------------------------------------------------------------------------- -25396819500111_00060 -25396519500111_03060 -25396219500111_06060 ..... ..... ..... 24019790111_00333 24319790111_03033 24619790111_06333 24919790111_09033 ..... ..... .....  Thefilecontains5columns,the5thismostrelevant: 1. hoursince19790101_00 2. dateinyyyymmdd_hh 3. eofattribution->timestepcontributingtoclusterXYbasedonEOFs(onlyEOFclusteringperiod11.1.1979-31.12.2019onlyfor061218UTC times,othertimesare“0”) 4. maxWRindex(MichelandRivière,2011).->basedonweatherregimeprojectioninphysicalspace 5. LCattributionbasedonWRindex(MichelandRivière,2011).->THISISTHELIFECYCLEattributionINCLUDINGNOREGIME.USETHISFOR MOSTPURPOSES. RRegimeindicesandregimeorder:egimeindicesandregimeorder: Thedataindices0-7 inTEXTfiles refertothefollowingregimes:NAME(ABBREVIATIONINFILES) 0-7:noATZOScTrAREuBLScBLGL 0=noregime[only5thcolumn]1=AtlanticTrough(AT)2=Zonalregime(ZO)3=ScandinavianTrough(ScTr)4=AtlanticRidge(AR)5=EuropeanBlocking (EUBL)6=ScandinavianBlocking(ScBL)7=GreenlandBlocking(GL) AsintheJupyternotebook,pleasewriteyourcodesothattheregimesappearsortedinthefollowingway(thiswillgrouprelatedregimes).PleasePlease alsousethisorderwhenplottingpanels/groupingregimes.alsousethisorderwhenplottingpanels/groupingregimes.Reason:relatedregimesaregroupednexttoeachother,andcyclonic/blockedare groupedtogether.Inallpreviousworksweusethisorder.MoreinformationonthereasoninginGrams(2025). abbreviationofregimesinpreferredorderanddatafilesabbreviationofregimesinpreferredorderanddatafiles“ATZOScTrAREuBLScBLGLno” correspondingregimeindicescorrespondingregimeindices“12345670” Wealsokindlyaskyoutousethefollowingcolourcodesforcolouringregimesinplots.Reasonagainisthatthemixedcoloursreflectrelations betweenregimes,andthisisthecoluorschemehasalreadybeenwidelyused(betterintercomparisonofstudies).TheRGBTableandpython matplotlibnamesusedinBueeleretal.2021doi:10.1002/qj.4178andOsmanetal.2023doi:10.1002/qj.4512arelistedbelowandanexample matplotlibnamesusedinBueeleretal.2021doi:10.1002/qj.4178andOsmanetal.2023doi:10.1002/qj.4512arelistedbelowandanexample providedintheJupyternotebook. ooriginalcolourschemeriginalcolourscheme wr_metadata_rgb_new_colors.txt LongnameNameColorRGB AtlantictroughATindigo(75,0,130) ZonalZOred(255,0,0) ScandinaviantroughScTrdarkorange(255,140,0) AtlanticridgeARgold(255,215,0) EuropeanblockingEuBLyellowgreen(154,205,50) ScandinavianblockingScBLdarkgreen(0,100,0) GreenlandblockingGLblue(0,0,255) Noregimenogrey(128,128,128)  ccolourblindfriendlycolourschemeclosetooriginalolourblindfriendlycolourschemeclosetooriginal WerecommendthissettingforbetterdistinctionofScTr-EuBLandZO-ScBLusedinGerighausenetal.(2025,inpress)doi:10.48550/arXiv. 2408.04302.Testedwithhttps://colororacle.org/. LongnameNameColorRGB AtlantictroughATindigo(75,0,130) ZonalZOrose(204,102,119) ScandinaviantroughScTrsand(221,204,119) AtlanticridgeARgold(255,215,0) EuropeanblockingEuBLteal(68,170,153) ScandinavianblockingScBLgreen(17,119,51) GreenlandblockingGLblue(0,0,255) Noregimenogrey(128,128,128)  ffullcolourblindfriendlyschemeullcolourblindfriendlyscheme seehttps://www.nki.nl/about-us/responsible-research/guidelines-color-blind-friendly-figures/ LongnameNameColorRGB AtlantictroughATwine(136,34,85) ZonalZOrose(204,102,119) ScandinaviantroughScTrsand(221,204,119) AtlanticridgeARolive(153,153,51) EuropeanblockingEuBLteal(68,170,153) ScandinavianblockingScBLgreen(17,119,51) GreenlandblockingGLindigo(51,34,136) Noregimenogrey(128,128,128)  Thefollowingdataarestoredinsub-folder./wr_data. RRegimeprojectiontimeseriesegimeprojectiontimeseries ThefollowingTEXTfilecontainsthetimeseriesofthestandardisedregimeprojection,whichistheregimeindexIWR,foreachofthe7regimesat eachthree-hourlytimestep. WRI_projections.txtWRI_projections.txt WRindexafterMichelandRiviere(2011)offiltereddataN161lowpass>10days,Z0@500normed:intersectiontimes ----------------------------------------------------------------------------------------------------------------------------------------- timeinhsince19790101_00,YYYYMMDD_HH,WRindexforregimes:ATZOScTrAREuBLScBLGL ----------------------------------------------------------------------------------------------------------------------------------------- -25396819500111_00-0.054339000.09829105-1.38683009-0.323979650.587072790.809974790.00612640 -25396519500111_03-0.088383090.09768835-1.34896004-0.299781620.606751800.79657406-0.00862692 -25396219500111_06-0.121887070.09700651-1.30812359-0.274941920.624192890.78114247-0.02308116 ........... ........... ........... 24019790111_000.865873460.750743031.35784054-0.45948577-1.18579698-1.07059395-0.34373909 24319790111_030.854416130.722678601.31580353-0.44945070-1.16703987-1.03862977-0.32952571 24619790111_060.839273690.693528231.27102554-0.43822104-1.14390016-1.00381625-0.31613618 24919790111_090.820963980.663789511.22433603-0.42610571-1.11709785-0.96681082-0.30378893 ........... ........... ...........  Thisfilecontainsthestandardisedprojectionofinstantaneous10-daylow-passfilterednormalizedZ500anomaliesineachoftheregime followingMichelandRivière(2011),seeGrams(2025)fordetails.Itdescribesacurrentflowsituationintermsofressemblancetoeachofthe7 clustermeanEOFpatternsinphysicalspace.Itisusedtoobjectivelyidentifytheregimelifecycles. Thefilescontains9columns 1. hoursince19790101_00 2. dateinyyyymmdd_hh 3. 3to9weatherregimeindex(IWR)followingMichelandRivière,2011correctlyorderedcorrectlyordered:ATZOScTrAREuBLScBLGL Part2oftheJupyternotebookgeneratestheexampletimeseriesplotbelowshowingeachIWRtimeseriesandtheidentifiedactivelifecycles(in bold).Onthebottomthe“dominantactivelifecycle”ismarked.Thelattercorrespondstotheunambigous“LCattribution”(5thcolumnin WR_LCattribution.txt)andistheactiveLCwithmaximumprojectionatthattime(iftwoormoreLCcoexist). era5_tseries_20241101_00_20250331_21.png WWeatherregimelifecyclefileseatherregimelifecyclefiles TheTEXTfilesWR_lifecycle_information*.txtWR_lifecycle_information*.txtcontaintheobjectivelifecycledefinition. Theheaderforregimes1-7lookasfollows,fornoregime(index0)itisreducedanddefineddifferently(seebelow): --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- LIFECYCLEINFORMATION AT clsfdEOF:7958/59860(13.2944%) totalmxI:31802/220728(14.4078%) --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- numberonsetsatstartmxsatenddecaydcfrdctodctoIDdctoDATEonfrontoonfrIDonfromDATEtrfrtrfrIDtrfromDATEtrtotrtoIDtrtoDATE ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 019500131_0919500202_1819500204_1219500214_0919500216_03ATnone-99919500216_06ScBLScBL019500131_06ScBL019500202_18none-99919500216_06 119500313_0619500316_0319500316_1819500317_0619500320_18ATnone-99919500320_21GLGL019500313_03GL019500314_18none-99919500320_21 219500709_1219500709_2119500723_0619500801_0619500801_06ATScBL219500804_03noneAT-99919500709_09none-99919500709_09none-99919500801_09 319500906_0619500913_1219500914_0919500915_1519500919_09ATnone-99919500919_12ZOZO119500906_03ZO119500913_15none-99919500919_12 419510108_0619510109_0619510111_1219510112_2119510114_00ATnone-99919510114_03noneAT-99919510108_03none-99919510108_03none-99919510114_03 519510310_0019510313_1519510315_0019510316_1219510320_09ATScTr519510322_18GLGL519510309_21GL519510314_06none-99919510320_12 ...  kkeyparametersdefiningthelifecycleeyparametersdefiningthelifecycle numbernumber:exclusiveIDofthelifecycle onsetonset:onsetdate satstart :beginofsaturationstagedate(notused) mxmx:maximumstagedate satend :endofsaturationstagedate(notused) decaydecay:decaydate TTransitionswithinatimewindowandbasedonlifecycle(usethese)ransitionswithinatimewindowandbasedonlifecycle(usethese) dcfr :regimetypeofactivedominantlifecycleat decay (notused) dctodcto:within4daysafterthedecay(dc,dc+96h),typeoffirstactivedominantlifecycleornone dctoIDdctoID:within4daysafterthedecay(dc,dc+96h),IDoffirstactivedominantlifecycleor-999fornone dctoDATEdctoDATE:within4daysafterthedecay(dc,dc+96h),datewhentheotheractivedominantlifecycleisidentifiedforthefirsttime.Fornone thisis dt afterthe decay onfronfr:upto4dayspriortoonset(on-96h,on),typeoffirst(backwardlooking)activedominantlifecycleornone onto :regimetypeofactivedominantlifecycleat onset (notused) onfrIDonfrID:upto4dayspriortoonset(on-96h,on),IDoffirstactivedominantlifecycleor-999fornone onfrDATEonfrDATE:upto4dayspriortoonset(on-96h,on),datewhentheotheractivedominantlifecycleisidentifiedforthefirsttime.Fornonethis is dt beforethe onset  IImmediatetransitionsbasedondominantactivelifecycle(notused)mmediatetransitionsbasedondominantactivelifecycle(notused) trfr :regimetypeofactivedominantlifecyclewhenthecurrentlifecyclebecomesdominantforthefirsttime.Itcanbethelifecycleitself(in thecasethatmaxprojectionisreachedforthefirsttimebutanotherprojectionwaslargerwithoutcontributingtoaLC(notpersistent thecasethatmaxprojectionisreachedforthefirsttimebutanotherprojectionwaslargerwithoutcontributingtoaLC(notpersistent enough)). trfrID :IDofthe trfr LC trfrDATE :datewhenthe trfr lifecyclewasdominantforthelasttime(thisis -dt h(onetimestep)beforetheconsideredLCbecomes dominantforthefirsttime) trto :regimetypeofactivedominantlifecyclewhenthecurrentlifecycledoesnolongerhavethestrongestprojectionforthefirsttime.It canbethelifecycleitself(inthecasethatanotherregimeindexishigherbutthisregimedoesnotbecomeanactivelifecycles(not persistentenough)). trtoID :IDofthe trto LC trtoDATE :datewhenthe trto lifecycleisdominantforthefirsttime FForthenoregimeasimplifiedfileiscontained:orthenoregimeasimplifiedfileiscontained: TEXTfileWR_lifecycle_information_no.txtcontainsasimplifiedlifecycleindicatingthebeginandendofanoregimeperiod. MMeanandstandarddeviationofregimeprojectionforweatherregimeindexcalculationeanandstandarddeviationofregimeprojectionforweatherregimeindexcalculation TheweatherregimeindexIWRisdefinedasthestandardisedprojection.Thisrequiresthestaticmeanandstandarddeviationoftheprojection whicharecomputedfortheperiod1979-2019.TEXTfileWRI_std_params.txtcontainsthisdata,witheachcolumncontainingthemean(3rd row)andstandarddeviation(4throw)foreachoftheregimesaslabelledin2ndrow. meanandstdproj.(MichelandRiviere,2011)19790111_00to20191231_18 ATZOScTrAREuBLScBLGL mean-0.0023841809-0.0078344550-0.00152507600.00211500610.00427300250.00898359530.0049633454 stdv0.17112939060.28185412290.20042714480.24922697250.22923269870.23321175580.3415428102  NNormalisationweightsfor500hPageopotentialheightormalisationweightsfor500hPageopotentialheight Textfilenormweights_Z0500.txtcontainsthecalendartimedependentnormalisationweights,seedescriptionofvariablenormwgt(time) below. EEOFpatternsas2DfieldOFpatternsas2Dfield NETCDFfileEOFs_WRs.nccontainsthespatialEOFpatternsoftheleading20EOFsandsomeimportantmetainformation: VariableEOF(eof,lat,lon):spatialpatternsofEOF1toEOF20fornormalised10-daylow-passfiltered500hPageopotentialheight anomaliessix-hourlyfrom19790111_00-20191231_18. Variablenormwgt(time)normwgt(time):thecalendartimedependentnormalisationweight(in6-hourlytimesteps,starting00UTC1January,ending18 UTC31Decemberforaleap(!)year),whichisthespatialmeanofthe“running”standarddeviationcomputedatagivencalendartimefor all1979-2019timestepsina+-15daywindow.Thedataarrayisvalidforaleapyear,meaningthearrayindex236refersto00UTC29 February,index240to00UTC1March.29Februaryhastobeoversteppedforanon-leapyear(seeexamplefortheif-statementinPart4 ofthe.ipynb). Variabletime:correspondingtimefornormwgtinhourssince180-01-0100UTC(1980isanexemplaryleapyear) Variablevariance_expl(eof):explainedvariancebyeachofthe20EOFs Inadditionnormalisationweightsarealsoprovidedintextfilenormweights_Z0500.txt. >ncdump-hEOFs_WRs.nc netcdfEOFs_WRs{ dimensions: eof=20; latitude=121; longitude=241; time=1464; variables: inteof(eof); floatlatitude(latitude); latitude:standard_name="latitude"; latitude:units="degrees_north"; floatlongitude(longitude); longitude:standard_name="longitude"; longitude:units="degrees_east"; int64time(time); time:standard_name="time"; time:units="hourssince1980-01-0100:00"; floatnormwgt(time); normwgt:units="geopotentialmetres"; floatEOF(eof,latitude,longitude); EOF:_FillValue=-999.f; EOF:ntimes=59860LL; EOF:method="notranspose"; EOF:matrix="covariance"; floatvariance_expl(eof); variance_expl:_FillValue=-999.f; }  RRegimepatternas2Dfieldonglobaldomainegimepatternas2Dfieldonglobaldomain NETCDFFileClusters_WRs.nccontainsthenon-normalised10-daylow-passfiltered500hPageopotentialheightanomaly(Z0500,0isan indicatorfortheLanczosfiltersetup)foreachoftheregimesontheglobaldomainat0.5degreehorizontalgridspacingof.Unitsaregeopotential metres(gpm).Foranapproximatecalculationofthefullfieldyoucanaddtheyear-roundclimatologyof500hPageopotentialheight(e.g.for plotting,seeexampleinPart5oftheJupyternotebook). VariableZ0500_mean(wr,lat,lon):10-daylow-passfiltered500hPageopotentialheightanomalymeanofall6-hourlytimesteps contributingtoregimewithdataindexwraccordingtoEOFattribution VariableZ0500_std(wr,lat,lon):10-daylow-passfiltered500hPageopotentialheightanomalystandarddeviationofall6-hourlytime stepscontributingtoregimewithdataindexwraccordingtoEOFattribution globalattributeClassNames:Stringindicatingtheabbreviationoftheregimesusedforindex‘wr’andthustheorderofregimepatternsin thefile(herestandardorder“ATZOScTrAREuBLScBLGL”) >ncdump-hClusters_WRs.nc netcdfClusters_WRs{ dimensions: wr=7; latitude=361; longitude=720; variables: intwr(wr); floatlatitude(latitude); latitude:standard_name="latitude"; latitude:units="degrees_north"; floatlongitude(longitude); longitude:standard_name="longitude"; longitude:units="degrees_east"; floatZ0500_mean(wr,latitude,longitude); Z0500_mean:_FillValue=-999.f; Z0500_mean:units="geopotentialmetres"; Z0500_mean:description="meanofnon-normalised10-daylow-passfiltered500hPageopotentialheightanomalyforalltimesattributedtotheregimeaccordingtotheEOFclustering"; floatZ0500_std(wr,latitude,longitude); Z0500_std:_FillValue=-999.f; Z0500_std:units="geopotentialmetres"; Z0500_std:description="standarddeviationofnon-normalised10-daylow-passfiltered500hPageopotentialheightanomalyforalltimesattributedtotheregimeaccordingtotheEOFclustering"; //globalattributes: :ClassNames="ATZOScTrAREuBLScBLGL"; }  RRegimepatternasnormalised2DfieldinEOFdomainegimepatternasnormalised2DfieldinEOFdomain NETCDFFileNormed_Z0500-patterns_EOFdomain.nccontainsthenormalisednormalised10-daylow-passfiltered500hPageopotentialheightanomaly foreachoftheregimesintheEOFdomainEOFdomain.Thisvariableisneededandusedforcomputingtheprojectionandweatherregimeindices.Before computingtheprojection,youneedtheinstanteoustimeconsidered,bythenormalisationweight,whichisstoredinthevariablenormwgt(time) inEOFs_WRs.ncandinthetextfilenormweights_Z0500.txt(seebeforeandexampleinPart4oftheJupyternotebook). >ncdump-hNormed_Z0500-patterns_EOFdomain.nc netcdfNormed_Z0500-patterns_EOFdomain{ dimensions: wr=7; latitude=121; longitude=241; variables: intwr(wr); floatlatitude(latitude); latitude:standard_name="latitude"; latitude:units="degrees_north"; floatlongitude(longitude); longitude:standard_name="longitude"; longitude:units="degrees_east"; floatZ0500_mean(wr,latitude,longitude); Z0500_mean:_FillValue=-999.f; Z0500_mean:units="normalisedwithspatialaverageinEOFdomainof30-dayrunningstandarddeviationatgivencalendartime"; Z0500_mean:description="WRs:ATZOScTrAREuBLScBLGL"; floatZ0500_stdd(wr,latitude,longitude); Z0500_stdd:_FillValue=-999.f; Z0500_stdd:units="normalisedwithspatialaverageinEOFdomainof30-dayrunningstandarddeviationatgivencalendartime"; Z0500_stdd:description="WRs:ATZOScTrAREuBLScBLGL"; //globalattributes: :ClassNames="ATZOScTrAREuBLScBLGL"; }  EExampledataxampledata Thisdataisstoredinsub-folder./example_data. CClimatologicalmeanof500hPageopotentialheightlimatologicalmeanof500hPageopotentialheight NETCDFFileCLIM_Z@500_year_1979-2019.nccontainstheyear-roundclimatologicalmean(ofall3-hourlytimesteps1979-2019)for500hPa geopotentialheightinvariableZ@500(latitude,longitude).Nofilterornormalisationisapplied. >ncdump-hCLIM_Z@500_year_1979-2019.nc netcdfCLIM_Z@500_year_1979-2019{ dimensions: latitude=361; longitude=720; variables: floatlatitude(latitude); latitude:standard_name="latitude"; latitude:units="degrees_north"; floatlongitude(longitude); longitude:standard_name="longitude"; longitude:units="degrees_east"; floatZ@500(latitude,longitude); Z@500:long_name="Z@500"; }  EExamplefileforlow-passfilteredgeopotentialheightanomalyxamplefileforlow-passfilteredgeopotentialheightanomaly NETCDFFileZ0500_20250601_00.nccontains10-daylow-passfiltered500hPageopotentialheightanomalies(abbreviatedZ0)computedwith respecttoa90-dayrunningmeanclimatology.DifferentLanczosfiltersareapplied,butonlyfilter0isrelevanthere.Thetimestepis00UTC1June 2025.ERA5tisused. variableZ0:10-daylow-passfiltereddata >ncdump-hZ0500_20250601_00.nc netcdfZ0500_20250601_00{ dimensions: time=1; lev=1; lat=361; lon=720; variables: floatZ0(time,lev,lat,lon); Z0:_FillValue=-999.f; doubletime(time); time:units="hourssince1979-01-0100:00"; time:calendar="standard"; intlev(lev); //globalattributes: :domxmin=-180.f; :domxmax=179.5f; :domymin=-90.f; :domymax=90.f; :date="20250601_00"; :lev=500; :lpass=240,120,24; :history="Lanczosfilteredanomalywithfilterwidth161timesteps(dt=3h);Z0islow-passfiltereddata240h,...;seelpass";  JJupyterNotebookandpythonscriptswithexamplesforworkingwiththedataupyterNotebookandpythonscriptswithexamplesforworkingwiththedata Thesefilesarestoredin./scripts_first_steps. WR_read_examples.ipynbcontainsaJupyterNotebookwithexamplesforfacilitatinganeasystarttoworkwiththedatainPython.Itshows howtoopentheregimedatafilesandreadingthemintoadictionary.Therearefiveexampleapplicationsasdescribedbelowandexplainedin moredetailinthenotebookannotations. WR_read_examples.htmlisanHTMLversion,whichshowshowtheoutputshouldlooklike,ifthenotebookrunssuccessfully. ChristianthanksSeraphineHauserandDominikBüelerforhelpwithcodingthisipynbandprovidingauxiliaryfunctions. Part1Part1usesfct_wrera_db(VNov2020)andfct_wrlcera(VSep2019)providedbyDominikBüelertoreadtheWRdata.Theformerreadsthefile containingIWRtimeseriesandthecategoricalmaxIWRandLCattrattributions.ThelattergeneratesLCobjects. Part2Part2generatesantimeseriesplotsofIWR,withtheactivelifecyclesmarked,andamarkerforthelifecycleattribution. Part3Part3computesafrequencyclimatologyinagivenperiodandplotsthefrequencyabsoluteaswellasananomaly. Part4Part4computestheprojectionineachoftheregimes(regimeindices),usingthenetcdffileswiththenormalisedregimepatternsandan instantaneouscurrentLanczosfilteredgeopotentialheightanomaly.Itprovidesandexamplehowtonormalisethedatapriortocomputingthe regimeindices. Part5Part5readstheregimepatternsandtheclimatologyforplottingtheoriginalregimepatterns. ChristianM.Grams,12September2025.