Atmospheric System Research

A confederation of experts considers the latest science on the workings of boundary layer processes

“All humans live there,” says University of Washington cloud physicist Rob Wood, explaining one of the main reasons scientists study the atmospheric boundary layer (ABL).

There are other reasons. The ABL, for instance, is where all weather happens.

It is also the portion of the atmosphere closest to the Earth’s surface. The exchange of heat, moisture, mass, and momentum in the ABL makes it the engine room of Earth’s water cycle, on which all planetary life depends.

The ABL “is in direct contact with the surface,” says Wood, and is heavily influenced by the surface over a longer time scale than are the upper regions of the atmosphere, where clouds form and precipitation initiates.

Wood co-chairs the Warm Boundary Layer Processes working group of the Atmospheric System Research (ASR) program at the U.S. Department of Energy (DOE). ASR funds observational research whose data go on to inform and improve predictive models of the atmosphere.

The group’s other co-chair is Colorado State University research scientist Christine Chiu, an expert on how clouds, precipitation, radiation, and aerosols interact.

Aerosols are the atmospheric particles that water condenses upon to form cloud droplets.

“Clouds respond to aerosol changes in many ways,” says Chiu, resulting in different precipitation characteristics and differences in cloud albedo. This measure of how much clouds reflect light impacts the Earth’s energy budget.

One Among Four

ASR sponsors three other working groups to encourage collaborative process-level research on aerosols, convection, and the Earth’s high latitudes.

Chiu and Wood coordinate the ASR working group devoted to processes in the warm boundary layer. This group focuses on the ABL in the tropics and midlatitudes, where clouds are dominated by liquid water instead of ice.

The areas of interest of the four working groups are separate, says Wood, though many scientists belong to more than one group.

“If we think about convection, shallow or deep, it starts from boundary layer processes,” says Chiu, pointing to storm activity as one among many ways that interests among all the ASR working groups cross over.

The warm boundary layer processes group is also the largest working group at ASR, she adds──a further sign that the ABL is a shared interest among atmospheric scientists.

As with any ASR working group, “membership” is a loose term, and depends any year on those who join with a warm boundary layer process in mind.

“The group kind of moves around,” says Wood, depending on where the latest science concerns lead.

To join the working group, create an account with ARM. Then, under “Subscriptions,” check “Warm Boundary Layer Processes.”

Lower Down, Higher Complexity

In the Earth-hugging ABL, atmospheric scientists must consider more than physics, which dominates studies of higher regions of the troposphere. About two additional miles extend above the ABL to the bordering stratosphere.

In the ABL, so many complex small-scale processes come into play, says Wood, that scientists have difficulty understanding the interacting processes.

One is evapotranspiration, the process of liquid water transforming into water vapor as it rises into the air. Understanding a land-atmosphere interaction like this requires mixing physics with “things like biology,” says Wood, since much of the evaporating water emits from plant matter.

To address the complexity of warm boundary layer issues, the group will begin holding bimonthly virtual meetings in January 2025.

Research Highlights

Chiu and Wood illustrate the growing complexity of warm boundary layer issues by naming a few recent papers submitted to ASR’s Research Highlights page. (Scientists with ASR-funded projects underway are encouraged to write these brief, understandable summaries of their work.)

They point to one paper that shows how machine learning neural networks can help simulate near-surface turbulence.

Chiu and Wood also name a study that uses conventional weather data as the basis for a deep neural network that estimates boundary layer height. That’s an important variable in the development of turbulence, which controls the transport of heat, moisture, and mass into the atmosphere.

Another study looks at “locally narrow” droplet size distributions in stratocumulus clouds, a nonuniform variability that models should reflect. Data were derived from a unique holographic instrument flown on a field campaign in the Azores funded by Atmospheric Radiation Measurement (ARM).

The DOE user facility operates six atmospheric observatories in climate-critical regions across the world, including its Eastern North Atlantic (ENA) site just west of Portugal. ARM is frequently a rich data source for ASR work on the warm boundary layer.

A Wide ‘Range of Activities’

Other 2024 papers assess warm cloud albedo (reflectivity), discuss the role of aerosol size on computer-simulated cloud transitions from overcast to broken conditions near ENA, and track shallow cumulus cloud behavior at ARM’s Southern Great Plains observatory by modeling the effects neighboring clouds have on growth and dissipation. (For one, it seems that a growing cloud displays higher vertical velocity when surrounded by “decaying” clouds: those at the end of their life cycles.)

“It is important to think about how these processes collectively determine the energy flow in our Earth system,” says Chiu, mentioning another recent paper, on investigating a “more transparent infrared window” in the atmosphere. The authors use ARM long-term measurements to evaluate our knowledge of water vapor continuum absorption, an outstanding issue that matters to the Earth’s cooling.

In one window-like infrared spectral region, from 8.0 to 12.8 microns, thermal radiation from the Earth’s surface passes almost unimpeded through the atmosphere, a “transparency” that has a planetary cooling effect. Using ARM data, the authors found an increase in this atmospheric transparency, and therefore an enhanced cooling effect.

Papers like these, says Wood, illustrate the working group’s “range of activities and foci.”

Yearly Breakout Sessions

Like the other ASR working groups, the warm boundary layer group has both a science and communications mission. Throughout the year, Chiu and Wood inform DOE program managers and principal investigators about emerging issues and concerns.

The primary way of communicating these issues is through a working group breakout session on warm boundary layer processes at the annual Joint ARM User Facility/ASR Principal Investigators (PI) Meeting. (The next is scheduled for March 3 to 6, 2025, in Rockville, Maryland.)

At the last such meeting, in August 2023, Chiu and Wood moderated a session with Yunyan Zhang, a former co-chair of the working group and a cloud life cycle researcher at Lawrence Livermore National Laboratory in California.

There were 15 talks, divided into the group’s traditional three main topic areas: boundary layer structure and interactions with land surface; aerosol-cloud interactions; and cloud dynamics and microphysics.

The quick presentations, backed with a slide or two, ranged from glimpses at the evolution of shallow cumulus clouds and moist downdrafts to biomass-burning aerosols and sea salt delivery to clouds.

“People can see what other people are doing,” says Wood.

Adds Chiu: “Through this kind of opportunity, we hope to promote the visibility of early-career scientists and to build a strongly connected and collaborative working group.”

The session’s key findings were published later in a 2023 breakout summary report.

Coming: Reports in Recent Research

The agenda for the 2025 breakout session is still being hammered out. Monthly planning meetings just started in November 2024.

Among other things, Chiu and Wood say they will decide which posters will be elevated to talks. Next will be soliciting presentations.

Following tradition, there will be updates from experts on ARM’s value-added products (VAPs), in which data are streamlined for easier use in models.

And, as always, there will be reports on recent or upcoming ARM field campaigns that have (or will) supply data relevant to warm boundary layer processes.

Likely entrants, says Chiu and Wood, include an update on the Bankhead National Forest (BNF) observatory in northern Alabama, where data collection started in October 2024.

BNF “obviously projects into more than one (ASR) working group,” says Wood. “There is considerable land-atmosphere exchange. There’s also deep convection evolving from shallow convection over the diurnal cycle──another boundary layer-related problem.”

Whatever the final agenda is, say Chiu and Wood, the main order of business, as always, will be to present new research and establish new collaborations. That’s the shared mission of every ASR working group.

Wood belongs to all of them.

“I like to see what they’re up to,” he says.

New particle formation, aerosol aging, and a long list of related issues captivate a changing cast of collaborative experts

Suspended in the atmosphere, tiny particles of liquids and solids work to make life on Earth possible.

These particles, called aerosols, can be as tiny as 2 nanometers wide, about the diameter of a strand of DNA. Others are ten thousand times bigger.

Big and small, taken together, they make clouds and precipitation possible.

Aerosols are the seeds upon which water rides in the planet’s vast water cycle. When numerous enough, they form clouds. When heavy enough, aerosols form water droplets that fall to Earth as rain or snow.

Across the world, scientists study the origin, shape, chemistry, and evolution of aerosols. Being scientists, they form communities of interest. One such community is the Aerosol Working Group within the Atmospheric System Research (ASR) program at the U.S. Department of Energy (DOE).

One of the group’s two co-chairs, Markus Petters, an atmospheric scientist at the University of California, Riverside, has a caution: There is no set list of members.

”Anyone interested in aerosol science is welcome to join,” he says, with two co-chairs acting as facilitators.

“We (the chairs) are not that important,” except as scientists who keep the wheels of conversation going, agrees co-chair Nicole Riemer, a University of Illinois at Urbana-Champaign professor.

Petters studies the physical and chemical properties of aerosols. Riemer uses surface and satellite observations to create computer simulations of how aerosols behave in the atmosphere.

Some of the surface data Riemer and others use come from Atmospheric Radiation Measurement (ARM), a user facility in the DOE’s Office of Science. ARM operates six observatories across the world; three are fixed locations, three are mobile facilities. The ARM Data Center has archived more than seven petabytes of remote-sensor measurements related to aerosols, clouds, precipitation, and other atmospheric properties.

The Main Task

The ASR group operates in concert with ARM’s own Aerosol Measurement Science Group (AMSG). (Petters and Riemer are ex officio members.)

The AMSG “is really a different group,” says Petters, with a focus on strategic planning for ARM’s aerosol measurement needs and challenges.

The ARM group, for one, creates periodic aerosol science planning documents. The ASR group does not.

In the ASR space, Petters and Riemer provide feedback to the AMSG regarding aerosol measurements of special value to the modeling community.

The ASR mission is to support observational research that will ultimately help inform and improve climate models.

Petters and Riemer enable ASR-related aerosol conversations that they in turn share with DOE managers and principal investigators (PIs). But they also oversee one main annual task: organizing an aerosol working group session and aerosol-related breakout sessions at the Joint ARM User Facility and ASR PI Meeting. (The last such meeting was in August 2023. The next is scheduled for March 3 to 6, 2025, in Rockville, Maryland.)

In the context of the annual PI meeting, Petters says, “We try to facilitate connections and discussions to solve the largest science questions.”

Those discussions take place among AMSG members, ARM and ASR PIs, and ARM translators──the experts who create value-added products (VAPs) to enhance the utility of data to modelers.

There are many large aerosol science questions, says Petters. One of them, for example, is the ongoing puzzle of how aerosols “flux” into the atmosphere, pulsing skyward to play their critical roles.

A Session Template

At the annual ARM/ASR meeting, the aerosol processes working group session Petters and Riemer oversee usually follows a common template, beginning with topical presentations. After that, participants have just one minute each to present on their current research: “Very fast-paced and quite entertaining for all parties involved,” says Riemer.

In 2023, to give a sense of things, the topical presentations started with John Shilling, an atmospheric chemist at Pacific Northwest National Laboratory. He introduced the ARM translator group he is a part of and presented an update on VAPs related to aerosols.

During the same session, Adam Theisen and Maxwell Grover of Argonne National Laboratory joined Giri Prakash of Oak Ridge National Laboratory to outline a series of topics in open science for the aerosol community.

Such annual working group sessions wrap up with a presentation by the AMSG chair. They also look back and look ahead at ARM field campaigns that yielded (or promise to yield) consequential aerosol data.

In 2023, for instance, presenters discussed two recent campaigns: the Tracking Aerosol Convection interactions ExpeRiment (TRACER) in and around Houston, Texas, and the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) in coastal Southern California.

That same year, working group presenters looked ahead by discussing aerosol plans for the Clouds, Aerosol, and Precipitation Experiment at kennaook Cape Grim (CAPE-k) and the ARM mobile facility deployment at what is now known as Bankhead National Forest (BNF).

Regarding future campaigns, “the organizers look for input,” says Riemer, recalling the 2023 session. “Chongai (Kuang, the BNF PI and aerosol processes lead) really wanted to hear from the working group.”

One Possible Agenda

What to discuss about a coming campaign at any annual aerosol working group session “is a long process in the making,” says Riemer.

Anticipated events like CAPE-k or BNF may get a spot on the agenda for a couple of years running.

For the 2025 ARM/ASR meeting, there is no working group agenda yet. However, Petters and Riemer speculate there will be short updates on CAPE-k (still underway) and EPCAPE (now in an intense data-analysis phase).

Also likely, they say, will be an early look at BNF data, as well as presentations on two upcoming ARM field campaigns with important implications for aerosol science.

One is slated to begin collecting data in December 2024: the Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE) in and around Baltimore, Maryland. Led by Kenneth Davis of Pennsylvania State University, CoURAGE will investigate aerosol patterns and sources in this urban-rural-coastal environment through November 2025.

Further in the future is ARM’s Desert-Urban SysTem IntegratEd Atmospheric Monsoon (DUSTIEAIM), which will span April 2026 to September 2027 in the Phoenix, Arizona, area. The lead scientist is Allison Aiken of Los Alamos National Laboratory in New Mexico, who plans to study how converging desert and urban atmospheric environments influence storm activity and precipitation. So far, she has assembled a team of 19 co-investigators.

DUSTIEAIM will fill in urban-rural atmospheric knowledge gaps along the Flagstaff-Phoenix-Tucson corridor by operating concurrently with the Southwest Urban Integrated Field Laboratory (SW-IFL).

SW-IFL is one of four DOE Urban Integrated Field Laboratory (UIFL) projects underway since 2023.

Remote Places, Too

The structure of DUSTIEAIM “is fairly mature,” says Petters, but every new ARM deployment raises questions the ASR aerosol working group can help with. “What should we sample? How often? What is needed to solve the larger problem?”

Matters such as a renewed interest in urban climates, he says, relate to “forces within DOE,” while working groups address finer-grained science questions.

Clearly, urban places are important, says Petters. “That’s where people live, and human-caused emissions are large.”

At the same time, says Riemer, in the aerosol science community there is still a strong emphasis in non-urban areas.

At one edge of the Southern Ocean, she says, CAPE-k data will add to what we know about cloud and ice formation in pristine environments, where aerosols are scarce. And ARM’s fixed observatory in the Azores, Eastern North Atlantic (ENA), is a window into another remote environment.

On a grand scale, the impact on climate is manifesting itself in cloud decks in both the Pacific and Southern oceans, says Petters. “Remote places will always be of interest. Aerosols there will have an impact on the earth system.”

Four Themes

Four main themes “that appear again and again,” says Riemer, are of broad concern to the ASR aerosol working group.

One is understanding the radiative effects of absorbing aerosols, which also reflect or scatter incoming solar energy.

Another is studying secondary organic aerosols (SOA): how they work, how they can be measured, and how they can be modeled. Such aerosols are formed when organic particles are transformed in the atmosphere via oxidation with volatile organic compounds, including isoprene from trees. In urban and remote areas, SOAs account for a high percentage of fine particles, so they are important to know more about.

A third big theme, says Riemer, is new particle formation, also called atmospheric nucleation. Such particles generate 50% of the seeds that form cloud droplets, but how are they born? How does nucleation work? In models that simulate a changing climate, the chemistry and physical properties of new particles remain a source of uncertainty. A fourth theme is the question of what happens to aerosols during their lifetimes in the atmosphere.

How do they age? That’s a term for the transformation aerosols undergo as they are transported through the atmosphere from their place of origin. Those origins might be as diverse as a wildfire, a burst of fungal spores during a rainstorm, and many more.

How do aerosols evolve to mix with others? How do their properties change? How do changes during aerosol life cycles impact the climate?

And what is the “removal” process? Riemer asks, a term for how aerosols disappear from the atmosphere. “We need to understand that as well.”

Step by Step

The ASR working group is one feature of the cumulative nature of progress in aerosol science, says Petters, which is rarely the result of “single revolutionary papers. It’s about providing robust data sets and showing in a wide scale of environments that these effects hold. So, it’s about statistics.”

In part, these statistics owe a lot to ARM, he adds, “which has excelled at providing long-term data sets” from its observatories in arctic, continental, and marine environments.

Along the way, these data and other data from long-term field campaigns provide rare looks at full annual cycles of aerosol behavior.

One example is an archive of vast new aerosol data sets from the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, a 13-month, 20-nation investigation of the Arctic’s atmosphere, snow, ice, and ecology that began in September 2019.

Work by MOSAiC fieldwork veteran Jessie Creamean, a research scientist at Colorado State University, is just one example of what annual cycles of aerosol behavior can yield. For example, she led a 2022 ARM- and ASR-supported study on the annual cycle of central Arctic INPs.

On behalf of ARM, Creamean also co-leads efforts to collect and analyze samples of ice nucleating particles (INPs).

‘We Keep Adding Knowledge’

Acquiring long-term aerosol statistics may not be glamorous, says Petters, but in the last 20 years, “we keep adding knowledge. We have a much deeper process-level understanding.”

That deeper understanding, for example, means knowing more about the sensitivity of clouds to greenhouse gases, the chemistry of aerosols, their vertical distribution in the atmosphere, aerosol hygroscopicity (how readily they attract water), and cloud condensation nuclei (CCN).

Water clings to CCN, making it possible for clouds to form.

In turn, a greater understanding of aerosol processes adds to the kind of insights needed to make better earth system models.

Knowing more comes with its own challenges, however, says Petters, including “exploding data streams and the increased complexity of analysis.”

Those challenges require the right people to confront them. The ASR aerosol working group exemplifies what is needed: a cast of multidisciplinary experts.

“Aerosols are diverse,” says Riemer. “So is our group.”

DOE announces $6 Million to fund ASR science

The U.S. Department of Energy (DOE) has announced plans to provide $6 million in new research grants for Atmospheric System Research (ASR) program science.

Key details and deadlines:

• Funding opportunity DE-FOA-0003484 can be found on the DOE/BER Funding Opportunities website.
• Pre-application due date: January 7, 2025, at 5:00 p.m. ET.
• Pre-application response from DOE: January 24, 2025.
• Submission Deadline for Applications: February 27, 2025, at 11:59 p.m. ET.

Successful applicants will focus their research on observational, data analysis, and/or modeling studies that use observations supported by DOE’s Biological and Environmental Research (BER) program, including the Atmospheric Radiation Measurement (ARM) user facility, to address one of the following research topics:

1. Atmospheric processes from ARM’s Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE)
2. High latitude and Southern Ocean atmospheric processes using ARM observations

“Researchers in the ASR community work on some of the most important and exciting questions facing atmospheric science today,” says ASR Program Manager Jeff Stehr. “This announcement will help fund critical research on cloud, aerosol, precipitation, and the radiative transfer processes that affect our planet’s radiative balance and hydrological cycle—especially those processes that limit the predictive ability of regional and global models.”

Funding will be awarded competitively based on peer review, and total award amounts are expected to range from $200,000 to $975,000, beginning in fiscal year 2025.

The funding opportunity announcement document outlines more details about the research topics, award amounts, length of research projects, eligibility, and other requirements. Pre-applications are required and will be reviewed by DOE program managers to determine their appropriateness for the preparation of an application.

Stehr advises those responding that a new pre-application format and new required elements have been introduced this year. “Please carefully review the pre-application instructions and note that using a previous year’s pre-application as a guide is not recommended.”

• Full details and application instructions are available in FY2025 funding announcement DE-FOA-0003484 on the DOE Funding Opportunities website.
• Pre-applications must be submitted by 5 p.m. ET Tuesday, January 7, 2025.
• DOE will respond to pre-application submitters, informing them whether a full application is encouraged or discouraged by January 24, 2025. Full applications will be due February 27, 2025.

The U.S. Department of Energy (DOE) Office of Science has issued a Notice of Funding Opportunity (NOFO) for the Climate Resilience Centers (CRCs). These new centers will be dedicated to rapidly developing new science and talent to address the nation’s most pressing climate resilience challenges.

• Pre-applications deadline: December 12, 2024 at 5:00 p.m. ET
• Climate Resilience Centers NOFO informational webinar: November 6, 2024, 1:00 p.m. ET (webinar registration)

CRCs will improve the availability and utility of DOE Biological and Environmental Research (BER) research, data, models, and capabilities to address climate resiliency, particularly by underrepresented or vulnerable communities. These science-based predictive tools and methods are critically needed to inform policies and plans for strengthening the security and resilience of critical infrastructure and natural resources.

“We anticipate the awards will go to a diversity of institutions and environments that haven’t previously had access to DOE resources in order to study and seek solutions to their local environmental and energy concerns,” said Dorothy Koch, Associate Director of Science for Biological and Environmental Research (BER).  “We are excited that these centers will expand the science and talent pool in tackling one of America’s most daunting challenges while also bringing benefits to local communities.”

CRCs will extend DOE climate science, capabilities, and research by supporting non-R1 Minority Serving Institutions (MSIs) and non-R1 Emerging Research Institutions (ERIs) to address regional resilience needs and impacts on natural, socioeconomic, and/or built systems and their intersections. CRCs also aim to foster capacity at regional and local scales by connecting with affected communities and stakeholders to translate basic research into actionable science to enhance climate resilience, as well as to identify research priorities for future DOE investments. CRCs will form a nucleus for building and empowering a future pool of local talent and expertise, including young scientists, engineers, and technicians, to address local resilience challenges and inform equitable solutions. CRCs will leverage ongoing DOE climate science and capabilities that exist at currently supported DOE national laboratories and universities and build two-way engagement between DOE-funded research and community stakeholders for improved climate resilience responses.

Non-R1 MSIs and non-R1 ERIs are eligible to apply as single-institution applicants or as the lead of a multi-institutional team. Please see the funding opportunity for agency contacts and more details.

Find the Climate Resilience Centers Notice of Funding Opportunity on the Office of Science website.

For more information, a webinar will be held on Zoom on November 6, 2024, at 1:00 p.m. ET. Register with the Zoom link. 

For those presenting at the 2024 American Geophysical Union (AGU) Annual Meeting, one of the best ways to draw attendees to your sessions is to be highlighted on the ASR and Atmospheric Radiation Measurement (ARM) websites.

If you or one of your team members will present a talk or poster at the AGU meeting—and if that presentation is based on your ASR-funded project or uses ARM data as a key data source—tell ASR and ARM about your presentation!

Using this form on the ASR website, it’s a simple three-step process to share your abstract information.

We will publish your abstracts on the ASR and ARM websites, which serve as an important guide for attendees. Your sessions may also be promoted on ARM social media and in ASR and ARM news stories.

See the ASR and ARM presentations that have been shared so far for the December 9–13 AGU Fall Meeting in Washington, D.C.