The improvement in air quality over Europe is a by-product of the coronavirus crisis, new data confirms. Lockdowns continue to suppress European pollution from nitrogen dioxide (NO2), a pollutant that mainly comes from the consumption of fossil fuels.
The reductions in economic activity resulting from the lockdown policies have seen emissions take a steep dive.
The Royal Netherlands Meteorological Institute (KNMI) produced the map showing the same.
Tropomi, the instrument on the Copernicus Sentinel-5P satellite of the Dutch met office, monitors several atmospheric gases, including NO2.
The concentrations in the air from 14 to 25 March compared with the monthly average of concentrations for March 2019.
One needs to take at least data of a 10-day average to get a good picture, says Dr Henk Eskes from KNMI: “You can’t just use one day of data,” he told BBC News.
“There’s a lot of variability in NO2 from day to day. And that’s real variability; it’s not a measurement artefact, but it’s just due to changes in the weather. So when the wind direction changes, or the wind speed changes, or the stability of the boundary layer changes – you will get different readings.”
After combining data for the 10 days, much of this variability was ironed out, and the impact of changes due to human activity can be seen.
Earlier Sentinel-5P (S5P) maps of China and Italy have been released. The new one of Italy again shows the marked reductions in the north of the country where the outbreak of Covid-19 has been a disaster.
And new maps of France, Spain, and Portugal are also there.
The Netherlands, the UK, and the other countries in northern Europe are being closely monitored. However, a more considerable variability owing to changing weather conditions has been observed by the KNMI scientists.
In the UK, the period is quite short to see the dip in concentrations as it went into lockdown following some of its Western European neighboring countries.
From this week, new measurements will help to assess the changes in nitrogen dioxide over the UK.
Sentinel-5P is a part of the EU’s Copernicus fleet of Earth observers managed by the European Space Agency.
S5P, built by Airbus in Britain, was launched in October 2017.
Tropomi is just the single instrument it carries. It is a spectrometer that observes the reflected sunlight coming up off the Earth after analyzing its many different colors.
It can detect the existence of a suite of trace gases such as nitrogen dioxide, ozone, formaldehyde, sulfur dioxide, methane, carbon monoxide and aerosols (small droplets and particles) in the atmosphere while doing so.
The data of S5P will be combined with a suite of atmospheric and transport models by the scientists to understand the observations fully.
“For China, I think we have now very solid results, and that’s in part because we have a long period already. And we have first indications of a recovery as people in China are starting to go back to work. We will closely follow the development to see if NO2 concentrations will return to pre-coronavirus levels,” Dr Eskes told BBC News.