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Discussion papers
https://doi.org/10.5194/acp-2019-160
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2019-160
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 02 Apr 2019

Research article | 02 Apr 2019

Review status
This discussion paper is a preprint. A revision of the manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP).

Measurement and model analyses of the ozone variation during 2006 to 2015 and its response to emission change in megacity Shanghai, China

Jianming Xu1,2, Xuexi Tie3,4, Wei Gao1,2, Yanfen Lin5, and Qingyan Fu5 Jianming Xu et al.
  • 1Yangtze River Delta Center for Environmental Meteorology Prediction and Warning, Shanghai Meteorological Service, Shanghai, 200135, China
  • 2Shanghai Key Laboratory of Health and Meteorology, Shanghai Meteorological Service, Shanghai, 200135, China
  • 3Key Laboratory of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Science, Xi'an, 710061, China
  • 4Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Science, Xiamen, 361021, China
  • 5Shanghai Environmental Monitoring Center, Shanghai, 200135, China

Abstract. The fine particles (PM2.5) in China decrease significantly in recent years as a result of the implement of Chinese Clean Air Action Plan since 2013, while the O3 pollution is getting worse, especially in megacities such as Beijing and Shanghai. Better understanding the elevated O3 pollution in Chinese megacities and its response to emission change is important for developing an effective emission control strategy in future. In this study, we analyze the significant increasing trend of O3 concentration from 2006 to 2015 in the megacity Shanghai with the variability of 1–1.3 ppbv yr-1. It is likely attributed to the notable reduction of NOx concentration with the decreasing rate of 1.86–2.15 ppbv yr-1 accompanied with the little change of VOCs during the same period excluding the weak trends of meteorological impacts on local dispersion (wind speed), regional transport (wind direction) and O3 photolysis (solar radiation). It is further illustrated by using a state of the art regional chemical/dynamical model (WRF-Chem) to explore the O3 variation response to the reduction of NOx emission in Shanghai. The control experiment conducted in September of 2009 shows very excellent performance for O3 and NOx simulations including both the spatial distribution pattern, and the day by day variation by comparing with 6 in-situ measurements from MIRAGE-shanghai field campaign. Sensitive experiments with 30 % reduction of NOx emission from 2009 to 2015 in Shanghai estimated by Shanghai Environmental Monitoring Center shows that the calculated O3 concentrations exhibit obvious enhancement by 4–7 ppbv in urban zones with the increasing variability of 0.96–1.06 ppbv yr-1, which is well consistent with the observed O3 trend as a result of the strong VOC-limited condition for O3 production. The large reduction of NOx combined with less change of VOCs during the past ten years promotes the O3 production in Shanghai to move towards NOx-limited regime. Further analysis of WRF-Chem experiments and O3 isopleths diagram suggests that the O3 production in downtown is still under VOC-limited regime after 2015 despite of the remarkable NOx reduction, while moves to the transition regime between NOx-limited and VOC-limited in sub-urban zones. Supposing the insignificant VOCs variation persists, the O3 concentration in downtown would keep increasing till 2020 with the further 20 % reduction of NOx emission after 2015 estimated by Shanghai Clean Air Action Plan. While there are less O3 change in other regions where the O3 production is not under VOC-limited regime. The O3 production in Shanghai will switch from VOC-limited to NOx-limited regime after 2020 except downtown area which is likely close to the transition regime. As a result the O3 concentration will decrease by 2–3 ppbv in sub-urban zones, and more than 4 ppbv in suburb response to 20 % reduction of NOx emission after 2020, whereas is not sensitive to both NOx and VOCs changes in downtown. This result reveals that the control strategy of O3 pollution is a very complex process, and needs to be carefully studied.

Jianming Xu et al.
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Short summary
The PM2.5 in China decrease significantly in recent years as a result of the implement of Chinese Clean Air Action Plan since 2013, while the O3 pollution is getting worse, especially in megacities. The work aims to better understanding the elevated O3 pollution in the megacity of Shanghai China and its response to emission change which is important for developing an effective emission control strategy in future.
The PM2.5 in China decrease significantly in recent years as a result of the implement of...
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