This study employs a parcel–DNS (direct numerical simulation) modeling framework to accurately resolve the aerosol–droplet–turbulence interactions in an ascending air parcel. The effect of turbulence, aerosol hygroscopicity, and aerosol mass loading on droplet growth and rain formation is investigated through a series of in-cloud seeding experiments in which hygroscopic particles were seeded near the cloud base.

Biogenic and anthropogenic air masses mix in the atmosphere, bringing plant-emitted monoterpenes and traffic-related nitrogen oxides together. There is debate whether the presence of nitrogen oxides reduces or increases secondary aerosol formation. This is important as secondary aerosols have cooling effects in the climate system but also constitute a health risk in populated areas. We show that the presence of NO_x alone should not much affect the mass yields of secondary organic aerosols.

Biomass burning aerosol can scatter and absorb light, contributing to the cooling or warming of the planet. The scattering and absorption properties (optical properties) change as aerosol ages and interacts with atmospheric gases. Optical properties also depend on burning conditions, fuel type, and morphology. Africa is a major source of biomass burning aerosols, but there are very few laboratory studies. This study focuses on the optical properties of aerosols from east African biomass fuels.

Biomass fuels used for domestic purposes in east Africa produce a significant atmospheric burden of aerosols and volatile organic compounds. The chemical properties and composition of these aerosols have not been investigated in the laboratory. In this work methanol extracts from filter samples of aerosol collected from an indoor smog chamber were analyzed to determine the chemical composition and identify the light absorption properties of organic aerosol constituents.

We studied the characteristics and sources of aerosol scattering for Nanjing. The method of aerosol scattering estimation was optimized based on field measurements, and the impacts of aerosol size and composition were quantified. To explore the reasons for the reduced visibility, source apportionment of aerosol scattering was conducted by pollution level. This work stressed the linkage between aerosols and visibility and improved the understanding of emissions and their role in air quality.

The idea that larger shallow cumulus clouds have stronger updrafts than small shallow cumulus clouds is as intuitive as it is old. In this paper we gather years of upward-pointing laser measurements from a plain in Oklahoma and combine them with 28 d of high-resolution simulations. Our approach, which has much more data than previous studies, confirms that updraft strength and cloud size are linked and that the simulations reproduce the observed cloud wind and moisture structure.

We investigate how well models represent the enhancement in scattering coefficients due to particle water uptake, and perform an evaluation of several implementation schemes used in ten Earth system models. Our results show the importance of the parameterization of hygroscopicity and model chemistry as drivers of some of the observed diversity amongst model estimates. The definition of dry conditions and the phenomena taking place in this relative humidity range also impact the model evaluation.

Smoke forecasts have been challenged by high uncertainty in fire emission estimates. We develop an inverse modeling system, the HYSPLIT-based Emissions Inverse Modeling System for wildfires, that estimates wildfire emissions from the transport and dispersion of smoke plumes as measured by satellite observations. Using NOAA HYSPLIT and GOES Aerosol/Smoke Product (GASP), the system resolves smoke source strength as a function of time and vertical level and outperforms current operational system.

There are statistically significant positive and negative correlations, respectively, between winter haze days (WHDs) in China's Jing-Jin-Ji region and eastern Pacific and central Pacific El Niño events. These opposite changes in WHDs are attributable to the anomalies of both large-scale circulation and local synoptic conditions corresponding to two types of El Niño. Our study highlights the importance of distinguishing the impacts of two types of El Niño on winter haze pollution in this region.

Rapid urbanization has increased the consumption of fossil fuel, contributing the degradation of urban air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. We quantify the burning efficiency of fossil fuel use over six megacities using satellite remote sensing data. City governance can use these results to understand air pollution scenarios and to formulate effective air pollution control strategies.

Source sensitivities and apportionments of PM_2.5 and ozone concentrations over Japan for 2016 were evaluated using multiple numerical techniques including BFM, HDDM, and ISAM, embedded in regional chemical transport models. Influences of stringent emission controls recently implemented in Asian countries were reflected. Differences between sensitivities and apportionments greatly helped distinguish various direct and indirect effects of emission sources on PM_2.5 and ozone concentrations.

Our observations provide detailed information on the abundance and vertical distribution of dicarboxylic acids, oxoacids and α-dicarbonyls in PM_2.5 collected at three heights based on a 325 m meteorological tower in Beijing in summer. Our results demonstrate that organic acids at the ground surface are largely associated with local traffic emissions, while long-range atmospheric transport followed by photochemical ageing contributes more in the urban boundary layer than the ground surface.

In the present study, simulations with the SPACCIM-SpactMod multiphase chemistry model are performed. The investigations aim at assessing the impact of a detailed treatment of non-ideality in multiphase models dealing with aqueous aerosol chemistry. The model studies demonstrate that the inclusion of non-ideality considerably affects the multiphase chemical processing of transition metal ions, oxidants, and related chemical subsystems such as organic chemistry in aqueous aerosols.

Measuring and quantifying the sources of elevated springtime ozone in the southwestern US is challenging but relevant to the implications for control policy. Here we use intensive field measurements and two global models to study ozone sources in the region. We find that ozone from the stratosphere, wildfires, and Asia is an important source of high-ozone events in the region. Our analysis also helps understand the uncertainties in ozone simulations with individual models.

This study provides a comprehensive evaluation of the global dust cycle in 15 models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). We assess the global budget and associated uncertainties. We also quantify the discrepancies in each model. The results highlight the large uncertainties in both the locations and intensities of dust emission. Our study will serve as a useful reference for model communities and help further model improvements.

We use numerical models to determine the origin of air masses measured for elemental gaseous mercury (GEM) at Cape Point (CPT), South Africa. Our analysis is based on 10 years of hourly GEM measurements at CPT from 2007 to 2016. Based on GEM concentration and the origin of the air mass, we identify source and sink regions at CPT. We find, that the warm Agulhas Current to the south-east is the major Hg source and the continent the major sink.

We compared the volatility distributions of secondary organic aerosol (SOA) constituents estimated from isothermal evaporation experiments from either particle size change data, by process modelling and global optimization, or from mass spectrometer data with positive matrix factorization analysis. Our results show that, despite the two very different estimation methods, the volatility distributions are comparable if uncertainties are taken into account.

We present direct measurements of NO₃ reactivity resulting from the oxidation of isoprene by NO₃ during an intensive simulation chamber study. Measurements were in excellent agreement with values calculated from measured isoprene amounts and the rate coefficient for the reaction of NO₃ with isoprene. Comparison of the measurement with NO₃ reactivities from non-steady-state and model calculations suggests that isoprene-derived RO₂ and HO₂ radicals account to ~ 50 % of overall NO₃ losses.

We combine the ground-based observations and radiative transfer model to quantify the impact of the 2017 solar eclipse on surface shortwave irradiation reduction. We find that the eclipse caused local reductions of time-averaged surface flux of about 379 W m^-2 (50 %) and 329 W m^-2 (46 %) during the ~ 3 h course of the eclipse at the Casper and Columbia sites, respectively. We estimate that the Moon’s shadow caused a reduction of approximately 7 %–8 % in global average surface broadband SW radiation.

This study introduces 2 years of continuous near-surface in situ observations of the stable isotopic composition of water vapour in parallel with precipitation in north-eastern Siberia. We evaluate the atmospheric transport of moisture towards the region of our observations with simulations constrained by meteorological reanalyses and use this information to interpret the temporal variations of the vapour isotopic composition from seasonal to synoptic timescales.

Chemical composition and sources of submicron aerosols (PM₁) were simultaneously investigated at a kerbside site in the Dublin city center and at a residential site in suburban Dublin (~5 km apart) during both a nonheating and a heating period in 2018. This study highlights the temporal and spatial variability of sources within the Dublin city center and the need for additional aerosol characterization studies to improve targeted mitigation solutions for a greater impact on urban air quality.

Winter winds in the stratosphere 10–50 km above the surface impact climate at the surface. Prior studies suggest that this interaction between the stratosphere and the surface is affected by ozone. We compare two ways of including ozone in computer simulations of climate. One method is more realistic but more expensive. We find that the method of including ozone in simulations affects the surface climate when the stratospheric winds are unusually weak but not when they are unusually strong.

Black carbon is a factor in the warming of the Arctic atmosphere due to its ability to absorb light, but the uncertainty is high and few observations have been made in the high Arctic above 80° N. We combine airborne and ground-based observations in the springtime Arctic, at and above 80° N, with simulations from a global model to show that light absorption by black carbon may be much larger than modelled. However, the uncertainty remains high.

The role of deep convection in the southwest Indian Ocean (the 3rd most active tropical cyclone basin) on the composition of the tropical tropopause layer (TTL) and the climate system is less understood due to scarce observations. Balloon-borne lidar and satellite measurements in the southwest Indian Ocean were used to study tropical cyclones' influence on TTL composition. This study compares the impact of a tropical storm and cyclone on the humidification of the TTL over the SW Indian Ocean.

Performances of the simulated deposition for different reduced N (N_r) species in China were conducted with the Model Inter-Comparison Study for Asia. Results showed that simulated wet deposition of oxidized N was overestimated in northeastern China and underestimated in south China, but N_r was underpredicted in all regions by all models. Oxidized N has larger uncertainties than N_r, indicating that the chemical reaction process is one of the most importance factors affecting model performance.

Statistical modelling of interdependencies between local, regional and global parameters on long-term trends of atmospheric SO₂, NO₂ and O₂ within proximity of the pollution hotspot in South Africa indicated that changes in meteorological conditions and/or variances in source influences contributed to temporal variability. The impact of increased anthropogenic activities and energy demand was evident, while the El Niño–Southern Oscillation made a significant contribution to O₃ levels.

The effects of shipping emissions on air quality and health in the harbour city of Gothenburg were simulated for different scenarios for the year 2040 with coupled regional and city-scale chemistry transport models to evaluate the impact of regional emission regulations and onshore electricity for ships at berth. The results show that contributions of shipping to exposure and associated health impacts from particulate matter and NO₂ decrease significantly compared to 2012 in all scenarios.

With strong public concern regarding air pollution problems in eastern China, where megacities like Beijing and Shanghai are located, smoke from agricultural fires burning during the post-harvest season has been blamed as one of the major causes. This research uses advanced satellite remote sensing data and methods to estimate the smoke emissions from agricultural fires in eastern China. Up to a 22 % contribution to PM_2.5 was found during extreme cases.

Ground-level ozone (O₃) is not directly emitted; it is formed chemically in the atmosphere. Some ground-level O₃ is transported from the stratosphere, but most O₃ is produced from reactive precursors that are emitted by both natural and anthropogenic sources. We present the results of a novel source apportionment method for ground-level O₃. Our results are consistent with previous work and also provide new insights. In particular, we highlight the roles of methane and international shipping.

Unresolved interaction between clouds and atmospheric radiation is a source of uncertainty in weather and climate models. The present study highlights the potential of the state-of-the-art Tripleclouds radiative solver for shallow cumulus clouds, exposing the significance of properly representing subgrid cloud horizontal heterogeneity. The Tripleclouds concept was thereby incorporated in the widely employed δ-Eddington two-stream radiation scheme within the comprehensive libRadtran library.

We carried out 19 city-circle-around Car MAX-DOAS experiments on the 6th Ring Road of Beijing in Jan, Sep, and Oct 2014. The tropospheric VCDs of NO₂ are retrieved and their temporal and spatial distributions are investigated. Then the NO_x emission rates in urban Beijing are estimated using the measured NO₂ VCDs together with the refined wind fields, NO₂-to-NO_x ratios, and NO₂ lifetimes simulated by the LAPS-WRF-CMAQ model system, and results are compared with the MEIC inventory in 2012.