During November 2017, very high pollution levels were measured in the northern part of India. In this study, satellite (TROPOMI) data and model (WRF) data on carbon monoxide (CO) are studied to investigate the main sources of the CO pollution over the Indo-Gangetic Plain. We found that residential and commercial combustion was a much more important source of CO than the post-monsoon crop burning during this period. Meteorology was found important in the accumulation and ventilation of CO.

The heavy air pollution in the Beijing-Tianjin-Hebei (BTH) region is a global hot topic. We established a unit-based industrial emission inventory for the BTH region. The inventory significantly improved air quality modeling results; this improvement subsequently contributes to an accurate source apportionment of haze pollution and more precisely targeted decision making.

Measurements of stable carbon and nitrogen isotopic compositions in the PM₁ atmospheric aerosol provide partial insight into the possible sources of aerosol at a Central European rural background station but mainly offers a deeper insight into the physical and chemical processes taking place between the gas phase and particulate matter. These processes are probably valid in general (not only at this site), especially for nitrogen compounds.

We have discovered a new compound in the atmosphere, octafluorooxolane (c-C₄F₈O), from measurements in archived air samples. From our laboratory studies, we find that c-C₄F₈O is a very powerful greenhouse gas thereby contributing to global warming, and that it has a very long atmospheric lifetime of more than 3500 years. Based on our measurements we could reconstruct its atmospheric evolution over more than 4 decades. Based on this, we could estimate the global emissions of c-C₄F₈O.

We evaluated the atmospheric oxidation capacity (AOC) in four Chinese megacities during photochemically polluted seasons. The chemical production of ozone and particle nitrate was diagnosed through a box model, which can be attributed to daytime radical chemistry. Our work highlights that the formation of both ozone and fine particles is largely driven by the atmospheric radical chemistry in China. Consequently, we suggest future pollution mitigation strategies should consider the role of AOC.

This paper describes a new global dataset of atmospheric composition data for the years 2003-2016 that has been produced by the Copernicus Atmosphere Monitoring Service (CAMS). It is called the CAMS reanalysis and provides information on aerosols and reactive gases. The CAMS reanalysis shows an improved performance compared to our previous atmospheric composition reanalyses; has smaller biases compared to independent O₃, CO, NO₂ and aerosol observations; and is more consistent in time.

In this paper we present an analysis of the unusual red sky event that occurred over the UK on 15 and 16 October 2017. We use measurements from the Met Office operational lidar and sun-photometer network, as well as other data and model output, to show that the event was caused by the passage of ex-hurricane Ophelia which transported unusual amounts of dust from the Sahara to the UK as well as smoke from forest fires in Portugal.

The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite provides carbon monoxide (CO) total column concentrations based on measurements in the 2.3 μm spectral range with a spatial resolution of 7 km x 7 km and daily global coverage. In this study, we analyzed local CO enhancements in an area around Iran from 1 November to 20 December 2017 using the WRF model and evaluated CO emissions from the cities of Tehran, Yerevan, Urmia, and Tabriz.

Tropospheric ozone has important implications for air quality and climate change but is poorly understood at a regional and seasonal level. Analysis of model simulations indicates that downward transport of ozone from the stratosphere has a larger influence than previously thought (as much as ~50 % even near the surface). Recent estimated changes in tropospheric ozone (1980–89 to 2001–10) are generally positive, with substantial attribution from the stratosphere identified over some regions.

A new approach describing the relationship between ice crystal mass (m) and dimension (D) is derived, characterizing it as a set of equally realizable parameters based on the natural variability in cloud conditions observed by aircraft over the Great Plains. Results from this approach address shortcomings of microphysical parameterization schemes and remote sensing retrievals that employ a single m–D relation for a given ice species or environment.

Aerosol mass spectrometry produces large amounts of complex data, the analysis of which necessitates chemometrics – the application of advanced statistical and mathematical tools to chemical data. Here, we perform a data-driven analysis of multiple aerosol mass spectrometric data sets, to show that the traditional separation of organics and inorganics is not necessary. The resulting 7-component aerosol speciation explains 83 % to 96 % of observed variability at our boreal forest experiment site.

In this study, we found that a cold front can transport air pollutants from the polluted North China Plain to the Yangtze River Delta (YRD), thereby deteriorating air quality over the YRD. Before the cold frontal passage, a warm and polluted air mass over YRD climbed to the free troposphere (1.0–2.0 km) along the frontal surface. After the cold frontal passage, high pressure behind the frontal zone resulted in a synoptic subsidence that trapped PM_2.5 in the surface.

Intense convective phenomena are a common climatic feature in the Indian tropical region which occur during the pre-monsoon to post-monsoon seasons (April–October) and are generally accompanied by intense thunderstorms, lightning, and wind gusts with heavy rainfall. Here we show long-term trends of the parameters related to convection and instability obtained from 27 radiosonde stations across six subdivisions over the Indian region during the period 1980–2016.

Among the different aerosols affecting the Euro-Mediterranean region, ammonium and nitrate (A&N) aerosols are expected to have a growing impact on regional climate. In this study, these aerosols have been introduced in the prognostic aerosol scheme of the ALADIN-Climate regional model. Results show that since 2005 over Europe, A&N aerosol optical depth is higher than sulfate and organics and they are responsible for a cooling of about −0.2 °C over Europe during summer.

We derive a new method to retrieve upper-tropospheric humidity (UTH) from High-resolution Infrared Radiation Sounder (HIRS) channel 12 brightness temperatures. With the new method we solve an old problem, namely that the wavelength change that occurred between HIRS 2 on NOAA 14 and HIRS 3 on NOAA 15 led to the retrieval of many more events with high UTH; that is, the time series shows strong jumps at high UTH values. This old problem is solved with the new retrieval.

Biogenic volatile organic compound (BVOC) emissions from vegetation are essential inputs for air quality models but their uncertainties are very high. In this study we show the importance of BVOC emissions for modelled ozone and aerosol concentrations in Europe. Using different biogenic emissions from MEGAN and PSI models significantly affected organic aerosols (smaller effect on ozone), indicating the importance of harmonising the BVOC emissions in the model inter-comparison studies.

The Na layer in the upper atmosphere is very sensitive to solar radiation and varies considerably during sunrise and sunset. In this paper, we use the lidar observations and an advanced model to investigate this process. We found that the variation is mostly due to the changes in several photochemical reactions involving Na compounds, especially NaHCO₃. We also reveal that the Fe layer in the same region changes more quickly than the Na layer due to a faster reaction rate of FeOH to sunlight.

Sulfates present in urban aerosols collected worldwide usually exhibit ³³S-anomalies whose origin remains unclear. Besides, the sulfate concentration is not very well modelled nowadays, which, coupled with the isotopic composition anomaly on the ³³S, would highlight the presence of at least an additional oxidation pathway, different from O₂+TMI, O₃, OH, H₂O₂ and NO₂. We suggest here the implication of two other possible oxidation pathways.

Wind gusts are a key driver of aerodynamic loading, and common approximations used to describe wind gust behavior may not be appropriate in complex terrain at heights relevant to wind turbines and other structures. High-resolution observations from sonic anemometers and vertically pointing Doppler lidars collected in the Perdigão experiment are analyzed to provide a foundation for improved wind gust characterization in complex terrain.

Mercury poses a threat to human health and the environment. Therefore, the reduction of emissions is a declared aim. Here, we quantified mercury emission for the city of Zurich, Switzerland, based on atmospheric measurements and box modeling. This so-called top-down approach allows us to better constrain mercury emissions from diffuse distributed sources. This is applicable to other regions and presents a cost-effective way of quantifying emissions, as a first step in the reduction thereof.

Atmospheric black carbon (BC) particles are strong light absorbers that contribute to global warming. In situ cloud measurements performed at a high-altitude site showed that cloud supersaturation mainly drives the activation of BC to cloud droplets. It was further shown how BC particle size and mixing state modulate this nucleation scavenging in agreement with simplified theoretical predictions. These findings can inform model simulations towards a better representation of the BC life cycle.

Summer surface ozone pollution has rapidly intensified recently, damaging human and ecosystem health. This study aims to examine the large-scale atmospheric circulations associated with the interannual variation in summer surface O₃ pollution in North China based on long-term meteorological observations. The impacts of Arctic sea ice were also revealed. The outcomes may provide a basis for understanding the interannual variation of 0₃ pollution and its seasonal to interannual prediction.

The contribution of soil carbonyl sulfate (COS) flux is probably the major limitation to the application of COS as a novel tracer of canopy-scale CO₂ uptake. We provide new, field-based high-resolution results on the spatial and temporal variations in soil COS flux, its relationships to CO₂ exchange and the key factors influencing it. We furthermore provide the only study, to our knowledge, that validate the surface dynamic chamber approach, increasingly used, with soil concentration profiles.

Using a backscatter N₂-Raman lidar deployed on the western part of the French Riviera, we investigate the vertical aerosol structure below 5 km. By coupling these observations with spaceborne instruments and trajectory modeling, we highlight plumes of particulate pollutants moving towards the French Riviera. This pollution, mainly due to traffic and petrochemical activities, originates from the Spanish coast (Costa Blanca and Costa Brava–Daurada) and mixes with local emissions.

A massive wildfire smoke episode impacted the western US and Canada in summer 2017. We measured CO, other trace gases, PM, BC, and aerosol optical properties at a heavily impacted, ground-based site affected by this event. Brown carbon diminished as smoke aged but was a persistent component of the regional smoke, accounting for about half of aerosol absorption at 401 nm on average. The PM / CO ratios suggested aerosol evaporation was dominant at the surface at smoke ages of up to ~ 1–2 days.

Horizontal moist static energy (MSE) transport patterns were extracted from reanalysis data using an artificial neuronal network for the winter months. The results show that during the last 30 years transport pathways that favour MSE transport through the North Atlantic are getting more frequent. This North Atlantic pathway is connected to positive temperature anomalies over the central Arctic, which implies a connection between Arctic amplification and the change in horizontal heat transport.

This paper documents the use of total column ozone data from the TROPOMI satellite in the global forecasting system of the Copernicus Atmosphere Monitoring Service (CAMS). The data are of good quality over large parts of the globe but have some issues at high latitudes, at low solar elevations and over snow/ice. Assimilating the data in the CAMS system has a small positive impact, especially in the tropical troposphere.

We used five atmospheric observatories in Europe measuring total column dry-air mole fractions of methane and carbon monoxide to infer methane emissions in the area between the observatories. We find that the methane emissions are overestimated by the state-of-the-art inventories, and that this is likely due, at least in part, to the inventory disaggregation. We find that there is significant uncertainty in the carbon monoxide inventories that requires further investigation.

Chlorine radicals have a broad range of implications for tropospheric chemistry, air quality, and climate. We present a comprehensive simulation of tropospheric chlorine in a global 3-D model, which includes explicit accounting of chloride mobilization from sea salt aerosol. We find the chlorine chemistry contributes 1.0 % of the global oxidation of methane and decreases global burdens of tropospheric ozone by 7 % and OH by 3 % through the associated bromine radical chemistry.

We present a 1-D model to simulate H₂O isotopologues of vapor and their vertical fluxes in the first kilometer above the sea surface. The model includes two processes not in earlier Craig–Gordon isotope evaporation models: height-dependent diffusion/mixing and ascending/converging air. Calculated isotopic ratios compare well with data from seven cruises. The model explains how sea surface meteorology can affect atmospheric vapor, precipitation isotope ratios, and paleoisotope records.

Iodine is an essential trace element for mammals and aquatic plants. Increasing alga populations due to serious eutrophication in the coastal waters of China promote iodine emission. China contributes about 60 % of the global cultivated seaweed production. Iodine is likely emitted to the atmosphere and transformed into nanoparticles during the farming, harvesting, and processing of seaweed. Wild and farmed algae make the coastal area of China a potential hotspot of new particle formation.

Methane emissions from biogenic sources, e.g. Arctic permafrost ecosystems, are associated with uncertainties due to the high variability of fluxes in both space and time. Besides the traditional eddy covariance method, we evaluated a method based on wavelet analysis, which does not require a stationary time series, to calculate fluxes. The occurrence of extreme methane flux events was strongly correlated with the soil temperature. They were triggered by atmospheric non-turbulent mixing.

We studied the evaporation of α-pinene secondary organic aerosol particles in clean air to derive their volatility from the observed size changes. We found that the particles became more resilient to evaporation with increased oxidative age, possibly increasing their lifetime in the atmosphere. Also, increased relative humidity increased the particle evaporation. Mass spectrometry measurements of the particles at different stages of evaporation revealed some water-induced composition changes.

The present calculations show that the sequential addition of CIs to HHPs affords oligomers containing CIs as chain units. The addition of an –OOH group in HHPs to the central carbon atom of CIs is identified as the most energetically favorable channel, with a barrier height strongly dependent on both CI substituent number (one or two) and position (syn- or anti-). In particular, the introduction of a methyl group into the anti-position significantly increases the rate coefficient.

We present the first data on the concentration of sea-salt aerosol throughout most of the depth of the troposphere and a wide range of latitudes. Sea-salt concentrations in the upper troposphere are very small. This puts stringent limits on how sea-salt aerosol affects halogen and nitric acid chemistry there. With a widely distributed source, sea-salt aerosol provides an excellent test of wet scavenging and vertical transport of aerosols in chemical transport models.

In this study, properties of clouds at the French–German Arctic research station in Ny-Ålesund are related to in-cloud thermodynamic conditions. The dataset used was collected within the Arctic Amplification project with a set of active and passive remote instruments. The results are compared with a model output. Significant divergence in observations and modelling of single-layer ice and mixed-phase clouds was found.

This study presents airborne observations of particles, starting from 1.5 nm in diameter, above the boreal forest from 100 m up to 2700 m. The aim was to study the extent of NPF and likely places for nucleation. We found that the highest concentrations of 1.5–3 nm particles were above the forest canopy top on NPF event mornings, and the concentration decreased with increasing altitude. This would indicate the importance of gaseous precursors from vegetation for NPF processes in this area.

It reports the long-term climatology of the intensity of E_s layers from COSMIC satellites. The global E_s maps present high-resolution spatial distributions and seasonal dependence. It mainly occurs at mid-latitudes and polar regions. Based on wind shear theory, simulation results indicate the convergence of vertical ion velocity could partially explain the E_s seasonal dependence and some disagreements between observations and simulations suggest other processes play roles in the E_s variations.