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Something in the Air

Although his research depends on flight, engineering Professor Chuck Wilson does not like to fly. Photo: Tim Ryan

Engineering Prof. James “Chuck” Wilson does not like to fly. The phobia isn’t all that unusual, but it is a bit ironic since Wilson’s research depends on flight and he loves working around airplanes. Instrumentation that his group designed has traveled from one pole to the other, making more than 150 flights at altitudes of up to 72,000 feet. Wilson’s instruments were even on the first research plane to fly through the hole in the Antarctic ozone layer, and photos of airplanes decorate the walls of his small, jumbled office tucked away in the physics building.

For 30 years, the John Evans Professor has been designing, building and operating instruments to study atmospheric particulates. Wilson founded and directs DU’s three-person Aerosol Group, which is among the top aerosol research programs in the world. The group, which includes Research Assist. Prof. Mike Reeves and PhD candidate Maryam Darbeheshti, focuses its work on ozone depletion, pollution, climate change and satellite validation. Since 1993, the Aerosol Group has received more than $6 million in funding from NASA, the National Oceanic and Atmospheric Administration (NOAA) and the National Science Foundation, among others.

Wilson’s findings have been widely published, including in the journals Science and Nature. But perhaps more important, Aerosol Group publications have been cited in every scientific assessment of ozone depletion produced for the United Nations since 1985. (The assessment documents are used by diplomats who periodically revisit and revise the Montreal Protocol, which calls for an international reduction in the use and production of chemicals that deplete the ozone layer.)

“Chuck is one of the foremost experts in the world in stratospheric aerosols,” says NOAA Research Scientist Chuck Brock, who spent nine years as a post-doctoral fellow and research associate professor in the Aerosol Group. “He’s quite well respected.”

Particle physics

Aerosols are a gaseous suspension of tiny solid or liquid particles — soot, dust, pollen and the like — that fill the air we breathe. Denver’s infamous brown cloud is loaded with aerosols from sources that include pulverized sand used on icy winter streets. Even “clean” air contains thousands of unseen particles per cubic foot, Wilson explains.

The Aerosol Group develops technologies that enable the collection of accurate aerosol samples and the measurement of the size and concentration of particles. That’s a tricky charge, since samples must be taken from an airplane hurtling through the atmosphere at up to 560 miles per hour — a velocity too great for most sampling instruments. “It’s not simply a matter of sticking a hose out of the window,” Wilson says.

One of the group’s instruments is the Low-Turbulence Inlet (LTI), which looks like an ordinary little nozzle sticking out of a plane. But, its looks belie its important purpose, which is to collect samples of super-micron (large and heavy) particles. “This inlet has opened our way for participation in airborne studies of low-altitude aerosols, allowing us to study the sources of particulate pollution,” Wilson says.

Other researchers and organizations have adopted DU technologies like the LTI for use in their own studies. The Nucleation-Mode Aerosol Size Spectrometer, for instance, measures ultra-fine particles and is used by NOAA and the U.S. Navy.

“Each of these instruments is part of a suite of measurements that are very powerful,” says Brock, who helped develop the Nucleation-Mode device when he worked for the Aerosol Group. “Each instrument measures a different component of a problem. Without them, our understanding would be incomplete.”

Adventures in air quality

When he’s not building air-sniffing machines or working with students, Wilson is analyzing the data that his creations collect and drawing conclusions about what particle size and concentration mean for the atmosphere. Painting a clear picture of aerosols is important, he says, because they can affect everything from human health to ozone depletion and climate change.

He has studied the air quality in Houston (“the dirtiest air in the United States”), tracked smoke particles from Canadian wildfires as they drifted high over Florida and monitored dust particles blowing in from Asia. “We go on adventures,” says Wilson, whose work has taken him to spots as remote as the Arctic Circle and Patagonia. “It’s a kick.”

Wilson’s role in enhancing knowledge about stratospheric ozone has been a particular source of satisfaction. “If you want to understand ozone depletion, you need to understand the air motions and temperatures, the chemical composition of the gases and the role of particles,” he explains.

His research has helped show that particles alter the chemical balance of the stratosphere and impact the ozone layer. Nature is always making and destroying ozone, Wilson explains. But “robust,” man-made chemicals like chlorofluorocarbons (CFCs) can alter the natural balance. When exposed to ultraviolet radiation, CFCs release chlorine molecules that essentially eat ozone, and chemical reactions on the surface of aerosol particles increase the number of ozone-gobbling molecules in the atmosphere.

As they’re collecting and studying air samples, the Aerosol Group researchers also invest a lot of lab time making sure that their measurements are accurate and that data gleaned by satellites are dead-on, too. To check the validity of satellite data, the researchers compare values derived from satellite readings to actual particulate concentrations measured from aircraft flying in the same air at the same time.

This validation work has identified shortcomings in atmospheric measurements based solely on satellite data. For instance, Wilson says, satellites did a good job of measuring particulate amounts when there was a lot of material in the atmosphere following a volcanic eruption. But, he notes, they have underestimated the amount when the stratosphere is relatively clean. That’s important because models predicting ozone recovery are based, in large part, on satellite characterizations of the atmosphere.

Wilson’s current research involves aerosol-cloud processes and their impacts on climate change. “Do particulate emissions from human activity impact high-altitude clouds in the tropics? Do they change the radiation balance by changing the number of cloud particles and their size?” he wonders. “Will human-generated pollution change the nature of tropical clouds, and what will that mean for the earth’s radiation balance?”

The role of clouds is one of the biggest unknowns in climate modeling, Wilson says, noting that understanding the impact of tropical clouds on climate change is becoming more important as development occurs in places like India.

Climate change activist

Lately, Wilson has added political activist to his CV. Recent changes within NASA resulted in the cancellation of a study Wilson had planned on for this summer, when a high-altitude NASA aircraft was to carry instruments from the Aerosol Group and others into tropical clouds to measure the movement of water vapor and particulates. Since the project was scrapped, Wilson has been talking to congressional staffers about the impact of reduced NASA funding for earth-science research. His views were featured in a March 21 New York Times article about NASA funding.

“I don’t want to whine about NASA, because they allowed me to live my dream, which was to do interesting science on things I think are important,” Wilson told the Times. But, he  added, in 25 years of involvement in NASA research projects, “I have never seen an announced mission canceled.”

“Most people think of NASA as the agency that put people on the moon,” Wilson says. “But for those of us interested in the ability of planet Earth to support healthy humans, NASA’s contributions to studies of ozone depletion are invaluable.

“NASA cutbacks could have a long-term impact on our ability to understand climate change,” he adds. NASA, after all, owns the satellites that provide critical atmospheric data and is the only U.S. agency with aircraft capable of reaching the upper levels of the atmosphere. Additionally, NASA dollars provide funding for the research training provided by programs like Wilson’s. This year, the Aerosol Group received just one-third of its anticipated NASA funding and has shrunk by half.

This is particularly concerning, Wilson maintains, because research entities like the Aerosol Group “contribute to scientific and technical manpower in the U.S. and the world by training undergraduates, graduate students and post docs.” Fewer students now will mean fewer scientists in the future.

Brock shares Wilson’s concern. “None of the scientists at NOAA and NASA would be anywhere without great graduate programs and post-doc experiences,” he says. “You can’t get that kind of experience anywhere except at a university.”

At DU, even undergraduate engineering students have opportunities to assist with important Aerosol Group work. This year, for instance, seniors Ryan McMillan, Sara Shuford and Jason Zachary developed a calibration kit that helped solve a problem with the LTI. The project was undertaken as part of the Senior Design Project course that Wilson teaches with Adjunct Prof. Bob Johnson.

“Chuck goes out of his way to make sure students — undergraduates, too — get opportunities to do things to advance their careers. They’re not just cleaning labs and sorting screws,” Brock says. “I learned a lot more from him than I ever did in grad school.”

“My research feeds my undergraduate teaching,” Wilson adds.

Despite recent funding hurdles, Wilson maintains an optimism born of passion.

“As a Peace Corps science teacher, I never would have predicted that I’d have the luck to work on problems like climate change and ozone depletion and involve students in solving those problems,” says Wilson, who did his Corps stint in Malaysia before starting graduate school in 1970. “It is a great privilege to work with students and colleagues who are exceedingly gifted, and at the end of the day, we can say we had an impact.”

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