A new online map tracks tropospheric global nitrogen dioxide concentrations—which we’ve seen drop sharply this year as the pandemic shut down economic activity. “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.” [ESA]

Previously: Mapping the Lockdown-Related Drop in Emissions; Emissions Drop Due to Coronavirus Outbreak.

The European Space Agency maps the drop in nitrogen dioxide concentrations in the atmosphere in the wake of coronavirus lockdowns in many countries (see above). [GIS Lounge]

Meanwhile, CESBIO researcher Simon Gascoin built a map that compares NO₂ concentrations over the last 30 days with the same period in 2019.

Data for these analyses generally come from the Copernicus Programme’s Sentinel-5P satellite. The Copernicus Atmosphere Monitoring Service issued a warning last week about using the data improperly.

Concentrations of NO₂ in the atmosphere are highly variable in space and time: they typically vary by one order of magnitude within each day and quite substantially from one day to another because of the variations in emissions (for example the impacts of commuter traffic, weekdays and weekend days) as well as changes in the weather conditions. This is why, even if observations are available on a daily (currently available from satellites) or even hourly (ground-based observations) basis, it is necessary to acquire data for a substantial period of time in order to check that a statistically robust departure from normal conditions has emerged.

Cloud cover is a factor that needs to be taken into account as well.

Previously: Emissions Drop Due to Coronavirus Outbreak.

As you may have seen elsewhere, the coronavirus pandemic is having an impact on air pollution, as countries shut down human and economic activity in an attempt to deal with the outbreak. Take nitrogen dioxide. Tropospheric NO₂ density decreased significantly over China between January and February, and the same seems to be happening in northern Italy, which normally has some of the most severe air pollution in Europe. See the ESA’s animation:

More broadly, try this online map, which compares NO₂ emissions before and after 20 February 2020 anywhere on the planet. [Maps Mania]

Previously: Mapping Nitrogen Dioxide Pollution.