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We discovered a process where large aerosols help small water droplets in Arctic clouds grow, even when conditions normally favor ice. Unlike the traditional view, this process may explain how liquid and ice can coexist in cold clouds. Based on theory and aircraft data, our findings provide new insight into the microphysics of mixed-phase clouds, which could improve understanding of how Arctic clouds affect climate.

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Ice in the Arctic clouds is initiated by rare particles, and their properties are not well understood due to atmospheric processing. By combining microscopy with freezing experiments, we found that both chemical composition and the thickness and morphological configuration of organic coatings influence ice formation. This finding highlights the importance of particle surface chemistry in cloud formation and offers new insights into how Arctic aerosols influence cloud formation.

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We use multiple global chemical models to quantify processes contributing to the ozone response to ENSO (El Niño–Southern Oscillation). We find that changes in transport patterns are the dominant factor in the overall ozone–ENSO responses, with the opposing effects of chemical depletion and increased biomass burning on ozone largely offsetting each other. Models consistently project an increase in tropical ozone–ENSO response associated with strengthening anomalous circulation and more abundant water vapor with global warming.

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We studied the water and ice phases of Arctic mixed-phase clouds (MPCs) using dual FOV polarization lidar and Doppler radar on board Polarstern during the MOSAiC expedition. Two long-lasting Arctic MPCs and year-round statistics show persistent droplet activation and dominant immersion freezing, indicating well-filled cloud condensation nuclei and ice-nucleating particle reservoirs. These findings help explain MPC longevity and may improve cloud life cycle representation in weather and climate models.

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Mixed phase clouds are difficult to model drivers of the climate system. This study presents novel, long-term observations of mixed-phase clouds in the Arctic using advanced remote sensing techniques, offering unprecedented insights into cloud microphysics and aerosol-cloud interactions. Leveraging the unique MOSAiC expedition measurements, for the first time, it provides height-resolved statistical analysis of mixed-phase cloud properties, with a particular focus on the characteristics of liquid phase clouds. The combination of novel lidar and radar retrieval techniques enables precise monitoring of phase transitions, ice formation via immersion freezing, and the influence of aerosol activation. Given the key role of mixed-phase cloud in regulating the Arctic energy balance and their significance in climate models, this study provides essential empirical data to help improve cloud representation and parameterizations. Based on these observations, the authors recommend to implement time-dependent parameterization schemes to properly account for the evolution of long-lasting mixed-phase cloud layers in models.

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We predicted global variations in atmospheric nine hazardous trace metal levels and assess their responses to COVID-19 lockdown measures. The rise in Pb and Zn concentrations during lockdowns was primarily linked to sustained coal combustion and non-ferrous smelting activities. The reduced emissions of Pb and As during the lockdown period yielded the greatest health benefits. Targeting fossil fuel combustion should be prioritized in Pb and As mitigation strategies.

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Condensation of vapour molecules onto aerosol particles is a key process regarding aerosol health and climate effects. The condensation sink (CS) estimates the attachment rate of vapour molecules onto existing particles. Here, we explore the concept of size-resolved CS as many of the effects related to condensation are dependent on the size of the existing particles. Our results show clear location-dependent differences in the CS size distributions which may have not been considered before.

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Based on high-time-resolution shipborne measurements, this study examines the sources of iron in aerosols over the Northwest Pacific. We found that non-dust emissions from ships and land-based activities contribute the majority of soluble iron capable of enhancing marine primary productivity, with particularly pronounced contributions in coastal regions and during the summer season. These findings provide improved insight into the influence of human activities on oceanic nutrient supply.

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Marine clouds play a major role in cooling the Earth by reflecting sunlight, but predicting how bright they appear is not straightforward. We used satellite data from 2003 to 2021 and examined whether the brightness of marine clouds can be explained by their main properties. We found that the relationship varies across the globe, and that regional differences need to be considered to better understand cloud impact on climate.

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Contrails are clouds that form behind aircraft and can warm the atmosphere as much as carbon dioxide emissions from those planes. This work compares two contrail models of different complexities to understand their lifecycle and impact. The models differ in how contrails evolve over time, implying that we may be significantly underestimating their climate impact. This highlights the need for model diversity and more evaluation against observations of long-lived contrails.

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Deposition is key in air quality modeling. An unprecedented evaluation of the Air Quality Model Evaluation International Initiative phase 4 models is performed on different deposition schemes in relation to the land use and land cover (LULC) used. Among the results, LULC masks have to be harmonized and up-to-date information used in place of masks that are outdated and too coarse. Alternatively, LULC masks should be evaluated and intercompared when multiple model results are analyzed.

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This study examines winter air quality in central Europe, focusing on the impact of domestic heating. Using a chemical transport model and measurements, it was found that the model underestimated organic particle concentrations. This was due to an underestimation of gases from domestic heating that form secondary organic particles. Improving the model by increasing these emissions and the particle formation led to better results, demonstrating the important role of heating emissions in winter.

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Atmospheric Oxidation Capacity (AOC) is the key driver for forming secondary pollutants like ozone (O₃) and Secondary Organic Aerosol (SOA). The secondary pollution remains severe in China and its co-control challenging. To address this, an atmospheric oxidation path tracking (AOCPT) approach was introduced. This approach facilitates the synergistic control of O₃ and SOA through source apportionment and targeted regulation of AOC, offering a strategy for effective air quality management.

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Ensuring the atmospheric relevance of experimental conditions is crucial for advancing understanding of secondary organic aerosols (SOA). We investigated the impact of CO, a common trace gas, on SOA particle mass yields and composition from biogenic and anthropogenic precursors and their mixture in the presence of NO_x. The results show different CO effects between single- and mixed-precursor systems, highlighting the need to capture atmospheric complexity in laboratory studies.

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This study evaluates how well an Arctic-specific model can capture two key cloud states that control how the region traps surface radiation. The model reproduces these states better than others but still produces too many thick, low clouds. With further improvements, it could offer valuable insight into how Arctic cloud behavior and surface heat balance may evolve under future climate change.

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NH₃ concentrations at a high-altitude mountain site closely resemble those at a regional background site in the North China Plain. Through measurements and modeling, the ways of agricultural emissions from the plains transported to both sites were found —via valley winds at the background site and upward air currents at the mountain site. This finding demonstrates how farming pollution can spread widely, even to high-altitude regions, highlighting the need for regional emission controls.

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The radiative forcing (RF) of PM_2.5 heavy pollution, its influencing factors and importance to precipitation in the Bohai Rim regions (China) during 2014–2023 is analyzed. The results show that the variations in PM_2.5 and RF values under different temperature profiles are not consistent. Pollution RFs were as important as vertical winds to the total precipitation. The results may improve understanding of the radiative effect of pollution and provide some assistance in precipitation forecasting.

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We assess the temperature, moisture, and dynamics in the upper troposphere-lower stratosphere simulated over South Asia in a high-resolution model relative to aircraft data. The lower stratosphere tends to be too warm, too dry, and too quiescent in the model, and as a result, too few ice clouds are predicted to form there. These biases could affect radiative balance and circulation in other areas also, as significant upward transport of moisture and pollutants occurs during the Asian monsoon.

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Sulfate aerosols from explosive eruptions can provide surfaces for chemical reactions destroying ozone. Assessing the effects of volcanic sulfate aerosols is crucial for understanding future ozone recovery. We find sporadic eruptions can induce a small delay in stratospheric ozone recovery by a few years over Antarctica and Southern Hemisphere mid-latitudes. Our results highlight the importance to continuously monitor atmospheric composition and processes to understand changes in ozone recovery.

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Due to the major radiative role of dust in Climate Change, a vertical assessment of the long-wave (and net) dust direct radiative effect of both fine and coarse dust, separately, is introduced. The study relies on an intense Saharan dust outbreak across the Iberian Peninsula, observed by five lidar stations with SW-centre-NE coverage. A comparative evaluation of the differences by considering the total dust (no separation) is also examined. It complements a similar study in the short-wave range.

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Nighttime rainfall often links to low-level jets (LLJs), but we lack clarity on nationwide LLJ features due to limited wind data. To address this, we used a nationwide radar wind profiler network to study LLJ changes 2 hours before rainfall, covering China’s 2023–2024 rainy seasons. 56 % nighttime rainfall had LLJs. The heavy rains linked to LLJs needed LLJs to strengthen quickly 30–120 minutes preceding rain. These findings show the importance of LLJ in nowcasting nighttime rainfall.

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The greater the stratospheric lifetime of chlorofluorocarbons (CFCs), the longer they will deplete ozone. This paper investigates four longer-lived CFCs, and discovers two of them have much shorter lifetimes than previously believed. Demonstrating emissions of these compounds are higher than assumed, to account for their abundance. Unusually this paper uses stratospheric whole-air samples, rather than models or lab-based experiments, to derive policy-relevant metrics for these compounds.

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Intensified heatwaves under global warming have influenced new particle formation (NPF) and related aerosol physicochemical properties. We show that aerosol optical hygroscopicity (f(RH)) was generally higher on NPF days than in non-event cases, likely due to enhanced secondary formation and subsequent growth of both pre-existing and newly formed particles with stronger photooxidation, specifically under persistent heatwaves. This would further impact the aerosol direct radiative forcing.

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A year-long set of submicron aerosol samples (PM₁) from Ny-Ålesund, Svalbard, was analyzed by proton nuclear magnetic resonance spectroscopy (H-NMR) and high-resolution time-of-flight aerosol mass spectrometry (HR-TOF-AMS) to characterize the organic fraction. Positive matrix factorization identified five organic aerosol sources. Winter–spring was dominated by Eurasian pollution and summer by marine biogenic aerosols, with occasional wildfire events.

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Clouds interact with solar radiation and can alter the surface temperature. The strength of this cloud impact is driven by cloud properties as well as solar elevation and surface reflection. As these dependencies are poorly represented in climate models, cloud, surface, and radiation observations are used to quantify the contributions of the drivers in the Arctic. It is shown that the weaker surface reflection dominates the stronger cooling effect of clouds over open ocean compared to sea ice.

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The Swedish satellite MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) conducts global measurements of atmospheric airglow in the mesosphere and lower thermosphere. In this article, we present the first global results from the mission. Observations from February to April 2023 show that the emission strength is largely controlled by atmospheric tides and by perturbations introduced by a propagating planetary wave.

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The mesosphere is a layer of the atmosphere in an altitude range of approximately 50-80km. Whilst the mass of the mesosphere is relatively very small, it is an important component of the climate system. Changes in the circulation and composition of the lower atmosphere may, for example, become evident through changes in the mesosphere. The recently launched MATS satellite will make valuable observations of mesospheric characteristics and this paper reports early observations of the oxygen airglow in particular. The global-scale structures in the airglow give valuable information on large-scale mesospheric dynamics.

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Using model simulations, we studied convective weather events to see how urban aerosol emissions influence cloud microphysics and precipitation. By tracing urban air masses from convective clouds back to their emission sources, we could isolate the effects of emissions. The results show a significant influence of urban emissions. Depending on the weather, urban emissions can either delay, enhance, or suppress precipitation, highlighting cities' complex role in shaping local rainfall.

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We analyzed ten years of satellite data to study ice particle numbers in cirrus clouds over the Tibetan Plateau. The north has fewer particles than the south due to weaker convection and differences in dust and smoke. Ice particles form through freezing, producing a “V” shaped profile, but weak upward winds in the north shift this peak lower. These findings help understand climate in high mountain regions.

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Our study shows that accurately representing atmospheric ice masses remains a major challenge. We compared climate models to satellite data, finding that conventional models consistently underestimate the amount of ice. While new, higher-resolution models perform better, both models and observations still have significant discrepancies. These shortcomings limit our confidence in cloud-related climate feedbacks, which are critical for our predictions of the future climate.

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Wildfire plume injection height is key for atmospheric impact but hard to model. This study simulates the 2019/2020 Australian wildfires, testing fire-atmosphere feedbacks. Heat release increases plume rise; moisture has minor effects. Aerosol-radiation interaction lowers injection height initially, then lofts it. Only the combined simulation matches observed upper troposphere aerosol layers, especially during peak fire intensity.

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Air pollution and extreme humid heat are both significant hazards, but their co-occurrence remains unstudied on a global scale. Using chemical and meteorological reanalyses, we find that in many areas, accounting for much of the global population, more humid heat tends to correspond with worse pollution than drier heat. We identify hotspots and study the mechanisms of this co-occurrence; our results imply it may be driven by more urban background chemistry and air stagnation during humid heat.

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We used a regional atmospheric transport model to simulate carbon dioxide mole fractions over Western Europe. The results show the importance of anthropogenic emission configurations, particularly near large emission sources, as well as the necessity of improving biogenic flux simulations. These findings contribute to enhancing the accuracy of carbon dioxide modeling and carbon budget inversions.

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The radioactive noble gas radon (²²²Rn) is a suitable natural tracer for atmospheric transport and mixing processes that can be used to validate and calibrate atmospheric transport models. However, this requires accurate estimates of the ²²²Rn flux from the soil into the atmosphere. In our study, we evaluate the reliability of process-based ²²²Rn flux maps for Europe using a ²²²Rn inversion. Our inversion results can give some indications on how to improve the process-based ²²²Rn flux maps.

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Half of the Earth’s surface precipitation events originate from snow. However, despite the increasing complexity of snow microphysics schemes employed in numerical models, whether the dominant snow microphysical process is reasonably identified remains an open question. This study using unprecedented triple-frequency radar observations for the first time unravels the key snow growth processes over various geographies.

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We studied the invisible gas isoprene, which trees and vehicles release into the air and which can worsen urban smog. Using advanced computer learning trained on measurements from many cities, we uncovered how temperature, sunlight, and city greening shape isoprene levels. Comparing Hong Kong and London, we found climate warming boosts isoprene and future ozone pollution, but strong cuts in traffic pollution could limit this impact.

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Machine learning reveals air quality patterns shaped by holiday activities, with fireworks driving major PM_2.5 spikes during Spring Festival.

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Across four reanalyses, the shallow branch of the stratospheric overturning circulation was found to be driven by planetary waves 1 to 3, and the deep branch of the circulation was found to be driven by smaller-scale waves (wave 4 and higher). However, the height of the level separating the branches is dependent on the reanalysis considered. Thus, using the appropriate separation levels in model inter-comparisons could reduce the spread between models regarding climatology and trends in the circulation.

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Performed under the umbrella of Phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII4), this study applies AQMEII4 diagnostic tools to better characterize how dry deposition removes pollutants from the atmosphere in regional-scale models. The results also strongly suggest that improvement and harmonization of the representation of land use in these models would serve the community in their future development efforts.

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Numerous lakes are shrinking, owing to climate change and human activities, releasing pollutants from dried lake beds as dust aerosols. The health risks remain unclear. Recently, Poyang and Dongting lakes faced record droughts, exposing 99 % and 88 % of their areas. We show that lake bed dust can raise PM₁₀ to 637.5 μg m^-³ and exceed non-carcinogenic (HQ = 4.13) and Cr carcinogenic (approx. 2.10 × 10⁻6) risk thresholds, posing growing health threats.

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Satellite remote sensing of atmospheric mixing ratios of greenhouse gases (GHGs) can provide information on their emissions. This study presents a novel method to use atmospheric mixing ratios observed by satellites with a Lagrangian model of atmospheric transport to estimate GHG emissions. This method can reduce model errors resulting from how an observation is represented by an atmospheric model, thereby helping to reduce the errors in the GHG emissions derived.

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Levels of hydroxymethanesulfonate (HMS) in a continental city and, for the first time, a marine atmosphere are reported. The effect of aerosol ionic strength (IS) on HMS formation was quantified; it first rises with increasing IS and then peaks at 4 mol kg⁻¹ before declining. Given the IS range of marine (2–6) and urban (6–20 mol kg⁻¹) aerosols and the clearly negative correlation between humidity and IS, moderate IS levels in humid conditions may notably boost ambient HMS formation.

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The scarcity of kinetic data for key aerosol aqueous-phase reactions contributes to large uncertainties in atmospheric models. We establish a computational strategy to rapidly predict acid-catalyzed hydrolysis kinetics of organic hydroperoxides, an aerosol constituent with high abundance. The kinetic parameters can be integrated into atmospheric models to improve simulations of the global hydrogen peroxide budget and secondary organic aerosol production.

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In this study, we developed a new global emission inventory for non-methane volatile organic compounds (NMVOC) for the period of 1970–2020, with a focus on improving the representation of NMVOC-emission-related technologies. Our analysis revealed that activity growth, technology advancements, and policy-driven emission controls were key driving forces of NMVOC emission changes, but their roles were different across sectors and regions.

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This study measured the compositions and mixing states of individual aerosol particles collected at different altitudes over the western North Pacific by simultaneous sampling from an aircraft and a research vessel. The results showed that they were strongly influenced by Siberian Forest biomass burning and mixed with sea spray, and various aerosol compositions were identified at different altitudes, sizes, and aerosol sources, highlighting a wide range of individual particle compositions.

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Polar mesospheric clouds (PMCs) reflect climate change and in turn influence mesospheric chemistry, but their ice formation remains unclear. We show that PMC height controls ice particle properties and propose a new formation mechanism involving charged meteoric smoke particle nucleation (CMN scheme). This scheme introduces the cold-trap effect for H₂O redistribution, which are fundamentally bottom-up driven by upwelling. These findings provide new insights into PMC formation and water dynamics.

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We studied how environmental factors influence the release of mercury from seawater to the atmosphere. We applied a novel approach in which prior knowledge about cause-and-effect is captured as graphical models and then used to estimate effect sizes. Results showed that sunlight affects mercury both directly and indirectly, with about 33 % of the effect explained by temperature increase. Thus, causal models can improve our understanding of pollution processes and the effect policies.

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Large volcanic eruptions introduce huge quantities of aerosols into the stratosphere. Volcanic aerosols heat the stratosphere, thereby altering the global circulation of air. This research uses simulations of the 1991 Mt. Pinatubo eruption to study the resulting circulation changes, and the dynamical processes which govern them. We find that stratospheric composition is altered by increased tropical vertical motion, and that the seasonal cycle of the global circulation is significantly dampened.

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This research turns unmanned aerial vehicles (UAVs) into sensitive weather stations by measuring how wind pushes and tilts them in flight. This method accurately gauges wind speed and direction without extra sensors, providing a low-cost way to map complex wind patterns. The findings are vital for improving air quality forecasts, tracking pollution, and ensuring safe drone operations, supporting smarter environmental management.

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This study reveals how air pollution affects cloud properties in eastern China using satellite data from 2008–2022. We find CER/LWP relationship exhibits three phases, modulated by aerosol concentration. The Twomey effect is confirmed, and its sensitivity shows significant spatial-scale dependence. Surprisingly, cleaner air after 2015 make clouds less sensitive to pollution's effects. The optimal buffer sizes show notable variations for the study area in the range from 6°×6° to 10°×10°.

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We examine boundary layer (BL) processes during summer rain in Germany, focusing on air mass exchange and precipitation effects. Using drone and ground observations, and ICON (ICOsahedral Nonhydrostatic) model data, we link delayed BL breakup and weak vertical mixing to aerosol formation and chemical processes. ICON predicts mixing layer height under stable conditions but underestimates it during cold pool events, enhancing understanding of frontal weather scenarios and atmospheric changes.

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Particle fragmentation makes snowflakes spherical during wind-drifting snow. However, no drifting snow model has presented this process so far. We established a drifting snow model considering particle fragmentation and investigated the effects of snow particle fragmentation on drifting and blowing snow. Our results show that fragmentation intensifies the sublimation of blowing snow and changes the airborne particle size distribution, which should not be ignored in current blowing snow models.

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This study applies machine learning (ML) techniques to classify aerosols using high-resolution multiwavelength lidar data from EARLINET network. We developed a reference dataset and evaluated six ML models, with LightGBM achieving over 90 % accuracy. Depolarization data proved critical for improving dust classification. Validated against independent datasets, our approach improves aerosol classification and may help refine lidar-based processing strategies.

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Methane (CH₄) emissions were measured in the megacity of Osaka, Japan, using mobile and eddy covariance methods. The CH₄ emissions were much higher than those reported in local inventories, with natural gas contributing up to 74 % of the emissions. Several CH₄ sources not accounted for in current inventories were identified. These results emphasize the need for more comprehensive emissions tracking in urban areas to enhance climate change mitigation efforts.

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This study explored pesticides in the air at a rural site in the Czech Republic. Older pesticides, banned decades ago, are still found due to their release from soils, especially in summer. While levels of many have declined over time, some show new emissions from local or distant sources. Newer pesticides peaked during application seasons but declined after bans, though traces lingered. These findings highlight the lasting impacts of pesticide use and the importance of regulations.

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In this study, we present the first report on the annual variation of stable oxygen isotope anomalies in nitrate (NO₃⁻) collected from the urban area of Lhasa, on the Tibetan Plateau, China. Using a Bayesian isotope mixture model, we found that the relative contribution of the NO₃ + volatile organic compound (VOC) pathway to NO₃⁻ formation in spring in Lhasa was several times higher than that in urban cities, highlighting the significant influence of VOCs transported from outside the Tibetan Plateau.

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Excessive levels of ultraviolet solar radiation at the Earth's surface have been linked to several types of skin cancer. The world's longest record of solar radiation intensities causing harmful skin redness comes from observations at Belsk, Poland, between 1976 and 2023. In this century, the intensity of such radiation is stable but 15 % higher than in the 1970s. This trend is due to the combined effects of a decrease in stratospheric ozone and an increase in cloud transparency before 2000.

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This study investigated how cloud–radiation interactions influence ozone formation in a warming climate. Using measurements, reanalysis data, and models, we found that cloud–radiation interactions can worsen O₃ pollution, and climate warming will amplify the influence. We highlight that climate change will pose greater challenges for China's O₃ pollution prevention and control, and actions such as reducing O₃ precursors emissions and mitigating climate change are urgently needed.

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Organosulfates (OSs) are an unrecognized and potentially important component in marine organic aerosols. In this study, we quantified and characterized the OSs over East Asian marginal seas. The chemical nature and spatiotemporal distribution of OSs were modified by the joint influence of marine emissions and transported terrestrial pollutants. The results highlight the vital roles of OSs in shaping organic aerosol formation and sulfur cycle during summer in the marine boundary layer.

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Aqueous-phase ^•OH oxidation can potentially act as an important atmospheric sink for α-pinene-derived organosulfates (OSs). Such oxidation can also generate a variety of new OS products, and can be as a potential source for some atmospheric OSs with previously unknown origins.

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Large-scale stratiform clouds play a decisive role in the Earth's radiation budget and precipitation patterns, yet global models historically exhibit major biases in their simulations. Our study addresses these gaps by implementing physically-based representations of secondary ice production pathways and advanced aerosol activation schemes, including bin-bulk microphysics. These improvements enable the robust simulation of both cloud droplet and ice formation.

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We report the isotopic composition of CH₄ emitted from 48 installations in the gas production region of Transylvania, Romania which confirm the biogenic origin of the Transylvanian gas, produced by hydrogenotrophic CO₂ reduction. This is similar to values reported previously from natural seeps and natural gas in a major city in the region. However, is more depleted in heavy isotopes than the oil-associated gas emitted in the Southern Romanian Plain, and gas leakages in the city of Bucharest.

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Decoupling aerosol and environmental impacts on convection is challenging. Using airborne data, we correlated convective metrics with aerosol concentrations in several different environments. Results were mixed, but some comparisons suggest that medium-to-high aerosol concentrations were occasionally strongly correlated with convective intensity and prevalence, especially when the atmosphere was relatively unstable. It is important to consider storm environment when evaluating aerosol effects.

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This paper presents an experimental investigation of the interactions between glyoxal, an important volatile organic compound, and mineral dust particles of size and composition typical of natural conditions. We show that their interactions modify, in a definitive way, the concentrations of the gas phase and the surface properties of the dust, which could have important implications for the atmospheric composition and the Earth's climate.

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We studied how the Intertropical Convergence Zone (ITCZ) interacts with atmospheric gravity waves high in the sky and how global climate patterns like El Niño affect them. Using RO, ERA5, and NCEP reanalysis data, we found that the ITCZ shifts with season but stays strong year-round, influencing weather and energy flow. Our findings show how climate patterns shape weather systems and help predict changes, improving understanding of the atmosphere and its effects on global climate.

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A more thorough understanding of the complex processes involved in the atmospheric Hg cycle has been achieved. The dynamics of the cycle are influenced by a rapid redox chemistry with several oxidation states and effects of multiphase interactions. This review provides a detailed analysis of the atmospheric chemistry of Hg in both the lower and the upper atmosphere, together with a synthesis of the latest kinetic, thermochemical, photochemical, and isotopic fractionation data.

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Global maps of the NH₃ emissions over 2019–2022 are derived using IASI NH₃ spaceborne observations, the LMDZ-INCA chemistry transport model at 1.27°×2.5° resolution, and the mass-balance approach. The average global NH₃ emissions over the period are ~97 Tg NH₃ yr^-1, which is significantly higher than three reference inventories. The analysis provides confidence in the seasonal variability and regional budgets and provides new insights into NH₃ emissions at global and regional scales.

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This study presents a year-long PM_2.5 study at Waliguan Baseline Observatory in the northeast of the Tibetan Plateau to investigate the optical properties of water-soluble brown carbon and its source. Our findings highlight that organic matter, sulfate, and nitrate are the dominant contributors to PM_2.5 mass concentrations. Notable seasonal variations in the light absorption capacity of water-soluble brown carbon, accompanied by a high degree of oxidation are also observed.

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Volcanic eruptions have major effects on atmospheric temperature and can be studied as a proxy for geo-engineering. The original aerosol module in the Energy Exascale Earth System Model v2 (E3SMv2) has problems simulating volcanic aerosols. We alter the aerosol module to simulate the 1991 Pinatubo eruption and implement a more complex chemistry scheme, producing results that better agree with observations. Process analyses of the volcanic aerosols help explain how they grow in the stratosphere.

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As climate change and human activities intensify in Africa, understanding how air pollution, climate, and natural cycles interact is crucial. This study explores how nitrogen oxide emissions from African soils, especially in dry regions, contribute to atmospheric pollution. By using a climate-chemistry model, we show that considering these emissions improves predictions of nitrogen dioxide, nitric acid and ozone, although some discrepancies remain compared to observations.

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The tropical tropopause layer (TTL) is a crucial region where the troposphere transitions into the stratosphere, influencing air mass transport. This study examines temperature trends in the TTL and lower stratosphere using data from weather balloons, satellites and reanalysis datasets. We found cooling trends in the TTL from 1980 to 2001, followed by warming from 2002 to 2023. These shifts are linked to changes in atmospheric circulation and impact water vapour transport into the stratosphere.

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We quantify diffusional ice crystal growth in natural clouds using cloud seeding experiments. We report growth rates for 14 experiments between −5.1 °C and −8.3 °C and observe strong variations depending on the cloud characteristics. Comparing our growth rates to laboratory data, we found similar temperature-dependent trends, but the laboratory rates are higher. These data fill the gap in quantitative in situ observation of ice crystal growth, helping to validate models and laboratory experiments.

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Understory ejections are distinct turbulent features emerging in prime tall-forest ecosystems. We share a method to isolate understory ejections based on H₂O–CO₂ anomaly quadrants. From these, we calculate the flux contributions of understory ejections and all flux quadrants. In addition, we show that a distinctly depleted isotopic composition can be found in the ejected water vapour. Finally, we explored the role of clouds as a potential trigger for understory ejections.

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This study investigates the complexation of Fe(II) and Fe(III) with glutamic acid under cloud water conditions and the effect on Fenton and photo-Fenton reactions and hydroxyl radical formation and their impact on amino acid oxidation.

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We applied various criteria to identify springtime ozone depletion events (ODEs) at Utqiaġvik, Arctic, and investigated the influence of using different criteria on conclusions regarding the characteristics of ODEs. We found that criteria using fixed thresholds or monthly average-based thresholds were more suitable for identifying ODEs than the others. Applying a threshold that varies with the monthly average or stricter fixed thresholds also indicated a more significant reduction in ODE occurrences.

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We studied air pollution transported from South Asia to the Himalayas during the pre-monsoon season. Using real-time instruments, we measured airborne particles and trace gases on the northern slope of the mountains. We found that burning biomass was a major source of these particles, which changed chemically as they travelled long distances. These changes were affected by photochemical and cloud processes, with important consequences for the regional climate and melting of glaciers.

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Climate models rely on uncertain adjustable parameters. We tested millions of combinations of these inputs to see how well the model matches real-world data. We found that no single set of inputs can match several observations at the same time, which suggests that the issue lies in the model itself. We developed a method to detect these conflicts and trace them back trace them to their source. The aim is to help modellers target improvements that reduce uncertainty in climate projections.

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This study examines how three reanalysis datasets represent water vapor during more than 100 typhoons in East Asia from 2020 to 2024. Using observations from satellites, radiosondes, and ground stations, we show that ERA5 performs best, JRA-3Q improves during typhoons, and MERRA-2 is less stable. The results provide new insights into typhoon moisture processes and support better monitoring and forecasting of extreme weather.

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We provide atmospheric measurements of halogenated olefins from the Advanced Global Atmospheric Gases Experiments and we calculate NorthWest European Emissions.

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The PM_2.5 concentration in China underwent significant changes in 2013. We examined the underlying causes from three perspectives: anthropogenic pollutant emissions, meteorological conditions, and CO₂ concentration variations. Our study highlighted the importance of considering the role of CO₂ in vegetation when predicting PM_2.5 concentrations and developing corresponding control strategies.

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Polar low-level clouds are most often of mixed-phase composition as they contain both liquid droplets and ice crystals. Such clouds are challenging to simulate in climate models, leading to uncertainties in the projection of polar climates. This study presents major advances in the representation of polar mixed-phase clouds in a climate model thanks to the adaptation of an original subgrid parameterization which considers interactions between turbulent eddies and clouds.

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Wind speed spectra analysis is very important for understanding boundary layer turbulence characteristics, atmospheric numerical model development, and wind energy assessment. However, wind speed spectra studies in mountainous areas are extremely scarce. In this study, using a 15-year time series of wind speed observed by a PBL tower and eddy-covariance tower at a site on the north slope of Mt. Everest, we investigated the characteristics of wind speed and wind speed spectrum.

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Mixed-phase clouds play a key role in Earth’s climate but remain poorly represented in climate models. We improved their representation in the EC-Earth model by introducing an aerosol-sensitive scheme for ice formation and a machine-learning approach for secondary ice production. These advances produce more realistic cloud properties and radiative effects, highlighting that both processes are essential for reliable climate projections.

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MethaneSAT was a satellite mission which generated data on methane emissions. In this work, we evaluate the potential of MethaneSAT to detect and quantify methane plumes, and use the existing data archive to evaluate the methane super-emissions from the most important oil and gas basins in the world.

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Global chemical transport models previously treated aerosols as a sink for reactive iodine (I_y); however, aerosol iodide is also a source of I_y via heterogeneous reactions involving hypohalous acids and halogen nitrates. We implemented this chemistry into GEOS-Chem, in addition to explicitly representing three aerosol iodine types: soluble organic iodine (SOI), iodide, and iodate. We found that aerosol recycling of iodide to form I_y is more than twice as fast as the other I_y sources combined.

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We explored how chemical and dynamical processes shape ozone in the tropical middle stratosphere. Using a method that identifies cause and effect with satellite data and a chemistry-transport model, we found that from 2004–2011 nitrous oxide quickly affected nitrogen dioxide and ozone, while from 2012–2018 this effect was delayed, weakening ozone loss. Large-scale winds also influenced this link, clarifying how different mechanisms control ozone.

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This study investigates how organics contribute to initial particle growth in the 3–10 nm size range. Through laboratory experiments, it was found that sulfuric acid dominates the growth of smaller particles, while organics play an increasingly important role as particle size increases. Elevated humidity also significantly enhances the contribution of organics. These findings further our understanding of new particle formation and subsequent growth.

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This work investigates the regulation of aerosol acidity in a coastal megacity under contrasting meteorological regimes. By integrating field observations with thermodynamic modeling, we show that ammonia and aerosol water dominate acidity control under typical conditions, whereas sea-salt cations prevail during typhoons. These findings reveal that extreme weather can alter the governing mechanisms of aerosol acidity, with implications for air quality and climate evaluation.

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This study is the first global assessment of aerosol-cloud interactions (ACI) and cloud adjustments that relies on vertically resolved aerosol retrievals that are vertically matched with the location of the cloud layer. We computed ACI metrics and cloud adjustments over the global ocean by combining retrievals from active and passive satellite sensors and found high sensitivity of clouds to changes in their cloud droplet number concentration due to aerosols.

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In 2019, a stratospheric warming event over Antarctica contributed to extreme heat and drought in Australia, intensifying that year's fire season. The impact of climate change on the occurrence of such events remains uncertain. Our climate model simulations indicate that in the coming decades, stratospheric warming events over Antarctica are likely to continue influencing extreme heat in regions such as Australia and Southern Africa, compounding the direct effects of global warming.

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Dust activity in East Asia and North America shows decadal variations, affecting radiation, air quality, and human health, especially in April and May. This study examines interannual and decadal changes in springtime dust emissions and quantifies the role of environmental factors and extratropical cyclones. Using multi-source datasets, a dust emission model, and cyclone tracking algorithms, we find that strong winds, particularly those linked to cyclones, are key drivers of these changes.

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This study investigates how the formation and aging processes of secondary organic aerosol (SOA) influence the evolution of SOA volatility in downwind regions. Our results reveal that elevated NOx levels enhanced the daytime SOA volatility by modifying gas-particle partitioning, particularly through suppressing the production of low-volatility organic vapors. In contrast, photochemical aging was associated with reduced SOA volatility.

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This study conducted long-term measurements for oxalic acid and several molecular markers of primary anthropogenic emissions in the Pearl River Delta. We found that the impact of reduction in anthropogenic precursors on SOA formation was limited. In addition, our results highlight the increasing importance of gas-phase oxidation in SOA formation under low-pollution conditions, underscoring the need for effective ozone control strategies to further reduce SOA in the future.

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We study the North Pacific westerly jet (NPWJ) using four reanalysis datasets and eight CMIP6 models. Our results show that between 1980 and 2019, the NPWJ core oscillates seasonally between north and south, weakening and shifting northward in summer and autumn. Single-forcing simulations further reveal aerosol forcing as the main driver. Incorporating interacting chemistry and time-varying ozone radiative forcing into Earth system models is crucial for simulating long-term atmospheric dynamics.

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Climate models help in the study of aerosol impacts on regional climate. However, the atmosphere's chaotic nature makes it hard to separate true aerosol impacts from chaotic effects. Our ensemble experiments show that while large-scale aerosol effects are consistent, regional aerosol impacts vary significantly among experiments. We give a formula showing the relationship between chaotic effects and ensemble sizes, emphasizing the necessity of adequate ensemble members to capture reliable aerosol impacts.

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We explore how Pacific low-level clouds influence projections of regional climate change by adjusting a climate model to enhance low-cloud response to surface temperatures. We find significant changes in projected warming patterns and circulation changes under increased CO₂ conditions. Our findings are supported by similar relationships across state-of-the-art climate models. These results highlight the importance of accurately representing clouds for predicting regional climate change impacts.

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The Arctic is changing rapidly, and we sought to better understand how Arctic clouds may change in the future through quantifying the ice-forming particles over a year and uncovering what they are made of. We determined their likely sources through concurrent DNA sequencing of airborne bacteria and fungi and found persistent mixtures of local and longer-range sources at all times.

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Gas-to-aerosol partitioning of organics was investigated in Shanghai during the 2023 dust storm period. We found the partitioning coefficients (F_p) of water-soluble organic compounds in the dust storm period (DS) were comparable to those during a haze episode (HE), and aerosol liquid water content primarily drove F_p variation in HE, while pH was the dominant factor in DS. Moreover, an enhanced light absorption of Asian dust by brown carbon, mainly in coarse mode, formation was revealed.

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This study describes the analysis of time series of the MODIS-derived aerosol optical depth (AOD) over China between 2010 and 2024. Emission reduction policies were effective with respect to reducing the AOD until 2018. Thereafter, the overall reduction until the end of the study was very small due to unfavorable meteorological factors cancelling favorable anthropogenic effects and resulting in an AOD increase during extended periods. The variations over different areas in China are discussed.

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Ammonia (NH₃) is a key air pollutant linked to fine particle pollution, yet its sources remain poorly understood. Using airborne infrared imaging and ground sensors, we mapped NH₃ emissions in California’s Salton Sea region with unprecedented detail. We found high emissions from farms, geothermal plants, and waste sites, including sources missing from inventories. These findings highlight the need for better NH₃ monitoring to improve air quality models and guide pollution reduction strategies.

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We have collected stratospheric air samples using balloon-borne cryogenic samplers over Japan since 1985 and analyzed them for δ¹³CO₂. δ¹³CO₂ has decreased through time in the mid-stratosphere with an average rate of change of −0.026 ± 0.001 ‰ yr⁻¹. We found that stratospheric δ¹³CO₂ variations are governed by airborne production of ¹³C-depleted CO₂ by CH₄ oxidation, gravitational separation, and propagation of the decreasing tropospheric δ¹³CO₂ trend into the stratosphere.

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Biogenic secondary organic aerosol (BSOA), as an important atmospheric component, is prevalent within the boundary layer and can influence air quality and human health. Our observations demonstrate that anthropogenic NO_x and the enhanced aerosol water driven by sulfate inhibit BSOA formation in lifting air masses, leading to a moderate reduction in the SOA burden in the upper boundary layer.

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