We investigated the formation of atmospheric pollutants from chlorine-initiated oxidation of alkanes, which may occur in polluted environments. We report for the first the formation of alkane-derived chlorinated organics. We also propose a new approach to representing the chemical composition, volatility, and thermal desorption behavior of organic aerosols. Overall, our study suggests that the oxidation of alkanes can be an important source of organic aerosols in polluted environments.

As communities worldwide analyse options to reduce methane emissions from energy use, agriculture, and waste management, there is an immediate need to build confidence in rapid assessment tools other than standard climate metrics – which misrepresent impacts over all timescales. In this paper, we show that a simplified climate model can easily and rapidly provide scientifically robust climate responses to changes in methane emissions, thereby improving mitigation analysis and decision-making.

We describe the first comparative study of noctilucent clouds (NLCs) and mesospheric summer echoes at midlatitudes. Therefore, this study compares fresh clouds (small particles) with fully evolved clouds in the mesosphere, hinting at their evolution. It is shown that, in contrast to higher latitudes, here only a thin layer of fresh particles exist above the NLCs. This gives evidence that NLCs are not formed locally but are typically advected. This needs to be acknowledged in trend studies.

We have applied the HTAP phase II multi-model data to investigate the long-range transport impacts on surface concentration and column density of PM from Europe and Russia, Belarus, and Ukraine to eastern Asia, with a special focus on the long-range transport contribution during haze episodes in China. We found that long-range transport plays a more important role in elevating the background concentration of surface PM during the haze days.

By integrating newly developed tracers for anthropogenic secondary organic aerosol in source apportionment for the first time, we estimate that this source contributes 28 % of fine particle organic carbon in the Houston Ship Channel. Our approach can be used to evaluate anthropogenic, biogenic, and biomass burning contributions to secondary organic aerosols elsewhere in the world. Because anthropogenic emissions are potentially controllable, they provide an opportunity to improve air quality.

The 2015–2016 stratospheric winter was the coldest in the 36-year climatological data record. The extreme conditions promoted the formation of persistent Arctic polar stratospheric ice clouds. An extended ice PSC detected by airborne lidar in January 2016 shows a second mode with higher particle depolarization ratios. Back-trajectories from the high-depol ice matched to CALIOP PSC curtains provide evidence for ice nucleation on NAT. The novel data consolidate our understanding of PSC formation.

GLORIA observations during two crossings of the polar front jet stream resolve the fine mesoscale structure of a tropopause fold in high detail. Tracer–tracer correlations of H₂O and O₃ are presented as a function of potential temperature and reveal an active mixing region. Our study confirms conceptual models of tropopause folds, validates the high quality of ECMWF IFS forecasts, and suggests that mountain waves are capable of modulating exchange processes in the vicinity of tropopause folds.

Using the concentrations of ice-nucleating particles (INPs) and total aerosol particles measured at three coastal marine sites, the ice-nucleating ability of aerosol particles on a per number basis and a per surface-area basis were determined as a function of size. The ice-nucleating ability was strongly dependent on size, with larger particles being more efficient. This type of information can help determine the sources of INPs and constrain the future modelling of INPs and mixed-phase clouds.

Biomass burning (BB) activities have a great impact on the particle number size distribution in the upper troposphere of the Tibetan Plateau (TP), which could affect regional and global climate. We found that the cloud condensation nuclei concentration was 2–8 times higher during BB influenced periods than during clean periods on the TP. An unexpectedly low new particle formation frequency was found in clean atmosphere on the TP, due to low concentrations of anthropogenic precursors, i.e., SO₂.

This article analyzes the health effects caused by changes in air pollution concentrations during the period of 1990–2015 in Stockholm, Gothenburg, and Malmö: the three largest cities in Sweden. The air pollutants that have been measured and analyzed are NO_x, NO₂, O₃, and PM₁₀. NO_x and NO₂ exhibit decreasing trends during this period, with beneficial effects on public health. An overall conclusion is that public health can largely benefit from reduced air pollution levels.

The terdiurnal solar tide is an atmospheric wave, owing to the daily variation of solar heating with a period of 8 h. Here, we present model simulations of this tide and investigate the relative importance of possible forcing mechanisms because they are still under debate. These are, besides direct solar heating, nonlinear interactions between other tides and gravity wave–tide interactions. As a result, solar heating is most important and nonlinear effects partly counteract this forcing.

Several new parameterizations and mechanisms for SOA formation are developed based on available experimental results. To evaluate the parameterizations, a box model was developed to simulate SOA formation from monoterpenes and aromatics in the environmental chamber EUPHORE. This box model takes oligomerization, nonideality of the aerosol, multiphase partitioning, aging, vapor wall losses and particle-phase diffusion into account. All these phenomena are rarely taken into account together.

Using light diffraction it is possible to detect microscopic features within ice particles that have not yet been fully characterized. Here, this technique was applied in airborne measurements, where it was found that majority of atmospheric ice particles have features that significantly change the way ice particles interact with solar light. The microscopic features make ice-containing clouds more reflective than previously thought, which could have consequences for predicting our climate.

Anthropogenic emissions of aerosol particles likely cool the climate system. We investigate the uncertainty in the strength of the cooling effect by exploring the representation of aerosols in a global climate model. We conclude that the specific representation of aerosols in global climate models has important implications for climate modelling. Important factors include the representation of aerosol mixing state, size distribution, and optical properties.

This study comprehensively analyzed the impacts of the marine transport sector to the concentrations of PM_2.5 and its components in eastern China on multiple temporal and spatial scales. Furthermore, a source-oriented CMAQ was used to identify the contributions of shipping emissions from different maritime areas to the inland air quality. This work supplemented the insufficiency of multi-scale researches on the influences of the shipping sector on the inland air quality.

Mercury is a trace metal with adverse health effects on human and wildlife. Its unique property makes it undergo long-range transport, and even remote Antarctica receives significant inputs. This paper presents the first model that aims to understand mercury behavior over the Antarctic Plateau. We find that mercury is quickly cycled between snow and air in the sunlit period, likely driven by bromine chemistry, and that several uncertain processes contribute to its behavior in the dark period.

We synthesized a compound, a tetraol, which is an atmospheric oxidation product in isoprene-derived secondary organic aerosols, and studied whether the tetraol is liquid or solid depending upon temperature and relative humidity, both in pure form and in mixtures with other compounds. Our results imply a liquid state of isoprene-derived aerosol particles in the lower troposphere at moderate humidity, but a solid state at colder upper tropospheric conditions, thus supporting modeling calculations.

Volcanic aerosol is an important source of sulfur for Antarctica, where local sources of sulfur are rare. Midlatitude and high-latitude volcanism can directly influence the aerosol budget of the polar stratosphere, but tropical volcanic eruptions can also enhance polar aerosols by transport. Our study investigates pathway and transport processes of volcanic aerosol from the tropics to the lower stratosphere over Antarctica by combining Lagrangian transport simulation and satellite observations.

A stand-alone automatic method for typing observations of the European Aerosol Research Lidar Network (EARLINET) is presented. The method compares the observations to model distributions that were constructed using EARLINET pre-classified data. The algorithm’s versatility and adaptability makes it suitable for network-wide typing studies.

Evaporation rates of H₂O and HCl were observed from a thin film condensate at low temperature at an average HCl mole fraction of 10(−5)–10(−3) in order to probe the evaporative lifetime of ice particles of the upper troposphere and lower stratosphere. The results show a decrease in the H₂O evaporation rate with increasing mass loss of the condensate under conditions where the saturation vapor pressure corresponded to pure ice. This supports gas–surface reactions of HCl-doped ice particles.

Surface particulate concentration has often been estimated from column-integrated aerosol optical depth (AOD). Their relationship is affected by various factors, such as the planetary layer height, meteorology (atmospheric stability, wind, relative humidity, etc.), and topography, which are investigated thoroughly using a combination of ~1500 surface station datasets, two ground-based lidars, and CALIPSO space-based lidar measurements made across China. Improved estimation of PM_2.5 is achieved.

Based on balloon-borne measurements performed in India and Nepal in 2016–2017, we infer the vertical distributions of water vapor, ozone and aerosols in the atmosphere, from the surface to 30 km altitude. Our measurements show that the atmospheric dynamics of the Asian summer monsoon system over the polluted Indian subcontinent lead to increased concentrations of water vapor and aerosols in the high atmosphere (approximately 14–20 km altitude), which can have an important effect on climate.

We assess the potential of using satellite observations of atmospheric methane to monitor global mean tropospheric OH concentration, a key parameter for the oxidizing power of the atmosphere.

The current understanding of atmospheric energy and mass transports is that the general circulation moves energy and mass from place to place in a relatively slow manner at the speed of the winds. This study challenges this view and provides evidence that considerable transfer can occur at the speed of sound. This transport mechanism is probably not adequately represented in current global models, which potentially could be a source of error that has yet to be evaluated.

Light-absorbing impurities enhance snowmelt by boosting the absorption of solar energy. It is therefore important for coupled aerosol–climate and ice sheet models to include this effect, and yet most do not. We conduct several thousand simulations and develop a kernel and linear equations relating melt runoff on the Greenland Ice Sheet to the timing and amount of black carbon within precipitation and dry deposition, which can be used to extend the utility of state-of-the-art aerosol models.

Solar UV irradiances were measured at Ushuaia (54° S) and Marambio (64° S) during 2000–2013. The measurements were part of the Antarctic NILU-UV network, which was maintained as a cooperation between Spain, Argentina and Finland. The time series of the network were analysed for the first time in this study. At both stations maximum UV indices and daily doses were measured when spring-time ozone loss episodes occurred. The maximum UV index was 13 and 12 in Ushuaia and Marambio, respectively.

We analyzed streamflow and flood frequency under the stratospheric aerosol geoengineering scenario simulated by climate models. Stratospheric aerosol geoengineering appears to reduce flood risk in most regions, but the overall effects are largely determined by the large-scale geographic pattern. Over the Amazon, stratospheric aerosol geoengineering ameliorates the drying trend here under a future warming climate.

Ice particles of noctilucent clouds (NLCs) are used as a tracer to investigate tidal signatures in the altitude range from 80 to 90 km. For the first time solar and lunar tidal parameters in NLCs were determined simultaneously from the same data set. Solar variations are dominated by diurnal and semidiurnal tidal components. For NLC occurrence the lunar semidiurnal amplitude is approx. 50 % of the solar semidiurnal amplitude. Phases of solar components indicate upward propagating tides.

Birch trees are possible sources of ice-nucleating macromolecules (INM). Pollen of birch trees are known to be ice nucleation active and were recently shown to release INM. For our work we examined 30 samples of birch branches, consisting of leaves, secondary wood (brown with no photosynthetic activity), and primary wood (green, photosynthetically active). The samples were milled and extracted aqueously. All samples contained INM. Most samples froze at temperatures comparable to birch pollen.

Mountain areas are key for studying the impact of diffuse pollution due to human activities on the continental areas. Polycyclic aromatic hydrocarbons (PAHs), human carcinogens with increased levels since the 1950s, are significant constituents of this pollution. We determined PAHs in monthly atmospheric deposition collected in European high mountain areas. The number of sites, period of study and sampling frequency provide the most comprehensive description of PAH fallout at remote sites.

The paper presents a new framework that can be used to identify emission scenarios in which aerosol populations are most likely modified by chemical processes in clouds. We show that in neither very polluted nor in very clean air masses is this the case. Only if the ratio of possible aerosol mass precursors (sulfur dioxide, some organics) and preexisting aerosol mass is sufficiently high will aerosol particles show substantially modified physicochemical properties upon cloud processing.

Urban air pollution is affected by both emissions and meteorology. Using the recent 18 yr long measurements of air pollutants in the East Asian megacity of Seoul, we quantitatively investigated effects on short-term and long-term air quality. Specific synoptic weather patterns were important for episodic PM₁₀ and O₃ events, while the long-term decrease in wind speed and the 2008 economic recession played roles in the recent improvement of PM₁₀ and deterioration of O₃ air quality in Seoul.

This work presents time-resolved data of non-methane hydrocarbons (NMHC) from automatic chromatographs, measured over a period of 5 months in the greater Athens area. The measured concentrations are higher relative to other recent studies for the majority of NMHCs. A remarkable day-to-day variability is also observed. The contributions from traffic and residential heating to NMHCs are investigated, as they were the major sources impacting the air quality during the study period.

Global models such as those participating in the Chemistry-Climate Model Initiative (CCMI) consistently simulate biases in tropospheric ozone compared with observations. We performed an advanced statistical analysis with one of the CCMI models to understand the cause of the bias. We found that emissions of ozone precursor gases are the dominant driver of the bias, implying either that the emissions are too large, or that the way in which the model handles emissions needs to be improved.

The evaluation of air pollution impacts, including on human health, vegetation, climate, and ecosystem health, is an essential component in the design of policies that affect air quality directly or indirectly. We have developed a tool that allows for a fast screening of relevant air pollution impacts from given emission scenarios at the regional to global scale, bypassing expensive numerical modelling of complex atmospheric processes. This paper provides a full documentation of the methodology.