‘Larger than life’ dust monitoring facility is one of a kind

A research center at the University of Miami in Barbados is responsible for one of the largest archives of aerosol filters in the world and provides essential information on the transport of Saharan dust particles through the Atlantic.

Located inside two shipping containers at the eastern end of a Barbados headland, the lab sports a cookie-cutter box-like exterior that belies its high-tech innards.

When Haley Royer, a researcher at the University of Miami, first saw the facility two years ago, she was a bit taken aback by its humble facade.

But then she went inside and took a closer look at the site’s monitoring equipment.

Among the cutting-edge gadgets, she saw high-volume aerosol samplers, particle size analyzers and a sun photometer that had arrived straight from NASA.

“Looking at the place from the outside, you wouldn’t think it was the source of one of the largest archives of aerosol filters in the world, or that it was absolutely vital to our understanding of the transport of dust in Africa,” said Royer, who holds a doctorate. student at the university’s Rosenstiel School of Marine and Atmospheric Science. “But it just goes to show that sometimes all it takes to do good science is creativity, ingenuity and passion.”

For more than half a century, scientists at the Barbados Atmospheric Chemistry Observatory (BACO) of the Rosenstiel School have documented the summer transport of Saharan dust particles across the Atlantic to the Caribbean Basin and South America, collecting the tiny portions of matter in filters mounted on a 55-foot Tower, analyzing them in the laboratory and studying their impact on clouds, climate and air quality.

Although the facility is physically small, its reputation in the atmospheric science community is “larger than life,” said Cassandra Gaston, assistant professor of atmospheric science, who has operated the site for three years.

“When the dust leaves the African continent, it crosses the ocean,” she said. “And once it hits the western Atlantic, Barbados is pretty much the first landmass it’s going to hit. That’s why our Barbados station is such an important monitoring site.”

She first discovered the station while conducting research as a doctoral student at the University of California, San Diego, Scripps Institution of Oceanography. It was inspired by the work of legendary atmospheric scientist and “father of dust” Joseph Prospero, professor emeritus of the Rosenstiel School who, in 1971, established the facility at Ragged Point, the furthest point to eastern Barbados.

“Anyone in aerosol research knows Joe and the station he built,” Gaston said. “When I was a graduate student, I told my adviser that I wanted to study tropical aerosols and that I was going to become an aerosol scientist, much like Joe. Fast forward to an interview for a professorship at the University of Miami and now running the station – it’s a dream come true.

Assistant Professor Cassandra Gaston with Emeritus Professor Joseph Prospero at Ragged Point, site of the Barbados Atmospheric Chemistry Observatory.

The lab has played a central role in Gaston’s work, helping her obtain the critical data she needs to characterize the size and composition of aerosols and to quantify trace gases in the atmosphere.

“I’m very interested in how aerosols affect health and the climate. And we used this platform to look at how dust affects clouds, which is important for thinking about tropical cyclones,” Gaston explained. “We used the facility to examine other sources of aerosols. There are natural emissions from ocean salts and organic matter.

Gaston is also studying how aerosols produced by burning biomass can be a source of nutrients that fertilize ecosystems like the Amazon rainforest.

“We are curious how human activities have disrupted this system,” she said. “Are we adding nutrients ourselves? Are we changing the distribution of these nutrients? How does this affect ecosystem health? So it’s important not just to think about the health of ecosystems and from a biological perspective, but it’s important because those ecosystems also sequester carbon dioxide from the atmosphere. If they are doing well, they can take more carbon dioxide out of the atmosphere than we put in.

Gaston supervises the BACO site remotely, in close contact with site manager Edmond Blades. A microbiologist at the Queen Elizabeth Hospital in Bridgetown, he has studied how pathogens that travel in dust from Africa could affect human health in Barbados, which has an unusually high incidence of asthma in children. “These high rates of asthma are thought to be related to dust transport,” Gaston said. “But no one has been able to prove it conclusively.”

In total, she has made about six trips to BACO, far fewer than the dozens of trips Prospero has made over the past five decades.

He remembers the trips well and remembers vividly how the small island nation of the Lesser Antilles has changed over the years, from the horse-drawn carriages and mules that once dominated its roads to the gas-powered vehicles of today. today.

“When we first went there, there was electricity along the highways for streetlights. But many residents didn’t have individual power lines or even water pipes,” recalls Prospero. “A lot of houses were prefabs with four sides and a roof, and they could literally be built on the side of the road. But since then the tourism industry has grown tremendously, and now it’s shocking to see fields once covered in sugar cane now covered in hundreds of cement block structures with air conditioning, electricity and water.

Throughout this time, BACO remained a mainstay on the island, with Prospero and researchers from other institutions using the site to conduct aerosol research of all kinds.

The station has also inspired groups from other scientific entities to settle on the island, all within earshot of BACO. In 1978, for example, the Advanced Global Atmospheric Gases Experiment established a research laboratory at Ragged Point, using BACO’s aluminum scaffolding tower to make continuous measurements of ozone-depleting chlorofluorocarbons and hydrochlorofluorocarbons. .

And 12 years ago, the Max Planck Institute for Meteorology in Hamburg, Germany established the Barbados Cloud Observatory on a cliff just south of BACO, studying the clouds of shallow trade winds to elucidate how they might change in response to global warming.

Yet none of these other facilities resemble BACO.

“There are very few operations that have developed the long record of aerosol measurements like we have,” Prospero said. “In recent years, other people have started measuring dust, not necessarily from stations like ours, but using remote sensing techniques, which don’t give you the composition and physical characteristics of aerosols. So we’re still quite unique in that regard.

Scientists around the world can attest to this. And some are students like Royer, the doctoral student from the Rosenstiel school who conducted field research at BACO during two of the coldest winter months, January and February 2020. “My initial goal was to study the ‘tropical Atlantic when dust is not present in order to understand the controls on cloud formation during a period of time that is not affected by dust,’ explained Royer.

But during those two winter months at Ragged Point, unusually high concentrations of dust and smoke, comparable to summer levels, hit the site, causing Royer to redirect his search.

“I started studying the impact of dust and smoke particles on cloud formation and nutrient transport in the tropical Atlantic,” she said. “And BACO was absolutely essential in conducting this research because its location is well situated in the trade winds that carry Saharan dust across the Atlantic to the Caribbean during the summer and is theoretically not aligned with the trade winds in January. and February, when they move South. This difference in alignment allowed us to show that the transport of dust and smoke is still relevant in the Caribbean, even though the Caribbean should theoretically not receive dust from the all.

Now Gaston wants to modernize the Ragged Point facility. She submitted a grant proposal for funding that will allow the site to produce more “data on the fly rather than having to process [aerosol] filters,” she said. “We want to encourage more research in the scientific community. This is the vision we have of it. »

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