We develop a computationally efficient space-based top-down method to inverting NO_x emissions in major urban areas at high resolution. The inversion method uses long-term OMI NO₂ data to enhance the horizontal resolution, and it accounts for the nonlinear effects of horizontal transport, chemical loss, and deposition on NO_x. The inversion results reveal fine-scale spatial information of emissions which is hardly captured by bottom-up inventories.

To understand the contribution of ground emission during heavy pollution in Beijing, Tianjin and Hebei, aerosol fluxes were estimated in Beijing and Gucheng areas. The results show that in the three stages of a heavy pollution process (transport, accumulative and removal stages: TS, AS and RS), the ground emissions in the TS and RS stages are stronger, while the ground discharge in the AS stage is weak. The weakened mass flux indicates that the already weak turbulence would be further weakened.

Traditionally, the real part of the refractive index (RRI) of ambient aerosols is calculated by their chemical components. In this study, we demonstrate that the RRI is highly related to effective density rather than chemical components using field measurements. For the first time, a parameterization scheme for ambient aerosol RRI using effective density is proposed. This simple scheme is more reliable and ready to use in the calculation of aerosol optics and radiation.

Different greenhouse gases (e.g. CO₂) and aerosols (e.g. black carbon) impact the Earth’s water cycle differently. Here we investigate how various gases and particles impact atmospheric water vapour and its lifetime, i.e., the average number of days that water vapour stays in the atmosphere after evaporation and before precipitation. We find that this lifetime could increase substantially by the end of this century, indicating that important changes in precipitation patterns are excepted.

Ozone (O3) pollution is increasing in China and the underlying reason for this is unknown, making effective control unrealistic. Using an innovative approach, we quantitatively identified the impact of meteorology and precursor emission changes, both local and nonlocal, on the long-term O3 trend in the PRD. Meteorology can contribute to up to 15 % of long-term O3 variations. The undesirable NOx/VOC control ratio over the past few years is most likely responsible for the O3 increase in the PRD.

Using both observations and a chemistry climate–model we establish that in most locations changes in the waviness of the 500 hPa flow field, as measured by the local anticyclonic wave activity (AWA), explain a significant fraction of the interannual variability in surface ozone over the United States. In addition, we find that the change in AWA in a future climate (circa 2100) is predicted to cause a change in surface ozone ranging between –6 ppb and 6 ppb.

In this study, a deep recurrent neural network system based on a long short-term memory (LSTM) model was developed for daily PM₁₀ and PM_2.5 predictions in South Korea. In general, the accuracies of the LSTM-based predictions were superior to the 3-D CTM-based predictions. Based on this, we concluded that the LSTM-based system could be applied to daily operational PM forecasts in South Korea. We expect that similar AI systems can be applied to the predictions of other atmospheric pollutants.

Emission inventory studies are an important regulatory tool for quantifying the amount of pollutants released in the atmosphere using the fuel consumption and emission rates for different fuels. This study developed an emission inventory over Nepal for 2001–2016 that reveals the changing fuel consumption and subsequently the pollution across different sectors of industrial, transport, agricultural, commercial and residential uses with the use of spatial distribution of anthropogenic activities.

Sectoral contributions of anthropogenic emissions in Denmark, Finland, Norway and Sweden on air pollution and mortality over the Nordic and the Arctic regions are calculated. 80 % of PM_2.5 over the Nordic countries is transported from outside Scandinavia. Residential combustion, industry and traffic are the main sectors to be targeted in emission mitigation. Exposure to ambient air pollution in the Nordic countries leads to more than 10 000 deaths in the region annually and costs EUR 7 billion.

This study evaluated and intercompared 14 CTMs with ozone observations in East Asia, within the framework of the Model Inter-Comparison Study for ASIA Phase III (MICS-Asia III). Potential causes of the discrepancies between model results and observation were investigated by assessing the planetary boundary layer heights, emission fluxes, dry deposition, chemistry and vertical transport among models. Finally, a multi-model estimate of pollution distributions was provided.

Interannual variations in net ecosystem exchange (NEE) estimated from the Greenhouse Gases Observing Satellite (GOSAT) XCO₂ measurements are shown to be correlated (P < 0.05) with temperature and FLUXCOM NEE anomalies. Furthermore, the GOSAT-informed NEE anomalies are found to be better correlated with temperature and FLUXCOM anomalies than NEE estimates from most terrestrial biosphere models, suggesting that GOSAT CO₂ measurements provide a useful constraint on NEE interannual variability.

Identifying the chemical pathways of condensable products such as carboxylic acids is essential for predicting SOA formation. This identification is inherently difficult, as such products reside in both the gas and particulate phases. We measured acids, produced from atmospheric oxidation of limonene, in both phases and scrutinised the mechanistic understanding of their formation. The mechanisms explain nearly 75 % of the gas-phase signal at the lowest concentration (8.4 ppb, 23 % acid yield).

An understanding of the chemical composition of the smallest particles in the air over the Amazon Basin provides insights into the natural and human-caused influences on particle production in this sensitive region. We present measurements of the composition of sub-100 nm diameter particles performed during the wet season and identify unique constituents that point to both natural and human-caused sources and processes.

Lightning NO_x represents > 80 % of the NO_x source in the upper troposphere. Despite its importance, lightning NO_x is poorly understood. This work improves model performance in representing lighting NO_x and reduces the uncertainty in satellite NO₂ retrievals caused by poor representation of lightning NO_x emissions in a priori assumptions.

Our study presents an analysis of the vertical and horizontal black carbon properties across northern India using aircraft measurements. The Indo-Gangetic Plain saw the greatest black carbon mass concentrations during the pre-monsoon season. Two black carbon modes were recorded: a small black carbon mode (traffic emissions) in the north-west and a moderately coated mode (solid-fuel emissions) in the Indo-Gangetic Plain. In the vertical profile, absorption properties increase with height.

This study characterizes the changes observed at Paris urban scale and attempts to identify the surface–atmosphere feedbacks likely to explain the trends observed as a function of the different configurations of large-scale dynamics. This article is interested in several atmospheric parameters and their possible retroactions. Finally, to study urban environments, the analysis at the local scale is essential because it is very poorly represented in the model.

The use of satellite data is of great interest for the determination of aerosol radiative forcing at regional or even global scales, as previous studies in the literature are predominantly only valid locally. A methodology to retrieve 2-D dust radiative effects with large spatial and temporal coverage based on combined satellite data from CALIPSO, MODIS and CERES is presented and evaluated against well-established methods based on ground-based lidar measurements, obtaining quite good results.

Characteristics of the black carbon size distribution (BCMSD) are studied by using our developed measurement system. Results show that the BCMSDs have two modes and the mean peak diameters are 150 nm and 503 nm, respectively. The coarser mode varies significantly under different pollution conditions, which gives rise to significant variation in aerosol bulk optical properties. Our study reveals that the BCMSD as well as the mixing state in estimating aerosol radiative forcing matters.

This study provides good insight into the chemical nature and complex origin of aerosols by combining comprehensive field observations and transport modelling. We suggest that factors related to topography, metrological conditions, local emissions, in situ formation and growth, regional transport, and the interaction of biogenic and anthropogenic compounds need to be considered for a comprehensive understanding of aerosol processes.

Organic aerosol simulation schemes were tested in climatic runs to assess their climate sensitivity. The test for each scheme contains five historic and five future years of simulation. Validation was performed for the three schemes to assess their performance compared to measured data. Results show that the scheme taking into account fragmentation and formation of nonvolatile secondary organic aerosol (SOA) shows higher relative biogenic SOA (BSOA) changes than historic and future scenarios.

The trends of meteorological parameters and surface downward shortwave radiation (DSR) and downward longwave radiation (DLR) were analysed at four stations (between 370 and 3580 m a. s. l.) in Switzerland for the 1996–2015 period. Trends in DSR and DLR were positive during cloudy as well as clear conditions. The trend due to the influence of clouds decreased in magnitude, which implies a reduction in cloud cover and/or a change towards a different cloud type over the four Swiss sites.

New particle formation (NPF) is a significant climate-relevant source of aerosols in the atmosphere. We show that during the eruptive periods of the Piton de la Fournaise in 2015, NPF was favoured compared to regular days. Using the largest dataset ever reported in volcanic plume conditions, we quantify the emission rates of particles over a broad size range and provide a new statistically robust parameterization to take into account this important source of atmospheric particles in models.

This research was conducted to quantify the impact of different prior global biosphere models on the estimate of terrestrial CO₂ fluxes when assimilating Orbiting Carbon Observatory-2 (OCO-2) satellite observations. To determine the prior model impact, we apply observing system simulation experiments (OSSEs). Even with the substantial spatiotemporal coverage of OCO-2 data, residual differences in posterior CO₂ flux estimates remain due to the choice of prior flux mean and uncertainties.

We conducted 1-year continuous measurement of HONO at the SORPES station. We obtained seasonal and diurnal variations of HONO and evaluated the contribution of HONO photolysis to OH radical and the missing daytime source of HONO. We separated the sources of nocturnal HONO into four parts: combustion emissions, soil emission, formation on ground and formation on aerosol, and estimate their contribution semi-quantitatively. The results highlighted ever-changing contributions of HONO sources.

This study assessed and quantified the transboundary air pollution (TAP) impact in Japan and South Korea. We found that ~70 % of annual ambient PM2.5 in Japan and South Korea was contributed by other countries in the region, and wet deposition had a greater impact on mixed forests in Japan and savannas in South Korea. Given these significant impacts of TAP in the region, it is paramount that cross–national efforts be taken to mitigate air pollution problems across East Asia.

The main aims of the study are to (a) detect whether mercury in the surface snow undergoes a daily cycle as determined in the atmosphere, (b) compare the mercury concentration in surface snow with the concentration in the atmosphere, (c) evaluate the effect of snow depositions, (d) detect whether iodine and bromine in the surface snow undergo a daily cycle, and (e) evaluate the role of metereological and atmospheric conditions. Different behaviours were determined during different seasons.