From the states of Washington, Texas, and Michigan, scientists tell tales of ARM data
Early Career Research Program awards from the U.S. Department of Energy (DOE), announced every summer, support outstanding national laboratory and university scientists beginning their careers. The money, time, and recognition they receive accelerates formative investigations that may guide the rest of their research lives.
Since starting in 2010, the program has granted 961 awards to fund projects up to five years in duration.
Let’s take a quick look at four early career projects that began in fiscal year 2019 and employed data from DOE’s Atmospheric Radiation Measurement (ARM) user facility.
All four awardees represent varieties of expertise in aerosols, the tiny particles suspended in the atmosphere that make clouds and precipitation possible.
And all four had to cope with the travel and time restrictions rising out of the COVID-19 pandemic, which was officially declared in March 2020.
While some of their projects are still in progress, all four are getting ready to present related research—or have their research presented—at the 2024 American Geophysical Union (AGU) Annual Meeting in Washington, D.C., and the 2025 American Meteorological Society (AMS) Annual Meeting in New Orleans, Louisiana.
Susannah Burrows, Earth Scientist, Pacific Northwest National Laboratory (PNNL)
Burrows devoted her Early Career Award to investigating the sources, chemistry, and physical properties of ice-nucleating particles (INPs).
INPs contribute to the formation of ice in mixed-phase clouds (those containing both water and ice) by acting as a matrix for water droplets to freeze upon. They are 10,000 times rarer in the atmosphere than other particles and commonly originate from mineral dusts and sea spray aerosols.
Burrows’ work looked at INPs from both land and sea.
To examine INPs from land, in the fall of 2021, Burrows deployed a team for a month to ARM’s Southern Great Plains (SGP) atmospheric observatory in Oklahoma to collect data as part of her first ARM field campaign, Agricultural Ice Nuclei at SGP (AGINSGP).
Burrows also directed research on how sea spray aerosols contribute to INP formation. Her team looked at how much organic particulate matter at the ocean surface transfers to sea spray and, in turn, how many INPs are transferred from the ocean to the atmosphere.
On land or at sea, the focus is on “immersion mode” INPs, which when fully immersed in a cloud droplet activate ice formation at relatively warm temperatures, as low as minus 15 C (5 F). Without an INP, pure water droplets do not freeze until about minus 36 C (minus 32.8 F) or colder.
On April 11, 2022, AGINSGP’s most productive day, the Burrows team collected 150 INPs, “the largest number collected in a single day” during a field experiment, she says.
A June 2024 paper led by PNNL earth scientist Gavin Cornwell used AGINSGP data to report for the first time that particles were more likely to be active as INPs if they contain organic matter, particularly phosphates, as well as lead (previously reported) and mixed soil-organic particles.
Burrows speculates that, on land, mineral dusts with phosphate markers are associated with microbial biological activity in soils: for instance, fragments of bacterial cell walls, fungal spores, particles ejected into the atmosphere from soil or leaf surfaces by splashing raindrops, or from wind erosion of soils.
“We would like to trace such particles back to their sources,” says Burrows.
Those sources will be one focus of Cornwell’s 2024 DOE Early Career Award, she says, “which will allow him to take the next step on some of the (AGINSGP) research questions.”
For the ocean portion of her research, Burrows co-authored a January 2022 study led by former PNNL postdoctoral researcher Isabelle Steinke. It introduces a numerical framework for estimating concentrations of INPs linked to organic matter at the ocean surface. The paper identified steps in the sea spray-to-INP process that contribute uncertainty in models.
“We know there is a connection between ocean biology and particle emissions,” she says. “But we have not yet been able to get a really good process model.”
In the future, Burrows says she aims to explore “ice processes in clouds more broadly.”
In October 2023, she co-chaired a workshop with international researchers on processes of ice formation and the evolution of ice in clouds. It’s a challenging subject, says Burrows. “There are a lot of open questions.”
Burrows’ research at AGU 2024: “Characterization of springtime sources and variability of ice-nucleating particles in the agricultural region of the U.S. central Great Plains” (poster), Wednesday, December 11, 8:30 a.m. to 12:20 p.m. Eastern, Hall B-C (Poster Hall), Walter E. Washington Convention Center.
Naruki Hiranuma, Aerosol Scientist, West Texas A&M University
Hiranuma, an expert in advanced aerosol measurement techniques, devoted the bulk of his Early Career Award work to field-testing a mobile and remotely operable device that counts the abundance of INPs in ambient air. About the size of a standard household refrigerator, the Portable Ice Nucleation Experiment (PINE) cloud chamber is a miniaturized version of a chamber operating at a laboratory in Germany.
INPs, which are hard to capture and measure, represent “one of the largest uncertainties in researching aerosol-cloud-climate interactions,” he says. They influence the life span and reflectivity of clouds containing ice.
Knowing more about regional variations of INPs around the world will help reduce predictive errors in present models of cloud-climate interactions. That is especially important because the “arctic amplification” of temperatures in a warming world is marked by an increase of INPs.
Hiranuma envisions a global network of robust, semi-autonomous PINE chambers for long-term INP measurements. PINE requires only a plug-in power source and an internet connection.
Because PINE is so easy to operate and monitor remotely, “it has opened new doors for new people to come into this research community,” says Hiranuma. He worked with two postdoctoral researchers and two master’s-level students. So far, three have published peer-reviewed papers. One published in May 2024 reported on a new Python toolkit for processing INP data.
There are only two PINE devices in the United States to date, with a third expected by late 2025. Hiranuma has an ongoing PINE data analysis collaboration with the pan-European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS), an ARM collaborator. It combines INP data around the world from ARM and ACTRIS sites.
During his Early Career Award work, Hiranuma executed the world’s first PINE field measurements, recorded its limitations (including measurable temperature ranges), and verified its readiness for the rigors of remote deployments in arctic, continental, and marine environments.
For 45 days in 2019, Hiranuma oversaw PINE field operations at the first of three ARM locations: the SGP. He says the deployment in Oklahoma was “the last sanity check before we went into really remote locations.”
In 2020, Hiranuma deployed PINE at ARM’s Eastern North Atlantic (ENA) observatory in the Azores, west of mainland Portugal. The six-month deployment during the pandemic, when travel restrictions were in place, demonstrated the device’s “extreme remote controllability,” he says.
Then, after a COVID-related delay, Hiranuma shipped PINE to Utqiaġvik (formerly Barrow), Alaska. It operated for two and a half years near ARM’s North Slope of Alaska (NSA) observatory, in what he calls his project’s “most challenging environment.”
The PINE chamber is back in Texas now, ready for U.S. field missions whose funding is pending. Hiranuma is focused on publishing the last few papers from his Early Career Award project.
Hiranuma is also thinking about next steps. Those include developing an airborne application for PINE as well as a PINE chamber capable of characterizing the physical and chemical properties of INPs.
The DOE project gave him valuable lessons in project and time management, he says, but also “so many new ideas.”
Hiranuma’s research at AMS 2025: “Multi-Seasonal Measurements of the Ground-Level Atmospheric Ice-Nucleating Particle Abundance in the North Slope of Alaska” (poster), Tuesday, January 14, 3 to 4:30 p.m. Central, Hall C, New Orleans Ernest N. Morial Convention Center.
Kerri Pratt, Atmospheric Chemist, University of Michigan
In November and December 2018, just months after the Early Career Awards were announced, Pratt made a quick start on her research.
She and her team deployed instruments to the NSA to identify the sources and chemical composition of wintertime aerosols for her Arctic Aerosol Sources and Mixing States (ARCAEROMIX) campaign.
The signature piece of equipment deployed for the ARM campaign was a single-particle mass spectrometer used to measure the composition of individual aerosol particles in real time.
Pratt’s fast start on the Early Career Award also included Aerosols in the Polar Utqiaġvik Night (APUN), a 2018 investigation of aerosol measurements at the beginning of polar night, when such measurements are historically rare. Key to APUN was a delayed ice freeze-up in the Arctic Ocean near the NSA, where Pratt and her team observed breaking waves at the shore.
When open water exists at an unusual time, “you have a source of sea spray aerosol that is highly uncharacterized,” she says.
Pratt continued her focus on the understudied arctic winter during the 2019–2020 Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic. She deployed a sampler to collect particles that are still being analyzed one by one at the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science user facility located on the PNNL campus.
In addition to studying sea spray aerosol, her group is investigating the speculation that sea salt aerosols are also produced by blowing snow or by snow sublimation—the process in which snow passes directly from a solid to a gas, bypassing the liquid state.
In the face of delays during this “highly COVID-impacted project,” says Pratt, “we went back to data collected during a prior ARM field campaign.”
The Summertime Aerosol across the North Slope of Alaska (SAANSA) campaign, led by Pratt, took place in 2015 and 2016 at the NSA and what was then an ARM site at Oliktok Point, Alaska, adjacent to the Prudhoe Bay oil fields. Pratt pointed to three related papers funded in part by her Early Career Award:
- A June 2021 study found that droplets from frequent fog events reacted with oil-field emissions to form an SOA “that had never been documented in the Arctic,” says Pratt.
- A March 2022 paper reported on what she called “the surprising observation” during arctic summer of solid-phase particles linked to new particle formation from open-water marine biogenic sources. This is more relevant than ever in a warming Arctic, where sea ice is declining and open water increasing.
- A July 2024 paper reported “the first measurement-based quantification of aerosol mixing state in the Arctic,” says Pratt. (Mixing state is a measure of how chemical species are distributed across a population of aerosols.) The heterogeneous aerosol population in the oil-field atmosphere she studied counters the view that the Arctic has only homogeneous aerosol populations.
“There is growing attention to local arctic pollution sources,” says Pratt. “They are usually not studied. But with growing development in the Arctic, this is really important.”
Pratt’s research at AGU 2024: “Revealing the Chemical Composition of Sea Spray Aerosols over the Central Arctic Ocean during the Year-Long MOSAiC Expedition” (poster presented by Pratt’s PhD student Tiantian Zhu), Thursday, December 12, 1:40 p.m. to 5:30 p.m. Eastern, Hall B-C (Poster Hall), Walter E. Washington Convention Center.
Manish Shrivastava, Earth Scientist, PNNL
Shrivastava set out to study secondary organic aerosols (SOAs).
SOAs are “secondary” because they are not directly emitted. Instead, they begin their life cycles in the gas phase; some go on to become particles in the “large chemical reactor” of the atmosphere, he says. From there, SOAs have far-reaching impacts on the climate.
For one, they account for most of the millions of particles in atmospheric haze, a common phenomenon that affects how much of the sun’s energy reaches the Earth’s surface. SOAs can also seed cloud formation.
Shrivastava focused on the interaction between SOAs and clouds. It’s a challenging task, complicated by the thousands of organic species involved in millions of dynamic atmospheric reactions, which occur both in the gas and aerosol phases.
Of special interest were SOA reactions with water in aerosols and cloud droplets, “the big missing pieces of the puzzle,” says Shrivastava. “We do not know what (these reactions) are doing to the climate and earth systems.”
He calls the SOA-cloud aqueous puzzle “too big to be solved in five years, but we have made a lot of progress.”
Since getting the Early Career Award, Shrivastava has stacked up around 55 publications and given more than 20 invited talks at universities and conferences.
One of his most recent papers, published in Cell in June 2024, used aircraft data over the Amazon to show new particle formation in biomass burning smoke that had previously been thought unlikely: ultrafine particles generated in the smoke from vegetation fires that modify both weather and climate by making shallow clouds deeper and precipitation heavier.
Ultrafine particles are less than 50 nanometers wide, or 2,000 times thinner than a sheet of paper.
In a February 2024 paper, Shrivastava and his team developed new measurement-based modeling approaches to simulate chemical processes that govern the reactions of biomass burning organic gases in clouds that form aqueous SOAs.
ARM data from the Amazon figured into a January 2022 paper reporting the importance of previously unrecognized soil and leaf chemistry pathways for production of SOAs and other atmospheric aerosols.
Shrivastava also made forays into machine learning. In an April 2022 paper, he and his team applied supervised machine learning techniques that facilitated and sped up an online analysis of aircraft aerosol mass spectrometer data to determine the sources of organic aerosols.
In addition, he co-wrote a March 2023 paper about embedding a physics-based deep learning neural network model within a detailed regional chemical transport model. This approach sped up calculations of SOA aqueous chemistry by the regional model.
Such machine learning applications, he says, can replace computationally expensive aerosol chemistry modules within current climate models, including those simulating chemical transport.
In a May 2024 study, Shrivastava and his team applied advanced mathematical causal analyses to identify key features affecting the formation of aqueous SOA from time-series data. They demonstrated that in certain applications, such mathematical approaches may surpass traditional machine learning techniques.
However, Shrivastava insists on the critical role of thoughtfully designed measurements in closing knowledge gaps in atmospheric processes. When integrated with models, he says, the right observational data provide the most valuable insights.
He tapped data from ARM field campaigns in the Amazon and at the SGP, as well as from laboratory experiments at EMSL.
In an October 2024 paper, Shrivastava and his team discovered the critical role of acid-base reactions in the formation of molecular clusters and their growth by extremely low volatility organic gases. Such atmospheric chemistry processes help explain measurements of newly formed particles at the SGP. The study also provides insights about the role of clouds in suppressing atmospheric chemistry that otherwise causes ultrafine particles to form.
In the same paper, Shrivastava conducted preliminary simulations of SOAs around ARM’s new Bankhead National Forest observatory in Alabama. The simulations showed that new particle formation in the forest might be limited by the availability of sulfuric acid gases.
“In all, it went really well,” he says of the Early Career Award work. “We achieved much more than we envisioned.”
Shrivastava’s research at AGU 2024: “Intense formation of ultrafine particles from Amazonian vegetation fires and their invigoration of deep clouds and precipitation” (poster), Wednesday, December 11, 8:30 a.m. to 12:20 p.m. Eastern, Hall B-C (Poster Hall), Walter E. Washington Convention Center.
# # #Author: Corydon Ireland, Staff Writer, Pacific Northwest National Laboratory
ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.