Ice formation is enabled by ice-nucleating particles (INP) at higher temperatures than homogeneous formation and can profoundly affect the properties of clouds. Our global model results show that K-feldspar is the most important contributor to INP concentrations globally, affecting mid-level mixed-phase clouds. However, quartz can significantly contribute and dominates the lowest and the highest altitudes of dust-derived INP, affecting mainly low-level and high-level mixed-phase clouds.

Using the MAX-DOAS network, we successfully analyzed three typical transport types (regional, dust, and transboundary long-range transport), emphasizing the unique advantages provided by the network in monitoring pollutant transport. We think that our findings provide the public with a thorough understanding of pollutant transport phenomena and a reference for designing collaborative air pollution control strategies.

Potential ship impact on air pollution in the Mediterranean Sea was simulated with five chemistry transport models. An evaluation of the results for NO₂ and O₃ air concentrations and dry deposition is presented. Emission data, modeled year and domain were the same. Model run outputs were compared to measurements from background stations. We focused on comparing model outputs regarding the concentration of regulatory pollutants and the relative ship impact on total air pollution concentrations.

Particle number concentrations and size distributions in the stratosphere are studied through model simulations and comparisons with measurements. The nucleation scheme used in most of the solar geoengineering modeling studies overpredicts the nucleation rates and particle number concentrations in the stratosphere. The model based on updated nucleation schemes captures reasonably well some aspects of particle size distributions but misses some features. The possible reasons are discussed.

We investigated the light absorption properties of brown carbon (BrC) in the Tibetan Plateau (TP). BrC made a substantial contribution to the submicron aerosol absorption, which is related to the cross-border transport of biomass burning emission and secondary aerosol from Southeast Asia. The radiative effect of BrC was half that of black carbon, which can remarkably affect the radiative balance of the TP.

The airborne megacity campaign EMeRGe provided an unprecedented amount of trace gas measurements. We combine measured volatile organic compounds (VOCs) with trajectory-modelled emission uptakes to identify potential source regions of pollution. We also characterise the chemical fingerprints (e.g. biomass burning and anthropogenic signatures) of the probed air masses to corroborate the contributing source regions. Our approach is the first large-scale study of VOCs originating from megacities.

Comparisons with ground-based correlative lidar measurements constitute a key component in the validation of satellite aerosol products. This paper presents the validation of the TROPOMI aerosol layer height (ALH) product, using archived quality assured ground-based data from lidar stations that belong to the EARLINET network. Comparisons between the TROPOMI ALH and co-located EARLINET measurements show good agreement over the ocean.

Differences in the microphysical properties of contrail cirrus and natural cirrus in a contrail outbreak situation during the ML-CIRRUS campaign over the North Atlantic flight corridor can be observed from in situ measurements. The cirrus radiative effect in the area of the outbreak, derived from satellite observation-based radiative transfer modeling, is warming in the early morning and cooling during the day.

We have rigorously characterized different sources of error in satellite-based HCHO / NO₂ tropospheric columns, a widely used metric for diagnosing near-surface ozone sensitivity. Specifically, the errors were categorized/quantified into (i) an inherent chemistry error, (ii) the decoupled relationship between columns and the near-surface concentration, (iii) the spatial representativeness error of ground satellite pixels, and (iv) the satellite retrieval errors.

We study the sensitivity of rain formation processes during a heavy-rainfall event over mountains to changes in temperature and pollution. Total rainfall increases by 2 % K⁻¹, and a 6 % K⁻¹ increase is found at the highest altitudes, caused by a mixed-phase seeder–feeder mechanism (frozen cloud particles melt and grow further as they fall through a liquid cloud layer). In a cleaner atmosphere this process is enhanced. Thus the risk of severe rainfall in mountains may increase in the future.

With this study, we investigated the processes leading to the formation, destruction, and recycling of radicals for four seasons in a rural environment. Complete knowledge of their chemistry is needed if we are to predict the formation of secondary pollutants from primary emissions. The results highlight a still incomplete understanding of the paths leading to the formation of the OH radical, which has been observed in several other environments as well and needs to be further investigated.

We investigate the impact of the homogeneous nucleation rate on nucleation events in cirrus. As long as the slope of the rate is represented sufficiently well, the resulting ice crystal number concentrations are not crucially affected. Even a change in the prefactor over orders of magnitude does not change the results. However, the maximum supersaturation during nucleation events shows strong changes. This quantity should be used for diagnostics instead of the popular nucleation threshold.

This study investigated the role of the secondary organic aerosol (SOA) loading on the molecular composition of wintertime urban aerosols by ultrahigh-resolution mass spectrometry. Results demonstrate that the SOA loading is an important factor associated with the oxidation degree, nitrate group content, and chemodiversity of nitrooxy–organosulfates. Our study also found that the hydrolysis of nitrooxy–organosulfates is a possible pathway for the formation of organosulfates.

The hygroscopic growth of single nanoparticles is important for hygroscopic characteristic analysis of atmospheric particles and for scientific studies involving atmospheric particles. Based on the hygroscopicity difference of subgroups of atmospheric nanoparticles, the classification and proportion analysis of atmospheric nanoparticles has been completed, which has potential significance in predicting the contribution of the atmospheric particulate hygroscopicity and particle growth mechanism.

This work presents novel advances in the estimation of open biomass burning emissions via the first fully "top-down" approach to exploit satellite-derived observations of fire radiative power and carbon monoxide over Africa. We produce a 16-year record of fire-generated CO emissions and dry matter consumed per unit area for Africa and evaluate these emissions estimates through their use in an atmospheric model, whose simulation output is then compared to independent satellite observations of CO.

This study has provided comprehensive baseline data of carbonaceous and inorganic aerosols as well as their isotope ratios in the Tianjin region, North China, found that Tianjin aerosols were derived from coal combustion, biomass burning and photochemical reactions of VOCs, and also implied that the Tianjin aerosols were more aged during long-range atmospheric transport in summer via carbonaceous and isotope data analysis.

In forests, the residence time of air influences canopy chemistry and atmospheric exchange. However, there have been few field observations. We use long-term open-air CO₂ enrichment measurements to show median daytime residence times are twice as long when the trees are in leaf versus when they are not. Residence times increase with increasing atmospheric stability and scale inversely with turbulence. Robust parametrisations for large-scale models are available using common distributions.

In this study, particle number size distribution analysis was performed with the purpose of characterizing new particle formation (NPF) events occurring in two areas of southern Italy over 5 years of measurements. The identification of NPF events produced different results in terms of frequency and seasonality. Some of the main variables involved in the process, the local atmospheric conditions in which the events occurred, and the role of the air masses were discussed and compared.

Our results emphasize how understanding the geographical variation in surface types across the Arctic is key to understanding secondary aerosol sources. We provide a harmonised analysis of new particle formation across the Arctic.

The results of comparing the polarimetric radio occultation observables and the ice water content retrieved from the CloudSat radar in a global and statistical way show a strong correlation between the geographical patterns of both quantities for a wide range of heights. This implies that horizontally oriented hydrometeors are systematically present through the whole globe and through all vertical levels, which could provide insights on the physical processes leading to precipitation.

Here, we examine whether several materials of meteoric origin can nucleate crystallisation in stratospheric cloud droplets which would affect ozone depletion. We find that material which could fragment on atmospheric entry without melting is unlikely to be present in high enough concentration in the stratosphere to contribute to observed crystalline clouds. Material which ablates completely then forms a new solid known as meteoric smoke can provide enough nucleation to explain observed clouds.

The promotion of soluble saccharides on sea spray aerosol (SSA) generation and the changes in particle morphology were observed. On the contrary, the coexistence of surface insoluble fatty acid film and soluble saccharides significantly inhibited the production of SSA. This is the first demonstration that hydrogen bonding mediated by surface-insoluble fatty acids contributes to saccharide transfer in seawater, providing a new mechanism for saccharide enrichment in SSA.

The radiative effect of aviation-induced cirrus is closely related to ambient conditions and its microphysical properties. Our study investigated the occurrence of contrail and natural cirrus measured above central Europe in spring 2014. It finds that contrail cirrus appears frequently in the pressure range 200 to 245 hPa and occurs more often in slightly ice-subsaturated environments than expected. Avoiding slightly ice-subsaturated regions by aviation might help mitigate contrail cirrus.

We collected 6 years of flux measurements at two southern taiga peatland ecosystems, namely a paludified spruce forest and ombrotrophic bog located in the same landscape in western Russia, which showed that the interannual variability in the environmental conditions affect CO₂ ecosystem–atmosphere exchange differently in forest and non-forest peatlands. We observed that an anomalously warm winter and spring led to increasing CO₂ uptake at the paludified forest (more than at the bog).

We measured CH₄ and CO₂ from aircraft over the Russian Arctic. Analyzing our data with the Lagrangian model FLEXPART, we find a sharp east–west gradient in atmospheric composition. Western Siberia is influenced by strong wetland CH₄ emissions, deep CO₂ gradient from biospheric uptake, and long-range transport from Europe and North America. Eastern flights document less variability. Over the Arctic Ocean, we find a small influence from marine CH₄ emissions compatible with reasonable inventories.