08 Jun 2021

08 Jun 2021

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

The role of emission reductions and the meteorological situation for air quality improvements during the COVID-19 lockdown period in Central Europe

Volker Matthias, Markus Quante, Jan A. Arndt, Ronny Badeke, Lea Fink, Ronny Petrik, Josefine Feldner, Daniel Schwarzkopf, Eliza-Maria Link, Martin O. P. Ramacher, and Ralf Wedemann Volker Matthias et al.
  • Helmholtz-Zentrum Hereon, Max-Planck-Straße 1, 21502 Geesthacht, Germany

Abstract. The lockdown measures taken to prevent a rapid spreading of the Corona virus in Europe in spring 2020 led to large emission reductions, particularly in road traffic and aviation. Atmospheric concentrations of NO2 and PM2.5 were mostly reduced when compared to observations taken for the same time period in previous years, however, concentration reductions may not only be caused by emission reductions but also by specific weather situations.

In order to identify the role of emission reductions and the meteorological situation for air quality improvements in Central Europe, the meteorology chemistry transport model system COSMO-CLM/CMAQ was applied to Europe for the period 1 January to 30 June 2020. Emission data for 2020 was extrapolated from most recent reported emission data and lockdown adjustment factors were computed from reported activity data changes, e.g. google mobility reports. Meteorological factors were investigated through additional simulations with meteorological data from previous years.

The results showed that lockdown effects varied significantly among countries and were most prominent for NO2 concentrations in urban areas with two-weeks-average reductions up to 55 % in the second half of March. Ozone concentrations were less strongly influenced (up to +/−15 %) and showed both, increasing and decreasing concentrations due to lockdown measures. This depended strongly on the meteorological situation and on the NOx/VOC emission ratio. PM2.5 revealed 2–12 % reductions of two-weeks-average concentrations in March and April, which is much less than a different weather situation could cause. Unusually low PM2.5 concentrations as observed in Northern Central Europe were only marginally caused by lockdown effects.

The lockdown can be seen as a big experiment about air quality improvements that can be achieved through drastic traffic emission reductions. From this investigation, it can be concluded that NO2 concentrations can be largely reduced, but effects on annual average values are small when the measures last only a few weeks. Secondary pollutants like ozone and PM2.5 depend more strongly on weather conditions and show a limited response to emission changes in single sectors.

Volker Matthias et al.

Status: open (until 20 Jul 2021)

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

Volker Matthias et al.

Volker Matthias et al.


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Short summary
COVID-19 lockdown measures in spring 2020 led to cleaner air in Central Europe. Densely populated areas benefitted mainly from largely reduced NO2 concentrations, while rural areas experienced lower reductions in NO2 but also lower ozone concentrations. Very low particulate matter (PM) concentrations in parts of Europe were not an effect of lockdown measures. Model simulations show that modified weather conditions are more significant for ozone and PM than severe traffic emission reductions.