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.
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.
The Copernicus Sentinel-5P NO2 measurements were first filtered for clouds according to the recommendation in the Product Readme file (only data with a qa_value > 0.75 was used). Then the two weeks of measurements are mapped on a fixed latitude-longitude grid of 8193 x 16385 pixels. The grid is turned into an EPSG:4326 geotiff file using the appropriate color scale, which is again turned into an EPSG:3857 tile map.
As of early December 2020 the Copernicus Sentinel-5P nitrogen dioxide (NO2) product data quality has been improved due to a change in the configuration of the NO2 data processing (new version 01.04.00). The effect of this change is an overall decrease of the input 'Cloud Pressure' parameter, which causes an increase of the tropospheric NO2 vertical column. This tropospheric NO2 vertical column amount increase is estimated to be in the range of about 25% especially for anthropogenic emissions situations and is in line with independent ground based measurements and model inter-comparisons. Time series including data before and after the activation of this new processor version might therefore show a bias in the data set. Hence, users should be very careful when performing trend studies using previous versions and version 01.04.00 of the data (e.g. COVID-19 impact on tropospheric NO2 columns). A full mission reprocessing is foreseen during 2021 to harmonise the NO2 dataset. This will then also be reflected in the maps on this website. Detailed information is provided within the dedicated Product Readme file.
This service is provided as part of the Sentinel-5P Product Algorithm Laboratory (S5P-PAL) and contains modified Copernicus Sentinel data processed by S[&]T.
Questions regarding this service can be send to the ESA EO Support Helpdesk.