Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: AGU Advances
The albedo change of marine clouds is achieved by targeted additions of aerosols, and in particular, sea salt. To assess the viability of Marine Cloud Brightening (MCB) requires a fundamental understanding of the impact of aerosols on cloud evolution and properties, and on the cloud environment.
Doherty et al. [2026] propose a framework for studying MCB across scales. This includes small-
The albedo change of marine clouds is achieved by targeted additions of aerosols, and in particular, sea salt. To assess the viability of Marine Cloud Brightening (MCB) requires a fundamental understanding of the impact of aerosols on cloud evolution and properties, and on the cloud environment.
Doherty et al. [2026] propose a framework for studying MCB across scales. This includes small- to large-scale studies aimed at systematically characterizing the life-cycle of aerosols and the diurnal cycle of cloud processes, how these change with the magnitude, duration and type of aerosol applied, and monitoring potential harmful direct or indirect consequences of aerosol injection, such as regional changes in temperature or precipitation.
Possible configuration for a Stage III study for measuring local scale cloud responses to a single plume of generated sea salt aerosol sized for marine cloud brightening. Credit: Doherty et al. [2026], Figure 4
Citation: Doherty, S. J., Diamond, M. S., Wood, R., & Hirasawa, H. (2026). Defining scales of field studies and experiments to assess marine cloud brightening. AGU Advances,7, e2025AV001939. https://doi.org/10.1029/2025AV001939
Per- and polyfluoroalkyl substances (or PFAS) have been widely used in thousands of common nonstick, waterproof, or stain-resistant products since the 1950s. These “forever chemicals” do not break down easily: PFAS make their way into the air, soil, and water, as well as into human and animal bloodstreams and to some of Earth’s most pristine environments. They have been detected even in Antarctica, despite its reputation as a relatively untouched landscape far from the types of products—fast-fo
Per- and polyfluoroalkyl substances (or PFAS) have been widely used in thousands of common nonstick, waterproof, or stain-resistant products since the 1950s. These “forever chemicals” do not break down easily: PFAS make their way into the air, soil, and water, as well as into human and animal bloodstreams and to some of Earth’s most pristine environments. They have been detected even in Antarctica, despite its reputation as a relatively untouched landscape far from the types of products—fast-food wrappers, firefighting foam, nonstick cookware—that contain PFAS.
“We know PFAS are very persistent, so that helps. By looking at the patterns of the PFAS contamination in [Antarctic snow] samples, it gives us clues as to how they’re transported.”
Research into how PFAS arrive in Antarctica is limited, and most tends to focus on the continent’s coasts, rather than its interior. A new study published in Science Advances aimed to fill some of these gaps by examining PFAS accumulation across a 1,200-kilometer stretch of Antarctica, from the snow pits of Zhongshan Station in East Antarctica to the 4,093-meter peak of Dome A. By examining layers of snow collected from the coast to the interior, researchers sought to better track and understand how PFAS levels vary by location and how these forever chemicals have been able to travel long distances through the upper atmosphere to be deposited in remote regions.
“For substances to get there, they have to be able to transport long distances,” said Ian Cousins, a chemist at Stockholm University and one of the study’s authors. “We know PFAS are very persistent, so that helps. By looking at the patterns of the PFAS contamination in the samples, it gives us clues as to how they’re transported.”
PFAS Arrive by Air and by Sea
Along the 1,200-kilometer route, researchers from the Chinese Academy of Sciences collected 39 snow samples at 30-kilometer intervals, scraping the first few centimeters of snow from the surface to analyze for traces of PFAS.
Zhongshan Station sits near Prydz Bay, and there, researchers collected snow from a 1-meter-deep pit, with samples taken every 5 centimeters. At Dome A, the summit of the East Antarctic Ice Sheet, samples were collected at 10-centimeter intervals from another snow pit; this one was 3 meters deep, providing information about the past several decades of PFAS use.
“It’s quite interesting that we see the historical production record of PFAS in this pit on the top of this mountain in Antarctica,” said Cousins.
PFAS pollution arrives in Antarctica in two ways: via upper atmospheric transport and sea spray. Some PFAS are formed in the atmosphere when volatile precursor chemicals like fluorotelomer alcohols used in textile and paper products break down through reactions with sunlight and oxidants into more stable compounds. The resulting PFAS are later deposited into the snow and ice through precipitation.
Storm winds near the coast create sea spray. “When you have waves, it makes bubbles in the ocean. When the bubbles burst, these sea spray aerosols can be super enriched with PFAS. This has been shown to be a very important transport route,” Cousins said.
To distinguish between sources, researchers measured sodium in the snow to trace the ocean’s salty influence. Sodium levels decreased farther inland, reflecting the fading influence of sea spray toward the interior of the continent. But surprisingly, PFAS concentrations actually increased moving from the coast into the interior.
“That was kind of a bit counterintuitive to me,” explained Cousins, who said he expected PFAS levels to be highest near the coast. “You see the opposite, actually.”
The inland increase is likely explained by higher snowfall totals in the coastal regions, which lead to PFAS concentrations becoming diluted. Inland, where snowfall is lower, even small amounts of PFAS can result in relatively higher concentrations within snow samples.
Additional factors shape PFAS distribution. PFAS levels are higher at the onset of precipitation events when they are rapidly removed from the air. Temperature inversions, too, can trap chemicals. In coastal areas, PFAS are more influenced by sea spray in the winter, whereas stronger sunlight drives the degradation of atmospheric precursors into PFAS in the summer months.
PFAS Presence at Both Poles
This new study also offers implications for the way that PFAS circulate globally. Though industrial activity in the Northern Hemisphere contributes most heavily to PFAS emissions, large-scale atmospheric circulation allows these compounds to reach polar regions. Rapid transport in the upper troposphere may act as an efficient pathway to shuttle PFAS across both hemispheres before they are deposited in the cold, remote regions at both ends of Earth.
“This completes the global picture with agreeing measurements at both poles, solidifying our understanding of the global distribution and drivers of PFAS contamination.”
Even though PFAS levels are higher in the Arctic, both polar regions show similar trends in PFAS concentrations since the 1990s. “It really matches decades of the same records that have been reported from the Arctic,” said Cora Young, an atmospheric chemist at York University, who was not involved in the new study.
“This completes the global picture with agreeing measurements at both poles, solidifying our understanding of the global distribution and drivers of PFAS contamination. The role of CFC [chlorofluorocarbon] replacements, changes in regulation, all of these things are important in the Northern Hemisphere and also the Southern Hemisphere,” said Young.
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Atmospheres
The 2018 Camp Fire was the deadliest and most destructive wildfire in California history. The Camp Fire spread extremely rapidly, driven by strong winds and dry fuels, but also by organized long-range spotting, i.e. lofting and downwind fallout of burning embers to ignite new fires.
Using operational Doppler radar and satellite observations, Lareau [2026] pr
Source: Journal of Geophysical Research: Atmospheres
The 2018 Camp Fire was the deadliest and most destructive wildfire in California history. The Camp Fire spread extremely rapidly, driven by strong winds and dry fuels, but also by organized long-range spotting, i.e. lofting and downwind fallout of burning embers to ignite new fires.
Using operational Doppler radar and satellite observations, Lareau [2026] provides the first high resolution depiction of spotting behavior during an extreme wildfire. Observations show that spot fire events for the Camp Fire occurred 5-10 kilometers ahead of the fire front, quickly merging into new fire lines. Spot fires are not random but aligned within coherent fallout zones that are shaped by plume dynamics and background winds. These results show that operational weather radar can identify lofting and fallout regions in real time, providing a new way to anticipate spotting-driven fire spread and improve early warnings for fast-moving wildfires.
(a) Along wind cross section of Camp Fire plume reflectivity observed by radar measurements, showing distinct updrafts (white arrows) and ashfall regions (blue dashed arrow). Spot fires within 10 minutes of these radar measurements are shown as filled cyan triangles. (b) Map of column maximum radar reflectivity and fire perimeter. In both panels the black dashed line indicates the eastern edge of the town of Paradise, California. Credit: Lareau [2026], Figure 6ab
Citation: Lareau, N. P. (2026). Plume-coupled long-range spotting drove the explosive spread of the 2018 Camp Fire. Journal of Geophysical Research: Atmospheres, 131, e2025JD045798. https://doi.org/10.1029/2025JD045798
Source: AGU Advances
The Sun continuously blasts charged, magnetic field–carrying particles, or plasma, in all directions. This solar wind interacts with the magnetic fields and atmospheres of several of our solar system’s planets and other bodies, sculpting long magnetic tails of charged particles—magnetotails—that stretch into space behind them.
Magnetotails contain thin layers of electric current–carrying plasma sheets, which sometimes “flap” in an up-and-down waving motion. Spacecraft
The Sun continuously blasts charged, magnetic field–carrying particles, or plasma, in all directions. This solar wind interacts with the magnetic fields and atmospheres of several of our solar system’s planets and other bodies, sculpting long magnetic tails of charged particles—magnetotails—that stretch into space behind them.
Magnetotails contain thin layers of electric current–carrying plasma sheets, which sometimes “flap” in an up-and-down waving motion. Spacecraft observations have revealed that flapping in Earth’s magnetotail can be driven by a process called magnetic reconnection, in which magnetic field lines rapidly break and then snap together in a new configuration, releasing stored energy. However, whether reconnection plays this same role beyond Earth has thus far been a mystery.
Wen et al. report the first evidence that magnetic reconnection may also trigger magnetotail flapping at Mars.
Unlike Earth, Mars lost its global magnetic field billions of years ago. But it still sports a magnetotail, thanks in large part to interactions between the solar wind and charged particles in its upper atmosphere. Strong magnetic fields embedded in certain patches of the Martian crust—remnants of its lost planet-wide field—also influence the magnetotail.
Until recently, Mars’s magnetotail could only be studied using observations from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. MAVEN showed that the Martian magnetotail is highly dynamic, with a structure that twists, shifts, and flaps—and from which charged particles may escape into space. But because MAVEN can observe only one part of the magnetotail at a time, it couldn’t identify what processes might trigger flapping.
Another spacecraft, China’s Tianwen-1 orbiter, has now provided a second set of eyes. The researchers analyzed simultaneous observations from the two spacecraft, finding that signatures of magnetic reconnection detected by MAVEN in the upstream part of the magnetotail tended to coincide with flapping events detected downstream by Tianwen-1.
Before or during flapping, the spacecraft also detected temporary, twisted plasma structures known as flux ropes. A similar link has previously been observed on Earth, and it suggests that flux ropes generated by magnetic reconnection upstream might propagate downstream, driving instabilities in the magnetotail’s plasma sheets and triggering flapping.
Though more research is needed to confirm these findings, they shed new light on how energy moves and is released in space around Mars—and possibly other planets and celestial objects. (AGU Advances, https://doi.org/10.1029/2026AV002343, 2026)
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Advances in Modeling Earth Systems
The purpose of atmospheric data assimilation is to obtain a 3-dimensional gridded representation of the fields of the atmospheric state variables (temperature, wind, pressure, etc.) for a specific time based on atmospheric observations. The product of data assimilation, called analysis, can be used to prepare weather maps and to start model-based weather forec
Source: Journal of Advances in Modeling Earth Systems
The purpose of atmospheric data assimilation is to obtain a 3-dimensional gridded representation of the fields of the atmospheric state variables (temperature, wind, pressure, etc.) for a specific time based on atmospheric observations. The product of data assimilation, called analysis, can be used to prepare weather maps and to start model-based weather forecasts. Analyses collected over a long period of time can also be used for research and to monitor variability and changes in the climate.
The main challenges of data assimilation are that observations are not collocated with the grid-points of the analysis, and most observations do not observe the variables of interest directly and have errors. For example, satellite-based observations, which form the bulk of the operationally assimilated observations, measure the intensity of electro-magnetic waves at the top of the atmosphere; a physical quantity that depends on the atmospheric state in highly complicated ways. The background-error covariance matrix is a key component of a data assimilation system, responsible for spreading information from observations to the unobserved locations and state variables. A good estimate of this matrix is essential to produce analyses in which the fields of the state variables are realistic and consistent with each other. Obtaining such an estimate is particularly challenging for tropical locations, where physics-based knowledge does not lead to a straightforward practical formulation.
In a new study, Melinc et al. [2026] propose a novel machine learning-based (ML-based) approach to define a background-error matrix that is equally effective in the midlatitudes and tropics. This approach takes advantage of the power of ML to learn quantitative relationships between different state variables at different locations-relationships that are either not known, or cannot be easily used for the formulation of a background-error matrix based on physics-based knowledge.
Citation: Melinc, B., Perkan, U., & Zaplotnik, Ž. (2026). A unified neural background-error covariance model for midlatitude and tropical atmospheric data assimilation. Journal of Advances in Modeling Earth Systems, 18, e2025MS005360. https://doi.org/10.1029/2025MS005360
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