Source Apportionments of Aerosols and Their Direct Radiative Forcing and Long‐Term Trends Over Continental United States

Abstract

Due to U.S. air pollution regulations, aerosol and precursor emissions have decreased during recent decades, while changes in emissions in other regions of the world also influence U.S. aerosol trends through long‐range transport. We examine here the relative roles of these domestic and foreign emission changes on aerosol concentrations and direct radiative forcing at the top of the atmosphere over the continental United States. Long‐term (1980–2014) trends and aerosol source apportionment are quantified in this study using a global aerosol‐climate model equipped with an explicit aerosol source tagging technique. Due to U.S. emission control policies, the annual mean near‐surface concentration of particles, consisting of sulfate, black carbon, and primary organic aerosol, decreases by about −1.1 (±0.1)/−1.4 (±0.1) μg/m3 in western United States and −3.3 (±0.2)/−2.9 (±0.2) μg/m3 in eastern United States during 2010–2014, as compared to those in 1980–1984. Meanwhile, decreases in U.S. emissions lead to a warming of +0.48 (±0.03)/+0.46 (±0.03) W/m2 in western United States and +1.41 (±0.07)/+1.32 (±0.09) W/m2 in eastern United States through changes in aerosol direct radiative forcing. Increases in emissions from East Asia generally have a modest impact on U.S. air quality but mitigated the warming effect induced by reductions in U.S. emissions by 25% in western United States and 7% in eastern United States. As U.S. domestic aerosol and precursor emissions continue to decrease, foreign emissions may become increasingly important to radiative forcing over the United States.

Aerosols in the E3SM Version 1: New Developments and Their Impacts on Radiative Forcing

“…In all EAMv1 simulations, emissions of anthropogenic and biomass burning aerosols are from CMIP6 data sets, except that SOAG emissions are derived from SOA formation rates from a S2015 simulation to improve the SOA representation in the model, as described in section . Instead of using yearly varying aerosol emissions for 2006–2007, we use the average between 2000–2014 to represent PD aerosol conditions by removing the interannual variation in emissions (Yang et al, , ) and in aerosol forcing estimates (e.g., Golaz et al, ). PI emissions use the CMIP6 data set for year 1850.…”

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…A number of studies have characterized the spatial distributions and physicochemical properties of biomass burning plumes over the Eastern U.S. and North Atlantic Ocean, especially in field campaigns already mentioned such as ICARTT (Clarke et al, 2007;Cook et al, 2007;de Gouw et al, 2006;Heald et al, 2006;Lewis et al, 2007;Martin et al, 2006;Peltier et al, 2007;Sullivan et al, 2006;Thornhill et al, 2008) and TCAP (Muller et al, 2014). Sources of such plumes, thus far mostly documented for summer months, are from distant upwind regions such as Alaska, Western and Central Canada, Western United States, and even Siberia (Honrath et al, 2004;Li et al, 2005;Owen et al, 2006;Parrington et al, 2012;Yang et al, 2018). Plumes transported from those regions have the ability to significantly impact surface sites along the North America East Coast (Millet et al, 2006;Rogers et al, 2019).…”

Black Carbon Amplifies Haze Over the North China Plain by Weakening the East Asian Winter Monsoon

“…A comprehensive aerosol model characterization can be found in Liu et al (2016). The model performance in simulating BC has been evaluated in previous studies (Liu et al, 2016;Yang, Wang, et al, 2017;Yang, Wang, Smith, Zhang, Lou, Yu, et al, 2018). Compared to CAWNET (China Meteorological Administration Atmosphere Watch Network; Zhang et al, 2012), the simulated December-January-February (DJF) near-surface BC concentration has a low bias of 5% in the North China Plain , far smaller than emissions uncertainty (Bond et al, 2007).…”

“…High concentrations of PM 2.5 particles harm human health by damaging respiratory and cardiovascular systems, causing morbidity and mortality (Fajersztajn et al, 2013;West et al, 2016;Zhang, Jiang, et al, 2017). In addition, these pollutants can reach distant regions through long-range transport, causing global air quality impacts Uno et al, 2008;Yu et al, 2012;Yang, Wang, et al, 2017;Yang, Wang, Smith, Zhang, Lou, Yu, et al, 2018;Yang, Wang, Smith, Zhang, Lou, Qian, et al, 2018). In addition, these pollutants can reach distant regions through long-range transport, causing global air quality impacts Uno et al, 2008;Yu et al, 2012;Yang, Wang, et al, 2017;Yang, Wang, Smith, Zhang, Lou, Yu, et al, 2018;Yang, Wang, Smith, Zhang, Lou, Qian, et al, 2018).…”

“…They also affect atmospheric visibility and transportation, hence, leading to adverse effects on economic and societal activities . In addition, these pollutants can reach distant regions through long-range transport, causing global air quality impacts Uno et al, 2008;Yu et al, 2012;Yang, Wang, et al, 2017;Yang, Wang, Smith, Zhang, Lou, Yu, et al, 2018;Yang, Wang, Smith, Zhang, Lou, Qian, et al, 2018).…”