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Abstract: 2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant which is preferentially used as defoamer in paints and printing ink and for the treatment of surfaces. Effluents of wastewater treatment plants (WWTPs) have been identified as the domination point sources for TMDD in rivers since the removal rate of the compound in the WWTPs is in general less than 70%. However, the dominating entry pathways of TMDD into the sewage were unknown so far. In this study effluents from both, municipal WWTPs with and without treatment of indirect industrial dischargers and from industrial WWTPs with direct discharge of wastewater into receiving rivers were analyzed for the first time to identify the proportions of TMDD coming from domestic wastewater and from various industrial sources. Moreover, rivers were samples before and after the influent of sewage water from WWTPs. The TMDD concentrations in the water samples were measured using solid phase extraction (SPE) followed by gas chromatography/mass spectrometry (GC/MS). High TMDD concentrations were found in rivers (up to 63.5μg/L), and in effluents of WWTPs (up to 310μg/L) affected by wastewater from paper recycling industry and factories producing paint and printing ink. Concentrations of TMDD revealed to be far higher in wastewater from factories processing recycled paper (up to 113μg/L) compared to wastewater from factories not processing recycled paper (0.066μg/L). The results indicate that the use of recycling paper in the paper production process is the dominating reason for increased TMDD concentrations in wastewaters and receiving rivers due to the wash out of TMDD from the paper impregnated with printing ink. Very high TMDD concentrations (up to 3300μg/L) were also detected in wastewater from a printing ink factory and a paint factory. [Copyright &y& Elsevier]

This study analyzed 1,636 top papers in the subject category of meteorology and atmospheric sciences about eleven years from 2011 to 2021, which included 1,636 highly cited papers and 24 hot papers in the field belonged to 20 Web of Science categories and 14 research areas. All top papers, written in English, were from 13,878 authors, 2,913 organizations, and 124 countries or territories, and published in 72 journals in the field. The top five journals are the Nature Climate Change (15.9% of the studied paper), Atmospheric Chemistry and Physics (12.1%), Journal of Climate (7.0%), Bulletin of the American Meteorological Society (6.7%), and Journal of Geophysical Research Atmospheres (4.6%), each published more than 76 papers. Top five countries were the USA, England, PR China, Germany, and France. Furthermore, top five organizations of National Oceanic and Atmospheric Administration (NOAA), National Center for Atmospheric Research (NCAR), National Aeronautics and Space Administration (NASA), Chinese Academy of Sciences, and University Colorado were popular based on contribution of articles more than 134 papers each. All keywords were separated into eight clusters for different research topic. Visualizations offer exploratory information on the current state in a scientific field or discipline, as well as can indicate possible developments in the future. [ABSTRACT FROM AUTHOR]

To improve paper recycling, the potential of an innovative deinking process using a reactive ozone/oxygen gas mixture instead of air was studied on two recovered paper furnishes (offset print and newsprint/magazine mixture). Using suitable O3 concentrations, ink removal, following first-order kinetics, increased and losses dropped leading to better selectivity than using air alone. The ozone benefits in term of selectivity depended on temperature and paper furnishes and reached 100% for newsprint/magazine furnish at ambient temperature. Finally deinking effluent COD was significantly reduced and the ozone-based flotation allowed the reduction of the alkaline chemistry used before flotation. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the influence of a modified, carbon dioxide-enriched atmosphere on the properties of paper. Types of paper used in the experiment; Properties of the paper samples treated in an atmosphere of carbon dioxide; Behavior of paper treated in a carbon dioxide modified atmosphere.

Which published papers have transformed our understanding of the chemical processes in the troposphere and shaped the field of atmospheric chemistry? By way of expert solicitation and interactive peer review, this paper explores the influence of the ideas in peer-reviewed articles based on input from our community of atmospheric scientists. We explore how these papers have shaped the development of the field of atmospheric chemistry and identify the major landmarks in the field of atmospheric chemistry through the lens of those papers' impact on science, legislation and environmental events. We also explore the ways in which one can identify the papers that have most impacted the field and discuss the advantages and disadvantages of the various approaches. Our work highlights the difficulty of creating a simple list, and we explore the reasons for this difficulty. The paper also provides a history of the development of our understanding of tropospheric chemistry and points some ways for the future. [ABSTRACT FROM AUTHOR]

This paper evaluates the current status of global modeling of the organic aerosol (OA) in the troposphere and analyzes the differences between models as well as between models and observations. Thirty-one global chemistry/transport and general circulation models have participated in this intercomparison, in the framework of AeroCom phase II. The simulation of OA varies greatly between models in terms of the magnitude of primary emissions, secondary OA (SOA) formation, the number of OA species used (2 to 62), the complexity of OA parameterizations (gas-particle partitioning, chemical aging, multiphase chemistry, aerosol microphysics), and the OA physical, chemical and optical properties. The diversity of the global OA simulation results has increased since earlier AeroCom experiments, mainly due to the increasing complexity of the SOA parameterization in models, and the implementation of new, highly uncertain, OA sources. Diversity of over an order of magnitude exists in the modeled vertical distribution of OA that deserves a dedicated future study. Furthermore, although the OA/OC ratio depends on OA sources and atmospheric processing and is important for model evaluation against OA and OC observations, it is resolved only by few global models. The median global primary OA (POA) source strength is 56 Tga-1 (range 34- 144 Tga-1) and the median secondary OA source strength (natural and anthropogenic) is 19 Tga-1 (range 13-121 Tga-1). Among the models that take into account the semi-volatile SOA nature, the median source is calculated to be 51 Tga-1 (range 16- 121 Tga-1), much larger than the median value of the models that calculate SOA in a more simplistic way (19 Tga-1; range 13-20 Tga-1, with one model at 37 Tga-1). The median atmospheric burden of OA is 1.4 Tg (24 models in the range of 0.6-2.0 Tg and 4 between 2.4-3.8 Tg) with a median OA lifetime of 5.4 days (range 3.8-9.6 days). In models that reported both OA and sulfate burdens, the median value of the OA/sulfate burden ratio of is calculated to be 0.77; 13 models calculate a ratio lower than 1, and 9 models higher than 1. For 26 models that reported OA deposition fluxes, the median wet removal is 70 Tga-1 (range 28-209 Tga-1), which is on average 85% of the total OA deposition. Fine aerosol organic carbon (OC) and OA observations from continuous monitoring networks and individual field campaigns have been used for model evaluation. At urban locations the model-observation comparison indicates missing knowledge on anthropogenic OA sources, both strength and seasonality. The combined model/measurements analysis suggests the existence of increased OA levels during summer due to biogenic SOA formation over large areas of the USA that can be of the same order of magnitude as the POA, even at urban locations, and contribute to the measured urban seasonal pattern. Global models are able to simulate the high secondary character of OA observed in the atmosphere as a result of SOA formation and of POA aging, although, the amount of OA present in the atmosphere remains largely underestimated, with a mean normalized bias (MNB) equal to -0.62 (-0.51) based on the comparison against OC (OA) urban data of all models at surface, -0.15 (+0.51) when compared with remote measurements, and -0.30 for marine locations with OC data. The correlations overall are low when comparing with OC (OA) measurements: 0.47 (0.52) for urban stations, 0.39 (0.37) for remote, and 0.25 for marine stations with OC data. The combination of high (negative) MNB and higher correlation at urban stations when compared with the low MNB and lower correlation at remote sites suggests that the knowledge about the processes, on top of the sources, are important at the remote stations. There is no clear change in model skill with increasing model complexity with regard to OC or OA mass concentration. However, the complexity is needed in models in order to separate between anthropogenic and natural OA and accurately calculate the impact of OA on climate. [ABSTRACT FROM AUTHOR]

In the Earth's atmosphere, greenhouse gases (GHGs) and reactive trace gases are essential components of chemistry–climate interactions. These trace gases are emitted from both natural and anthropogenic sources over terrestrial and marine regions. Air–sea exchange is the dominant process controlling the distribution of several important trace gases over remote marine regions. Although the ocean–atmosphere interface covers ~70% of the Earth's surface, the quantitative air–sea exchange of reactive trace gases is estimated over the limited oceanic regions. The production and air–sea exchange of trace gases are controlled by physical conditions at both sides of the interface and ocean biogeochemistry. The northern Indian Ocean (NIO) experiences strong seasonal monsoon winds and intense tropical cyclones. Consisting of the Arabian Sea and the Bay of Bengal, it is one of the most biologically productive regimes of the world ocean and home to the intense oxygen minimum zone (OMZ) of the Arabian Sea with dissolved oxygen concentrations. Thus, the NIO offers a unique system to investigate the air–sea exchange processes of reactive trace gases. So far, most of the studies of air–sea exchange of trace gases is focused on the Atlantic and Pacific Oceans, while studies over the northern Indian Ocean are very limited and reported mainly for CH4, CO2 and N2O. Although progress has been made in recent years, studies of air–sea exchange of reactive trace gases such as non-methane hydrocarbon (NMHCs), oxygen-, sulfur- and halogen-containing hydrocarbons remain scarce. This paper addresses the current understanding of air–sea exchange processes and fluxes of reactive trace gases, including NMHCs, dimethyl sulfide (DMS), oxygenated volatile organic compounds (OVOCs), halocarbons, carbon monoxide (CO) and ozone (O3) in the northern Indian Ocean. This review summarizes the studies on the air–sea exchange of trace gases over the northern Indian Ocean and common parametrization approaches used to estimate the air–sea flux of gases. Flux range for ethene (3–10.35 µmol m–2 d–1), isoprene (0.215–0.172 µmol m–2 d–1), acetaldehyde (–6.75–11.35 µmol m–2 d–1), acetone (–9–9 µmol m–2 d–1), DMS (0.03–41.4 µmol m–2 d–1) and CO (1.4–5.4 µmol m–2 d–1) over the NIO were summarized from various in-situ and modelling studies. The paper addresses the importance of the northern Indian Ocean apropos the production and exchange of reactive trace gases, the knowledge gaps and the future scientific scope. Additionally, it emphasizes the need for a multidisciplinary study of oceanic reactive trace gas cycling and its impact on regional atmospheric chemistry over the northern Indian Ocean. [ABSTRACT FROM AUTHOR]

The optimization of aircraft trajectories involves balancing operating costs and climate impact, which are often conflicting objectives. To achieve compromised optimal solutions, higher-level information such as preferences of decision-makers must be taken into account. This paper introduces the SolFinder 1.0 module, a decision-making tool designed to identify eco-efficient aircraft trajectories, which allow for the reduction of the flight's climate impact with limited cost penalties compared to cost-optimal solutions. SolFinder 1.0 offers flexible decision-making options that allow users to select trade-offs between different objective functions, including fuel use, flight time, NOx emissions, contrail distance, and climate impact. The module is included in the AirTraf 3.0 submodel, which optimizes trajectories under atmospheric conditions simulated by the ECHAM/MESSy Atmospheric Chemistry model. This paper focuses on the ability of the module to identify eco-efficient trajectories while solving a bi-objective optimization problem that minimizes climate impact and operating costs. SolFinder 1.0 enables users to explore trajectory properties at varying locations of the Pareto fronts without prior knowledge of the problem results and to identify solutions that limit the cost of reducing the climate impact of a single flight. [ABSTRACT FROM AUTHOR]

A scientific biography is presented as an introduction to a collection of papers by his colleagues and co-workers honouring the scientific contributions and legacy of the late Dr. Timothy J. Lee (1959–2022). Tim Lee performed highly regarded research on the methods and applications of computational quantum chemistry, particularly coupled cluster theory, and computational spectroscopy, with impacts in interstellar chemistry, aiding NASA missions, atmospheric chemistry, as well as fundamental science. His presence is deeply missed. [ABSTRACT FROM AUTHOR]

Proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography mass spectrometry GC-MS) allow real-time measurements of various atmospheric volatile organic compounds (VOC). By taking parallel measurements in ambient conditions, two PTR-MSs and two GC-MSs were studied for their ability to measure methanol, acetaldehyde, acetone, benzene and toluene. The measurements were conducted at a rural boreal forest site in southern Finland between 13 April and 14 May 2012. This paper presents correlations and possible biases between the concentrations measured using the four instruments. This paper presents correlations and possible biases between the concentrations measured using the four instruments. A very good correlation was found for benzene and acetone measurements between all instruments (the mean R value was 0.88 for both compounds), while for acetaldehyde and toluene the correlation was weaker (with a mean R value of 0.50 and 0.62, respectively). For some compounds, notably for methane, there were considerable systematic differences in the mixing ratios measured by the different instruments, despite the very good correlation between the instruments (mean R = 0.90). The systematic difference arises as a difference in the linear regression slope between measurements conducted between instruments, rather than as an offset. This mismatch indicates that the systematic uncertainty in the sensitivity of a given instrument can lead to an uncertainty of 50-100% in the methanol emissions measured by commonly used methods. [ABSTRACT FROM AUTHOR]

Data from the standard cloud physics payload during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100-200 cm-3 in the southernmost profiles. Sub-micron (0.06-3. Analysis of back trajectories and atmospheric chemistry observations revealed that while conditions in the troposphere were more typical of a clean remote ocean airmass, there was some evidence of continental or anthropogenic influence. However, the hypothesis of long range transport of continental aerosol fails to explain the magnitude of the aerosol and cloud droplet concentration in the boundary layer. Instead, the gale force surface winds in this case (wind speed at 167 m above sea level was >25 m s-1) were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean. [ABSTRACT FROM AUTHOR]

The Coupled Chemistry Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS, version 4.5) is an online regional chemical transport model designed for local and regional studies of atomospheric chemistry from surface to the lower stratosphere suitable both for operational and research purposes. It includes gaseous/aqueous chemistry, photochemistry, scavenging and dry deposition. The CCATT-BRAMS model takes advantages of the BRAMS specific development for the tropics/subtropics and of the recent availability of preprocessing tools for chemical mechanisms and of fast codes for photolysis rates BRAMS includes state-of-the-art physical parameterizations and dynamic formulations to simulate atmospheric circulations of scales down to meters. The online coupling between meteorology and chemistry allows the system to be used for simultaneous atmospheric weather and chemical composition forecasts as well as potential feedbacks between them. The entire system comprises three preprocessing software tools for chemical mechanism (which are user defined), aerosol and trace gases emission fields and atmospheric and chemistry fields for initial and boundary conditions. In this paper, the model description is provided along evaluations performed using observational data obtained from ground-based stations, instruments aboard of aircrafts and retrieval from space remote sensing. The evaluation takes into account model application on different scales from megacities and Amazon Basin up to intercontinental region of the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

The article presents a study on the use of Global Ozone Monitoring Experiment (GOME-2) Flight Model (FM3) spectrometer to measure the temperature dependent ozone absorption cross section spectra and first application in satellite retrievals. The study records Huggins, Hartley and Chappuis bands and their temperature dependence. Results show that the GOME-2 FM cross section is within 3% and the total ozone column retrieved from satellite is within 1%.

The article presents a study which explores the usability of optical spectrum analyzers (OSA) in measuring atmospheric carbon dioxide and methane column densities. It is inferred that carbon dioxide and methane are the highest contributors to overall global radiative forcing. Two measurement campaigns are outlined which involve high resolution Fourier transform spectroscopy (FTS) and calibration method against aircraft carbon dioxide profiles.

The article focuses on a study which attempts to examine the Bremen Aerosol Retrieval (BAER) surface approach for aerosol optical thickness retrieval over land surface. It discusses the use of the normalized difference vegetation index (NDVI) and the vegetation continuous field (VCF) to summarize surface characteristic. Information about atmospheric aerosols is provided.

Biogenic volatile organic compounds (BVOCs) are essential in atmospheric chemistry because of their chemical reactions that produce and destroy tropospheric ozone, their effects on aerosol formation and growth, and their potential influence on global warming. As one of the important BVOC groups, monoterpenes have been a focus of scientific attention in atmospheric research. Detailed regional measurements and model estimates are needed to study emission potential and the monoterpene budget on a global scale. Since the use of empirical measurements for upscaling is limited by many physical and biological factors such as genetic variation, temperature and light, water availability, seasonal changes, and environmental stresses, comprehensive inventories over larger areas are difficult to obtain. We applied the boundary layer-chemistry-transport model SOSA to investigate Scots pine (Pinus sylvestris) monoterpene emissions in a boreal coniferous forest at the SMEAR II site, Southern Finland. SOSA was applied to simulate monoterpene emissions with three different emission modules: the semi-empirical G95, MEGAN 2.04 with improved descriptions of temperature and light responses and including also carbonyl emissions, and a process-based model SIM-BIM. For the first time, the emission models included seasonal and diurnal variations in both quantity and chemical species of emitted monoterpenes, based on parameterizations obtained from field measurements. Results indicate that modelling and observations agreed reasonably well, and that the model can be used for investigating regional air chemistry questions related to monoterpenes. The predominant modelled monoterpene concentrations, α-pinene and Δ³-carene, are consistent with observations. [ABSTRACT FROM AUTHOR]

The first paper published in this SI, by Mazzeo et al. [[1]], used an air quality model, coupled online with a meteorological model, to simulate the impact of emission reductions on PM2.5 in the West Midlands region of the United Kingdom. Atmospheric dispersion and chemical transport models (CTMs) are a key tool in both atmospheric chemistry and environmental sciences. Liu et al. [[4]] analyzed the relationship between sandstorm periods and the transport and dispersion of particulate emissions from coal bases in northwest China, assisted by a backward trajectory analysis performed with an atmospheric dispersion model. [Extracted from the article]

Total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde and Global Positioning System (GPS) observations. The comparisons are performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The comparisons are performed for the period of January 2007-July 2013 (GOME- 2A) and from December 2012 to July 2013 (GOME-2B). Radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by National Climatic Data Center (NCDC) and screened for soundings with incomplete tropospheric column. Ground-based GPS observations from COSMIC/SuomiNet network are used as the second independent data source. Good general agreement between GOME-2 and the ground-based observations is found. The median relative difference of GOME-2 to radiosonde observations is -2.7% for GOME-2A and -0.3% for GOME-2B. Against GPS observations, the median relative differences are 4.9 and 3.2% for GOME-2A and B, respectively. For water vapour total columns below 10 kgm-2, large wet biases are observed, especially against GPS observations. Conversely, at values above 50 kgm-2, GOME-2 generally underestimates both ground-based observations. [ABSTRACT FROM AUTHOR]

We investigated the behaviour of light scattering by particulates of various sizes (0.1 μm to 100 μm) at a small scattering angle. It was previously shown that for a small angle, the scattered intensities are weakly dependent upon the particulates’ nature (Renard et al., 2010). Particles found in the atmosphere exhibit roughness that leads to large discrepancies with the classical Mie solution in terms of scattered intensities in the low angular set-up. This article focuses on building an effective theoretical tool to predict the behaviour of light scattering by real particulates at a small scattering angle. We expose both the classical Mie theory and an adaptation to the case of rough particulates with a fairly simple roughness parametrisation. An experimental device was built, corresponding to the angular set-up of interest (low scattering angle and therefore low angular aperture), and measurements are presented that confirm the theoretical results with a good agreement. It is found that the differences between the classical Mie solution and actual measurements, especially for large particulates, can be attributed to the roughness of particulates. It is also found that, in this low angular set-up, saturation of the scattered intensities occurs for relatively small values of the roughness parameter. This confirms the low variability in the scattered intensities for particulates of different kinds. A direct interest of this study is a broadening of the dynamic range of optical counters: using a small angle of aperture for measurements allows greater dynamics in terms of particle size, and thus enables a single device to observe a broad range of particle sizes whilst utilising the same electronics. [ABSTRACT FROM AUTHOR]

The article focuses on a study which aims at measuring atmospheric column carbon dioxide (CO2) from a sun photometer in Beijing, China from 2010-2012. In the study, CO2 measurements were acquired, translated into cloud free data, and converted into an index related to column CO2 amount. Seasonal variations of CO2 levels in the atmosphere were also analyzed.

The article discusses a study conducted to test the performance of a new Hybrid Eulerian Lagrangian (HEL) transport scheme with a module for atmospheric chemistry. It is informed that HEL was compared with two other traditional advection schemes including a classical pseudospectral Eulerian method the Accurate Space Derivative (ASD) scheme and the bi-cubic semi-Lagrangian (SL) scheme.

We present the development of the Adjoint of the Global Eulerian-Lagrangian Coupled Atmospheric (A-GELCA) model that consists of the National Institute for Environmental Studies (NIES) model as an Eulerian three-dimensional transport model (TM), and FLEXPART (FLEXible PARTicle dispersion model) as the Lagrangian plume diffusion model (LPDM). The tangent and adjoint components of the Eulerian model were constructed directly from the original NIES TM code using an automatic differentiation tool known as TAF (Transformation of Algorithms in Fortran; http://www.FastOpt.com), with additional manual pre- and post-processing aimed at improving the performance of the computing, including MPI (Message Passing Interface). As results, the adjoint of Eulerian model is discrete. Construction of the adjoint of the Lagrangian component did not require any code modification, as LPDMs are able to track a significant number of particles back in time and thereby calculate the sensitivity of observations to the neighboring emissions areas. Eulerian and Lagrangian adjoint components were coupled at the time boundary in the global domain. The results are verified using a series of test experiments. The forward simulation shown the coupled model is effective in reproducing the seasonal cycle and short-term variability of CO2 even in the case of multiple limiting factors, such as high uncertainty of fluxes and the low resolution of the Eulerian model. The adjoint model demonstrates the high accuracy compared to direct forward sensitivity calculations and fast performance. The developed adjoint of the coupled model combines the flux conservation and stability of an Eulerian discrete adjoint formulation with the flexibility, accuracy, and high resolution of a Lagrangian backward trajectory formulation. [ABSTRACT FROM AUTHOR]

Hemispheric transport of air pollutants can have a significant impact on regional air quality, as well as on the effect of air pollutants on regional climate. An accurate representation of hemispheric transport in regional chemical transport models (CTMs) depends on the specification of the lateral boundary conditions (LBCs). This study investigates the use of new LBCs of two moderately long-lived trace gases, CO and O3, for the European model domain. The LBCs are generated by use of the global EMEP MSC-W model; they are evaluated at the lateral boundaries by comparison with satellite observations of the Terra/MOPITT sensor (CO) and the Aura/OMI sensor (O3) for use with European domain calculations with the Swedish Multi-scale Atmospheric Transport and CHemistry (MATCH) model. The LBCs from the global EMEP model lie well within the satellite uncertainties for both CO and O3. The biases increase below 700 hPa for both species, although it should be noted that satellite data below this height are more influenced by a priori data and hence less reliable than at e.g. 500 hPa. CO is, on average, underestimated by the global model, while O3 tends to be overestimated during winter, and underestimated during summer. Next, the validated LBCs are applied in a dynamical and climatological setup, respectively, to the MATCH model, set up over the European domain. The MATCH results obtained with climatological and dynamic LBCs are then validated against independent satellite retrievals from the Aqua/AIRS sensor at 500 hPa, and against in situ ground observations from the Global Atmospheric Watch (GAW) network. The application of the EMEP LBCs in the regional MATCH model greatly impacted the model results. The direct impact on ground-level concentrations strongly depends on the distance from the inflow boundary. The improvements of dynamic over climatological LBCs become most apparent when using AOT40 as a metric. Also, when focusing at ground observations taken near the inflow boundary of the model domain, one finds that the use of dynamical LBCs yields a more accurate representation of the seasonal variation, as well as of the variability of the trace gas concentrations on shorter time scales. The greatest impact from the new LBCs, was seen aloft in the free troposphere. Taking AIRS retrievals as a reference, the use of LBCs substantially improves spatial pattern correlations in the free troposphere as compared to results obtained with the LBCs that were originally used in MATCH. Also, the magnitude of the bias is reduced by the new LBCs for both trace gases. [ABSTRACT FROM AUTHOR]

The article presents a study which describes a fourier transform infrared (FTIR) trace gas analyser for atmospheric applications. It is inferred that the precision and the accuracy of the gas analyser have met the compatability targets established by the World Meteorological Organization (WMO). The capabilities of the gas analyser in measuring the atmospheric levels of carbon dioxide, methane and nitrous oxide are discussed.

The article presents a study which investigates the trends in the subtropical ozone profiles obtained from different ground-based fourier transform infrared (FTIR) retrieval setups from 1999 to 2010. The precision of ground-based FTIR systems in profiling the stratospheric ozone is emphasized. The influence of temperature retrieval on the efficiency of subtropical ozone profiling is highlighted.

The detection of hydrogen chloride (HCl) in the atmosphere of Mars was among the primary objectives of the ExoMars Trace Gas Orbiter (TGO) mission. Its discovery using the Atmospheric Chemistry Suite mid‐infrared channel (ACS MIR) showed a distinct seasonality and possible link to dust activity. This paper is part 2 of a study investigating the link between HCl and aerosols by comparing gas measurements made with TGO to dust and water ice opacities measured with the Mars Climate Sounder (MCS). In part 1, we showed, and compared, the seasonal evolution of vertical profiles of HCl, water vapor, temperature, dust opacity, and water ice opacity over the dusty periods around perihelion (solar longitudes 180°–360°) across Mars years 34–36. In part 2, we investigated the quantitative correlations in the vertical distribution between each quantity, as well as ozone. We show that there is a strong positive correlation between HCl and water vapor, which is expected due to fast photochemical production rates for HCl when reacting with water vapor photolysis products. We also show a strong positive correlation between water vapor and temperature, but are unable to show any correlation between temperature and HCl. There are weak correlations between the opacities of dust and water ice, and dust and water vapor, but only very low correlations between dust and HCl. We close with a discussion of possible sources and sinks and that interactions between HCl and water ice are the most likely for both, given the inter‐comparison. Plain Language Summary: The ExoMars Trace Gas Orbiter (TGO) has observed three Martian dusty seasons (summer in the southern hemisphere). In mid‐2018, we made the first detection of hydrogen chloride (HCl) in the Martian atmosphere using the Atmospheric Chemistry Suite (ACS). Finding this gas, among others, was a priority of ExoMars because its primary source may be volcanic. Since then, we have observed two more dusty periods with the reappearance of HCl each time. In part 1, we presented the climatology of HCl over these three dusty periods (in Mars years 34, 35, and 36) and investigate their relationships with temperature and water vapor measured by ACS, and with airborne dust and water ice measured with the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO). In this paper, part 2, we quantify the correlations between HCl, water vapor, ozone, dust, temperature, and water ice. We show that HCl is closely correlated to water vapor, which is, in turn, correlated to temperature. There is only a very low correlation between HCl and dust or water ice, which both impact water vapor. Possible mechanisms for seasonal HCl production and destruction are discussed, concluding that the freeze‐thaw cycle of atmospheric water is most likely. Key Points: Comparison of trace gases and aerosol opacity between ACS on ExoMars TGO and MCS on MROLow correlations between HCl and the opacities of dust or water ice, but very strong correlation with water vapor and the formation of icesHCl source and sink possibilities are discussed, concluding that frost activity may be the most likely possibility for both [ABSTRACT FROM AUTHOR]

Atmospheric sensitivities (gradients), quantifying the atmospheric response to emissions or other perturbations, can provide meaningful insights on the underlying atmospheric chemistry or transport processes. Atmospheric adjoint modeling enables the calculation of receptor-oriented sensitivities of model outputs of interest to input parameters (e.g., emissions), overcoming the numerical cost of conventional (forward) modeling. The adjoint of the GEOS-Chem atmospheric chemistry-transport model is a widely used such model, but prior to v36 it lacked extensive stratospheric capabilities. Here, we present the development and evaluation of the discrete adjoint of the global chemistry-transport model (CTM) GEOS-Chem unified chemistry extension (UCX) for stratospheric applications, which extends the existing capabilities of the GEOS-Chem adjoint to enable the calculation of sensitivities that include stratospheric chemistry and interactions. This development adds 37 new tracers, 273 kinetic and photolysis reactions, an updated photolysis scheme, treatment of stratospheric aerosols, and all other features described in the original UCX paper. With this development the GEOS-Chem adjoint model is able to capture the spatial, temporal, and speciated variability in stratospheric ozone depletion processes, among other processes. We demonstrate its use by calculating 2-week sensitivities of stratospheric ozone to precursor species and show that the adjoint captures the Antarctic ozone depletion potential of active halogen species, including the chlorine activation and deactivation process. The spatial variations in the sensitivity of stratospheric ozone to NO x emissions are also described. This development expands the scope of research questions that can be addressed by allowing stratospheric interactions and feedbacks to be considered in the tropospheric sensitivity and inversion applications. [ABSTRACT FROM AUTHOR]

The Community Earth System Model (CESM1), maintained by the United States National Centre for Atmospheric Research (NCAR) is connected with the Modular Earth Submodel System (MESSy). For the MESSy user community, this offers many new possibilities. The option to use the CESM1(CAM) atmospheric dynamical cores, especially the spectral element (SE) core, as an alternative to the ECHAM5 spectral transform dynamical core will provide scientific and computational advances for atmospheric chemistry and climate modelling with MESSy. The SE dynamical core does not require polar filters since the grid is quasi-uniform. By advecting the surface pressure rather then the logarithm of surface pressure the SE core locally conserves energy and mass. Furthermore, it has the possibility to scale to up to 105 compute cores, which is useful for current and future computing architectures. The well-established finite volume core from CESM1(CAM) is also made available. This offers the possibility to compare three different atmospheric dynamical cores within MESSy. Additionally, the CESM1 land, river, sea ice, glaciers and ocean component models can be used in CESM1/MESSy simulations, allowing to use MESSy as a comprehensive Earth System Model. For CESM1/MESSy setups, the MESSy process and diagnostic submodels for atmospheric physics and chemistry are used together with one of the CESM1(CAM) dynamical cores; the generic (infrastructure) submodels support the at ospheric model component. The other CESM1 component models as well as the coupling between them use the original CESM1 infrastructure code and libraries, although in future developments these can also be replaced by the MESSy framework. Here, we describe the structure and capabilities of CESM1/MESSy, document the code changes in CESM1 and MESSy, and introduce several simulations as example applications of the system. The Supplements provide further comparisons with the ECHAM5/MESSy atmospheric chemistry (EMAC) model and document the technical aspects of the connection in detail. [ABSTRACT FROM AUTHOR]

The convective transport module, CVTRANS, of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model has been revised to better represent the physical flows and incorporate recent findings on the properties of the convective plumes. The modifications involve (i) applying intermediate time stepping based on a settable criterion, (ii) using an analytic expression to account for the intra time step mixing ratio evolution below cloud base, and (iii) implementing a novel expression for the mixing ratios of atmospheric compounds at the base of an updraft. Even when averaged over a year, the predicted mixing ratios of atmospheric compounds are significantly affected by the intermediate time stepping. For example, for an exponentially decaying atmospheric tracer with a lifetime of 1 day, the zonal averages can locally differ by more than a factor of 6 and the induced root mean square deviation from the original code is, weighted by the air mass, higher than 40% of the average mixing ratio. The other modifications result in smaller differences. However, since they do not require additional computational time, their application is also recommended. [ABSTRACT FROM AUTHOR]

The chlorine atom (Cl·) has a high potential to perturb atmospheric photochemistry by oxidizing volatile organic compounds (VOCs), but the exact role it plays in the polluted troposphere remains unclear. The Master Chemical Mechanism (MCM) is a near explicit mechanism that has been widely applied in the atmospheric chemistry research. While it addresses comprehensively the chemistry initiated by the OH, O3 and NO3 radicals, its representation of the Cl· chemistry is incomplete as it only considers the reactions for alkanes. In this paper, we develop a more comprehensive Cl· chemistry module that can be directly incorporated within the MCM framework. A suite of 199 chemical reactions describes the Cl·-initiated degradation of alkenes, aromatics, aldehydes, ketones, alcohols, and some organic acids and nitrates, along with the inorganic chemistry involving Cl· and its precursors. To demonstrate the potential influence of the new chemistry module, it was incorporated into a MCM box model to evaluate the impacts of nitryl chloride (ClNO2), a product of nocturnal halogen activation by nitrogen oxides (NOx), on the following-day's atmospheric photochemistry. With constraints of recent observations collected at a coastal site in Hong Kong, southern China, the modeling analyses suggest that the Cl· produced from ClNO2 photolysis may substantially enhance the atmospheric oxidative capacity, VOC oxidation, and O3 formation, particularly in the early morning period. The results demonstrate the critical need for photochemical models to include more fully chlorine chemistry in order to better understand the atmospheric photochemistry in polluted environments subject to intense emissions of NOx, VOCs and chlorine-containing constituents. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a key atmospheric compound that can be remotely sensed by satellite on the global scale. Fifteen years of continuous observations are now available from the MOPITT/Terra mission (2000 to present). Another fifteen and more years of observations will be provided by the IASI/MetOp instrument series (2007-2023>). In order to study long term variability and trends, a homogeneous record is required, which is not straightforward as the retrieved products are instrument and processing dependent. The present study aims at evaluating the consistency between the CO products derived from the MOPITT and IASI missions, both for total columns and vertical profiles, during a six year overlap period (2008-2013). The analysis is performed by first comparing the available 2013 versions of the retrieval algorithms, and second using a dedicated reprocessing of MOPITT CO profiles and columns based on the IASI a priori constraints. MOPITT v5T total columns are generally slightly higher over land (bias ranging from 0 to 13 %) than IASI v20100815 data. When IASI and MOPITT data are retrieved with the same a priori constraints, correlation coefficients are slightly improved. Large discrepancies (total column bias over 15 %) observed in the Northern Hemisphere during the winter months are reduced by a factor of 2 to 2.5. The detailed analysis of retrieved vertical profiles compared with collocated aircraft data from the MOZAIC-IAGOS network, illustrates the advantages and disadvantages of a constant vs. a variable a priori. On one hand, MOPITT agrees better with the aircraft profiles for observations with persisting high levels of CO throughout the year due to pollution or seasonal fire activity (because the climatology-based a priori is supposed to be closer to the real atmospheric state). On the other hand, IASI performs better when unexpected events leading to high levels of CO occur, due to the less constrained variance-covariance matrix. [ABSTRACT FROM AUTHOR]

Uptake (or negative flux) of nitrous oxide (N2O) in agricultural soils is a controversial issue which has proven difficult to investigate in the past due to constraints such as instrumental precision and unknown methodological uncertainties. Using a recently developed high-precision quantum cascade laser (QCL) gas analyser combined with a closed dynamic chamber, a well defined detection limit of 4 μgN2O-Nm-2 h-1 could be achieved for individual soil flux measurements. 1220 measurements of N2O flux were made from a variety of UK soils using this method, of which 115 indicated uptake by the soil (i.e. a negative flux in the micrometeorological sign convention). Only 4 of these apparently negative fluxes were greater than the detection limit of the method, which suggests that the vast majority of reported negative fluxes from such measurements are actually due to instrument noise. As such, we suggest that the bulk of negative N2O fluxes reported for agricultural fields are most likely due to limits in detection of a particular flux measurement methodology and not as a result of microbiological activity consuming atmospheric N2O. [ABSTRACT FROM AUTHOR]

In recent years, non-thermal plasma technology has emerged as one of the most promising candidates for decomposing CO 2. The fluid model, a powerful tool to investigate the plasma dynamics, is computationally costly in simulating complex CO 2 plasma with tens of particles and hundreds of reactions, especially driven by short pulsed voltages. In this paper, a deep neural network (DNN) is proposed to describe the discharge characteristics and plasma chemistry of CO 2 pulsed discharge at atmospheric pressure. The DNN is trained using the simulation data obtained from the fluid model and then continuously optimized by minimizing the loss function. The effectiveness and feasibility of the DNN are verified by comparing with the experimental measurement and the numerical simulation results. Compared to the time-consuming fluid simulations with tens of hours, the well-trained DNN typically requires only a few seconds to obtain the essential characteristics of CO 2 pulsed discharges with high accuracy, significantly improving the computational efficiency. The DNN prediction results show that increasing the pulse rise rate at a given voltage amplitude can effectively raise the discharge current and breakdown voltage, and the electric field in the sheath region also increases with the pulse rise rate. In addition, the density of the surface charge accumulated on the dielectric layer increases with the plateau duration, and then a strong induced electric field by the surface charges is established, which obviously improves the discharge current during the pulse fall phase. The predicted data also show that increasing the pulse rise rate and the plateau duration could effectively improve the density of product species, such as CO and O 2 , leading to an increase in CO 2 conversion. This study demonstrates that the DNN method is a reliable tool for obtaining the essential discharge characteristics of atmospheric CO 2 pulsed plasma and provides a promising avenue for future applications of DNN-based methods in non-thermal plasmas. [ABSTRACT FROM AUTHOR]

Dinitrogen pentoxide (N2O5) and the nitrate radical (NO3) play important roles in atmospheric chemistry, yet accurate measurements of their concentrations remain challenging. A thermal dissociation chemical ionization mass spectrometer (TD-CIMS) was deployed to an urban site in Hong Kong to measure the sum of N2O5 and NO3 in autumn 2010. To our surprise, very high concentrations of N2O5 +NO3 were frequently observed in daytime, with mixing ratios in the range of 200–1000 pptv. To investigate this unusual phenomenon, various interference tests and measurements with different instrument configuration were conducted. It was found that peroxy acetyl nitrate (PAN) contributed to measurable signals at 62 amu, and more importantly, this interference increased significantly with co-existence of NO2. Nitric acid (HNO3), on the other hand, had little interference to the detection of N2O5/NO3 via the NO3− ion in our TD-CIMS. According to the test results, the interference from PAN and NO2 could have contributed to 30–50% of the average daytime (12:00–16:00 LT) N2O5 +NO3 signal at our site. However, evidence exists for the presence of elevated daytime N2O5, in addition to the daytime signal at 62amu. This includes: (1) daytime N2O5 measured via the I(N2O5)− cluster ion with an unheated inlet, which subjects to minimum interferences, and (2) observation of elevated daytime ClNO2 (a product of N2O5 hydrolysis) during a follow-up study. In view of the difficulty in accurately quantifying the contribution from the interferences of PAN and NO2 and un-tested potential interfering chemicals in the real atmosphere, we caution the use of 62amu in the TD-CIMS for measuring ambient N2O5 in a high NOx environment like Hong Kong. Additional studies are needed to re-examine the daytime issue using other measurement techniques. [ABSTRACT FROM AUTHOR]

The article discusses the technical characteristics, evolution and calibration of airborne sunphotometer or Phtomètre Léger Aéroporté pour la Surveillance des Masses d'Air (PLASMA) and concept, comparison and measurements of aerosol extinction vertical profile with lidar. It says that the instrument provides aerosol optical depths (AOD) over a wide spectral range. It also mentions the use of Langley method to calibrate the instrument.

The article presents a study which describes the retrieval algorithm and examines the impact of the most significant parameters affecting the accuracy of the aerosol extinction profile retrieval. It states that profiles of the stratospheric aerosol are recovered from SCIAMACHY/Envisat limb-scatter observations. Results show that surface albedo is the parameter with the largest impact, in particular is the SCHIAMACHY observations in the Southern Hemisphere.

The article focuses on the different simulation methods used in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The study introduces several simulation approaches to determine the long-term changes in the atmospheric composition between 1850 and 2100 though the ACCMIP project. It outlines the result of the study, which indicates that the present-day climate diagnostics are consistent with the state-of-the-art climate models.

The article presents a study which focuses on the development of an integrated flask sample collection system for greenhouse gas (GHG) measurements. It is inferred that GHG measurements are essential in understanding the carbon cycle, climate change and air quality problems. A detailed description on the process of air collection with the flask sampling system is provided.