( 2012) also highlighted the importance of the simultaneous adjustment of concentrations and emissions for improving tropospheric O 3 budget and profile analyses. ( 2011) reported that simultaneously assimilating ozone (O 3), nitrogen oxide, and volatile organic compound observations and their emissions can result in better 1-hr and 24-hr O 3 forecasts than through the individual assimilation of concentrations or emissions. Such efforts include variational approaches (Chai et al., 2007 Elbern et al., 2007 Guerrette & Henze, 2015 Hakami et al., 2005 Henze et al., 2007, 2009 Wang et al., 2012 Yumimoto et al., 2007, 2008 Zhang et al., 2016 Zhu et al., 2013) and ensemble-based approaches (Barbu et al., 2009 Constantinescu et al., 2007a, 2007b Heemink & Segers, 2002 Huneeus et al., 2012, 2013 Miyazaki et al., 2014 Schutgens et al., 2010 Sekiyama et al., 2010 Tang et al., 2011 Wang et al., 2016).Īccurately estimating source emissions is crucial for PM 2.5 prediction and can also provide timely instructions for the design of future emissions regulations. Data assimilation approaches are frequently used to estimate or improve estimations of source emissions. However, this is difficult because most emissions inventories are developed based on a bottom-up approach, which is dependent on land use, the source sector, and sector-specific emissions factors, which introduces considerable uncertainty in the data (Ding et al., 2015). First, it is vital to be able to estimate real-time emissions sources accurately. With the government and public paying increasing levels of attention to air pollution control, quantitatively evaluating the achievements in the air quality resulting from various regulation measures is imperative and valuable for government policy makers. These temporary regulations resulted in the so-called “Olympic blue” and “APEC blue” in the years those events took place. In addition to long-term air pollution control, temporary air pollution regulations have also occasionally been implemented to guarantee good air quality during major events, such as the 2008 Beijing Olympic Games (Okuda et al., 2011 Streets et al., 2007 Wang, Liang, et al., 2010 Wang, Nie, et al., 2010 Wang et al., 2014 Zhou et al., 2012) and the 2014 Asia-Pacific Economic Cooperation (APEC) Summit held in Beijing (Huang et al., 2015 Tang et al., 2015 Wen et al., 2016 Zhang et al., 2016). Consistent efforts, such as the “Atmospheric Pollution Prevention and Control Action Plan,” have been implemented by the government to control PM 2.5 (particulate matter with an aerodynamic diameter of 2.5 μm or less) pollution and to improve air quality. Key Pointsĭuring recent decades China has been suffering from severe air pollution, especially in urban areas with high population densities (Chan & Yao, 2008 Chen et al., 2014), which is a byproduct of rapid economic growth. More intense emissions regulation will lead to a greater reduction in PM 2.5 concentrations. Sensitivity simulations forced by the averaged emissions before the regulations and during the regular- and stringent-regulation periods further highlighted the valuable impacts of emissions regulations, under different strategy and intensity scenarios, on the improvement of air quality. As a result, the PM 2.5 concentrations consistently reduced during the regulations period, and the largest reduction occurred under the stringent-regulations period. The updated emissions were about 80% and 50% of the prior anthropogenic emissions during the regular- and stringent-regulations periods, respectively. Numerical results showed that the variations of the anthropogenic emissions before, during, and after the emissions regulations were reasonably simulated. The ensemble square root filter was employed to optimize the initial conditions and the emissions simultaneously. This period therefore allowed us to quantitatively estimate the reduction in emissions as a result of the emissions regulations under different intensity and strategy scenarios. During this period, the intensity of the emissions regulation was enhanced step by step in the run-up to the event. In order to guarantee good air quality for the 15th International Association of Athletics Federations World Championships (22–30 August) and the China Victory Day parade (3 September) in Beijing, a series of comprehensive emissions regulations were implemented in Beijing and the surrounding provinces from 20 August to 3 September 2015.
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