An integrated observation on aerosol aminiums over a coastal city in eastern China, a nearby island and the surrounding marginal seas was conducted. Aminium concentrations exhibited significant spatiotemporal variation, which is dependent on their sources and environmental factors, including boundary layer height, temperature, atmospheric oxidizing capacity and relative humidity. The contributions of terrestrial and marine sources to aminiums over coastal areas were quantitatively calculated.

The effects of the chemical composition and size of sea-salt-containing particles on their cloud condensation nuclei activity are incompletely understood. Our results showed that submicron sea-salt-containing particles can enrich in small cloud droplets, likely due to change in the chemical composition, while supermicron sea-salt-containing particles tended in the large cloud droplets less affected by chemical composition. This difference might further influence their atmospheric residence time.

In this study, we investigated molecular compositions of organic aerosols (OAs) in summertime PM_2.5 at a rural site in the North China Plain. We found that regional emission from field biomass burning (BB) significantly affects the concentration and molecular distribution of aliphatic lipids, sugars, and terpene-derived SOA, but has limited influence on PAHs, hopenes, and phthalates. The contribution of BB to OA increased by more than 50 % during the period influenced by regional open-field BB.

A comprehensive assessment of the global and regional AOD trends over the past 37 years (1980–2016) is presented. AOD observations from both AERONET and CARSNET were used for the first time to assess the performance of the MERRA-2 AOD dataset on a global scale. Based on statistical models, we found the meteorological parameters explained a larger proportion of the regional AOD variability (20.4 %–2.8 %) when compared with emission factors (0 %%–56 %).

Northern African mineral dust provides the Amazon Basin with essential nutrients, although the process is still poorly understood. In our study, we utilise high-resolution satellite data to analyse northern African dust sources of the 2015–2017 winter dust seasons. We find that the majority of dust is emitted from palaeolake and palaeoriver systems. Specifically, palaeorivers have been mostly overlooked to date. Furthermore, we find that dune fields do not produce much dust.

Atmospheric aerosols have significant effects on human health and the climate. A large fraction of these aerosols originate from new particle formation, where atmospheric vapors form small nanosized particles that grow into larger sizes, thus becoming climatically relevant. We show that large amounts of fast-growing particles are formed frequently at a site located in western Saudi Arabia and that these particles are likely connected to strong nearby emissions from human activities.

The study of HONO, the primary source of OH radicals, is crucial for atmospheric photochemistry and heterogeneous chemistry. Heterogeneous NO₂ conversion was shown to be one of the missing sources of HONO on the North China Plain, but the reaction path is still under debate. In this work, evidence was found that NH₃ was the key factor that promoted the hydrolysis of NO₂, leading to the explosive growth of HONO and nitrate, suggesting that NH₃ emission control measures are urgently needed.

This study aims to explore Arctic cloud properties in the atmospheric circulation model ECHAM6. We compare cloud properties in the model to satellite observations using a satellite simulator and show that ECHAM6 overestimates low-level liquid-containing clouds. In sensitivity studies, we show that this bias can be related to cloud microphysics and surface fluxes.

The Forests gAses aeRosols Clouds Exploratory (FARCE) campaign was conducted in March–April 2015 on the tropical island of La Réunion. For the first time, several scientific teams from different disciplines collaborated to provide reference measurements and characterization of La Réunion vegetation, volatile organic compounds (VOCs), biogenic VOCs (BVOCs), (bio)aerosols and composition of clouds, with a strong focus on the Maïdo mount slope area.

New nitrogen dioxide (NO₂) retrieval algorithms are developed for Pandora zenith-sky measurements. A column-to-surface conversion look-up table was produced for the Pandora instruments; therefore, quick and practical Pandora-based surface NO₂ concentration data can be obtained for air quality monitoring purposes. It is demonstrated that the surface NO₂ concentration is controlled not only by the planetary boundary layer height but also by both boundary layer dynamics and photochemistry.

The reaction between the OH radical and nitrogen dioxide plays a critical role in controlling abundances of HO_x and NO_x from the boundary layer to the stratosphere. Uncertainties associated with the rate coefficient for this reaction lead to uncertainty in model predictions of the oxidizing capacity of the atmosphere and photochemical ozone production. We present accurate measurements of the rate coefficient over a range of temperatures and pressures.

This study concentrates on airborne lidar measurements conducted during the NARVAL field experiments over the western subtropical North Atlantic Ocean to study differences between shallow marine cloud macro-physical properties (i.e. cloud fraction, cloud top height, cloud length, cloud gap length) in Saharan-dust-laden and dust-free trade wind regions. Cloud top heights, cloud fractions and cloud lengths are found to be lower and smaller in Saharan-dust-laden compared to dust-free regions.

This study is the first to report size-resolved PM mass and composition in metro Manila, Philippines. The results, which focus on the southwest monsoon season (SWM), are important with regard to understanding the competition between local sources and long-range transport, characterizing the properties of aerosol impacted by both aqueous processing and wet scavenging, and providing contextual data for comparison with other monsoonal regions and coastal megacities.

We flew a small single-engine instrumented aircraft in a large valley of California to study the factors that determine air pollutant levels in a region of the US that faces serious air quality challenges. After carefully accounting for atmospheric mixing, we found that agriculture is likely a significant and currently underestimated source of nitrogen oxide, a precursor to both ozone and particulate matter pollution and methane, a potent greenhouse gas.

It is useful to divide a cloud into two regions: core and margin. Three parameters used to define a core are compared: buoyancy (B), relative humidity (RH), and vertical velocity (W). Using theoretical arguments and simulations, we show that during most of a cloud's lifetime, the cores are subsets of one another: B_core ⊆ RH_core ⊆ W_core. Moreover, the core–shell cloud model applies to all core definitions. Our findings can serve as a benchmark in the partition the core and margin.

The effects of aerosol concentration on a cloud's partition to core and margin are examined. The main finding from Part I (i.e. B_core ⊆ RH_core ⊆ W_core) is seen for all aerosol concentrations. Clouds can produce positive buoyancy due to both saturated updrafts or unsaturated downdrafts; the latter are dependent on low aerosol concentrations. We show that a cloud's mass is mainly dependent on core processes (condensation), while its volume is mainly dependent on margin processes (evaporation).

We study the partitioning of inorganic chlorine into active (ozone-depleting) and reservoir species in the lowermost stratosphere of the Arctic polar vortex, using novel in situ aircraft measurements in winter 2015/2016. We observe a change in recovery pathways of the reservoirs HCl and ClONO₂ with increasing potential temperature. A comparison with the CLaMS model relates the observations to the vortex-wide evolution and confirms unresolved discrepancies in the mid-winter HCl distribution.

We address the GEOS-GOCART sea salt simulations constrained by NASA EVS ATom measurements, as well as those by MODIS and the AERONET MAN. The study covers remote regions over the Pacific, Atlantic, and Southern oceans from near the surface to ~ 12 km altitude and covers both summer and winter seasons. Important sea salt fields, e.g., mass mixing ratio, vertical distribution, size distribution, and marine aerosol AOD, as well as their relationship to relative humidity and emissions, are examined.

Background climate can affect the aerosol concentration (AC). It is found that when negative NAO overlaps El Niño, the anomalous circulations are not favorable for the transportation of aerosol, resulting in enhanced AC over eastern China. By contrast, a sole negative NAO event is linked with increased AC over central China. The results suggest that both the extratropical and tropical climate systems play an important role in impacting the AC over China.

We used a global chemical transport model to examine the historical changes in severe winter haze days (SWHDs) in Beijing–Tianjin–Hebei (BTH) in China. Simulated frequency of SWHDs in BTH showed an increasing trend over 1985–2017 with obvious fluctuations. We found that meteorology has dominated the frequency decrease in 1992–2001, and both anthropogenic emissions and meteorology contributed to the increase in 2003–2012. These results have important implications for the control of SWHDs in BTH.

Oxidation of bromide and iodide is an important process in the troposphere that leads to gas-phase halogen compounds which impact the oxidation capacity of the atmosphere. Imidazole-2-carboxaldehyde (IC), an aromatic carbonyl, is a product of the multiphase chemistry of glyoxal (an oxidation product of isoprene), a major biogenic volatile organic compound. In this study we demonstrate that IC photochemistry leads to efficient oxidation of bromide and iodide and liberation of halogen compounds.

When combustion particles are deposited to the ground, they darken Earth's snow and ice surfaces by even tiny quantities. This darkening reduces the back reflection of sunlight and induces an additional climate warming. Particles from fresh snow samples were investigated according to their light absorption strength. Enhanced absorption was found in the snow that cannot fully be attributed to combustion particles. Dust and biogenic matter are likely the cause of this additional snow darkening.

The formation mechanism of a severe haze episode that occurred over North China in December 2015, the aerosol radiative impacts on the haze event and the influence mechanism were examined. The PM_2.5 increase during the aerosol accumulation stage was mainly attributed to strong production by the aerosol chemistry process and weak removal by advection and vertical mixing. Restrained vertical mixing was the main reason for near-surface PM_2.5 increase when aerosol radiative feedback was considered.

Severe pollution of the Beijing atmosphere is a frequent occurrence. The airborne particles which characterize the episodes of haze contain a wide range of chemical constituents but organic compounds make up a substantial proportion. In this study individual compounds are analysed under both haze and non-haze conditions, and the measurements are compared with samples collected in London, where the air pollution climate and sources are very different.

For the diverse aerosol on Cyprus, we found the following: new particle formation can be a source of cloud condensation nuclei. Particle hygroscopicity showed that particles ~<100 nm contained mostly organic material, while larger ones were more hygroscopic. Two separate methods obtained similar concentrations of ice-nucleating particles (INP), with mostly no evidence of a local origin. Different parameterizations overestimated INP concentration in this rather polluted region.

The ice nucleation ability of singly immersed feldspar particles in suspended water droplets relevant for ice crystal formation under mixed-phase cloud conditions is presented. The effects of particle size, crystal structure, trace metal and mineralogical composition are discussed by testing up to five different diameters in the submicron range and nine different feldspar samples at conditions relevant for ice nucleation in mixed-phase clouds.

Global distributions of aerosol radiative effects are calculated using aerosol properties of the MACv2 climatology and a satellite-retrieval-based relationship for the first indirect effect. Present-day climate cooling by anthropogenic aerosol is likely within a −0.7 to −1.6 W m⁻² range – with a best estimate at −1.0 W m⁻². Only about 1/3 of this TOA cooling is contributed by direct effects, which are more variable (even in sign) and stronger near pollution source regions than indirect effects.

In this study, a first attempt at comparing and evaluating two classification tools developed within EARLINET that provide near-real-time aerosol typing information for the lidar profiles of Thessaloniki is presented. Our aim is (i) to check the performance of both supervised learning techniques in their low-resolution mode and (ii) to investigate the reasons for typing agreement and disagreement with respect to the uncertainties and the threshold criteria applied.

Aerosols and the ground provide two kinds of surfaces for multiphase reactions in the planetary boundary layer. However, the relative importance of these two surfaces for gas uptake has not been quantified. We compare the uptake fluxes of aerosols and the ground surface for reactive trace gases under various conditions. More studies regarding O₃ uptake on liquid organic aerosols and H₂O₂ uptakes on various aerosols are needed considering their potential important roles in atmospheric chemistry.

We conducted a large study focusing on the daily (24 h) PM₁₀ sugar compound (SC) concentrations for 16 increasing space-scale sites in France (local to nationwide) over at least 1 complete year. Our main results clearly show distance-dependent covariation patterns, with SC concentrations being highly synchronous at an urban city scale and remaining well correlated throughout the same geographic regions. However, sampling sites located in two distinct geographic areas are poorly correlated.

Observed annual mean PM_2.5 decreased by 30–50 % in China from 2013–2018. However, meteorologically PM_2.5 variability complicates trend attribution. We used a stepwise multiple linear regression model to quantitatively separate contributions from anthropogenic emissions and meteorology. Results show that 88 % of the PM_2.5 decrease across China is attributable to anthropogenic emission changes, and 12 % is attributable to meteorology.