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Offenbach / Bremen (dpa) - At least for the earth's atmosphere, corona-related lockdowns have positive consequences: The ozone in the free troposphere up to about ten kilometers in height fell by an average of seven percent in the northern hemisphere in the spring and summer of last year.
This is the result of a study that was published under the leadership of the German Weather Service (DWD) and in which scientists from the University of Bremen also participated.
In total, the data from 45 measuring stations worldwide were evaluated.
One of them is in Bremen and is operated by the Institute for Environmental Physics (IUP).
Among other things, data was collected on the interaction between nitrogen oxide and ozone - in the free troposphere, less nitrogen oxide also leads to less ozone.
Since traffic is a major source of nitrogen oxide in the atmosphere, the decline in air travel and mobility on the road has caused global nitrogen oxide emissions from land transport to fall by around 14 percent, and by 40 percent in air traffic, it said.
However, an increase in ground-level ozone levels as a result of the lockdown has been recorded in urban areas with heavily polluted air worldwide.
Because in polluted air, close to the emission sources, nitrogen oxide destroys ozone, as it was said.
The reduction of nitrogen oxide emissions then leads to more ozone.
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The drop in ozone in the free troposphere is remarkably large and extensive, said Wolfgang Steinbrecht, head of the regional ozone center at the DWD's Hohenpeißenberg meteorological observatory.
At Hohenpeißenberg, as little ozone was last measured in the free troposphere in summer in 1976 as in 2020 after the lockdowns.
"The unplanned global 'corona large-scale test' clearly shows how complex the atmosphere can react to emission reductions," said Steinbrecht.
"But it also shows what could be achieved with internationally coordinated measures for global air quality."
Ozone is an important trace gas in the earth's atmosphere.
Around 90 percent of the ozone is in the stratospheric ozone layer between 10 and 50 km above sea level.
As natural "sunglasses", this ozone layer protects life on the earth's surface by almost completely blocking harsh and dangerous UV radiation from the sun.
Sufficient ozone in the stratosphere is fundamentally important for life on earth.
Around ten percent of the ozone is in the troposphere at a height of up to ten kilometers.
Here ozone acts as a greenhouse gas.
At higher concentrations, it can also cause irritation and damage to the respiratory tract of humans and animals, and damage to plants and crop failures.
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© dpa-infocom, dpa: 210217-99-479774 / 2
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