“Peeling back the layers of the onion”: Tracey Holloway’s use of computer models to study air pollutants

This article, by Rachel King, is part of a series highlighting members of the Office of Sustainability’s Experts Database. In a collaboration with instructor Madeline Fisher’s course, LSC 561: Writing Science for the Public, students interviewed campus sustainability experts and produced short feature stories. 

Tracey Holloway headshotCarbon dioxide is likely the first air pollutant people think of. However, the reality of air pollution is far more complex. Types of pollutants, their sources, and their interactions with each other and other atmospheric processes are all factors that impact air quality. Isolating each piece to understand its real contribution to the quality of air requires advanced techniques, like Tracey Holloway’s computer models. 

Holloway is a professor at the University of Wisconsin–Madison based in the Nelson Institute’s Center for Sustainability and the Global Environment (SAGE). Equipped with satellite data of gases and particles, as well as data from other ground monitors, Holloway’s team uses advanced computer models to answer questions on how the different sources of chemicals in the atmosphere, weather, and other atmospheric processes interact and affect the quality of air. 

“Science has a lot to offer: it can help find common solutions, help move the conversation forward, help see the problems,” Holloway said. “Because if we don’t know a problem is there, we can’t fix it. So I view the work we’re doing as bridging science and policy.”

Holloway’s career in atmospheric science began after an internship with the NASA Johnson Space Flight Center. As an applied mathematics major, she had a limited background in atmospheric science. But after coming across a picture of a hurricane, she was intrigued by the connections she could make between space flight and atmospheric science. In her graduate career at Princeton, she joined the Geophysical Fluid Dynamics Laboratory, which builds computer models of the atmosphere. Eventually she pivoted to connecting the models she worked with to real-world decision making.  

The first step to Holloway’s research uses the computer models. They receive inputs like weather, as well as emissions from places like power plants, and output changes to the chemicals in the air. The models Holloway’s team uses shed light on how each piece of the puzzle of air pollution comes together to affect air quality. In this way, conversations on improving the current state of air quality can be more productive and informed.

“The models are a decoder ring to understand what data is telling us,” Holloway said. “The models can help peel back the layers of the onion to say, how much of it is weather, how much of it is chemistry, how much is coming from outside the United States, and how much is power plants?”

From here, Holloway pivots toward communicating her results to decision makers around the world. While regulations in the United States exist to help ensure clean air, many other areas in the world are not as fortunate. Investing in monitors and cleaner energy sources is an expensive process, making it much harder to find effective solutions to clean air that are affordable. Holloway helps to move the conversation forward so policy makers and stakeholders globally can invest in clean air, while also spending resources effectively.

“All the work we’re doing is working with real world partners to try to understand: how can we harness the power of advanced models, satellite data, and other science to inform better decision making?”