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

Abstract

Abstract. The Pacific-North America teleconnection (PNA) is the leading general circulation pattern in the troposphere over the region of North Pacific to North America during wintertime. This study examined the impacts of monthly variation of the PNA phase (positive or negative phase) on wintertime surface-layer aerosol concentrations in the US by analyzing observations during 1999–2013 from the Air Quality System of Environmental Protection Agency (EPA-AQS) and the model results for 1986–2006 from the global three-dimensional Goddard Earth Observing System (GEOS) chemical transport model (GEOS-Chem). The composite analyses on the EPA-AQS observations over 1999–2003 showed that the average concentrations of PM2.5, sulfate, nitrate, ammonium, organic carbon, and black carbon aerosols over the US were higher in the PNA positive phases than in the PNA negative phases by 1.4 μg m−3 (12.7 %), 0.1 μg m−3 (6.4 %), 0.3 μg m−3 (39.1 %), 0.2 μg m−3 (22.8 %), 0.8 μg m−3 (21.3 %), and 0.2 μg m−3 (34.1 %), respectively. The simulated geographical patterns of the differences in concentrations of all aerosol species between the PNA positive and negative phases were similar to observations. Based on the GEOS-Chem simulation driven by the assimilated meteorological fields, the PNA-induced variation in planetary boundary layer height was found to be the most dominant meteorological factor that influenced the concentrations of PM2.5, sulfate, ammonium, organic carbon, and black carbon, and the PNA-induced variation in temperature was the most important parameter that influenced nitrate aerosol. Results from this work have important implications for understanding and prediction of air quality in the United States.