If you’ve ever seen Star Wars, they’re like the midi-chlorians of our atmosphere,” says Mayra Oyola-Merced, an assistant professor in the Department of Atmospheric and Oceanic Sciences. “They can switch between the dark side and light side of the force.”
She’s talking about aerosols, which are tiny particles that are suspended in the atmosphere. They can come from natural sources (such as dust) or be man-made (for example air pollutants). Recent research, including important contributions from Oyola-Merced’s work, has revealed that they play a significant role in cloud formation, weather and climate. These tiny aerosols can be the explanation for why clear skies turn cloudy, or fluffy cumulus clouds transition into gray, stormy days.
They also play a huge role in extreme weather events.
Oyola-Merced says a prime example of this shows up in Africa, where winds lift dust particles up from the Sahara Desert floor and push them over the ocean. The dust gets into the Caribbean, eventually leading to the U.S. East Coast where they tamper with the hurricane season. Research shows that the more forecasters pay attention to dust storms in the Saharan region, the better they can predict tropical weather patterns in America.
“It’s the butterfly effect in action,” Oyola-Merced explains. “A small difference somewhere can ripple across the system. The fact that our forecasts routinely capture reality as closely as they do is a remarkable achievement.”
Hurricane season and extreme weather events play a huge role in Oyola-Merced’s interest in forecasting research. Born, raised and educated in Puerto Rico, she has a lot of life experience with tropical storms. Creating more accurate forecasting practices that can help protect lives, property and business interests has always been at the heart of her work here at UW–Madison and during her time serving in government roles at the National Oceanic and Atmospheric Administration (NOAA) and the United States Naval Research Laboratory (NRL). Oyola-Merced had a breakthrough after moving to the Midwest. Despite generally good air quality at the surface, she found that during certain times of year, wildfire smoke can linger aloft — coinciding with severe storms and highlighting aerosols as a hidden driver of Midwest severe weather.
Today’s models aren’t fully equipped to capture these aerosol influences. Our goal is to bridge that gap and help make forecasts even stronger.
“When you compare hailstorm and tornado reports with aerosol patterns, the alignment is striking,” Oyola-Merced says. “I had been thinking about this since my student days, but seeing it so clearly was a real ‘whoa’ moment.”
Despite Oyola-Merced’s years of suspicion, historically aerosols have not been factored into weather forecasts as highly as other parameters such as wind, humidity and temperature. She believes that plays a large role in why forecasting can be frustratingly fickle — and she wants to change that.
One way to do this is by looking at times when predictions did not line up with reality. In the Midwest, she sees that in 2023.
“There was one day in June when the National Weather Service issued severe weather warnings across Wisconsin to make sure people were prepared,” Oyola-Merced says. “But the storms never developed. It stayed unexpectedly cool for summer — I was even wearing a light jacket.”
The opposite happened, too, in cases when severe weather spun up seemingly out of nowhere. But why were the forecasts so far off? Oyola-Merced has the answer: aerosols. More specifically, smoke. That year, there were massive wildfires in Canada that heavily impacted U.S. air quality. Photos of New York’s hazy skyline made headlines worldwide, but other areas, including Madison, were also impacted. And while the haze from the smoke was visible, the full impact went unseen for months because those aerosols went up into the atmosphere and traveled through currents around the globe, leaving confusing weather patterns in their wake.
“Changing the clouds and their properties can actually change how much severe weather a region experiences,” Oyola-Merced says. “But today’s models aren’t fully equipped to capture these aerosol influences. Our goal is to bridge that gap and help make forecasts even stronger.”
For Oyola-Merced, that means factoring in wildfire smoke not just from California, but also from Canada and the Yucatán Peninsula, and understanding how long-range aerosol transport can influence Midwestern hailstorms and severe weather. It also means recognizing how aerosols can dry out the atmosphere, contributing to drought conditions and eventually helping to improve early warnings. The goal is simple: When the forecast says sunny, people can trust it — and plan without fear of a sudden downpour.
“It’s not an easy problem, because aerosols are tiny,” she says. “But they are here, and they are altering weather patterns, and that’s something we need to observe.”
