Abstract
Abstract. We used the nested grid version of the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem) to examine the interannual variations (IAVs) of aerosols over heavily polluted regions in China for years 2004–2012. The role of variations in meteorological parameters was quantified by a simulation with fixed anthropogenic emissions at year 2006 levels and changes in meteorological parameters over 2004–2012. Simulated PM2.5 (particles with a diameter of 2.5 μm or less) aerosol concentrations exhibited large IAVs in North China (NC; 32–42° N, 110–120° E), with regionally averaged absolute percent departure from the mean (APDM) values of 17, 14, 14, and 11% in December-January-February (DJF), March-April-May (MAM), June-July-August (JJA), and September-October-November (SON), respectively. Over South China (SC; 22–32° N, 110–120° E), the IAVs in PM2.5 were found to be the largest in JJA, with the regional mean APDM values of 14% in JJA and of about 9% in other seasons. The concentrations of PM2.5 over the Sichuan Basin (SCB; 27–33° N, 102–110° E) were simulated to have the smallest IAVs among the polluted regions examined in this work, with APDM values of 8–9% in all seasons. All aerosol species (sulfate, nitrate, ammonium, black carbon, and organic carbon) were simulated to have the largest IAVs over NC in DJF, corresponding to the large variations in meteorological parameters over NC in this season. Process analyses were performed to identify the key meteorological parameters that determined the IAVs of different aerosol species in different regions. While the variations in temperature and specific humidity, which influenced the gas-phase formation of sulfate, jointly determined the IAVs of sulfate over NC in both DJF and JJA, wind (or convergence of wind) in DJF and precipitation in JJA were the dominant meteorological factors to influence IAVs of sulfate over SC and the SCB. The IAVs in temperature and specific humidity influenced gas-to-aerosol partitioning, which were the major factors that led to the IAVs of nitrate aerosol in China. The IAVs in wind and precipitation were found to drive the IAVs of organic carbon aerosol. We also compared the IAVs of aerosols simulated with variations in meteorological parameters alone with those simulated with variations in anthropogenic emissions alone; the variations in meteorological fields were found to dominate the IAVs of aerosols in northern and southern China over 2004–2012. Considering that the IAVs in meteorological fields are mainly associated with natural variability in the climate system, the IAVs in aerosol concentrations driven by meteorological parameters have important implications for the effectiveness of short-term air quality control strategies in China.
Highlights
Aerosols are major air pollutants that have adverse effects on human health, reduce atmospheric visibility, and influence global climate change
The scientific goals of this work are (1) to quantify the interannual variations (IAVs) in surface-layer aerosol concentrations in China resulted from the variations in meteorological conditions during the 2004–2012 period, using the global threedimensional chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model), and (2) to identify the key meteorological parameters that influenced the IAVs of aerosols in different polluted regions of China by the integrated process rates (IPR) analyses
Since we aimed to examine the IAVs in surface-layer aerosol concentrations, our process analyses for an aerosol species were performed for each region (NC, South China (SC), or Sichuan Basin (SCB)) from the surface to 1 km altitude
Summary
Aerosols are major air pollutants that have adverse effects on human health, reduce atmospheric visibility, and influence global climate change. Since concentrations of chemical species are the net results from comprehensive physical and chemical processes, the integrated process rates (IPR) (Im et al, 2011) have been used to identify the dominant processes (such as horizontal and vertical transport, emissions of primary species, gas-phase chemistry, dry deposition, cloud processes, and aerosol processes) that influence the concentrations of chemical species in the Community Multi-scale Air Quality model (CMAQ) for episodic events (Jose et al, 2002; Goncalves et al, 2009) as well as for yearly (Zhang et al, 2009) to decadal simulations (Civerolo et al, 2010). The scientific goals of this work are (1) to quantify the IAVs in surface-layer aerosol concentrations in China resulted from the variations in meteorological conditions during the 2004–2012 period, using the global threedimensional chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model), and (2) to identify the key meteorological parameters that influenced the IAVs of aerosols in different polluted regions of China by the IPR analyses.
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