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https://doi.org/10.5194/acp-2020-966
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-966
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  12 Oct 2020

12 Oct 2020

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This preprint is currently under review for the journal ACP.

Observed decreases in on-road CO2 concentrations in Beijing during COVID-19

Di Liu1, Wanqi Sun2, Ning Zeng3,4, Pengfei Han1, Bo Yao2, Zhiqiang Liu1, Pucai Wang5, Ke Zheng1, Han Mei1, and Qixiang Cai1 Di Liu et al.
  • 1Laboratory of Numerical Modeling for Atmospheric Sciences & Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences
  • 2Meteorological Observation Centre, China Meteorological Administration, Beijing, China
  • 3Department of Atmospheric and Oceanic Science, University of Maryland, USA
  • 4Earth System Science Interdisciplinary Center, University of Maryland, USA
  • 5Laboratory for Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences

Abstract. To prevent the spread of the COVID-19 epidemic, restrictions such as lockdown, were conducted globally, which led to significant reduction in fossil fuel emissions, especially in urban regions. However, CO2 concentrations in urban regions are affected by many factors, such as weather and background CO2 fluctuations. Thus, it is difficult to directly observe the reductions in CO2 concentrations with sparse ground observations. Here, we focus on urban ground transportation emissions, which were dramatically affected by the prohibitions, to determine the reduction signals. We conducted six on-road CO2 observations in Beijing using mobile platforms before (BC), during (DC) and after COVID-19 prohibitions (AC). To reduce the weather and background impacts, we chose trips with the most similar weather as possible and calculated the enhancement, which mean the difference in the CO2 concentration between on-road and the background level measured at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP) tower. The results showed that DC CO2 enhancement decreased by 41 parts per million (ppm) and 26 ppm compared to those during BC and AC, respectively, after eliminating the fluctuations in CO2 concentrations on polluted days. Detailed analysis showed that, during COVID, there was no difference between weekdays and weekends. The enhancements during rush hours were almost twice those during working hours, indicating that emissions during rush hours were much higher. Compared with DC and BC, the reductions in the enhancements during rush hours were much larger than those during working hours. Our findings showed a clear decrease during COVID, which are consistent with the CO2 concentration and emissions reductions due to the pandemic. The enhancement way used in this study is an effective method to reduce the impacts of weather and background fluctuation and should be regularly and more frequently conducted in future work.

Di Liu et al.

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Di Liu et al.

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Short summary
It is difficult to directly observe the COVID-19 signals in CO2 due to the strong weather induced variations. Here we determined the on-road CO2 concentration declines in Beijing using mobile observatory data before (BC), during (DC) and after COVID-19 (AC). We chose trips with the most similar weather, and calculated the enhancement, the difference between on-road and the city background. We showed a clear on-road CO2 decrease in DC, which are consistent with the emissions reductions in DC.
It is difficult to directly observe the COVID-19 signals in CO2 due to the strong weather...
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