Organic sea spray particles influence aerosol and cloud processes over the ocean. This study introduces the emission, cloud droplet activation, and ice nucleation (IN) of marine organic aerosol (MOA) into the Community Earth System Model. Our results indicate that MOA IN particles dominate primary ice nucleation below 400 hPa over the Southern Ocean and Arctic boundary layer. MOA enhances cloud forcing over the Southern Ocean in the austral winter and summer.

Brown carbon (BrC) emission factors from household biomass fuels were measured with an integrating sphere optics approach supported by iterative calculations. A novel algorithm to directly estimate the absorption contribution of BrC relative to that of BrC + black carbon (FBrC) was proposed based purely on the absorption exponent (AAE) (FBrC = 0.5519 lnAAE + 0.0067). The FBrC for household biomass fuels was as high as 50.8 % across the strongest solar spectral range of 350−850 nm.

In the past, additional sodium peaks occurring above the main sodium layer of the upper mesosphere were discussed. Here, formation of an additional sodium peak below the main sodium layer peak is discussed in detail. The event coincided with passage of multiple mesospheric bores, which are step-like disturbances occurring in the upper mesosphere. Hence, this work highlights the importance of such mesospheric bores in causing significant changes to the minor species concentration in a short time.

Impacts of anthropogenic aerosols on deep convective clouds (DCCs) and precipitation are examined using both the Morrison bulk and spectral bin microphysics (SBM) schemes. With the SBM scheme, anthropogenic aerosols notably invigorate convective intensity and precipitation, causing better agreement between the simulated DCCs and observations; this effect is absent with the Morrison scheme, mainly due to limitations of the saturation adjustment approach for droplet condensation and evaporation.

Biomass burning is a major source of trace gases to the troposphere; however, the composition and quantity of emissions vary greatly between different fuel types. This work provided near-total quantitation of non-methane volatile organic compounds from combustion of biofuels from India. Emissions from cow dung cake combustion were significantly larger than conventional fuelwood combustion, potentially indicating that this source has a disproportionately large impact on regional air quality.

Biomass burning releases many lower-molecular-weight organic species which are difficult to analyse but important for the formation of organic aerosol. This study examined a new high-resolution technique to better characterise these difficult-to-analyse organic components. Some burning sources analysed in this study, such as cow dung cake and municipal solid waste, released extremely complex mixtures containing many thousands of different lower-volatility organic compounds.

Column ozone protects life on Earth from radiation damage. Stratospheric chlorine compounds cause immense ozone loss in polar winter. Whether similar loss processes can occur in the lower stratosphere above North America today or in future is a matter of debate. We show that these ozone loss processes are very unlikely today or in future independently of whether sulfate geoengineering is applied and that less than 0.1 % of column ozone would be destroyed by this process in any future scenario.

Based on long-term measurements, we discovered that the collision of H₂SO₄–amine clusters is the governing mechanism that initializes fast new particle formation in the polluted atmospheric environment of urban Beijing. The mechanism and the governing factors for H₂SO₄–amine nucleation in the polluted atmosphere are quantitatively investigated in this study.

This paper informs realistic simulation of stratospheric water vapour by clearly attributing each of the two key influences on water vapour entry to the stratosphere. Presenting modified trajectory models, the results of this paper show temperatures dominate on annual and inter-annual variations; however, transport has a significant effect in reducing the annual cycle maximum. Furthermore, sub-seasonal variations in temperature have an important overall influence.

The physical mechanisms of synoptic patterns affecting the decay process of air pollution episodes are investigated in this work. Three dominant circulation patterns are identified, which usually decrease the ambient PM_2.5 concentrations by 27%–41% after they arrive around Beijing. Emission reductions led to a 4.3–5.7 μg (m³ yr^-1)^-1 decrease in PM_2.5 concentrations around Beijing during 2014 to 2020.

The direct inversion of the 2D continuity equation allows us to infer the effective meridional transport velocity of trace gases in the middle stratosphere. This method exploits the information both given by the displacement of patterns in measured trace gas distributions and by the approximate balance between sinks and horizontal as well as vertical advection. The robustness of this method has been tested and characterized using model recovery tests and sensitivity studies.

Chemical lateral boundary condition (CLBC) impact is essential for regional air quality prediction during intrusion events. We present a model mapping Goddard Earth Observing System (GEOS) to Community Multi-scale Air Quality (CMAQ) CB05–AERO6 (Carbon Bond 5; version 6 of the aerosol module) species. Influence depends on distance from the inflow boundary and species and their regional characteristics. We use aerosol optical thickness to derive CLBCs, achieving reasonable prediction.

The freezing of water drops in clouds is a prime example for the role of ice-nucleating particles (INPs). Mercuric iodide particles and a few other substances can be conditioned to become very effective INPs after previous ice formation and moderate heating to melt temperatures, opening a new pathway to ice formation in the atmosphere and in other systems like tissue preservation, artificial snow making, and more.

We performed chassis dynamometer experiments to investigate the emissions and secondary organic aerosol (SOA) formation potential of intermediate volatility organic compounds (IVOCs) from an on-road Chinese gasoline vehicle. High IVOC emission factors (EFs) and distinct volatility distribution were recognized. Our results indicate that vehicular IVOCs contribute significantly to SOA, implying the importance of reducing IVOCs when making air pollution control policies in urban areas of China.

Amino acids (AAs), as important organic nitrogen compounds, play key roles in the nitrogen cycles, climate change and public health. The sources and transformation of AAs in two size-segregated aerosol particles were explored. This study presents the first isotopic evidence that the sources of AAs for fine and coarse aerosol particles may be similar. And the potentially significant role of bacterial degradation processes in aerosol protein degradation state was suggested.

This study demonstrates that the intensity of the western Pacific subtropical high (WPSH), a major synoptic pattern in the northern Pacific during summer, can induce a dipole change in surface ozone pollution over eastern China. Ozone concentration increases in the north and decreases in the south during the strong WPSH phase, and vice versa. The change in chemical processes associated with the WPSH change plays a decisive role, whereas the natural emission of ozone precursors accounts for ~ 30 %.

Atmospheric pollutants from anthropogenic activities and biomass burning are usually regarded as ozone precursors. Monocyclic aromatics are no exception. Calculations with a comprehensive atmospheric model are consistent with this view but only for air masses close to pollution source regions. However, the same model predicts that aromatics, when transported to remote areas, may effectively destroy ozone. This loss of tropospheric ozone rivals the one attributed to bromine.

Accurate representation of aerosols in the atmosphere is hard to achieve due to their complex microphysical and optical properties and uncertain emissions. In our work, we employ a data assimilation method which integrates model simulations with satellite observation related to the amount, size and the light absorption of aerosol. The use of these observations in an experiment improves aerosol representation and it is recommended for utilization in future data assimilation practices.

Following the transmission of SARS-CoV-2 to Europe, social distancing rules were introduced to prevent further spread. We investigate the impacts of the European lockdowns on black carbon (BC) emissions by means of in situ observations and inverse modelling. BC emissions declined by 23 kt in Europe during the lockdowns as compared with previous years and by 11 % as compared to the period prior to lockdowns. Residential combustion prevailed in Eastern Europe, as confirmed by remote sensing data.

Global models consistently underestimate atmospheric secondary organic aerosol (SOA), which has significant climatic implications. We use a perturbed parameter model ensemble and ground-based observations to reduce the uncertainty in modelling SOA formation from oxidation of volatile organic compounds. We identify plausible parameter spaces for the yields of extremely low-volatility, low-volatility, and semi-volatile organic compounds based on model–observation match for three key model outputs.

Numerical air quality models (AQMs) are being applied extensively to address diverse scientific and regulatory compliance associated with deteriorating air quality in China. For any AQM applications, model performance evaluation is a critical step that guarantees the robustness and reliability of the baseline modeling results and subsequent applications. We provided benchmarks for model performance evaluation of AQM applications in China to demonstrate model robustness.

Using the Community Earth System Model, we simulate the surface aerosols lifted to the Asian tropopause (the ATAL layer), its composition and trend, covering a long-term period (2000–2015). We identify a double-peak aerosol vertical profile that we attribute to dry and convective cloud-borne aerosols. We find that natural aerosol (mineral dust) is the dominant aerosol type and has no long-term trend. ATAL's anthropogenic fraction, by contrast, shows a marked positive trend.

We use satellite observations of shallow cumulus clouds to investigate the influence of cloud size on the ratio of cloud water path to rainwater (WRR) in different environments. For a fixed temperature and relative humidity, WRR increases with cloud size, but it varies little with aerosols. These results imply that increasing WRR with rising temperature relates not only to deeper clouds but also to more frequent larger clouds.

Prior research has found a maximum in deep stratosphere-to-troposphere mass/ozone transport over the western United States in boreal spring, which can enhance surface ozone concentrations, reducing air quality. We find that the winter-to-summer evolution of the north Pacific jet increases the frequency of stratospheric intrusions that drive transport, helping explain the observed maximum. The El Niño–Southern Oscillation affects the timing of the spring jet transition and therefore transport.

This study provides annual emissions of transportation, manufacturing industries and construction, and residential areas at 1 km resolution from 2009 to 2016 for Ho Chi Minh City, Vietnam. Our originality is our use of satellite-derived urban land use morphological maps. These maps which are based on building height provided by a coarse-resolution satellite-derived digital surface model (DSM) and urban built-up area classified from Landsat images allow spatial disaggregation of annual emissions.

Energetic particle precipitation (EPP) is the rain of solar energetic particles into the Earth's atmosphere. EPP is known to deplete O₃ in the polar mesosphere–upper stratosphere via the formation of NO_x. NO_x also causes chlorine deactivation in the lower stratosphere and has, thus, been proposed to potentially result in reduced ozone depletion in the spring. We provide the first evidence to show that NO_x formed by EPP is able to remove active chlorine, resulting in enhanced total ozone column.

We used air quality modeling to study an extreme pollution episode in November 2017 in India. We found both local and regional emissions contribute to high pollution levels. The extreme pollution values were the result of agricultural fires in the northwest of India. Ozone should be considered in future air quality management strategies.

The distribution of the monthly mean nucleation frequency possessed a characteristic pattern. Its shape was compared to those of environmental variables, including vegetation-derived properties. The spring maximum in the occurrence frequency often overlapped with the positive T anomaly. The link between the heat stress and the occurrence minimum in summer could not be proven, whereas an association between the occurrence frequency and vegetation growth dynamics was clearly identified in spring.

This study provides insight into hydration of two significant atmospheric compounds, glyoxal and methylglyoxal. Using synchrotron radiation excited X-ray absorption spectroscopy, we confirm that glyoxal is fully hydrated in water, and for the first time, we experimentally detect enol structures in aqueous methylglyoxal. Our results support the contribution of these compounds to secondary organic aerosol formation, known to have a large uncertainty in atmospheric models and climate predictions.

Volatile organic compounds (VOCs) are an important constituent in the Arctic atmosphere due to their effect on aerosol and ozone formation. However, an understanding of their sources is lacking. This research presents a multiseason high-time-resolution dataset of VOCs in the Arctic and details their temporal characteristics and source apportionment. Four sources were identified: biomass burning, marine cryosphere, background, and Arctic haze.