UnprecedentedHeatwaveinWesternNorthAmericaduringLateJuneof2021:RolesofAtmosphericCirculationandGlobalWarmingChunzaiWANG*1,2,3,JiayuZHENG*1,2,3,5,WeiLIN2,4,andYuqingWANG2,41SouthernMarineScienceandEngineeringGuangdongLaboratory(Guangzhou),Guangzhou511458,China2StateKeyLaboratoryofTropicalOceanography,SouthChinaSeaInstituteofOceanology,ChineseAcademyofSciences,Guangzhou510301,China3InnovationAcademyofSouthChinaSeaEcologyandEnvironmentalEngineering,ChineseAcademyofSciences,Guangzhou510301,China4UniversityofChineseAcademyofSciences,Beijing100049,China5StateKeyLaboratoryofNumericalModelingforAtmosphericSciencesandGeophysicalFluidDynamics,InstituteofAtmosphericPhysics,ChineseAcademyofSciences,Beijing100029,China(Received18March2022;revised12June2022;accepted30June2022)ABSTRACTAnextraordinaryandunprecedentedheatwavesweptacrosswesternNorthAmerica(i.e.,thePacificNorthwest)inlateJuneof2021,resultinginhundredsofdeaths,amassivedie-offofseacreaturesoffthecoast,andhorrificwildfires.Here,weuseobservationaldatatofindtheatmosphericcirculationvariabilitiesoftheNorthPacificandArctic-Pacific-Canadapatternsthatco-occurredwiththedevelopmentandmaturephasesoftheheatwave,aswellastheNorthAmericapattern,whichcoincidedwiththedecayingandeastwardmovementoftheheatwave.ClimatemodelsfromtheCoupledModelIntercomparisonProject(Phase6)arenotdesignedtosimulateaparticularheatwaveeventlikethisone.Still,modelsshowthatgreenhousegasesarethemainreasonforthelong-termincreaseofaveragedailymaximumtemperatureinwesternNorthAmericainthepastandfuture.Keywords:heatwave,climatechange,atmosphericcirculationpattern,PacificNorthwestCitation:Wang,C.Z.,J.Y.Zheng,W.Lin,andY.Q.Wang,2023:UnprecedentedheatwaveinwesternNorthAmericaduringlateJuneof2021:Rolesofatmosphericcirculationandglobalwarming.Adv.Atmos.Sci.,40(1),14−28,https://doi.org/10.1007/s00376-022-2078-2.ArticleHighlights:•TheNorthPacificandArctic-Pacific-Canadapatternsco-occurwiththedevelopmentandmaturephasesoftheheatwaveinwesternNorthAmerica.•TheNorthAmericapa...
