Deep in a pine-oak forest in northern Alabama, a 140-foot tower rises above the canopy. Equipped with scientific instruments, it anchors the Bankhead National Forest (BNF) observatory, a distinctive research site for studying how forests interact with the atmosphere in the southeastern United States.
The long-term mobile observatory, which began operating in October 2024, is part of the U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) user facility, a multi-laboratory scientific user facility sponsored by DOE's Office of Science, Biological and Environmental Research program. DOE's Argonne National Laboratory manages observatory operations.
In less than two years, Bankhead has already begun helping researchers better understand how forests influence humidity, aerosols, clouds, rainfall and storms. The observatory combines an instrumented tower, supplemental field sites, scanning radars, tethered balloon campaigns and open-source analysis tools to investigate interactions between land and atmosphere.
Researchers are using the site to develop new precipitation and radar-tracking products, compare rainfall above and below the canopy and build a growing scientific community through monthly collaborations and the ARM Summer School. Together, these efforts highlight Bankhead's potential as a long-term platform for advancing atmospheric science and improving Earth system models.
Forests to Clouds
What sets Bankhead apart is its location. "The Bankhead deployment is unique because it sits in the middle of a deep forest canopy," said Joseph O'Brien, Argonne atmospheric science software specialist. "That gives us an unusual opportunity to study how airflow, precipitation, temperature, humidity, aerosol and moisture changes interact with the local environment."
Located southwest of Hunstville, the observatory gives scientists a chance to study weather and land-atmosphere processes in a region known for strong thunderstorms, abundant vegetation and complex land-atmosphere interactions.
The 140-foot tower is significant to that work. It allows researchers to measure conditions below the canopy, within it and above it, offering a fuller picture of how forests affect the air around them.
"One of the biggest milestones in the first year was getting the tower installed," said Mark Spychala, Argonne observatory manager for the site. "Deploying a tall, instrumented tower in the middle of a forest is a major accomplishment, and it has already generated a lot of interest from researchers."
In addition to the main site, the observatory includes three supplemental sites spread across the surrounding landscape. These locations help researchers compare conditions in the forest with those in managed grassland, agricultural areas and places influenced by the Tennessee River. Together, they create a broader regional view of how different land surfaces affect the atmosphere.
Bankhead also supports scanning radars and tethered balloon campaigns. The radars help scientists observe rainfall and storm structure, while the tethered balloons can be raised, lowered or held at certain heights to measure different layers of the atmosphere. These capabilities help researchers study everything from moisture and temperature to airborne particles and cloud formation.
Early Momentum
In its first year, Bankhead has already shown strong signs of scientific progress. Researchers are using its data to better understand precipitation, storm development and how forest canopies can change the amount of precipitation that actually reaches the ground during rain events.
At the site, radar measures rainfall above the treetops, while rain gauges track how much water reaches the forest floor. Comparing those measurements helps scientists understand how forests influence rainfall at the ground.
Researchers are also developing radar-based tools to better track fast-changing storms - an important advance in the Southeast, where storms can develop and evolve quickly.
Building Scientific Community
The impact of the Bankhead observatory reaches beyond the forest itself.
"One really important part of Bankhead has been building a scientific community around it," O'Brien said. "Our monthly meetings bring together researchers from DOE labs and universities to talk about active campaigns, emerging observations and new scientific opportunities."
The 2025 ARM Summer School, "Open Science in the Forest," was held at the BNF observatory and hosted by ARM workforce development coordinator and Argonne atmospheric scientist Scott Collis, along with former Argonne scientist Max Grover. Undergraduate and graduate students toured the site, explored early BNF data and worked on team projects focused on atmospheric science questions.
The observatory is also helping expand open science through the development and use of open-source software tools.
Developed by former Argonne scientist Jonathan Helmus and Collis, and supported by ARM and Argonne, Py-ART, the Python ARM Radar Toolkit, helps researchers read, process, visualize and analyze radar observations. Essentially, it helps turn raw radar measurements into usable information about storms, rainfall and cloud behavior.
ACT - the Atmospheric Data Community Toolkit - works with a wider range of atmospheric data. Originally developed by Argonne atmospheric scientist Adam Theisen and now maintained by Argonne software developer Zachary Sherman, it helps researchers combine datasets from multiple instruments, improve data quality checks and build workflows that others can reuse.
At Bankhead, scientists use ACT alongside Py-ART to blend radar datasets, compare observations from different systems and connect what radar sees above the forest canopy with what is measured at the ground.
Two Years and Counting
Researchers see Bankhead as a long-term platform for new discoveries in land-atmosphere interactions, precipitation and storm development in the Southeast.
One promising development is ADAPT, an emerging open-source radar capability that helps researchers identify and track storm cells within radar scan volumes. Being developed by Argonne scientists Siddhant Gupta and Bhupendra Raut, the goal is to detect important features more quickly and eventually allow radars to focus on the most interesting parts of a storm, rather than waiting for a full conventional scan.
This capability is important because storms can change dramatically in the six to 10 minutes it often takes to complete a full scan. By helping researchers follow storms in greater detail, ADAPT could improve understanding of how storms grow, how precipitation develops and how shallow clouds sometimes evolve to become more intense convective storms.
Spychala said the continued interest from researchers is one of the clearest signs that the observatory is meeting an important need.
"The fact that people are eager to operate in this location means we put it in the right place," Spychala said. "We listened to the needs of the scientific community and deployed it in a way that makes it a useful observatory. If we continue to see people hungry for these data and wanting to deploy their instrumentation alongside ours, then we can say we did this in a truly successful way."
As Bankhead enters its next phase, it is expected to remain a hub for collaboration, training and open science, helping researchers test new ideas and develop methods that can be used across the broader ARM network.
Scientists interested in joining the BNF community are encouraged to reach out to Mark Spychala.