The scientists of the Earth Observation Center (EOC) of the German Aerospace Center (DLR) have scientifically proven the Corona effect on air quality with their analyses. The lockdown in Lombardy, which was hit hard by the Corona pandemic, led to a real reduction in nitrogen dioxide pollution of about 20 µg/m³ in March. This corresponds to a reduction of 45 per cent.
On 8 March 2020, the government of Italy enforced quarantine measures in quick succession. Since then, satellite and ground measurements have shown deviations from the long-term mean value - but the researchers interpret this only as an initial indication. Instead, they went deeper into the analysis and integrated the influence of the weather. To do this, they simulated the pollutant load on the computer.
The evaluation of the emission values of pollutants served to form an average value over several years. This mean value now represents the normal situation. The real weather conditions were included - hour by hour. The researchers then compared this data with the measured data for 2020, subtracting the modelled normal situation from the actual measured soil values. The result is clear: when the lockdown measures began in Lombardy on 8 March, there was the described real reduction in nitrogen dioxide pollution of about 20 µg/m³.
Researchers combined different data to prove corona effect
To validate these results on the corona effect, the scientists combined satellite measurements, in-situ data and the results of the computer models. Because atmospheric events are far too complex for blanket assessments. Only through further analysis can it be determined whether the measured values are due to special local weather conditions or a later onset of the lockdown measures, according to the scientists. For the detailed analysis of the situation in Lombardy, data from the European satellite MetOp-A were used.
Since 2018, the Sentinel-5P satellite has also provided measurements with higher resolution - but these are currently only sufficient for comparisons between 2019 and 2020. In order to reduce the weather effect in this analysis as well, global monthly averages were formed - taking into account 1.2 trillion individual measurements by DLR. These data also show a clear reduction in emissions - even if not independent of the weather. This higher-resolution data should then help to better understand emission sources and pollutant transports in the future.
