This online platform uses data from the Copernicus Sentinel-5P satellite and shows the averaged nitrogen dioxide concentrations across the globe – using a 14-day moving average. Concentrations of short-lived pollutants, such as nitrogen dioxide, are indicators of changes in economic slowdowns and are comparable to changes in emissions. Using a 14 day average eliminates some effects which are caused by short term weather changes and cloud cover. The average gives an overview over the whole time period and therefore reflects trends better than shorter time periods.
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The maps show the concentration of nitrogen dioxide (NO2) in the lowest kilometers of the atmosphere. Nitrogen oxides are mainly produced by human activity and the combustion of (fossil) fuels, such as road traffic, ships, power plants and other industrial facilities. Burning activities and wildfires also contribute significantly to the NO2 concentrations observed. NO2 can have a significant impact on human health, both directly and indirectly through the formation of ozone and small particles.
The nitrogen dioxide map shown here is measured by the Tropomi instrument on the Sentinel 5 Precursor satellite. The Tropomi measurements are performed in the visible part of the spectrum. Because Tropomi cannot see through thick clouds, the concentrations near the surface can only be measured under cloud-free or partly cloudy conditions. More information on the Tropomi NO2 measurements and quality assessment can be found in the Product Readme file.
Nitrogen dioxide concentrations in our atmosphere, as well as the cloud cover, vary widely from day to day owing to the fluctuations of emissions, as well as variations in weather conditions. In order to visualise longer-term variations in NO2, for instance the impact of COVID-19 lockdown measures on the NO2 concentrations, the maps show the concentration averaged over a period of two weeks (14 days), in steps of one week. Note that even after averaging over two weeks there are still remaining signatures of persistent weather situations. The quantification of changes in nitrogen oxide emissions requires more detailed analyses, combining the measurements with models that describe the day-to-day variability of air pollution.
