EGU21-12035, updated on 20 Jul 2023
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Impacts of COVID-19 lockdown restrictions on urban NO2 and O3 level in Germany with consideration of meteorological impacts and seasonal variation

Vigneshkumar Balamurugan1, Xiao Bi1, Johannes Gensheimer1, Jia Chen1, Frank Keutsch2, Shrutilipi Bhattacharjee3, and Ankit Shekhar4
Vigneshkumar Balamurugan et al.
  • 1TUM Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany (
  • 2Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States (
  • 3Department of Information Technology, National Institute of Technology Karnataka, Surathkal, India (
  • 4Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland (

In 2020, the entire world population has witnessed an unprecedented virus outbreak in terms of COVID-19, which led to restrictions in human activities across the world. Strict measures in Germany started on March-21, 2020 and ended on April-30, 2020, while more relaxed measures continued until July 2020. Vehicle traffic volume and industrial activities were drastically reduced, and, as a result, pollutant emission rates were expected to be reduced. Changes in atmospheric pollutant concentrations are an indicator for changes in emission rates although they are not directly proportional as concentrations are heavily influenced by meteorological conditions and as atmospheric photochemical reactions can be non-linear. Without accounting for the influence of meteorology and atmospheric photochemical reactions, a simple comparison of the lockdown period pollutant concentration values with pre-lockdown only to estimate emissions could be misleading. To normalize the effects of meteorological conditions and atmospheric chemical transformation and reactions, we adopted a method of comparing the predicted Business As Usual (BAU) NO2 and O3 concentrations, i.e., the expected value of NO2 and O3 concentration for 2020 meteorological conditions without lockdown restrictions, with the observed NO2 and O3 concentrations. BAU NO2 and O3 concentrations corresponding to 2020 meteorological conditions were predicted based on wind speed and sunshine duration (and season of the day) using the previous year NO2 and O3 concentrations as the references. Compared to BAU levels, big metropolitan cities in Germany show a decline in observed NO2 level (-24.5 to -37.7 %) in the strict lockdown period and rebound to the BAU level at the end of July 2020. In contrast, there is a marginal change in O3 level (+9.6 to -7.4 %). We anticipate that the imbalanced changes in precursors emission (decrease in NOX and increase in volatile organic compounds (VOCs) emission) are attributed to the marginal changes in observed O3 level compared to BAU level; decreased NOX would decrease the O3 concentration due to NOX-limited conditions, and increased VOCs would increase the O3 concentration. These results imply that the balanced emission control between the VOCs and NOX are required to limit the secondary pollutant (O3) formation.

How to cite: Balamurugan, V., Bi, X., Gensheimer, J., Chen, J., Keutsch, F., Bhattacharjee, S., and Shekhar, A.: Impacts of COVID-19 lockdown restrictions on urban NO2 and O3 level in Germany with consideration of meteorological impacts and seasonal variation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12035,, 2021.


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