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Abrupt decline in tropospheric nitrogen dioxide over China after the outbreak of COVID-19

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Science Advances  10 Jul 2020:
Vol. 6, no. 28, eabc2992
DOI: 10.1126/sciadv.abc2992
  • Fig. 1 Average OMI tropospheric NO2 vertical column densities (TVCDs) over China in 2020.

    (A) −20 to −1, (B) 0 to 19, and (C) 20 to 39 days relative to the 2020 LNY.

  • Fig. 2 Daily variations in 7-day moving averages of OMI NO2 TVCDs over China.

    Shading shows SE of the mean. Points are plotted at the midpoint of the 7-day moving average. Values are normalized to the mean of the pre period. Note that we account for the annually varying dates of the LNY.

  • Fig. 3 Reductions in NO2 TVCDs along highways.

    Average TROPOMI NO2 TVCD over Changchun, China (black dots) for 20 days (A) before and (B) after the 2020 LNY and (C) their difference. The locations of large power plants and other industrial plants are indicated by triangles and crosses, respectively. The lines show China National Highways.

  • Table 1 Effects of the government policies on NO2 TVCD.

    NO2 TVCD is based on OMI. We use a fixed-effects model (Eqs. 1 to 3) with the first case announced and lockdown coded as binary indicator variables. We control for the average 2015–2019 OMI NO2 TVCDs to adjust for seasonal variation and include provinces’ fixed-effects to adjust for geographical variation. The “Constant” term is the average province fixed-effect used as a baseline to compare the relative effect of the policy interventions. All SEs (shown in parentheses) are clustered at the province level.

    Outcome variable
    NO2 TVCD (1015 molecules/cm2)
    (1)(2)(3)
    First case
    announced in
    province, β
    −1.282**−0.770*
    (0.384)(0.376)
    Lockdown of
    province, λ
    −1.073***−0.722***
    (0.215)(0.151)
    Average NO2
    TVCD
    2015–2019, δ
    0.00010.004−0.001
    (0.019)(0.018)(0.019)
    Constant, α4.8474.4404.897
    Number of
    observations
    102310231023
    R20.5530.5550.559
    Adjusted R20.5390.5400.544

    *P < 0.05.

    **P < 0.01.

    ***P < 0.001.

    Supplementary Materials

    • Supplementary Materials

      Abrupt decline in tropospheric nitrogen dioxide over China after the outbreak of COVID-19

      Fei Liu, Aaron Page, Sarah A. Strode, Yasuko Yoshida, Sungyeon Choi, Bo Zheng, Lok N. Lamsa, Can Li, Nickolay A. Krotkov, Henk Eskes, Ronald van der A, Pepijn Veefkind, Pieternel F. Levelt, Oliver P. Hauser, Joanna Joiner

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