Between July and October, biomass burning smoke is advected over the southeastern Atlantic Ocean, leading to climate forcing. Model calculations of forcing by this plume vary significantly in both magnitude and sign. This paper compares aerosol and cloud properties observed during three NASA ORACLES field campaigns to the same in four models. It quantifies modeled biases in properties key to aerosol direct radiative forcing and evaluates how these biases propagate to biases in forcing.

The recently proposed multiphase buffer theory provides a framework to reconstruct long-term trends and spatial variations in aerosol pH, while non-ideality is a major limitation for its broad applications. Here we proposed a parameterization method to estimate the impact of non-ideality and validated it against long-term observations and global simulations. With this method, the multiphase buffer theory can reproduce well aerosol pH variations estimated by comprehensive thermodynamic models.

An important mechanism for the appearance of ice particles in the upper troposphere at low temperatures is homogeneous nucleation. This process is commonly described by the Koop line, predicting the humidity at freezing. However, laboratory measurements suggest that the freezing humidities are above the Koop line, motivating the present study to investigate the influence of different physical parameterizations on the homogeneous freezing with the help of a detailed numerical model.

The use of different spatio-temporal sulfur injection strategies with different magnitudes to create an artificial reflective aerosol layer to cool the climate is studied using sectional and modal aerosol schemes in a climate model. There are significant differences in the results depending on the aerosol microphysical module used. Different spatio-temporal injection strategies have a significant impact on the magnitude and zonal distribution of radiative forcing and atmospheric dynamics.

The Southern Ocean (SO) covers a large area of our planet and its boundary layer is dominated by sea salt aerosols during winter. These aerosols have large implications for the regional climate through their direct and indirect effects. Using satellite and reanalysis data, we document if and how the aerosol properties over the SO are dependent on different local meteorological parameters. Such an observational assessment is necessary to improve the understanding of atmospheric aerosol processes.

The effect of meteorological elements on the three-dimensional distribution structure of particles was studied by making vehicle-based multi-lidar observations in the western Guangdong–Hong Kong–Macao Greater Bay Area of China. Results showed that distribution of particles was closely related to horizontal wind speed and direction, vertical wind speed, and temperature. A model for meteorological elements affecting the vertical distribution of urban particles was offered in this study.

For atmospheric aerosol particles to take part in cloud formation, they need to be at least a few tens of nanometers in diameter. By using a particle condensation model, we investigated how two types of chemical reactions, oligomerization and decomposition, of organic molecules inside the particle may affect the growth of secondary aerosol particles to these sizes. We show that the effect is potentially significant, which highlights the importance of increasing understanding of these processes.

Arctic warming is pronounced, and one factor in this is the poleward atmospheric transport of heat and moisture. This study assesses the 4D structure of an Arctic moisture intrusion event which occurred in June 2017. For the first time, high-resolution pan-Arctic ICON simulations are performed and compared with global models, reanalysis, and observations. Results show the added value of high resolution in the event representation and the impact of the intrusion on the surface energy fluxes.

Specified dynamics schemes attempt to constrain the atmospheric circulation in a climate model to isolate the role of transport in chemical variability, evaluate model physics, and interpret field campaign observations. We show that the specified dynamics scheme in CESM2 erroneously suppresses convection and induces circulation errors that project onto errors in tracers, even using the most optimal settings. Development of a more sophisticated scheme is necessary for future progress.

We use a combination of models for gas-phase chemical reactions and equilibrium gas–particle partitioning of isoprene-derived secondary organic aerosols (SOAs) informed by dark ozonolysis experiments conducted in the CLOUD chamber. Our predictions cover high to low relative humidities (RHs) and quantify how SOA mass yields are enhanced at high RH as well as the impact of inorganic seeds of distinct hygroscopicities and acidities on the coupled partitioning of water and semi-volatile organics.

Chlorine dioxide (OClO) is an indicator for chlorine activation. New OClO data by TROPOMI (S5P) are interpreted in a meteorological context and related to CALIOP PSC observations. We report very high OClO levels for the northern hemispheric winter 2019/20 with an extraordinarily long period with a stable polar vortex. A minor stratospheric warming in the Southern Hemisphere was also observed in September 2019, where usual OClO values rapidly deactivated 1–2 weeks earlier.

Biomass burning (BB) is a global phenomenon that releases large quantities of pollutants such as phenols and aromatic carbonyls into the atmosphere. These compounds can form secondary organic aerosols (SOAs) which play an important role in the Earth’s energy budget. In this work, we demonstrated that the direct irradiation of vanillin (VL) could generate aqueous SOA (aqSOA) such as oligomers. In the presence of nitrate, VL photo-oxidation can also form nitrated compounds.

We use different methane ground- and space-based remote sensing data sets for investigating the emission strength of three waste disposal sites close to Madrid. We present a method that uses wind-assigned anomalies for deriving emission strengths from satellite data and estimate their uncertainty to 9–14 %. The emission strengths estimated from the remote sensing data sets are significantly larger than the values published in the official register.

Fog forecasting is one of the biggest problems for numerical weather prediction. By comparing many models used for fog forecasting with others used for fog research, we hoped to help guide forecast improvements. We show some key processes that, if improved, will help improve fog forecasting, such as how water is deposited on the ground. We also showed that research models were not themselves a suitable baseline for comparison, and we discuss what future observations are required to improve them.

This study uses ground-based observations to investigate the physical processes in the aerosol–cloud interactions in non-precipitating marine boundary layer clouds, over the eastern North Atlantic Ocean. Results show that the cloud responses to the aerosols are diminished with limited water vapor supply, while they are enhanced with increasing water vapor availability. The clouds are found to be most sensitive to the aerosols under sufficient water vapor and strong boundary layer turbulence.

The irregular shape of dust particles makes it difficult to treat them correctly in optical models. Atmospheric measurements of dust optical properties are therefore of great importance. The present study increases the space of observed parameters from 355 and 532 nm towards 1064 nm, which is of special importance for large dust particles. The lidar ratio influenced by mineralogy and the depolarization ratio influenced by shape are measured for the first time at all three wavelengths.

There has been a lack of research into HONO in coastal cities with low concentrations of PM_2.5, but strong sunlight and high humidity. Insufficient research on coastal cities with good air quality has resulted in certain obstacles to assessing the photochemical processes in these areas. Furthermore, HONO contributes to the atmospheric photochemistry depending on the season. Therefore, observations of HONO across four seasons in the southeastern coastal area of China are urgently needed.

We evaluate methane emissions and trends for 2010–2017 in the gridded national emission inventories for the United States, Canada, and Mexico by inversion of in situ and satellite methane observations. We find that anthropogenic methane emissions for all three countries are underestimated in the national inventories, largely driven by oil emissions. Anthropogenic methane emissions in the US peak in 2014, in contrast to the report of a steadily decreasing trend over 2010–2017 from the US EPA.

Using multi-year data, this study reveals the slump of sea land breeze (SLB) at Brisbane during mega fires and investigates the impact of fire-induced aerosols on SLB. Different aerosols have different impacts on sea wind (SW) and land wind (LW). Aerosols cause the decrease of SW, partially offset by the warming effect of black carbon (BC). The large-scale cooling effect of aerosols on sea surface temperature (SST) and the burst of BC contribute to the slump of LW.

We focus on anomalous moisture transport events known as atmospheric rivers (ARs). During ACLOUD and PASCAL, three AR events were identified: 30 May, 6 June, and 9 June 2017. We explore their spatio-temporal evolution and precipitation patterns using measurements, reanalyses, and a model. We show the importance of the following: Atlantic and Siberian pathways during spring–summer in the Arctic, AR-associated heat/moisture increase, precipitation phase transition, and high-resolution datasets.

Water-soluble organic compounds (WSOCs) play important roles in atmospheric particle formation, migration, and transformation processes. In this work, size-segregated atmospheric particles were collected in a rural area of Beijing, and 3D fluorescence spectroscopy was used to investigate the optical properties of WSOCs as a means of inferring information about their atmospheric sources. It was found that these data could efficiently reveal the secondary transformation processes of WSOCs.

In this study we combined aerosol particle measurements at the surface with a scanning Doppler lidar providing vertical profiles of the atmosphere to study the effect of different boundary layer conditions on aerosol particle properties in the understudied Arabian Peninsula region. The instrumentation used in this study enabled us to identify periods when pollution from remote sources was mixed down to the surface and initiated new particle formation in the growing boundary layer.

We present here the results obtained during an intensive field campaign conducted in March to April 2019 in Reunion. Our study integrates a comprehensive chemical and microphysical characterization of cloud water. Our investigations reveal that air mass history and cloud microphysical properties do not fully explain the variability observed in their chemical composition. This highlights the complexity of emission sources, multiphasic exchanges, and transformations in clouds.

We explore the benefits and consistency in adding lidar dust observations in a dust optical depth assimilation. We show that adding lidar data to a dust optical depth assimilation has valuable benefits and the dust analysis improves. We discuss the impact of the narrow satellite footprint of the lidar dust observations on the assimilation.

We analyzed 9-year measurements of BC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in BC and light extinction coefficient due to the Clean Air Action Plan. As a response, both SSA and mass extinction efficiency (MEE) showed considerable increases, demonstrating a future challenge in visibility improvement. The primary and secondary BrC was also separated and quantified, and the changes in radiative forcing of BC and BrC were estimated.

In this study we look at the ability of meteorological ensembles (multiple realisations of the meteorological data) to provide information about the uncertainty in the dispersion model predictions. Statistical measures are used to evaluate the model predictions, and these show that on average the ensemble predictions outperform the non-ensemble predictions.

Duff is decomposed forest fuel under ground. Duff burning often occurs at the smoldering phase with low intensity and long periods, which has little impact on regional air quality. However, there is increasing evidence for duff burning during flaming phases. This study simulates the air quality impacts of duff burning during flaming phases in the southeastern US using a regional air quality model. The results indicate the important contributions of such burning to regional PM_2.5 concentrations.

The gasoline SOA formation potential was simulated by using the UNIPAR model coupled with CB6r3 mechanism under varying NO_x levels, aerosol acidity, humidity, temperature, and concentrations of aqueous salts and gasoline vapor. The model predicts SOA formation via multiphase reactions in the absence of wall bias. The simulation shows that both heterogeneous reactions in the aqueous phase and the implementation of model parameters corrected for GWP are critical to accurately predict SOA mass.

Trace gases and aerosols (tiny airborne particles) are released from a variety of point sources around the globe. Examples include volcanoes, industrial chimneys, forest fires, and ship stacks. These sources provide opportunistic experiments with which to quantify the role of aerosols in modifying cloud properties. We review the current state of understanding on the influence of aerosol on climate built from the wide range of natural and anthropogenic laboratories investigated in recent decades.

This study summarizes continuous measurements of surface air concentrations and deposition of radiocesium in Fukushima city over 8 years after the Fukushima nuclear accident. The concentration in the city was high in winter and low in summer (inverse of the forest area). The decreasing trends were much faster in the earlier stage, probably because dissolved cesium discharged faster from the local environment. Biotite might play a key role in circulation of particulate cesium in Fukushima city.

Aerosols enhance plant photosynthesis by increasing diffuse radiation. In this study, we found that the aerosol impacts are quite different for varied species. Scattering aerosols such as sulfate and organic carbon promote photosynthesis while absorbing aerosols such as black carbon have negative impacts. Earth system models should consider the impacts of cloud and aerosol species on terrestrial ecosystems so as to better predict carbon cycles under different emission scenarios.