Ask the Weather Guys: Is COVID-19 response leading to cleaner air?

Ask the Weather Guys: Is COVID-19 response leading to cleaner air?

India's air

In this April 10, 2020, photo, the snow-capped Dhauladhar range of the Himalaya mountains is clearly visible in Dharmsala, India. India’s extended lockdown to curb the coronavirus outbreak has led to an unexpected bonus in the country with six out of 10 of the world's most polluted cities: cleaner air. (AP Photo/Ashwini Bhatia)

Q: Is COVID-19 leading to cleaner air?

A: Many states have implemented lockdowns and shelter-in-place or “safer at home” orders to help contain the spread of the disease caused by the new coronavirus.

This response to the COVID-19 pandemic has reduced traffic and reduced production by industrial plants. This response has improved the quality of the air we breathe.

Atmospheric nitrogen dioxide is a byproduct of burning fossil fuels for transportation and electricity generation. Nitrogen dioxide, or NO2, is also a harmful substance and is an indicator of air quality.

NASA manages instruments on satellites that can monitor global pollution. One of those instruments is the Ozone Monitoring Instrument (OMI). In addition to monitoring global ozone, OMI also makes measurements of the atmospheric concentration of NO2.

The OMI measurements show less air pollution over the northeast United States in March 2020, when compared with the average values for the month of March between 2015 and 2019. The nitrogen dioxide levels are down about 30% over major metropolitan areas, including Washington, D.C., New York City, Philadelphia and Boston.

The European Space Agency (ESA) also manages satellites that observe and track air pollution. Those satellites also observed a sharp decrease in nitrogen dioxide over Italy after stay-at-home orders.

The reduced emissions suggest that people are taking steps to reduce their exposure by staying home. Measurements from satellites showed decreasing concentrations of NO2 over China in late January, coinciding with its nationwide quarantine.

"Weather Guys" Steve Ackerman and Jonathan Martin are professors in the University of Wisconsin-Madison department of atmospheric and oceanic sciences.


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