New data has demonstrated improvement in the air quality in Europe amidst the lockdown policies implemented to combat the coronavirus pandemic.
The Royal Netherlands Meteorological Institute (KNMI) produced maps showing the improvement of air quality over Europe as lockdown policies and the reduced economic activity limited emissions.
The Dutch meteorological office gathered data using the Tropomi instrument on the Copernicus Sentinel-5P satellite, which monitors a number of atmospheric gases, including nitrogen dioxide (NO2).
The scientists compared data on NO2 concentrations in the air from March 14 to 25 with the monthly average of concentrations for March 2019.
Dr. Henk Eskes from KNMI explained that a 10-day average is typically needed to get a good snapshot. He said: "You can't just use one day of data."
"There's a lot of variability in NO2 from day to day. And that's real variability; it's not a measurement artifact, 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," Dr. Eskes.
Previously, Sentinel-5P (S5P) maps have been released but there are also new maps here of France, Spain and Portugal. KNMI scientists have been monitoring other northern European countries, including the Netherlands and the UK.
However, they have observed a larger variability owing to changing weather conditions. In the case of UK, the time period to see the dip in concentrations is also considered quite short as it went into lockdown after some of its Western European neighbors.
Built by Airbus and launched in October 2017, the Sentinel-5P is part of the EU's Copernicus fleet of Earth observers, which are managed by the European Space Agency. It carries just the single instrument, the Tropomi, a spectrometer that observes the reflected sunlight coming up off the Earth, analyzing its many different colors.
