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The Pacific–North America teleconnection (PNA) is the leading generalcirculation pattern in the troposphere over the region of North Pacific toNorth America during wintertime. This study examined the impacts of monthlyvariations of the PNA phase (positive or negative phase) on wintertimesurface-layer aerosol concentrations in the United States (US) by analyzing observationsduring 1999–2013 from the Air Quality System of the EnvironmentalProtection Agency (EPA-AQS) and the model results for 1986–2006 from theglobal three-dimensional Goddard Earth Observing System (GEOS) chemicaltransport model (GEOS-Chem). The composite analyses on the EPA-AQSobservations over 1999–2013 showed that the average concentrations ofPM2.5, sulfate, nitrate, ammonium, organic carbon, and black carbonaerosols over the US were higher in the PNA positive phases (25 % of thewinter months examined, and this fraction of months had the highest positivePNA index values) than in the PNA negative phases (25 % of the wintermonths examined, and this fraction of months had the highest negative PNAindex values) by 1.0 µg m−3 (8.7 %), 0.01 µg m−3(0.5 %), 0.3 µg m−3 (29.1 %), 0.1 µg m−3(11.9 %), 0.6 µg m−3 (13.5 %), and 0.2 µg m−3(27.8 %), respectively. The simulated geographical patterns of thedifferences in concentrations of all aerosol species between the PNApositive and negative phases were similar to observations. Based on theGEOS-Chem simulation, the pattern correlation coefficients were calculatedto show the impacts of PNA-induced variations in meteorological fields onaerosol concentrations. The PNA phase was found (i) to influencesulfate concentrations mainly through changes in planetary boundary layer height (PBLH), precipitation (PR), and temperature; (ii) toinfluence nitrate concentrations mainly through changes in temperature; and(iii)to influence concentrations of ammonium, organic carbon, and black carbonmainly through changes in PR and PBLH. Results from this work have importantimplications for the understanding and prediction of air quality in the US

atmospheric chemistry and physics

The impact of monthly variation of the Pacific–North America (PNA) teleconnection pattern on wintertime surface-layer aerosol concentrations in the United States