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Ogochukwu Enekwizu with a suite of instruments at Brookhaven National Laboratory to make and study soot-seeded clouds. Photo courtesy of BNL

By Daniel Dunaief

Combining forces to form a three-part team, they strive to understand processes that are as visually stunning and inspirational as they are complex and elusive.

Clouds, which are so important to weather and climate, are challenging to understand and predict, as numerous processes affect properties at a range of scales.

A team from Brookhaven National Laboratory has provided the atmospheric sciences community with a host of information that advances an understanding of clouds.

In the atmospheric sciences community, “we typically talk about the three legs of a stool: modeling/ theory; field measurements; and targeted laboratory studies,” explained Arthur Sedlacek, Chemist in the Environmental and Climate Science Department.

Sedlacek conducts field experiments by collecting air samples from clouds in a range of locations such as flying through wildfire plumes.

In the beginning of 2021, BNL added postdoctoral researcher Ogochukwu Enekwizu to bolster another leg of that stool. Enekwizu conducts the kind of laboratory studies that provide important feedback and data for the work of Sedlacek and cloud modelers like Nicole Riemer, Professor in the Department of Atmospheric Sciences at the University of Illinois-Urbana Champaign.

Enekwizu studies how soot aerosols from wildfires influence the lifetime and formation of clouds. She’s also investigating how soot-cloud interactions affect the absorption and scattering of light by soot particles.

Wildfires provide kindling for the climate, as fires release warming agents that contribute to increases in global temperatures which result in more wildfires. By determining how these smaller scale processes in soot affect clouds, Enekwizu can reduce the so-called error bars or level of uncertainty in the models other scientists create and that rely on the data she develops.

Enekwizu’s collaborators appreciate her contribution. As a modeler, Riemer suggested that Enekwizu’s work provided key information.

“While the microscale processes of soot restructure are incredibly complicated, [Enekwizu] was able to boil it down to a few simple parameters,” Riemer explained. “This makes it feasible to implement this process in a model like ours, which look at aerosol populations, not just a few individual particles. From there, we can come up with ways to implement this knowledge into climate models, which are still much more simplified than the model that we are developing.”

Sedlacek, who is her supervisor, suggested that Enekwizu’s work is “now on the cusp of answering important questions of how aerosols interact with clouds.” He descried her set up as “truly unique” and expects her results to inform the community about wildfire aerosol-cloud interactions and will offer guidance on other necessary field measurements.

In broader research terms, wildfires can be important for the ecosystem, as they remove decaying material, clear out underbrush, release nutrients back into the soil and aid the germination of seedlings

The increasing frequency, duration and intensity of these fires has been important to the scientific community. The general public has become increasingly aware of its importance as well, Enekwizu said.

Collaborations

Recruited to BNL by Sedlacek and Atmospheric Scientist Ernie Lewis, Enekwizu is considering collaborations with other researchers at BNL.

She has started speaking with scientists at the Center for Functional Nanomaterials about exploring soot microstructure in a planned joint collaboration with her New Jersey Institute of Technology PhD advisor Dr. Alexie Khakizov. For this effort, Enekwizu has been in discussions with Dmitri Zakharov, who is in charge of the environmental transmission electron microscope at the CFN.

She hopes to take samples and introduces forces under a controlled environment in the transmission electron microscope to see how that affects the structure of soot in fine detail.

Looking at the news with one wildfire event after another, Enekwizu feels compelled to conduct research in the lab and share data amid “a heightened sense of urgency to get this work done” and to share it with the world at large.

Scientific origins

Born in the southeastern part of Nigeria in Enugu and raised in Enugu, Lagos and Abuja, Enekwizu developed an interest in science at 13. She enjoyed classes in a range of sciences and said chemistry was her favorite.

“I knew I was not going to go into medicine because I was squeamish,” she said.

Chemical engineering fascinated her and also appeared to offer career opportunities.

During a chemical engineering internship, she worked at the Nigerian National Petroleum Corporation where she learned about flaring practices. It inspired her final year project on biogas as a renewable energy source and sparked her curiosity on the fate of pollutants and particulate matter that arise from legal and illegal flaring activities. 

In flaring, companies burn off excess gas to control pressure variations, increasing the safety of the operation at the expense of burning a potential resource.

When Enekwizu was at NJIT, Lewis, who is a longtime collaborator with Sedlacek, reached out to Khakizov to inquire about someone with a background in carbonaceous aerosols. After interviewing with Lewis, Sedlacek and others, Enekwizu received the job offer and began working in January of 2021.

A resident of Ridge, Enekwizu, who goes by the name “Ogo,” enjoys festivals and events around Long Island. She also appreciates the area’s ubiquitous beaches and has delighted in strawberry picking.

She hopes to explore Montauk later this spring or summer.

Mentoring

Enekwizu is passionate about mentoring students, particularly those who might be under represented in the field of Science, Technology, Engineering and Medicine.

She served as a graduate student mentor for Divyjot Singh, who was an undergrad at NJIT. Enekwizu taught Singh, who had grown up in Bhopal, India and had only been in the United States for six months when they met, “how to come up with research questions, how to develop hypotheses, how to write a proposal, how to make good presentations for conferences and everything in between,” he explained in an email.

While working with her, Singh found his passion for research and decided to pursue a PhD. 

Enekwizu is also passionate about supporting young women in science. She suggested that young black girls sometimes feel intimidated by STEM classes and careers. She urges a hands on approach to teaching and hopes to be a role model.

“If young girls see people like me thrive in STEM, they’ll be encouraged not to give up,” she said. “That is a huge win, in my opinion.”

Michael Jensen on a container ship in the Pacific Ocean, where he was measuring marine clouds. Photo from M. Jensen

By Daniel Dunaief

They often seem to arrive at the worst possible time, when someone has planned a picnic, a wedding or an important baseball game. In addition to turning the sky darker, convective clouds can bring heavy rains and lightning.

For scientists like Michael Jensen, a meteorologist at Brookhaven National Laboratory, these convective clouds present numerous mysteries, including one he hopes to help solve.

Aerosols, which come from natural sources like trees or from man-made contributors, like cars or energy plants, play an important role in cloud formation. The feedbacks that occur in a cloud system make it difficult to understand how changes in aerosol concentrations, sizes or composition impact the properties of the cloud.

“One of the big controversies in our field is how aerosols impact convection,” Jensen explained in an email. “A lot of people believe that when a storm ingests aerosols, it makes it stronger, because there are changes to precipitation and particles in the clouds.”

This process is called convective invigoration, which could make it rain more.

Another group of scientists, however, believes that the aerosols have a relatively small effect that is masked by other storm processes, such as vertical winds. 

Strong vertical motions that carry air, water and heat through the atmosphere are a signature of convective storms.

Jensen will lead an effort called Tracking Aerosol Convection Interactions Experiment, or TRACER, starting in April of 2021 in Houston that will measure the effect of these aerosols through a region where he expects to see hundreds of convective storm clouds in a year. 

From left, Donna Holdridge, from Argonne National Laboratory; Michael Jensen, kneeling; and Petteri Survo, from Vaisal Oyj in Helsinki, Finland during a campaign in Oklahoma to study convective storms. The team is testing new radiosondes, which are instruments sent on weather balloons. Photo from M. Jensen

The TRACER team, which includes domestic and international collaborators, will measure the clouds, precipitation, aerosol, lighting and atmospheric thermodynamics in considerable detail. The goal of the campaign is to develop a better understanding of the processes that drive convective cloud life cycle and convective-aerosol interactions.

Andrew Vogelmann, a technical co-manager of the Cloud Properties and Processes Group at BNL with Jensen, indicated in an email that the TRACER experiment is “generating a buzz within the community.” 

While other studies have looked at the impact of cities and other aerosol sources on rainfall, the TRACER experiment is different in the details it collects. In addition to collecting data on the total rainfall, researchers will track the storms in real time and will focus on strong updrafts in convection, which should provide specific information about the physics.

Jensen is exploring potential sites to collect data on the amount of water in a cloud, the size of the drops, the phase of the water and the shapes of the particles. He will use radar to provide information on the air velocities within the storm.

He hopes to monitor the differences in cloud characteristics under a variety of aerosol conditions, including those created by industrial, manufacturing and transportation activities.

Even a perfect storm, which starts in an area with few aerosols and travels directly through a region with many, couldn’t and wouldn’t create perfect data.

“In the real atmosphere, there are always complicating factors that make it difficult to isolate specific processes,” Jensen said. To determine the effect of aerosols, he is combining the observations with modeling studies.

Existing models struggle with the timing and strength of convective clouds.

Jensen performed a study in 2011 in Oklahoma that was focused on understanding convective processes, but that didn’t hone in on the aerosol-cloud interactions.

Vogelmann explained that Jensen is “well-respected within the community and is best known for his leadership” of this project, which was a “tremendous success.”

Since that study, measurement capabilities have improved, as has modeling, due to enhanced computing power. During the summer, Long Island has convective clouds that are similar to those Jensen expects to observe in Houston. Weather patterns from the Atlantic Ocean for Long Island and from the Gulf of Mexico for Houston enhance convective development.

“We experience sea breeze circulation,” Jensen said. Aerosols are also coming in from New York City, so many of the same physical processes in Houston occur on Long Island and in the New York area.

As the principal investigator, Jensen will travel to Houston for site selection. The instruments will collect data every day. During the summer, they will have an intensive operational period, where Jensen and other members of the TRACER team will forecast the convective conditions and choose the best days to add cloud tracking and extra observations.

Jensen expects the aerosol impact to be the greatest during the intermediate strength storms. 

The BNL meteorologist described his career as jumping back and forth between deep convective clouds and marine boundary layer clouds.

Jensen is a resident of Centerport and lives with his wife Jacqui a few blocks from where he grew up. Jacqui is a banker for American Community Bank in Commack. The couple has a 22-year-old son Mack, who is a substitute teacher at the Harborfields school district.

Jensen describes his family as “big music people,” adding that he plays euphonium in a few community band groups, including the North Shore Community Band of Longwood and the Riverhead Community Band.

As an undergraduate at SUNY Stony Brook, Jensen was broadly interested in science, including engineering. In flipping through a course catalog, he found a class on atmospheric science and thought he’d try it.

Taught by Robert Cess, who is now a professor emeritus at SBU, the class “hooked” him.

Jensen has been at BNL for almost 15 years. Over that time, he said the team has “more influence in the field,” as the cloud processing group has gone from six to 18 members. The researchers have “expanded our impact in the study of different cloud regimes and developed a wide network of collaborations and connections throughout the globe.”

As for his work in the TRACER study, Jensen hopes to “solve this ongoing debate, or at least provide new insights into the relative role of aerosols and dynamics.”