The experiment was remarkable for its timing as much as its location. Natal sits at 5.79 degrees south latitude and 35.2 degrees west longitude, right on the transition between land and ocean, and the eclipse reached its maximum obscuration of about 88.5 percent there very close to sunset. That combination, a near-total annular eclipse at the edge of dusk over a coastline, has almost no precedent in the observational record. The balloon lifted off at 18:29:44 UTC, just as the penumbra, the lighter outer shadow, had begun to shade the city. Its flight lasted roughly 1.45 hours, and the umbra itself overtook the balloon at 19:50:16 UTC, when the instrument package was ascending at an altitude of about 22.35 kilometers.

For 3 minutes and 36 seconds, the balloon floated inside the Moon’s shadow, climbing more than 1.4 kilometers while the ring of fire burned overhead. During that window the sensors logged roughly 216 individual measurements. The payload, part of the long-running Southern Hemisphere ADditional OZonesondes project, recorded temperature, pressure, relative humidity, wind speed and direction, and ozone concentration. Ozone was measured with an electrochemical concentration cell, a sensor that relies on an iodine-iodide reaction in a potassium iodide solution to detect the gas. With the balloon rising at about 5 meters per second and the sensor responding within 20 to 30 seconds, the vertical resolution of the profiles reached approximately 100 to 150 meters, fine enough to resolve small-scale structures that satellites would blur.

To judge whether the eclipse-day profiles were truly unusual, the team compared them against a rich baseline: every October sounding from Natal between 1999 and 2023, excluding the eclipse day itself, a total of 62 flights. They also drew on the NRLMSISE-00 empirical model of the atmosphere and the ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts. Statistical significance was assessed with a hypothesis test at the 90 percent confidence level, treating the climatological October profiles as a normally distributed population. A sounding from 13 October, the day before the eclipse, provided an additional control for day-to-day variability.

The temperature results were striking. In the tropopause region near 14 kilometers altitude, the eclipse-day profile showed a cooling of 4 to 5 kelvin relative to both the October climatology and the model, a difference that extended well beyond the natural variability of the record and remained statistically significant around 18 kilometers. The tropopause itself appeared to rise by about a kilometer compared with the climatological mean. Higher up, in the lower stratosphere, the profile oscillated with unusually large amplitude, and above 24 kilometers the measurements revealed a cooling of roughly 8 kelvin. Notably, these stratospheric fluctuations were almost perfectly anti-correlated with the profile from the day before, mirroring it in reverse, a pattern the authors interpret as strong evidence that the eclipse, not ordinary weather, drove the perturbation.

Pressure told a complementary story. Above about 12 kilometers, the eclipse-day pressure ran 0.2 to 0.7 hectopascals below the climatological profile, a deficit that shrank with altitude and was significant at the 99 percent confidence level. Surface pressure drops during eclipses have been documented before, including during the 21 August 2017 total eclipse over the United States, but capturing the vertical structure of that pressure deficit from a balloon is far rarer. The physics is intuitive: when the shadow cools a column of air, the air contracts and the horizontal pressure gradients that result can launch atmospheric gravity waves, a mechanism long proposed to explain the traveling pressure waves recorded during past eclipses.

Ozone, perhaps the most chemically sensitive of the measured variables, behaved in a way that will excite atmospheric chemists. Below 20 kilometers, where ozone concentrations are typically less than 1 part per million, the profile showed a significant decrease between about 4 and 9 kilometers and an increase between 10 and 14 kilometers. Above 20 kilometers, and especially after the umbra passed the balloon, ozone concentrations climbed persistently above the October average, reaching an enhancement of up to 1.7 parts per million near 29 kilometers, a rise that fell within the 90 percent confidence region. The enhancement is consistent with eclipse photochemistry: when sunlight is blocked, the photodissociation reactions that normally destroy ozone slow down faster than the slower chemical loss processes, so ozone accumulates within the shadowed column.

That said, the ozone story is not settled science. Theoretical work dating back to the 1960s predicted ozone enhancements during eclipses, but later analyses revised the expected photochemical change downward, and a 2025 study concluded that the true column change may be too small to measure confidently. Earlier ground-based observations with Dobson spectrophotometers reported total column increases of about 4 percent, and satellite-era studies found changes of roughly 30 Dobson units attributable to shifts in diffuse radiation. The Natal sounding, being a local, in situ measurement with fine vertical resolution, avoids some of the averaging problems that plague remote sensing, and its agreement with balloon observations from the 26 December 2019 eclipse over Gadanki, India, where tropospheric ozone rose by a few parts per billion, lends weight to the result.

Relative humidity added a final layer of complexity. From about 5 to 18 kilometers, humidity on eclipse day was almost always higher than in the control profiles, with statistically significant enhancements around 5 to 7 kilometers and again near 13 to 14 kilometers. Above 21 kilometers, coincident with the umbra’s passage, humidity dropped below the other measurements, though the absolute values there are tiny, under 1 percent, and within the spread of the climatology. The pattern matches expectations: blocking sunlight suppresses evaporation and cooling reduces the air’s capacity to hold water vapor, raising relative humidity. Similar increases were reported across eight Indian cities during the 21 June 2020 eclipse and over the United States during the 8 April 2024 eclipse, although a 1966 eclipse over Brazil famously produced a humidity drop, a reminder that each eclipse writes its own signature on the atmosphere.

Taken together, the Natal sounding demonstrates that an annular eclipse, which preserves nearly 12 percent of sunlight, is still a powerful enough perturbation to leave coherent fingerprints across the vertical structure of the atmosphere, from a cooled and lifted tropopause to pressure deficits, ozone enhancements, and humidity anomalies. Because the Moon’s shadow is only about 270 kilometers wide and races along at roughly 470 meters per second, catching it with a balloon requires precise forecasting and a dose of nerve; satellites, by contrast, can only help when their orbits happen to cross the shadow path. The authors argue that their near-sunset, coastal observation confirms annular eclipses as significant drivers of localized atmospheric dynamics, and it offers a template for future campaigns: when the next ring of fire crosses a well-instrumented coastline, a balloon in the right place at the right minute can turn a celestial show into a laboratory for the whole depth of the lower atmosphere.

Subject of Research: Vertical atmospheric response to the 14 October 2023 annular solar eclipse measured by balloon sounding over Natal, Brazil

Article Title: A near-sunset atmospheric sounding during the 14 October 2023 annular solar eclipse over Natal

Article References: Paulino, I., da Silva, F. R., Paulino, A. R., & Borba, G. (2026). A near-sunset atmospheric sounding during the 14 October 2023 annular solar eclipse over Natal. Annales Geophysicae, 44(2), 765-772. https://doi.org/10.5194/angeo-44-765-2026

Image Credits: AI Generated

DOI: 10.5194/angeo-44-765-2026

Keywords: solar eclipse, stratospheric balloon, atmospheric sounding, ozone, tropopause, relative humidity, gravity waves, Natal Brazil, annular eclipse, atmospheric dynamics, SHADOZ, ring of fire

The stakes of this question are considerable. Dust particles that reach the upper troposphere can serve as ice nuclei, seeding the formation of cirrus clouds that modulate how much sunlight Earth reflects and how much infrared radiation it traps. Because cirrus clouds exert a complex influence on the planet’s radiation budget, the abundance and composition of particles available to nucleate ice crystals matter for climate projections. Dust in the upper troposphere is also positioned for long-range travel: once entrained in the strong westerly jet streams that circle the globe at mid-latitudes, particles can be carried across entire continents before gravitational settling, precipitation, or mixing removes them from the airstream. Understanding how dust gets to those altitudes in the first place is therefore a prerequisite for modeling both its climatic effects and its intercontinental journeys.

Observational evidence at these heights has been fragmentary. Ground-based and satellite lidar instruments can detect dust layers aloft by their optical signatures, and aircraft campaigns and balloon-borne sensors have sampled particles directly in the upper troposphere on occasion. Simulations have traced plausible transport pathways connecting source deserts to remote sampling sites. What has remained scarce, however, is in situ evidence capturing how dust is distributed layer by layer as it rises through the troposphere and crosses the tropopause, the transition zone that separates the troposphere, where most weather occurs, from the stably stratified stratosphere above. That observational gap has left a key stage of the dust journey poorly documented, forcing modelers to rely on indirect constraints when validating how their schemes lift and loft mineral particles.

The new measurements come from a location unusually well suited to the task. The launch site is Golmud, a city sitting at roughly 2,800 meters above sea level in the Qaidam Basin on the northern flank of the Qinghai-Tibet Plateau. While Golmud is not among the highest points of the plateau, a balloon released from there already begins several kilometers closer to the tropopause than one launched from a lowland site. That head start shortens the ascent, reduces the time and battery resources consumed before the instrument package reaches the critical layers, and improves the odds of capturing clean, high-resolution data on how particles behave near the troposphere-stratosphere boundary. In effect, the plateau’s elevation converts a routine sounding into a targeted probe of one of the atmosphere’s most consequential interfaces.

The observations were carried out as part of the Sounding Water Vapour, Ozone, and Particle campaign, known by the acronym SWOP, organized by the Institute of Atmospheric Physics. Corresponding author Jianchun Bian led the campaign, working with co-authors including atmospheric scientist Dan Li, senior engineer Zhixuan Bai, and other specialists. Since 2009, the team has used instrumented balloons to measure the composition of the atmosphere over the Qinghai-Tibet Plateau, building one of the longer continuous records of vertical profiles in this topographically complex region. The plateau itself plays an outsized role in Asian meteorology: its massive elevated terrain redirects winds, pumps air upward through deep convection and orographic lifting, and influences the very circulation systems that can carry aerosols to extreme altitudes.

This was not the team’s first encounter with high-altitude dust. In March 2021, a SWOP balloon sounding over Golmud documented dust in the upper troposphere and lower stratosphere, with trajectory analysis tracing the particles near the tropopause back to a dust storm over the Middle East and northeastern Africa. That earlier detection demonstrated the potential of the technique but left open the question of whether such events could be observed again under more favorable circumstances. The 2023 campaign provided exactly that opportunity, because a dust event was directly affecting Golmud at the time of the observations, allowing the researchers to design their soundings around a known transport episode rather than stumbling upon one after the fact.

The experimental design was elegantly simple. The team conducted two balloon soundings: the first before the dust arrived, establishing a reference profile of the particle population over Golmud, and a second during the event, with an instrumented balloon rising through the atmosphere carrying a compact particle counter. When the researchers compared the two vertical profiles, the difference was unmistakable. Larger particles associated with dust were more abundant throughout the troposphere during the event, and critically, the enhancement extended above the tropopause itself. A balloon sounding, as Bian explained, provides a vertical snapshot of the atmosphere, giving researchers a direct, layer-by-layer view of its particles; combined with satellite observations and atmospheric simulations, that snapshot can help reveal how dust travels from distant deserts into the lower stratosphere.

Having established that the particles were present, the team turned to the question of origin. By combining the balloon records with satellite observations and atmospheric transport simulations, the researchers traced the air masses carrying the dust back to their source regions, and the answer revealed a layered transport story. Dust at lower altitudes came mainly from the nearby Taklamakan Desert, the vast sand sea of northwestern China that lies within relatively short reach of the Qaidam Basin. The dust found above the tropopause, by contrast, was traced to the much more distant Thar Desert, on the Indian subcontinent, in an air-mass journey of roughly thirty hours to reach Golmud. The evidence suggests that a trough and jet streams helped lift dust over the Thar Desert, southwesterly winds then carried it toward Golmud, and the high terrain of the Tibetan Plateau provided the final lift that pushed the particles even higher.

That sequence illustrates why the Tibetan Plateau occupies a special place in aerosol transport science. The plateau’s bulk acts as an elevated heating surface and a physical barrier, and air approaching it from the south and west is forced to rise, in some cases carrying embedded aerosol layers across altitude thresholds they could not otherwise attain. For dust originating in the Thar Desert, the plateau appears to function as the last step of an elevator, converting a long-range transport episode into a stratosphere-adjacent injection. The distinction between the local Taklamakan contribution at lower levels and the remote Thar contribution above the tropopause also underscores that different source regions populate different vertical layers, a nuance that coarse models may struggle to reproduce without targeted observational validation.

The measurements arrive at a moment when the scientific community is working to constrain how much mineral dust enters the lower stratosphere and what that influx means for climate. The new dataset provides valuable observational benchmarks for evaluating dust-transport models, offering vertical structure information that satellites alone cannot supply, and it highlights the value of sustained, long-term balloon observations over the Qinghai-Tibet Plateau. As the SWOP record continues to grow, each dust episode captured by these soundings adds a data point to a sparsely sampled but climatically important corner of the atmosphere, where the fate of desert dust, and its influence on ice clouds and the energy balance of the planet, is ultimately decided.

Subject of Research: Balloon-borne in situ measurements of desert dust transport to the tropopause layer over the northern Qinghai-Tibet Plateau

Article Title: A balloon offers a fresh eye on desert dust’s journey to the tropopause

Article References: A balloon offers a fresh eye on desert dust’s journey to the tropopause. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: desert dust, tropopause, Qinghai-Tibet Plateau, balloon sounding, aerosol transport, ice nuclei, cirrus clouds, Taklamakan Desert, Thar Desert, SWOP campaign, upper troposphere, lower stratosphere

The research team, led by Kai Qie and Pengfei Yu of Jinan University together with colleagues at the Chinese Academy of Sciences, Lanzhou University, the NSF National Center for Atmospheric Research, NOAA, and the University of Colorado Boulder, assembled an unusually broad evidence base. They combined in situ aerosol measurements from nine airborne field campaigns, including ACCENT, CR-AVE, Pre-AVE, POSIDON, ACCLIP, ATom, StratoClim, ACRIDICON-CHUVA, and OP3, with simulations from a state-of-the-art sectional aerosol climate model, CESM1-CARMA. This pairing of direct observations with a microphysically detailed model allowed the researchers to quantify both what is floating in the lower stratosphere and how it got there.

The first headline finding is striking: biogenic secondary organic aerosol, particles formed when reactive gases emitted by vegetation are oxidized in the atmosphere, accounts for roughly forty percent of the global mean annual background stratospheric aerosol burden. In other words, nearly half of the quiet-time particle load above the weather is made of material that began its journey as volatile organic compounds wafting from leaves. The particles are transported into the upper troposphere and lower stratosphere through convective pathways that the authors describe as previously underappreciated, operating over the monsoon systems of South America, central Africa, Indonesia-Australia, and southern Asia.

The second discovery concerns the sheer scale of this vertical flux. The team estimates that between 0.42 and 0.72 teragrams of biogenic organic aerosol cross the tropopause each year. Set against the average rate of volcanic aerosol injection into the stratosphere over the past two decades, a period of relative volcanic quiescence, this biogenic flux is five to ninety percent larger. That comparison reframes the stratospheric aerosol budget: during years without major eruptions, forests may deliver as much particulate matter aloft as the volcanoes that have traditionally dominated thinking about the layer.

The physical mechanism hinges on the peculiar power of monsoon convection. Monsoon systems host some of the deepest and most vigorous thunderstorms on Earth, with updrafts capable of lifting air from the boundary layer to the tropical tropopause layer within hours. Satellite measurements of outgoing longwave radiation, used by the team as a proxy for deep convection, show that aerosol extinction in the lower stratosphere peaks seasonally in step with monsoon activity over each region. The Asian summer monsoon, long recognized as a pathway for pollution and short-lived chlorine compounds into the stratosphere, emerges here as one node in a global network that also includes the tropical monsoons of the Amazon, the Congo basin, and the maritime continent.

The chemistry behind the particles is equally consequential. Plants emit enormous quantities of isoprene and other biogenic volatile organic compounds, and recent work has shown that under the cold, low-pressure conditions of the upper troposphere these compounds can oxidize and nucleate into new particles, with isoprene-derived products such as epoxydiols and isoprene nitrates playing key roles. The new simulations reproduce observed isoprene column densities from the CrIS satellite and match vertical profiles measured during the CAFE Brazil and POSIDON campaigns, lending credibility to the modeled chain that runs from forest canopy to stratospheric particle.

Not everything that rises is delivered. Deep convection is a double-edged sword for aerosols, because the same updrafts that loft particles also drive precipitation that scavenges them. Earlier modeling work by some of the same authors quantified how efficiently in-cloud removal strips aerosols from convective outflow, which is precisely why the survival of a substantial biogenic fraction in the upper troposphere and lower stratosphere is notable. The new analysis suggests that gas-phase precursors carried upward in monsoon outflow continue to form particles after reaching the upper troposphere, effectively manufacturing aerosol at altitudes where wet removal can no longer touch it.

The observational fingerprints come from an impressive suite of instruments. Aircraft-based particle spectrometers and aerosol mass spectrometers measured size distributions and composition from the boundary layer to around nineteen kilometers, while the SAGE II and SAGE III-ISS satellite instruments provided two decades of stratospheric extinction profiles that the team compared against model output during the volcanically quiet 1999 to 2004 window. The agreement between cloud-removed satellite extinction statistics and CESM1-CARMA simulations across the tropical eastern Pacific, southern Atlantic, and southern Indian Ocean supports the conclusion that the model captures the real background aerosol budget rather than an artifact of parameterization.

Why does this matter beyond atmospheric chemistry? Stratospheric aerosols scatter sunlight and alter stratospheric heating rates, and they host heterogeneous reactions central to ozone depletion chemistry. Any accurate accounting of climate sensitivity, geoengineering proposals that would deliberately inject sulfur into the stratosphere, or projections of ozone recovery must therefore include a realistic background, and that background now appears to be substantially organic and biologically sourced. The findings also connect land use to the upper atmosphere: deforestation reduces forest volatile emissions, and earlier work has suggested such changes can cool climate by cutting organic aerosol production, a linkage this study sharpens considerably.

The study, published on 25 September 2026 in Nature Geoscience, carries implications that reach from the Amazon canopy to the edge of space. It demonstrates that the boundary between the living surface of the planet and the chemically stratospheric realm is far more porous than textbook pictures suggest, and that the seasonal breathing of tropical forests, funneled upward by monsoon circulations, leaves a measurable signature in the stratospheric aerosol layer year after year. As the authors emphasize, global monsoon convections play an important role in the background stratospheric aerosol budget, a conclusion that will now need to be woven into climate models, ozone assessments, and any serious discussion of deliberate climate intervention.

Subject of Research: Transport of biogenic secondary organic aerosols into the lower stratosphere via global monsoon convection

Article Title: Persistent contribution of biogenic emissions to lower stratospheric aerosols via global monsoon convections

Article References: Qie, K., Shao, M., Peng, Y., Wang, X., Chen, W., Pan, L. L., Schill, G., Rosenlof, K. H., Toon, O. B., Bian, J., & Yu, P. (2026). Persistent contribution of biogenic emissions to lower stratospheric aerosols via global monsoon convections. Nature Geoscience. https://doi.org/10.1038/s41561-026-02115-w

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02115-w

Keywords: stratospheric aerosols, biogenic emissions, secondary organic aerosol, monsoon convection, isoprene, upper troposphere, CESM1-CARMA, SAGE II, tropopause, atmospheric chemistry, climate, Persistent