The importance of the atmospheric boundary layer (ABL) is recognized, but little is known about the Tibetan Plateau (TP) ABL due to the scarce data. Based on new observations from the Third Tibetan Plateau Atmospheric Scientific Experiment, we reveal a big drop in the ABL height from the west to the east of the TP for the first time, which is more remarkable than in the United States and all of China. This steep inhomogeneity in the TP is due to the difference in local climate and environment.

The performance of LOTOS-EUROS v2.2.001 regional chemical transport model NO₂ simulations is investigated over Greece from June to December 2018. Comparison with in situ NO₂ measurements shows a spatial correlation coefficient of 0.86, while the model underestimates the concentrations mostly during daytime (12 to 15:00 local time). Further, the simulated tropospheric NO₂ columns are evaluated against ground-based MAX-DOAS NO₂ measurements and S5P/TROPOMI observations for July and December 2018.

This paper presents measures of the severity of the Antarctic ozone hole covering the period 1979 to 2019. The paper shows that while the severity of Antarctic ozone depletion grew rapidly through the last two decades of the 20th century, the severity declined thereafter and faster than expected from declines in stratospheric concentrations of the chlorine- and bromine-containing chemical compounds that destroy ozone.

We compared the characteristics of individual particles at ground level and above the mixed-layer height. We found that the particles above the mixed-layer height during haze periods are more aged compared to ground level. More coal-combustion-related primary organic particles were found above the mixed-layer height. We suggest that the particles above the mixed-layer height are affected by the surrounding areas, and once mixed down to the ground, they might contribute to ground air pollution.

A global long-term (1995–2015) data set of total column water vapour (TCWV) derived from satellite observations is used to quantify the influence of teleconnections. Based on a newly developed empirical method more than 40 teleconnection indices are significantly detected in our global TCWV data set. After orthogonalisation, only 20 indices are left significant. The global distribution of the cumulative influence of teleconnection indices is strongest in the tropics and high latitudes.

We assess how consistently reanalyses represent potential vorticity (PV) among each other. PV helps describe dynamical processes in the stratosphere because it acts approximately as a tracer of the movement of air parcels; it is extensively used to identify the location of the tropopause and to identify and characterize the stratospheric polar vortex. Overall, PV from all reanalyses agrees well with the reanalysis ensemble mean.

The variation in aerosol 355 nm lidar ratio and its influence factors were analyzed in Shanghai. About 90 % of the lidar ratio was distributed in 10 sr–80 sr, with an average of 41.0±22.5 sr, and the lidar ratio decreased with the increase in height. Due to aerosol radiative effects, the vertical slope of the lidar ratio presented a decreasing trend with increasing atmospheric turbidity. A large lidar ratio above 1 km was related to biomass burning aerosols and high relative humidity.

We investigate factors contributing to the severe and persistent air quality degradation in northern India that has worsened during every winter over the last decade. This is achieved by implementing atmospheric modelling and using recently available Sentinel-5 P satellite data for carbon monoxide. We see a minimal role of biomass burning, except for the state of Punjab. The aim is to focus on residential and industrial emission reduction strategies to tackle air pollution over northern India.

This study focuses on fully discriminating the origins of particulates by tackling specific secondary organic aerosol (SOA) sources that are difficult to resolve using traditional datasets, especially at a city scale. This is done through the use of additional fit-for-purpose tracers in the Positive Matrix Factorization (PMF) model, which can be obtained using simpler and more targeted techniques, and the comparison of the PMF models from sites in close range but with different urban typologies.

The impact of aerosols on clouds is a large source of uncertainty for future climate projections. Our results show that the radiative properties of a complex convective cloud field in the Saharan outflow region are sensitive to the temperature dependence of ice-nucleating particle concentrations. This means that differences in the aerosol source or composition, for the same aerosol size distribution, can cause differences in the outgoing radiation from regions dominated by tropical convection.

Here aerosol volatility and viscosity at a rural site (Gucheng) and an urban site (Beijing) in the North China Plain (NCP) were investigated in summer and winter. Our results showed that organic aerosol (OA) in winter in the NCP is more volatile than that in summer due to enhanced primary emissions from coal combustion and biomass burning. We also found that OA existed mainly as a solid in winter in Beijing but as semisolids in Beijing in summer and Gucheng in winter.

Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation. We present a case study that involves aircraft, lidar and radar observations of water and clouds in a WCB ascending from western Europe across the Alps towards the Baltic Sea during the field campaigns HyMeX and T-NAWDEX-Falcon in October 2012. A probabilistic trajectory measure and an airborne tracer experiment were used to confirm the long pathway of the WCB.

Fog, cloud and haze are very common natural phenomena. Sulfuric acid (SA) is one of the key compounds forming those suspended particles, technically called aerosols, through gas-to-particle conversion. Therefore, the concentration level, source and sink of SA is very important. Our results show that ozonolysis of alkenes plays a major role in nighttime SA formation under unpolluted conditions in urban Beijing, and nighttime cluster mode particles are probably driven by SA in urban environments.

This work highlights a new algorithm using data collected from the 2016–2018 NASA ORACLES field campaign. This algorithm synthesizes cloud and rain measurements to attain estimates of cloud and precipitation properties over the southeast Atlantic Ocean. Estimates produced by this algorithm compare well against in situ estimates. Increased rain fractions and rain rates are found in regions of atmospheric instability. This dataset can be used to explore aerosol–cloud–precipitation interactions.

The present study explores the detailed structure, dynamics, and trace gas variability in the Asian summer monsoon anticyclone (ASMA) in the extreme El Niño of 2015/16. The results find the structure of the ASMA shows strong spatial variability between July and August. A West Pacific mode of the anticyclone is noticed in August. A significant lowering of tropospheric tracers and strong increase in stratospheric tracers are found. The tropopause temperatures also exhibit a warming in the ASMA.

In this study, we quantify PM_2.5 oxidative potential (OP), a metric widely suggested as a potential measure of particle toxicity, in Beijing in summer and winter using four acellular assays. We correlate PM_2.5 OP with a comprehensive range of atmospheric and particle composition measurements, demonstrating inter-assay differences and seasonal variation of PM_2.5 OP. Using multivariate statistical analysis, we highlight specific particle chemical components and sources that influence OP.

This paper documents the evolution of the cloud of volcanic aerosol introduced into the stratosphere by the eruption of Raikoke in June 2019. The measurements were made by a UV lidar (laser radar) operated at Capel Dewi, Wales, between June 2019 and May 2020. They show how the cloud of volcanic aerosol arrived at the site and how its optical depth decreased by a factor of 5 over the 11 months of measurements.

We build a novel system that utilizes an aerodynamic aerosol classifier (AAC) combined with a single-particle aerosol mass spectrometry (SPAMS) to simultaneously characterize the volume equivalent diameter (D_ve), chemical compositions, and effective density (ρ_e) of individual particles in real time. A test of the AAC-SPAMS with both spherical and aspherical particles shows that the deviations between the measured and theoretical values are less than 6 %.

Black carbon (BC), an aerosol that contributes to glacier melt, is important for central Himalayan hydrology because glaciers are a water source to rivers that affect 25 % of the global population in Southeast Asia. Using the Dasuopu ice core (1781–1992 CE), we find that drought-associated biomass burning is an important source of BC to the central Himalaya over a period of months to years and that hemispheric changes in atmospheric circulation influence BC deposition over longer periods.

An assessment of mercury emissions from a burning boreal forest was made by flying an aircraft through its plume to collect in situ gas and particulate measurements. Direct data show that in-plume gaseous elemental mercury concentrations reach up to 2.4× background for this fire and up to 5.6× when using a correlation with CO data. These unique data are applied to a series of known empirical emissions estimates and used to highlight current uncertainties in the literature.

We conducted an extensive analysis of the structural uncertainty of the Emissions Database for Global Atmospheric Research (EDGAR) emission inventory of greenhouse gases, which adds a much needed reliability dimension to the accuracy of the emission estimates. The study undertakes in-depth analyses of the implication of aggregating emissions from different sources and/or countries on the accuracy. Results are presented for all emissions sectors according to IPCC definitions.

Arctic mixed-phase clouds significantly influence the energy budget of the Arctic. We show that a climate model considering secondary ice production (SIP) can explain the observed cloud ice number concentrations, vertical distribution pattern, and probability density distribution of ice crystal number concentrations. The mixed-phase cloud occurrence and phase partitioning are also improved.

The meteorological effect of aerosols on tropospheric ozone is investigated using global atmospheric modelling. We found that aerosol-induced meteorological effects act to reduce modelled ozone concentrations over China, which brings the simulation closer to observed levels. Our work sheds light on understudied processes affecting the levels of tropospheric gaseous pollutants and provides a basis for evaluating such processes using a combination of observations and model sensitivity experiments.

This article reports the molecular composition of smoke particles people in SF Bay Area were exposed to during northern California wildfires in Oct. 2017. Major components are sugars, acids, aromatics, and terpenoids. These observations can be used to better understand health impacts of smoke exposure. Tracer compounds indicate which fuels burned, including diterpenoids for softwood and syringyls for hardwood. A statistical analysis reveals a group of secondary compounds formed in daytime aging.

The influence of aerosol radiative forcing (ARF) on the boundary layer structure is nonlinear. The threshold of the modification effects of ARF on the boundary layer structure was determined for the first time, highlighting that once ARF exceeded a certain value, the boundary layer would quickly stabilize and aggravate air pollution. This could provide useful information for relevant atmospheric-environment improvement measures and policies.

The hydroxyl radical (OH) dominates the removal of atmospheric pollutants, with nitrous acid (HONO) recognised as a major OH source. For remote regions HONO production through the action of sunlight on aerosol surfaces can provide a source of nitrogen oxides. In this study, HONO production rates at illuminated aerosol surfaces are measured under atmospheric conditions, a model consistent with the data is developed and aerosol production of HONO in the atmosphere is shown to be significant.