When scientists ran the instrument aboard a new satellite this summer, they got a preview of what will soon become the first continuous record of air pollution in the country.
The satellite will remain parked over North America and will provide scientists with hourly, daytime updates on air pollution nationwide. On Thursday, researchers released their first images, which show changes in nitrogen dioxide pollution over the United States over the course of a single day.
“It’s really exciting to see the instrument work as expected,” said Xiong Liu, deputy mission director and physicist at the Center for Astrophysics run by Harvard University and the Smithsonian Institution. The satellite instrument, called TEMPO, will be able to measure many other pollutants as well.
The images come during a summer of exceptionally poor air quality in the United States, with smoke from wildfires covering multiple cities and regions. But even before this summer, over the past decade or so, Americans have enjoyed gains in air quality since the passage of the Clean Air Act in 1970. have begun to plateau.
Dr. Liu said that while air pollution has improved over the years, “a third of Americans still live with unhealthy levels of air pollution.”
Nitrogen dioxide comes from burning fuel and creates other types of pollution through chemical reactions in the air. The images show clear gas hotspots around major cities, with higher levels during the morning and evening when there is more traffic.
In addition to looking down at Earth via the new satellite, scientists fanned out across the country on foot and on research planes this past July and August, in a meticulously designed production to try to understand why air quality hasn’t improved.
Because pollutants can be transported thousands of miles by wind, it has been difficult for scientists to pinpoint the largest sources of pollution on a national scale. TEMPO’s hourly updates are expected to be a “real game-changer” in giving researchers the ability to track air pollution at its source, said Brian McDonald, an environmental engineer with the National Oceanic and Atmospheric Administration who coordinates field research this summer with the satellite. .
Historically, motor vehicle traffic has been one of the largest contributors to air pollution, but stricter emissions standards for motorized vehicles have reduced pollution from driving. At the same time, Dr MacDonald explained, the relative importance of products and consumables, such as paint and pesticides, that emit pollutants known as volatile organic compounds (VOCs) has risen.
These compounds react with nitrogen dioxide in the air to form the harmful ozone layer at ground level, which has a significant effect It remained stubbornly high in places, especially in California and in major metropolitan areas across the country. While the ozone layer high in the atmosphere protects us from cancer-causing UV rays, the ozone found near the ground can aggravate or cause respiratory diseases such as asthma, bronchitis, and emphysema.
Another persistent problem is particulate matter contamination, made up of microscopic particles small enough to enter the bloodstream and cause heart and lung disease, strokes and even premature death in severe cases. This pollution, also known as PM2.5, started to increase again around 2016 after years of decline.
Wildfires, which are becoming more frequent and intense as climate change creates hotter and drier conditions, appear to be the main reason behind this reversal, according to a study published last fall.
This research relied on an old satellite providing daily measurements, said Marshall Burke, a professor of environmental policy at Stanford University and one of the study’s authors. Currently, he and his colleagues rely heavily on computer models of how pollutants move with the wind to fill in the spaces between actual observations.
Dr Burke, who is not involved in the TEMPO mission, said he was looking forward to getting hourly data from the satellite, which would be “akin to video”. “As you have more and more images, it’s much easier to fill in the map where the things came from,” he added.
TEMPO will be able to track air pollution with an accuracy of about four square miles. That’s where coordinated flights, drives, and walks come in this summer.
“The data from these field campaigns act as a decoder loop” for the satellite, said Tracy Holloway, a professor of energy analysis and policy at the University of Wisconsin-Madison who studies air quality but is not involved in the project.
One place where scientists collect data at the micro-local level is New York City. Even cities that routinely monitor their air usually don’t have enough equipment to cover all neighborhoods. This is a problem because within individual cities or regions, air pollution tends to be unevenly distributed.
Since late July, dozens of researchers led by Audrey Gowdel and Prathap Ramamurthy of the National Oceanic and Atmospheric Administration (NOAA) have taken turns walking in pairs around town, carrying a backpack full of air quality sensors. Onlookers often wondered if scientists would go fishing, because of the long, thin tubes that stick out of the packaging to suck up air samples.
Each day, a colleague would track the flight paths of NASA research planes and provide updates on WhatsApp so hikers could walk under the planes. The datasets will be compared at a later time. The researchers covered dozens of tracks, making sure to include neighborhoods that are economically disadvantaged and neighborhoods with larger populations of color. These regions often face disproportionate air pollution, but their data is sparse.
“Hopefully we’ll have better models and better predictions at the street level,” said Yoshira Ornelas van Horn, a professor of environmental health at Columbia University and another TEMPO collaborator.
It will take a few months to analyze all the data, but the walks themselves have already shed light on the relationship between climate change and air quality. (Dr. Ramamurthy said some long hours of walking in the height of summer was “terrible.”) Higher temperatures are generally associated with higher levels of ozone pollution, and on the hottest sampling day, ozone readings rose above the national standards set by the government. Dr. Gowdel pointed to the Environmental Protection Agency.
The data from the TEMPO satellite is supposed to be available to the general public in the spring of 2024. In the meantime, more than 400 users, including several state and federal agencies, have signed up as “early users.”
Researchers at Mount Sinai Health System in New York plan to use the TEMPO data to study how air pollutants affect asthma symptoms in children. The Connecticut Office of the Air Department plans to use the data to investigate the source of the state’s unusually high ozone pollution.
Dr. Ornelas Van Horn hopes this summer’s research will provide decision-makers with the information needed to do something about the country’s unresolved air quality problems. “We all agree that air pollution is bad,” she said.
