The nitrogen dioxide levels over the DC/Philadelphia/New York region at 12:14 and 4:24 p.m. on August 2, as measured by TEMPO. Credit: Kel Elkins, Trent Schindler, and Cindy Starr/NASA's Scientific Visualization Studio
This summer, as wildfires swept across Canada, millions of Americans watched the sky turn orange and headed warnings to stay indoors. Even doing so, some with pre-existing conditions like asthma were forced to travel to the hospital to breathe easy again.
While air quality ultimately improved, there are still many air pollutants littering the air across North America. And now, thanks to NASA’s TEMPO instrument, we have an idea of where those pollutants are better and worse.
Last week, NASA released the first data maps from TEMPO, which launched to space in April. The instrument makes hourly daytime scans of the lower atmosphere over North America from the Atlantic Ocean to Pacific coast and from roughly Mexico City to central Canada. The primary instrument is an advanced spectrometer that detects pollution normally hidden within reflected sunlight. Essentially, TEMPO measures sunlight reflected and scattered off Earth’s surface, clouds, and atmosphere. Gases in the atmosphere absorb the sunlight, and the resulting spectra are then used to determine the concentrations of several elements in the air, including ozone, nitrogen dioxide, formaldehyde, aerosols, water vapor, and several trace gases.
The first maps from the mission (above) show concentrations of nitrogen dioxide gas from pollution around large cities and major transportation routes in North America. (View more maps here.)
According to NASA, the visualizations show six scans made between 11:12 a.m. and 5:27 p.m. EDT on August 2. Closeup views focus on the southwestern U.S. from Los Angeles to Las Vegas; from central and eastern Texas to New Orleans; and the Interstate 95 corridor between New York and Washington. The data were gathered during TEMPO’s "first light" period from July 31 to August 2, when mission controllers opened the spectrometer to look at the sun and Earth and start a variety of tests and solar calibrations.
From its orbit 22,000 miles above the equator, TEMPO is the first space-based instrument designed to continuously measure air quality with the resolution of a few square miles. The research team says there are already almost 50 new studies being planned that are based around this new way to collect data.
As of Monday morning EDT, the following five major cities in the U.S. are the most polluted, according to IQAir:
- Portland, Oregon
- Seattle, Washington
- Los Angeles, California
- Washington, D.C.
- San Francisco, California
To create the rankings, IQAir uses a median value from all stations in the cities that monitor PM2.5 as one of their pollutants. The organization says it prioritizes readings from stations that measure PM2.5 since it is widely regarded as the pollutant that is most hazardous to human health. The five cities listed above are all ranked “moderate” for polluted air.
Globally, Portland is ranked 12, followed by Seattle. The top five most polluted major cities worldwide includes: Dubai, United Arab Emirates; Doha, Qatar; Wuhan, China; Johannesburg, South Africa; and Kuwait City, Kuwait. The only North American city in the top-10 is Vancouver BC, Canada, which is ranked 7th as “unhealthy for sensitive groups.” Dubai and Doha are the only two cities on the list ranked “unhealthy.”
Pollution impact
Observations by TEMPO will significantly improve studies of pollution caused by rush-hour traffic, the movement of smoke and ash from forest fires and volcanoes and the effects of fertilizer application on farmland. In addition, TEMPO data will help scientists evaluate the health impacts of pollutants and aid in the creation of air pollution maps at the neighborhood scale, improving understanding of disparities in air quality within a community.
Data will be shared with other agencies that monitor and forecast air quality, such as the Environmental Protection Agency and the National Oceanic and Atmospheric Administration.
TEMPO is part of NASA's Earth Venture Instrument program, which includes small, targeted science investigations designed to complement NASA's larger research missions. The instrument forms part of a virtual constellation of air pollution monitors for the Northern Hemisphere, which includes South Korea’s Geostationary Environment Monitoring Spectrometer and ESA’s Sentinel-4 satellite.