Preprints
https://doi.org/10.5194/acp-2021-1089
https://doi.org/10.5194/acp-2021-1089

  10 Jan 2022

10 Jan 2022

Review status: this preprint is currently under review for the journal ACP.

Space borne tropospheric nitrogen dioxide (NO2) observations from 2005–2020 over the Yangtze River Delta (YRD), China: variabilities, implications, and drivers

Hao Yin1,2, Youwen Sun1, Justus Notholt3, Mathias Palm3, and Cheng Liu2,4,5,6 Hao Yin et al.
  • 1Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
  • 2Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
  • 3University of Bremen, Institute of Environmental Physics, P. O. Box 330440, 28334 Bremen, Germany
  • 4Anhui Province Key Laboratory of Polar Environment and Global Change, University of Science and Technology of China, Hefei 230026, China
  • 5Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 6Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230026, China

Abstract. Nitrogen dioxide (NO2) is mainly affected by local emission and meteorology rather than long-range transport. Accurate acknowledge of its long-term variabilities and drivers are significant for understanding the evolutions of economic and social development, anthropogenic emission, and the effectiveness of pollution control measures on regional scale. In this study, we quantity the long-term variabilities and the underlying drivers of NO2 from 2005 to 2020 over the Yangtze River Delta (YRD), one of the most densely populated and highly industrialized city clusters in China, using OMI space borne observations and the multiple linear regression (MLR) model. We have compared the space borne tropospheric results to the surface in-situ data, yielding correlation coefficients of 0.8 to 0.9 over all megacities within the YRD. As a result, the tropospheric NO2 column measurements can be used as representatives of near-surface conditions, and we thus only use ground-level meteorological data for MLR regression. The inter-annual variabilities of tropospheric NO2 vertical column densities (VCDs) from 2005 to 2020 over the YRD can be divided into two stages. The first stage was from 2005 to 2011, which showed overall increasing trends with a wide range of (1.91 ± 1.50) to (6.70 ± 0.10) × 1014 molecules/cm2·yr−1 (p < 0.01) over the YRD. The second stage was from 2011 to 2020, which showed over all decreasing trends of (−6.31 ± 0.71) to (−11.01 ± 0.90) × 1014 molecules/cm2·yr−1 (p < 0.01) over each of the megacities. The seasonal cycles of tropospheric NO2 VCDs over the YRD are mainly driven by meteorology (81.01 % – 83.91 %) except during winter when anthropogenic emission contributions are pronounced (16.09 % – 18.99 %). The inter annual variabilities of tropospheric NO2 VCDs are mainly driven by anthropogenic emission (69.18 % – 81.34 %) except for a few years such as 2018 which are partly attributed to meteorology anomalies (39.07 % – 91.51 %). The increasing trends in tropospheric NO2 VCDs from 2005 to 2011 over the YRD are mainly attributed to high energy consumption associated with rapid economic growth which cause significant increases in anthropogenic NO2 emissions. The decreasing trends in tropospheric NO2 VCDs from 2011 to 2020 over the YRD are mainly attributed to the stringent clean air measures which either adjust high energy industrial structure toward low energy industrial structure or directly reduce pollutant emissions from different industrial sectors.

Hao Yin et al.

Status: open (until 21 Feb 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Hao Yin et al.

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Short summary
In this study, we quantity the long-term variabilities and the underlying drivers of NO2 from 2005 to 2020 over the Yangtze River Delta (YRD), one of the most densely populated and highly industrialized city clusters in China. We reveal the significant effect of the Action Plan on the Prevention and Control of Air Pollution since 2013 adopted by the Chinese government in reducing NOx pollution. Our study can improve the understanding of pollution control measures on regional scale.
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