The formation mechanisms of organic matter and sulfate in winter haze in the North China Plain remain unclear. This paper presents the identification and quantification of hydroxymethanesulfonate (HMS) in PM_2.5 in Beijing winter and elucidates the heterogeneous HMS chemistry in favorable winter haze conditions. We show that the HMS not only contributes a substantial mass of organic matter, but also leads to an overestimation of sulfate in conventional measurements.

By combining long-term observational data analyses, synoptic classifications, and meteorology–chemistry coupled simulations, the complicated impacts of large-scale synoptic forcing and local boundary layer processes on the aerosol pollution in the Beijing–Tianjin–Hebei region have been investigated. The influences of the aerosol radiative effect on boundary layer structure and pollution were also examined. This study has important implications for better understanding pollution in China.

Air pollution can result in changes to the amount and properties of aerosols, which in turn could influence climate by acting as cloud condensation nuclei (CCN). This study investigated the composition and hygroscopicity of aerosols (PM_2.5) at a station under influences of eastern Asian (EA) outflows and local air mass during respective seasons. The results show that the EA aerosols were more hygroscopic, whereas new particle formation and coagulation could also influence local CCN activity.

Analysis of multiple numerical experiments over the Himalayas and Tibetan Plateau (TP) shows that the complex topography results in 50 % stronger overall cross-Himalayan transport during the pre-monsoon season primarily due to the strengthened efficiency of near-surface meridional transport towards the TP, enhanced wind speed in some valleys and deeper valley channels associated with larger transported BC mass volume, which leads to 30–50 % stronger BC radiative heating over the TP.

By utilizing a new analysis approach, we investigated atmospheric oxidation of biogenic volatile emissions in a Finnish forest, measured by chemical ionization mass spectrometry. We identified several new compound groups, including low-volatility accretion products and their formation pathways. Results from this study are important for understanding atmospheric aerosol formation, as well as providing new perspectives on future lab studies and data analysis of short-lived species.

The Weather Research Forecast with Chemistry (WRF-Chem) model was used to simulate spatial and temporal O₃ evolution in the Yangtze River Delta (YRD) region. Various atmospheric processes were analyzed to determine the influential factors of ozone formation through the integrated process rate method. This paper provides insight into urban O₃ formation and dispersion during tropical cyclone events and supports the Model Intercomparison Study Asia Phase III (MICS-Asia Phase III).

This work highlights that trace metals and refractory black carbon (rBC), and their inclusion in a source–receptor model, can provide important insight into the source apportionment of carbonaceous aerosols. In Singapore, we evidenced that 90 % of rBC originated from traffic/industrial emissions. The association of aged OA with K and Rb underlines the influence of regional biomass burning sources, while rBC fragmentation patterns and V/Ni were used to identify industrial and shipping pollutants.

The GoAmazon 2014/5 field campaign took place near the city of Manaus, Brazil, isolated in the Amazon rainforest, to study the impacts of urban pollution on natural air masses. We simulated this campaign with an extremely detailed organic chemistry model to understand how the city would affect the growth and composition of natural aerosol particles. Discrepancies between the model and the measurements indicate that the chemistry of naturally emitted organic compounds is still poorly understood.

This study examines the effect of aerosol optical depth (AOD) retrieved from the Korean Geostationary Ocean Color Imager (GOCI) sensors on surface PM_2.5 forecasts using the online coupled WRF-Chem forecasting model and the GSI 3D-Var analysis system. During the KORUS-AQ campaign period, the assimilation of GOCI AOD retrieved at the 550 nm wavelength greatly improved air quality forecasting up to 24 h when assimilated with surface PM_2.5 observations, particularly for heavy pollution events.

In 2017, new measurements of UV radiation started in Marambio, Antarctica, by the Finnish Meteorological Institute in collaboration with the Argentinian Servicio Meteorológico Nacional. The paper presents the results of UV irradiance measurements from March 2017 to March 2019, and it compares them with those from 2000–2008 and also with UV measurements at other Antarctic stations. In 2017/2018, below average UV radiation levels were recorded due to favourable ozone and cloud conditions.

Organic aerosol is ubiquitous in the atmosphere and can change its phase state from liquid to solid in response to temperature. Our laboratory measurements demonstrate that the chemical reactivity of typical organic aerosol species with atmospheric oxidants is modulated by the species’ phase state. We find that under temperatures typical of the middle and upper troposphere the chemical lifetime of organic aerosol can be significantly extended due to the reduced reactive uptake of gas oxidants.

Marine regions where deep nutrient-rich water is pushed towards the surface are called upwelling regions. In these nutrient-rich waters large algal blooms form which are the basis of the marine food web. We measured methane sulfonamide, a molecule containing sulfur and nitrogen, for the first time in ambient air and could show that the origin of this emission is an algal bloom near the Somalia upwelling. Sulfur-containing compounds from algae can promote particle formation over the oceans.

Brown carbon (BrC) aerosol can be produced by the smoldering combustion of peat, a wildland fuel common at high latitude, often adjacent to the cryosphere. However, little is known about how BrC deposition onto snow changes snow optical and radiative properties. Here, we artificially deposited BrC onto natural snow surfaces, monitored changes of the spectral surface albedo, characterized optical properties of deposited aerosol, and compared to modeled values of albedo and radiative forcing.

The composition and light-induced evolution of a water-soluble organic carbon mixture from fresh biomass burning aerosols was investigated with direct infusion electrospray ionisation high-resolution mass spectrometry (HRMS) and liquid chromatography coupled with HRMS. Our findings indicate that the water-soluble organic fraction of combustion-derived aerosols has the potential to form more oxidised organic matter, contributing to the highly oxygenated nature of atmospheric organic aerosols.

The interaction of water vapor and cloudiness poses challenges for weather and climate models. In this study we compare airborne lidar measurements from two field campaigns in the tropical Atlantic with high-resolution simulations. We find that at kilometer-scale grid spacing, the simulations show good skill in reproducing the water vapor distribution in the trades but struggle to capture the transition from cloud-free to low cloud fraction with increasing moisture.

ClNO₂ and Cl₂ can be photolyzed by sunlight to produce a highly reactive Cl atom which affects air quality and climate. We observed high ClNO₂ and Cl₂ concentrations during a recent field study in east China. We analyzed the data and proposed a new hypothesis on the Cl₂ production mechanism. Yields of ClNO₂ and Cl₂ from N₂O₂ uptake were parameterized using observational constraints, and they can be used in air quality models to improve simulations of atmospheric photochemistry and air quality.

The Tibetan Plateau lacks ground-level O₃ observation due to its unique geographical environment. It is imperative to employ modelling methods to simulate the O₃ level. The present study proposed a novel technique for estimating the surface O₃ level in remote regions. The result captured long-term O₃ concentration on the Tibetan Plateau, which was beneficial for assessing the effects of O₃ on climate change and ecosystem safety, especially in a vulnerable area of the ecological environment.

Biomass-burning-induced large areas of dark char (i.e. surface darkening) could influence the radiative energy balance. During the harvest season in eastern China, satellite retrieval shows that surface albedo was significantly decreased. Observational evidence of meteorological perturbations from the surface darkening is identified, which is further examined by model simulation. This work highlights the importance of burning-induced albedo change in weather forecast and regional climate.

Australian cities with a high biogenic influence will see higher pollution levels in a warmer climate. We show that four Eucalyptus species grown in future-climate conditions can emit isoprene at temperatures 9 K above the peak temperatures capping isoprene in biogenic-emission models. With these measurements, we predict up to 2 ppb increases in isoprene in 2050, causing up to 21 ppb of ozone and 0.4 µg m⁻³ of aerosol in Sydney. The ozone increase is one-fifth of the hourly air quality limit.

Microphysical effects of aerosols were found to weaken precipitation in a Euro-Mediterranean area. The present numerical study quantifies the processes that may be involved through the use of the temperature–precipitation relationship. It shows larger aerosol effects at low temperatures. At these temperatures, the process that contributes most is the increase in atmospheric stability through an enhanced aerosol cooling effect in the lower troposphere compared to the upper troposphere.

Aerosols, or small, suspended droplets in the atmosphere, are released from anthropogenic activity and interact with warm clouds, leading to changes in the clouds' brightness and size. Our study evaluates how aerosols alter warm clouds and their ability to cool the Earth's surface. We find aerosols make clouds brighter and grow larger in the atmosphere; however, the cooling effect due to whiter, brighter clouds is 5 times the cooling due to an increased extent.

A new approach to bridging different fields of science by studying the air–sea interface is described. An untargeted ambient mass-spectrometry-based metabolomics method enables the study of enriched organic compounds found on the sea surface for air–water transfer processes. Results from the metabolomics experiments and a lab-to-field approach provide new opportunities for characterizing the seawater organic-matter content and discovering compounds involved in aerosol-formation processes.