Typical haze events in Chengdu at the beginning of 2023 were investigated with bulk-chemical and single-particle analyses along with numerical model simulations. By integrating the obtained chemical composition, source, mixing state and numerical simulation results, we infer that Haze-1 was mainly caused by pollutants related to fossil fuel combustion, especially local mobile sources, while Haze-2 was triggered by the secondary pollutants, which mainly came from regional transmission.

The study analyzed a year of atmospheric aerosol composition at Col Margherita in the Italian Alps. Over 100 chemical markers were identified, including major ions, organic compounds, and trace elements. It revealed sources of aerosol, highlighted impacts of Saharan dust events, and showed anthropogenic pollution's influence despite the site's remoteness. Enrichment factors emphasized non-natural sources of trace elements. Source apportionment identified four key factors affecting the area.

Aerosol chemical composition (ions, sugars, carbonaceous matter) from 2011 to 2020 was studied at Mt. Chacaltaya (5380 m a.s.l., Bolivian Andes). Minimum concentrations occur in the rainy season with maxima in the dry and transition seasons. The origins of the aerosol are located in a radius of hundreds of kilometers: nearby urban and rural areas, natural biogenic emissions, vegetation burning from Amazonia and Chaco, Pacific Ocean emissions, soil dust, and Peruvian volcanism.

Global measurements of cloud condensation nuclei (CCN) are essential for understanding aerosol–cloud interactions and predicting climate change. To address this gap, we introduced a remote sensing algorithm that retrieves vertically resolved CCN number concentrations from airborne and spaceborne lidar systems. This innovation offers a global distribution of CCN concentrations from space, facilitating model evaluation and precise quantification of aerosol climate forcing.

Due to the intrinsic connection between the formation pathways of O₃ and HOMs, the ratio of HOM dimers or non-nitrate monomers to HOM organic nitrates could be used to determine O₃ formation regimes. Owing to the fast formation and short lifetimes of HOMs, HOM-based indicating ratios can describe O₃ formation in real time. Despite the success of our approach in this simple laboratory system, applicability to the much more complex atmosphere remains to be determined.

The aerosol indirect effect (AIE) depends on cloud states, which exhibit significant diurnal variations in the northeastern Atlantic. Yet the AIE diurnal cycle remains poorly understood. Using satellite retrievals, we find a pronounced “U-shaped” diurnal variation in the AIE, which is contributed to by the transition of cloud states combined with the lagged cloud responses. This suggests that polar-orbiting satellites with overpass times at noon underestimate daytime mean values of the AIE.

The interplay between aerosols and moisture is one of the most crucial atmospheric processes. However, to date, literature results on the influence of phase separation on water diffusion in aerosols are divergent. This work directly unveiled the water diffusion process in single suspended phase-separated microdroplets and quantitatively analyzed the diffusion rate and extent. The results show that diffusion limitations and certain molecule clusters existed in the phase-separated aerosols.

In Heidelberg, Germany, methane and its stable carbon isotope composition have been measured continuously with a cavity ring-down spectroscopy (CRDS) analyser since April 2014. These 6-year time series are analysed with the Keeling plot method for the isotopic composition of the sources, as well as seasonal variations and trends in methane emissions. The source contributions derived from atmospheric measurements were used to evaluate global and regional emission inventories of methane.

Surface tension and water activity are key thermodynamic parameters determining the impact of atmospheric aerosols on human health and climate. However, these parameters are not well constrained for nanoparticles composed of organic and inorganic compounds. In this study, we determined for the first time the water activity and surface tension of mixed organic/inorganic nanodroplets by applying a differential Köhler analysis (DKA) to hygroscopic growth measurements.

During severe wildfire seasons, smoke can have a significant impact on air quality in Australia. Our study demonstrates that characterization of the smoke plume injection fractions greatly affects estimates of surface smoke PM_2.5. Using the plume behavior predicted by the machine learning method leads to the best model agreement with observed surface PM_2.5 in key cities across Australia, with smoke PM_2.5 accounting for 5 %–52 % of total PM_2.5 on average during fire seasons from 2009 to 2020.

We compute CH₄ emissions and uncertainty on a mine-by-mine basis, including underground, overground, and abandoned mines. Mine-by-mine gas and flux data and 30 min observations from a flux tower located next to a mine shaft are integrated. The observed variability and bias correction are propagated over the emissions dataset, demonstrating that daily observations may not cover the range of variability. Comparisons show both an emissions magnitude and spatial mismatch with current inventories.

In the scorching August 2022 heatwave, China's Sichuan Basin saw a stark contrast in ozone (O₃) levels between Chengdu and Chongqing. The regional disparities were studied considering meteorology, precursors, photochemistry, and transportation. The study highlighted the importance of tailored pollution control measures and underlined the necessity for region-specific strategies to combat O₃ pollution on a regional scale.

In a May–June 2021 expedition in the South China Sea, we analyzed black and brown carbon in marine aerosols, key to light absorption and climate impact. Using advanced in situ and microscope techniques, we observed particle size, structure, and tar balls mixed with various elements. Results showed biomass burning and fossil fuels majorly influence light absorption, especially during significant burning events. This research aids the understanding of carbonaceous aerosols' role in marine climate.

Brown carbon (BrC), a light-absorbing aerosol, plays a pivotal role in influencing global climate. However, assessing BrC radiative effects remains challenging because the required observational data are hardly accessible. Here we develop a new BrC radiative effect estimation method combining conventional observations and numerical models. Our findings reveal that BrC absorbs up to a third of the sunlight at 370 nm that black carbon does, highlighting its importance in aerosol radiative effects.

The formation mechanisms for secondary brown carbon (SBrC) contributed by multifunctional  reduced nitrogen compounds (RNCs) remain unclear. Hence, from combined laboratory experiments and quantum chemical calculations, we investigated the heterogeneous reactions of glyoxal (GL) with multifunctional RNCs, which are driven by four-step indirect nucleophilic addition reactions. Our results show a possible missing source for SBrC formation on urban, regional, and global scales.

Clouds play a critical role in our climate system. At present and in the near future, satellite-based remote sensing is the only means to obtain regional and global observations of cloud properties. The current satellite remote sensing algorithms are mostly based on the so-called 1D radiative transfer. This deviation from the 3D world reality can lead to large errors. In this study we investigate how this error affects our estimation of cloud radiative effects.

Fire management has long been a challenge. Here we report that spring-peak fire activity over southern Mexico and Central America (SMCA) has a distinct quasi-biennial signal by measuring multiple fire metrics. This signal is initially driven by quasi-biennial variability in precipitation and is further amplified by positive feedback of fire–precipitation interaction at short timescales. This work highlights the importance of fire–climate interactions in shaping fires on an interannual scale.

Organic aerosols of marine origin are important for aerosol climatic effects but are poorly understood. For the first time, an online coupled regional chemistry–climate model is applied to explore the characteristics of emission, distribution, and direct and indirect radiative effects of marine organic aerosols over the western Pacific, which reveals an important role of marine organic aerosols in perturbing cloud and radiation and promotes understanding of global aerosol climatic impact.

High-resolution spatial fields of surface ozone are used to understand spikes in ozone concentration and predict their impact on public health. Such fields are routinely output from complex mathematical models for atmospheric conditions. These outputs are on a coarse spatial resolution and the highest concentrations tend to be biased. Using a novel data-driven machine learning methodology, we show how such output can be corrected to produce fields with both lower bias and higher resolution.

Brown carbon (BrC) emissions were estimated, for residential wood combustion (RWC) from various northern European appliances, utilizing an extensive seven-wavelength aethalometer dataset and thermal–optical carbon analysis. The contribution of BrC_370–950 to the absorption of visible light varied between 1 % and 21 %, and was linked with fuel moisture content and combustion efficiency. This study provides important information required for assessing the climate effects of RWC emissions.

Ice-nucleating particles (INPs) have important influences on cirrus clouds and the climate system; however, the understanding of their global impacts is still uncertain. We perform numerical simulations with a global aerosol–climate model to analyse INP-induced cirrus changes and the resulting climate impacts. We evaluate various sources of uncertainties, e.g. the ice-nucleating ability of INPs and the role of model dynamics, and provide a new estimate for the global INP–cirrus effect.

Field observations were conducted at the summit of Changbai Mountain in northeast Asia. The cumulative number concentration of ice-nucleating particles (INPs) varied from 1.6 × 10⁻³ to 78.3 L⁻¹ over the temperature range of −5.5 to −29.0 ℃. Biological INPs (bio-INPs) accounted for the majority of INPs, and the proportion exceeded 90% above −13.0 ℃. Planetary boundary layer height, valley breezes, and long-distance transport of air mass influence the abundance of bio-INPs.

Fine particle (PM₁) pollution is a major health issue in the city of Marseille, which is subject to numerous pollution sources. Sampling carried out during the summer enabled a fine characterization of the PM₁ sources and their oxidative potential, a promising new metric as a proxy for health impact. PM₁ came mainly from combustion sources, secondary ammonium sulfate, and organic nitrate, while the oxidative potential of PM₁ came from these sources and from resuspended dust in the atmosphere.

Atmospheric water vapour isotopes at Kathmandu recorded significantly low δ¹⁸O_v and δD_v values during cyclones Tauktae and Yaas in 2021, originating in the Arabian Sea and Bay of Bengal, respectively. Such depletion was associated with the intense moisture convergence and strong convection near the sampling site. The lower δ¹⁸O_v and higher d-excess_v values during cyclone Yaas may be attributed to the occurrence of robust downdrafts during the rainfall.

The quasi-biennial oscillation, which governs the tropical stratospheric circulation, is driven primarily by small-scale wave processes. We employ a novel method to realistically represent these wave processes in a global model, thereby revealing an aspect of the oscillation that has not been identified before. We find that the oblique propagation of waves, a process neglected by existing climate models, plays a pivotal role in the stratospheric circulation and its oscillation.

We quantified different global- and regional-scale drivers of biogenic volatile organic compound (BVOC) emission trends over the past 20 years. The results show that global greening trends significantly boost BVOC emissions and deforestation reduces BVOC emissions in South America and Southeast Asia. Elevated temperature in Europe and increased soil moisture in East and South Asia enhance BVOC emissions. The results deepen our understanding of long-term BVOC emission trends in hotspots.

Recent studies on DMS have provided new challenges to our mechanistic understanding. Here we synthesise a number of recent studies to further develop and extend a state-of-the-art mechanism. Our new mechanism is shown to outperform all existing mechanisms when compared over a wide set of conditions. The development of an improved DMS mechanism will help lead the way to better the understanding the climate impacts of DMS emissions in past, present, and future atmospheric conditions.

We investigate Cl⁻ depletion in sea salt particles over the northwest Atlantic from December 2021 to June 2022 using an airborne dataset. Losses of Cl⁻ are greatest in May and least in December–February and March. Inorganic acidic species can account for all depletion observed for December–February, March, and June near Bermuda but none in May. Quantifying Cl⁻ depletion as a percentage captures seasonal trends in depletion but fails to convey the effects it may have on atmospheric oxidation.