Abstract
Abstract. Severe wintertime PM2.5 pollution in Beijing has been receiving increasing worldwide attention, yet the decadal variations remain relatively unexplored. Combining field measurements and model simulations, we quantified the relative influences of anthropogenic emissions and meteorological conditions on PM2.5 concentrations in Beijing over the winters of 2002–2016. Between the winters of 2011 and 2016, stringent emission control measures resulted in a 21 % decrease in mean mass concentrations of PM2.5 in Beijing, with 7 fewer haze days per winter on average. Given the overestimation of PM2.5 by the model, the effectiveness of stringent emission control measures might have been slightly overstated. With fixed emissions, meteorological conditions over the study period would have led to an increase in haze in Beijing, but the strict emission control measures have suppressed the unfavorable influences of the recent climate. The unfavorable meteorological conditions are attributed to the weakening of the East Asia winter monsoon associated particularly with an increase in pressure associated with the Aleutian Low.
Highlights
In recent years, persistent and severe haze episodes with high PM2.5 concentrations occur frequently in China, attracting worldwide attention (Cheng et al, 2016; Gao et al, 2016a)
Meteorological conditions over the study period would have led to an increase in haze in Beijing, but the strict emission control measures have suppressed the unfavorable influences of the recent climate
The unfavorable meteorological conditions are attributed to the weakening of the East Asia winter monsoon associated with an increase in pressure associated with the Aleutian Low
Summary
Persistent and severe haze episodes with high PM2.5 concentrations occur frequently in China, attracting worldwide attention (Cheng et al, 2016; Gao et al, 2016a). Specific control measures included eliminating small coal-fired boilers, phasing out small high-emitting factories, installing control facilities for emissions of VOCs (volatile organic compounds), and replacing residential coal burning with electricity and natural gas among others (Zheng et al, 2018) With these rigorous control measures, China has made impressive progress, with annual mean PM2.5 concentrations reduced in major metropolitan regions by 28 %–40 % between 2013 and 2017 (Zheng et al, 2018). Yang et al (2016) used the GEOS-Chem model to simulate PM2.5 in China between 1985 and 2005 and concluded that the increase in winter PM2.5 was dominated over this period by the increase in anthropogenic emissions They found that weakening of winds was the dominant meteorological factor. The two questions highlighted above are addressed in detail in Sect. 3; Sect. 4 provides an overall summary of the study
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