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In this paper we describe the EARLINET Single Calculus Chain (SCC) a tool for the automatic analysis of lidar measurements. The development of this tool started in the framework of EARLINET-ASOS (European Aerosol Research Lidar Network - Advanced Sustainable Observation System) project and it is still continuing within ACTRIS (Aerosol, Clouds and Trace gases Research InfraStructure Network) project. The main idea was to develop a chain which allows all EARLINET stations to retrieve in a full automatic way the aerosol backscatter and extinction profiles starting from the raw lidar data of the lidar systems they operate. The calculus subsystem of the SCC is composed by two modules: a pre-processor module that handles the raw lidar data and corrects them for instrumental effects and an optical processing module for the retrieval of aerosol optical products from the pre-processed data. All the input parameters needed to perform the lidar analysis are stored in a database to get them in an effcient way and also to keep track of all the changes that may occur on any EARLINET lidar system over the time. The two calculus modules and the data are coordinated and synchronized by a further module (deamon) which makes fully automatic the whole analysis process. The end-user can interact with the SCC using a user-friendly web interface. All the SCC modules are developed using open source and free available software packages. The final products retrieved by the SCC fulfill all constraints fixed in the framework of the EARLINET quality assurance programs on both instrumental and algorithm levels. Moreover the man power needed to provide aerosol optical products is greatly reduced improving the near-real time availability of lidar data. The high quality of the SCC products is demonstrated by the good agreement between the SCC analysis and the corresponding independent manual retrievals. Finally, a real example of the applicability of the SCC in providing high quality aerosol optical products in case of intense observation period is provided. [ABSTRACT FROM AUTHOR]

Here we present the online meteorology and chemistry adjoint and tangent linear model, WRFPLUS-Chem, which incorporates modules to treat boundary layer mixing, emission, aging, dry deposition, and advection of black carbon aerosol. We also develop land surface and surface layer adjoints to account for coupling between radiation and vertical mixing. Model performance is verified against finite difference derivative approximations. A second order checkpointing scheme is created to reduce computational costs and enable simulations longer than six hours. The adjoint is coupled to WRFDA-Chem, in order to conduct a sensitivity study of anthropogenic and biomass burning sources throughout California during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. A cost function weighting scheme was devised to increase adjoint sensitivity robustness in future inverse modeling studies. Results of the sensitivity study show that, for this domain and time period, anthropogenic emissions are over predicted, while wildfire emissions are under predicted. We consider the diurnal variation in emission sensitivities to determine at what time sources should be scaled up or down. Also, adjoint sensitivities for two choices of land surface model indicate that emission inversion results would be sensitive to forward model configuration. The tools described here are the first step in conducting four-dimensional variational data assimilation in a coupled meteorology-chemistry model, which will potentially provide new constraints on aerosol precursor emissions and their distributions. Such analyses will be invaluable to assessments of particulate matter health and climate impacts. [ABSTRACT FROM AUTHOR]

This paper describes the pre-operational analysis and forecasting system developed during MACC (Monitoring Atmospheric Composition and Climate) and continued in MACC-II (Monitoring Atmospheric Composition and Climate: Interim Implementation) European projects to provide air quality services for the European continent. The paper gives an overall picture of its status at the end of MACC-II (summer 2014). This system is based on seven state-of-the art models developed and run in Europe (CHIMERE, EMEP, EURAD-IM, LOTOS-EUROS, MATCH, MOCAGE and SILAM). These models are used to calculate multi-model ensemble products. The MACC-II system provides daily 96 h forecasts with hourly outputs of 10 chemical species/aerosols (O3, NO2, SO2, CO, PM10, PM2.5, NO, NH3, total NMVOCs and PAN+PAN precursors) over 8 vertical levels from the surface to 5 km height. The hourly analysis at the surface is done a posteriori for the past day using a selection of representative air quality data from European monitoring stations. The performances of the system are assessed daily, weekly and 3 monthly (seasonally) through statistical indicators calculated using the available representative air quality data from European monitoring stations. Results for a case study show the ability of the median ensemble to forecast regional ozone pollution events. The time period of this case study is also used to illustrate that the median ensemble generally outperforms each of the individual models and that it is still robust even if two of the seven models are missing. The seasonal performances of the individual models and of the multi-model ensemble have been monitored since September 2009 for ozone, NO2 and PM10 and show an overall improvement over time. The change of the skills of the ensemble over the past two summers for ozone and the past two winters for PM10 are discussed in the paper. While the evolution of the ozone scores is not significant, there are improvements of PM10 over the past two winters that can be at least partly attributed to new developments on aerosols in the seven individual models. Nevertheless, the year to year changes in the models and ensemble skills are also linked to the variability of the meteorological conditions and of the set of observations used to calculate the statistical indicators. In parallel, a scientific analysis of the results of the seven models and of the ensemble is also done over the Mediterranean area because of the specificity of its meteorology and emissions. The system is robust in terms of the production availability. Major efforts have been done in MACC-II towards the operationalisation of all its components. Foreseen developments and research for improving its performances are discussed in the conclusion. [ABSTRACT FROM AUTHOR]

Strong diurnal variation of aerosol has been observed in many heavy polluted regions in China. This variation could alter the distribution of the direct aerosol radiative forcing (DARF) during the whole daytime that could increase the uncertainty of the normally used averaged values To quantify the effect of using the daily averaged DARF, 196 days of high temporal resolution ground-based data collected in SKYNET Hefei site during the period from 2007 to 2013 is used to perform an assessment. We demonstrate that strong diurnal changes of heavy aerosol loading have an impact on the 24 h averaged DARF when daily averaged optical properties are used to retrieve this quantity. Though there is a high temporal sampling of aerosol properties to be used for calculation of daily averaged ones, statistical errors (up to 5.3Wm-2 absolutely and 14.6% relatively) in the computed DARF still occur. These errors increase with increasing daily aerosol optical depth (AOD) is also found which indicated the high temporal resolution DARF dataset should be used in the model instead of the normal daily-averaged one, especially under heavy aerosol loading condition. [ABSTRACT FROM AUTHOR]

The article presents a study that demonstrates the capabilities of Parallel Offline Radiative Transfer (PORT) model in diagnosing radiative forcing. It states that the model separates the radiation code from the Community Atmosphere Model (CAM4) in the Community Earth System Model (CESM1). It also notes that the model can effectively provide accurate computation of radiative forcing from doubling of carbon dioxide from the ozone concentration.

An automated function control unit was developed to regularly check the ambient particle number concentration derived from a mobility particle size spectrometer as well as its zero-point behaviour. The aim of the new feature is to conduct unattended quality control experiments under field conditions at remote air quality monitoring or research stations. The automated function control also has the advantage of being able to get a faster system stability response than the recommended on-site comparisons with reference instruments. The method is based on a comparison of the total particle number concentration measured by a mobility particle size spectrometer and a condensation particle counter removing the diffusive particles approximately smaller than 25 nm in diameter. In practice, the small particles are removed by a set of diffusion screens, as traditionally used in a diffusion battery. The other feature of the automated function control is to check the zero-point behaviour of the ambient aerosol passing through a high-efficiency particulate air (HEPA) filter. An exemplary one-year data set is presented for the measurement site Annaberg- Buchholz as part of the Saxon air quality monitoring network. The total particle number concentration derived from the mobility particle size spectrometer overestimates the particle number concentration by only 2% (grand average offset). Furthermore, tolerance criteria are presented to judge the performance of the mobility particle size spec trometer with respect to the particle number concentration. An upgrade of a mobility particle size spectrometer with an automated function control enhances the quality of long-term particle number size distribution measurements. Quality assured measurements are a precondition for intercomparison studies of different sites. Comparable measurements will improve cohort health and also climate-relevant research studies. [ABSTRACT FROM AUTHOR]

A simultaneous analysis of 13 years of remotely sensed data of land cover, fires, precipitation, and aerosols from the MODIS, TRMM, and MISR satellites and the AERONET network over Southeast Asia is performed, leading to a set of robust relationships be- tween land-use change and fire being found on inter-annual and intra-annual scales over Southeast Asia, reflecting the heavy amounts of anthropogenic influence over land use change and fires in this region of the world. First, we find that fires occur annually, but with a considerable amount of variance in their onset, duration, and intensity from year to year, and from two separate regions within Southeast Asia from each other. This variability is already partially understood from previous works, including the impacts of both inter-annually and intra-annually occurring influences such as the Monsoon and El-Nino events, but yet there are other as of yet unknown influences that also are found to strongly influence the results. Second, we show that a simple regression-model of the land-cover, fire, and precipitation data can be used to recreate a robust representation of the timing and magnitude of measured AOD from multiple measurements sources of this region using either 8-day (better for onset and duration) or monthly based (better for magnitude) measurements, but not daily measurements. We find that the reconstructed AOD matches the timing and intensity from AERONET measurements to within 70 to 90% and the timing and intensity of MISR measurements from to within 50 to 95%. This is a unique finding in this part of the world, since could-covered regions are large, yet the robustness of the model is still capable of holding over many of these regions, where otherwise no fires are observed and hence no emissions source contribution to AOD would otherwise be thought to occur. Third, we determine that while Southeast Asia is a source region of such intense smoke emissions, that it is also impacted by transport of smoke from other regions as well. There are regions in northern Southeast Asia which have two annual AOD peaks, one during the local fire season, and the second smaller peak corresponding to a combination of some local smoke sources as well as transport of aerosols from fires in southern Southeast Asia, and possibly even from anthropogenic sources in South Asia. Conversely, we show that southern Southeast Asia is affected exclusively by its own local fire sources during its own local fire season. Overall, this study highlights the importance of taking into account a simultaneous use of land-use, fire, and precipitation for understanding the impacts of fires on the atmospheric loading and distribution of aerosols in Southeast Asia over both space and time. [ABSTRACT FROM AUTHOR]

In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DRE) of above-cloud aerosols (ACAs) over global oceans using eight years of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: Southeast (SE) Atlantic region where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over African Savanna; Tropical Northeast Atlantic and Arabian Sea where ACAs are predominantly windblown dust from the Sahara and Arabian desert, respectively; and Northwest Pacific where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in TNE Atlantic and Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015Wm-2 (range of -0.03 to 0.06W-2) at TOA. The DREs at surface and within atmosphere are -0.15W-2 (range of -0.09 to -0.21W-2), and 0.17W-2 (range of 0.11 to 0.24W-2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region the JJA (July ∼ August) seasonal mean cloudy-sky DRE is about 0.7W-2 (range of 0.2 to 1.2W-2) at TOA. The uncertainty in our DRE computations is mainly cause by the uncertainties in the aerosol optical properties, in particular aerosol absorption, and uncertainties in the CALIOP operational aerosol optical thickness retrieval. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions, and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty. [ABSTRACT FROM AUTHOR]

Sea spray aerosols (SSA) impact the particle mass concentration and gas-particle partitioning in coastal environments, with implications for human and ecosystem health. Despite their importance, the emission magnitude of SSA remains highly uncertain with global estimates varying by nearly two orders of magnitude. In this study, the Community Multiscale Air Quality (CMAQ) model was updated to enhance fine mode SSA emissions, include sea surface temperature (SST) dependency, and reduce coastally-enhanced emissions. Predictions from the updated CMAQ model and those of the previous release version, CMAQv5.0.2, were evaluated using several regional and national observational datasets in the continental US. The updated emissions generally reduced model underestimates of sodium, chloride, and nitrate surface concentrations for an inland site of the Bay Regional Atmospheric Chemistry Experiment (BRACE) near Tampa, Florida. Including SST-dependency to the SSA emission parameterization led to increased sodium concentrations in the southeast US and decreased concentrations along parts of the Pacific coast and northeastern US. The influence of sodium on the gas-particle partitioning of nitrate resulted in higher nitrate particle concentrations in many coastal urban areas due to increased condensation of nitric acid in the updated simulations, potentially affecting the predicted nitrogen deposition in sensitive ecosystems. Application of the updated SSA emissions to the California Research at the Nexus of Air Quality and Climate Change (CalNex) study period resulted in modest improvement in the predicted surface concentration of sodium and nitrate at several central and southern California coastal sites. This SSA emission update enabled a more realistic simulation of the atmospheric chemistry in environments where marine air mixes with urban pollution. [ABSTRACT FROM AUTHOR]

Our understanding of formation processes, physical properties and climate/health effects of organic aerosols is still limited in part due to limited knowledge of organic aerosol composition. We present speciated measurements of organic aerosol composition by two methods: in-situ thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) and offline two-dimensional gas chromatography with a timeof- flight mass spectrometer (GC×GC/TOF-MS). 153 compounds were identified using the GC×GC/TOF-MS, 123 of which were matched with 64 ions observed by the TDPTR- MS. A reasonable overall correlation of 0.67 (r2) was found between the total 10 matched TD-PTR-MS signal (sum of 64 ions) and the total matched GC×GC/TOF-MS signal (sum of 123 compounds). A reasonable quantitative agreement between the two methods was observed for most individual compounds with concentrations which were detected at levels above 2 ngm-3 using the GC×GC/TOF-MS. The analysis of monocarboxylic acids standards with TD-PTR-MS showed that alkanoic acids with molecular 15 masses below 290 amu are detected well (recovery fractions above 60%). However, the concentrations of these acids were consistently higher on quartz filters (quantified offline by GC×GC/TOF-MS) than those suggested by in-situ TD-PTR-MS measurements, which is consistent with the semivolatile nature of the acids and corresponding positive filter sampling artifacts. [ABSTRACT FROM AUTHOR]

The article focuses on an analysis of the sensitivity of short-term cloud feedback to various aspects such as temperature datasets, top-of-atmosphere (TOA) and radiative flux data. It explores the difference among radiative flux data sources as well as potential limitations of the method. It concludes that the variations in cloud forcing are due to climatological changes and fast response to aerosol forcing.

To date, size distributions obtained from the aerosol robotic network have been fit with bi-lognormals defined by six secondary microphysical parameters: the volume concentration, effective radius, and the variance of fine and coarse particle modes. However, since the total integrated volume concentration is easily calculated and can be used as an accurate constraint, the problem of fitting the size distribution can be reduced to that of deducing a single free parameter - the mode separation point. We present a method for determining the mode separation point for equivalent-volume bi-lognormal distributions based on optimisation of the root mean squared error and the coefficient of determination. The extracted secondary parameters are compared with those provided by AERONET's Level 2.0 Version 2 inversion algorithm for a set of benchmark dominant aerosol types including: desert dust, biomass burning aerosol, urban sulphate and sea salt. The total volume concentration constraint is then also lifted by performing multimodal fits to the size distribution using nested Gaussian mixture models and a method is presented for automating the selection of the optimal number of modes using a stopping condition based on Fisher statistics and via the application of statistical hypothesis testing. It is found that the method for optimizing the location of the mode separation point is independent of the shape of the AVSD, does not require the existence of a local minimum in the size interval 0.439 μm⪡ r ⪡ 0.992 μm, and shows some potential for optimizing the bi-lognormal fitting procedure used by AERONET particularly in the case of desert dust aerosol. The AVSD of impure marine aerosol is found to require 3 modes. In this particular case, bi-lognormals fail to recover key features of the AVSD. Fitting the AVSD more generally with multi-modal models allows automatic detection of a statistically-significant number of aerosol modes, is applicable to a very diverse range of aerosol types, and gives access to the secondary microphysical parameters of additional modes currently not available from bi-lognormal fitting methods. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various papers that discuss the effect of aerosols on atmosphere with their emission sources that affect visibility in urban areas.

Broadband optical cavity spectrometers are maturing as a technology for trace gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene+NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulphate particles the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols. [ABSTRACT FROM AUTHOR]

Multi-Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of trace gases can be strongly influenced by clouds and aerosols. Thus it is important to identify clouds and characterise their properties. In a recent study Wagner et al. (2014) developed a cloud classification scheme based on the MAX-DOAS measurements themselves with which different "sky conditions" (e.g. clear sky, continuous clouds, broken clouds) can be distinguished. Here we apply this scheme to long term MAX-DOAS measurements from 2011 to 2013 in Wuxi, China (31.57° N, 120.31° E). The original algorithm has been modified, in particular in order to account for smaller solar zenith angles (SZA). Instrumental degradation is accounted for to avoid artificial trends of the cloud classification. We compared the results of the MAX-DOAS cloud classification scheme to several independent measurements: aerosol optical depth from a nearby AERONET station and from MODIS, visibility derived from a visibility meter; and various cloud parameters from different satellite instruments (MODIS, OMI, and GOME-2). The most important findings from these comparisons are: (1) most cases characterized as clear sky with low or high aerosol load were associated with the respective AOD ranges obtained by AERONET and MODIS, (2) the observed dependences of MAX-DOAS results on cloud optical thickness and effective cloud fraction from satellite indicate that the cloud classification scheme is sensitive to cloud (optical) properties, (3) separation of cloudy scenes by cloud pressure shows that the MAX-DOAS cloud classification scheme is also capable of detecting high clouds, (4) some clear sky conditions, especially with high aerosol load, classified from MAX-DOAS observations corresponding to the optically thin and low clouds derived by satellite observations probably indicate that the satellite cloud products contain valuable information on aerosols. [ABSTRACT FROM AUTHOR]

The article investigates the application of multi-angular total and polarized remote sensing for aerosol optical depth and fine-mode fraction retrieval in East Asia. It states that the algorithm retrieves aerosol optical depth (AOD), fine-mode fraction (FMF) for studying the climatic impact of aerosol. It indicates that the best features of aerosol model over East Asia are constrained using the cluster analysis technique based on the AERONET sun-photometer observation over East Asia.

The article discusses the new aerosol microphysics and gas aerosol and its fractioning submodel for Global Modal-aerosol eXtension (GMXe). It states that aerosol has its importance particularly for climate and atmospheric process that can cause development of global aerosol models which can be use to treat aerosol species including black carbon, mineral dust, and particulate organic carbon. It adds several tables and graphs of Global Modal-aerosol eXtension.

The first measurements of bubble size spectra within the near-surface waters of open leads in the central Arctic pack ice were obtained during the Artic Summer Cloud-Ocean Study (ASCOS) in August 2008 at 87-87.6° N, 1-11°W. A significant number of small bubbles (30-100 μm diameter) were present, with concentration decreasing rapidly with size from 100-560 μm; no bubbles larger than 560 μm were observed. The bubbles were present both during periods of low wind speed (U<6 m/s) and when ice covered the surface of the lead. The low wind and short open-water fetch precludes production of bubbles by wave breaking suggesting that the bubbles are generated by processes below the surface. When the surface water was open to the atmosphere bubble concentrations increased with increasing heat loss to the atmosphere. The presence of substantial numbers of bubbles is significant because the bursting of bubbles at the surface provides a mechanism for the generation of aerosol and the ejection of biological material from the ocean into the atmosphere. Such a transfer has previously been proposed as a potential climate feedback linking marine biology and Arctic cloud properties. [ABSTRACT FROM AUTHOR]

The article focuses on the use of multivariate probability density function (PDF) to solve scale gap problems on climate models and to analyze cloud fraction, condensate and droplet. It mentions the use of grid flow description language (GFDL) single column model (SCM) simulations and general circulation models to determine aerosol concentration and cloud droplet number concentration in low-level clouds. It suggests assessing the effect of aerosols in droplet number and on cloud properties.

This article is the second in a series of studies investigating the benefits of multispectral measurements to improve the atmospheric parameter retrievals. In the first paper, we presented an information content (IC) analysis from the thermal infrared (TIR) and shortwave infrared (SWIR) bands of Thermal And Near infrared Sensor for carbon Observations-Fourier Transform Spectrometer (TANSO-FTS) instrument dedicated to greenhouse gas retrieval in clear sky conditions. This second paper presents the potential of the spectral synergy from TIR to visible for aerosol characterization, and their impact on the retrieved CO2 and CH4 column concentrations. The IC is then used to determine the most informative spectral channels for the simultaneous retrieval of greenhouse gas total columns and aerosol parameters. The results show that a channel selection spanning the four bands can improve the computation time and retrieval accuracy. Therefore, the spectral synergy allows obtaining up to almost seven different aerosol parameters, which is comparable to the most informative dedicated instruments. Moreover, a channel selection from the TIR to visible bands allows retrieving CO2 and CH4 total columns simultaneously in the presence of one aerosol layer with a similar accuracy to using all channels together to retrieve each gas separately in clear sky conditions. [ABSTRACT FROM AUTHOR]

Interest in climate engineering research has grown rapidly owing to the slow progress of international climate negotiations. As some scientists are proposing to expand research and conduct field tests, there is an emerging debate about whether and how it should proceed. It is widely accepted both by the supporters and critics that public engagement from the early stage of research is necessary. Nonetheless, most, if not all, of existing research projects of climate engineering were designed predominantly by experts. To produce socially relevant knowledge, and hence, pursue transdisciplinary research that integrates interdisciplinary research and public engagement, it is desirable for scientists to decide together with the public on what kind of research should be done. In this paper, we both as Japanese scientists and stakeholders collaboratively identify 40 socially relevant research questions on climate engineering with a particular emphasis on stratospheric aerosol injection, using a method designed to encourage science-policy collaboration. While we acknowledge some methodological problems and the difficulty in obtaining active participation from stakeholders, the list of identified questions covers broad interdisciplinary perspectives and diverse interests, and may provide an important foundation for future transdisciplinary research on climate engineering. Given the dynamic nature of climate change and policy responses, research agendas should be periodically and iteratively reviewed and updated through transdisciplinary processes. [ABSTRACT FROM AUTHOR]

To examine the effect of pollution control measures on Beijing air quality during the 2008 Olympic Games, this paper analyzes the variation of aerosol extinction coefficient observed with a Dual-wavelength Polarized Lidar in Beijing during the Olympic Games. The results show that (1) during the Beijing Olympic Games, the aerosol extinction coefficient decreased to about 42.3% in the surface layer (below 250 m) compared with that in 2007 under almost the same meteorological conditions, indicating the effectiveness of local air pollution control measures in Beijing areas; (2) the analysis of the aerosol extinction coefficient obtained before (Jul. 20-Aug. 7, 2008) and during the Beijing Olympic Games (Aug. 8-Aug. 24, 2008) shows a maximum decrease of daily aerosol extinction coefficient in layer of 0.5-1.5 km. To elucidate such a phenomenon, the transport of PM10 from surrounding areas to Beijing was simulated by NAQPMS (the Nested Air Quality Prediction Modeling System) during Jul. 20 to Aug. 24, 2008. Analysis of PM10 transport from neighboring areas indicated a decrease of 36.6% during the Olympic Games. This demonstrated the efficiency of pollution control measures in surrounding areas in improving air quality in Beijing. [ABSTRACT FROM AUTHOR]

Since the emergence of the global contemporary graffiti and street art, urban spaces have become filled with a variety of techniques and art pieces, whether as a beautification method, commemorative and community art, or even activism. Ecology has also been a small part of this, with growing concern over our environment's health (as well as our own), disappearing living species and habitats, and trying to imagine a better, less destructive humankind (see: Arrieta, 2014). But, how can this art - based mostly on aerosol spray cans and thus not very eco-friendly - in urban spaces contribute to ecological awareness? Do nature, animal and plant motifs pave a way towards understanding the environment, or simply serve as aesthetic statements? This paper will examine these questions with the example of Belgrade, Serbia, and several local (but also global) practices. This text is based on ongoing research as part of Street Art Walks Belgrade project (STAW BLGRD) and interviews with a group of artists. [ABSTRACT FROM AUTHOR]

This paper examines the role of occupational hygiene in the overall framework of occupational health. It draws attention to the unique combination of required individual science subjects, and to the way in which occupational hygiene science contributes to the practice of occupational hygiene in the real world. It focuses in particular on occupational exposure standards. The paper provides, as an example, the specific case of occupational aerosol exposures. It is here that scientific research has made a notable impact on standards and led to a considerable degree of international harmonization. Finally, some broader insights into occupational exposure standards are given, based on experience gained during visits to a number of contrasting countries. The similarities and differences between the various national approaches help indicate what is generic in how standards are set. Such insights provide a basis for further international harmonization in the future. It is concluded that occupational exposure standards appear to be most effectively applied in countries where there are strong occupational hygiene cultures. [ABSTRACT FROM PUBLISHER]

The Advanced Along-Track Scanning Radiometer (AATSR) on board the ENVISAT satellite is used to study aerosol properties. The retrieval of aerosol properties from satellite data is based on the optimized fit of simulated and measured reflectances at the top of the atmosphere (TOA). The simulations are made using a radiative transfer model with a variety of representative aerosol properties. The retrieval process utilizes a combination of four aerosol components, each of which is defined by their (lognormal) size distribution and a complex refractive index: a weakly and a strongly absorbing fine-mode component, coarse mode sea salt aerosol and coarse mode desert dust aerosol). These components are externally mixed to provide the aerosol model which in turn is used to calculate the aerosol optical depth (AOD). In the AATSR aerosol retrieval algorithm, the mixing of these components is decided by minimizing the error function given by the sum of the differences between measured and calculated path radiances at 3-4 wavelengths, where the path radiances are varied by varying the aerosol component mixing ratios. The continuous variation of the fine-mode components allows for the continuous variation of the fine-mode aerosol absorption. Assuming that the correct aerosol model (i.e. the correct mixing fractions of the four components) is selected during the retrieval process, also other aerosol properties could be computed such as the single scattering albedo (SSA). Implications of this assumption regarding the ratio of the weakly/strongly absorbing fine-mode fraction are investigated in this paper by evaluating the validity of the SSA thus obtained. The SSA is indirectly estimated for aerosol plumes with moderate-to-high AOD resulting from wildfires in Russia in the summer of 2010. Together with the AOD, the SSA provides the aerosol absorbing optical depth (AAOD). The results are compared with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products. The RMSE (root mean square error) is 0.03 for SSA and 0.02 for AAOD lower than 0.05. The SSA is further evaluated by comparison with the SSA retrieved from the Ozone Monitoring Instrument (OMI). The SSA retrieved from both instruments show similar features, with generally lower AATSR-estimated SSA values over areas affected by wildfires. [ABSTRACT FROM AUTHOR]

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution – an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident. [ABSTRACT FROM AUTHOR]

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In this paper, we discuss the results of 2000-2100 simulations following the emissions associated with the Representative Concentration Pathways (RCPs) with a chemistry-climate model, focusing on the changes in 1) atmospheric composition (troposphere and stratosphere) and 2) associated environmental parameters (such as nitrogen deposition). In particular, we find that tropospheric ozone is projected to decrease (RCP2.6, RCP4.5 and RCP6) or increase (RCP8.5) between 2000 and 2100, with variations in methane a strong contributor to this spread. The associated tropospheric ozone global radiative forcing is shown to be in agreement with the estimate used in the RCPs, except for RCP8.5. Surface ozone in 2100 is projected to change little compared from its 2000 distribution, a much-reduced impact from previous projections based on the A2 high-emission scenario. In addition, globally-averaged stratospheric ozone is projected to recover at or beyond pre-1980 levels. Anthropogenic aerosols are projected to strongly decrease in the 21st century, a reflection of their projected decrease in emissions. Consequently, sulfate deposition is projected to strongly decrease. However, nitrogen deposition is projected to increase over certain regions because of the projected increase in NH emissions. [ABSTRACT FROM AUTHOR]

The assessment of the climatic impacts and adverse health effects of atmospheric aerosol particles requires detailed information on particle properties. However, very limited information is available on the morphology and phase state of secondary organic aerosol (SOA) particles. The physical state of particles greatly affects particulatephase chemical reactions, and thus the growth rates of newly formed atmospheric aerosol. Thus verifying the physical phase state of SOA particles gives new and important insight into their formation, subsequent growth, and consequently potential atmospheric impacts. According to our recent study, biogenic SOA particles produced in laboratory chambers from the oxidation of real plant emissions as well as in ambient boreal forest atmospheres can exist in a solid phase in size range >30 nm. In this paper, we extend previously published results to diameters in the range of 17- 30 nm. The physical phase of the particles is studied by investigating particle bounce properties utilizing electrical low pressure impactor (ELPI). We also investigate the effect of estimates of particle density on the interpretation of our bounce observations. According to the results presented in this paper, particle bounce clearly decreases with decreasing particle size in sub 30 nm size range. The comparison measurements by ammonium sulphate and investigation of the particle impaction velocities strongly suggest that the decreasing bounce is caused by the differences in composition and phase of large (diameters greater than 30 nm) and smaller (diameters between 17 and 30 nm) particles. [ABSTRACT FROM AUTHOR]

In this paper, spectra of aerosol optical thickness from the AERONET (AErosol RObotic NETwork) station at Hornsund in the southern part of Spitsbergen were employed to study the impact of air mass history on aerosol optical thickness for wavelength λ=500 nm - AOT(500) - and the Ångström exponent. Backward trajectories computed, using the NOAA HYSPLIT model, were used to trace air history. It was found that in spring, the changes in AOT values over the Hornsund station were strongly influenced by air mass trajectories 8 days or longer in duration, arriving both in the free troposphere and at an altitude of 1 km above sea level. Nevertheless, free tropospheric advection was dominant. AOT variability in summer was best explained by the local direction and speed of advection (1-day trajectories) and was dominated by the effectiveness of cleansing processes. During the ASTAR 2007 campaign, the aerosols near Hornsund displayed low AOT values ranging from 0.06 to 0.09, which is lower than the mean AOT(500) for spring seasons from 2005 to 2007 (0.110 ±0.007; mean ± standard deviation of mean). 9 April 2007 with AOT(500)=0.147 was exceptional. The back-trajectories belonged to clusters with low and average cluster mean AOT. Apart from the maximum AOT of 9 April 2007, the observed AOT values were close to or lower than the means for the clusters to which they belonged. [ABSTRACT FROM AUTHOR]

This paper presents experiments of PM10 data assimilation with the optimal interpolation method. The observations are provided by BDQA (Base de Données sur la Qualité de l'Air), whose monitoring network covers France. Two other databases (EMEP and AirBase) are used to evaluate the improvements in the analyzed state over January 2001 and for several outputs (PM10, PM2.5 and chemical composition). The method is then applied in operational-forecast conditions. It is found that the assimilation of PM10 observations significantly improves the one-day forecast of total mass (PM10 and PM2.5), whereas the improvement is non significant for the two-day forecast. The errors on aerosol chemical composition are sometimes amplified by the assimilation procedure, which shows the need for chemical data. Since the observations cover a limited part of the domain (France versus Europe) and since the method used for assimilation is sequential, we focus on the horizontal and temporal impacts of the assimilation and we study how several parameters of the assimilation system modify these impacts. The strategy followed in this paper, with the optimal interpolation, could be useful for operational forecasts. Meanwhile, considering the weak temporal impact of the approach (about one day), the method has to be improved or other methods have to be considered. [ABSTRACT FROM AUTHOR]

South Africa, and especially its industrial highveld, is a significant source of anthropogenic and natural aerosols and trace gases. This region produces more than 1 million tonnes of sulfur dioxide (SO[sub 2]) a year, mainly from the burning of coal. Through atmospheric gas-to-particle conversion, SO[sub 2] is transformed into hygroscopic sulfates, which are potentially active as cloud condensation nuclei (CCN). These additional nuclei can affect rainfall formation in clouds. The Aerosol Recirculation and Rainfall Experiment (ARREX) was started in 1998 to investigate the distribution of aerosols and trace gases over southern Africa and their possible effect on rainfall production efficiency. In southern Africa this is an important issue as water is a scarce resource. This paper presents preliminary findings on continental-maritime contrast in aerosol, CCN and cloud droplet properties under typical summer-time conditions that could explain the differences in rainfall production efficiency between the highveld and the eastern seaboard. These results form the basis for evidence to support the hypothesis that SO[sub 2] sources affect cloud properties that influence precipitation production efficiency. The complex nature of the processes involved is highlighted and suggestions made for research that should be conducted in future experiments in the region. [ABSTRACT FROM AUTHOR]

The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), is NASA's latest reanalysis for the satellite era (1980 onward) using the Goddard Earth Observing System, version 5 (GEOS-5), Earth system model. MERRA-2 provides several improvements over its predecessor (MERRA-1), including aerosol assimilation for the entire period. MERRA-2 assimilates bias-corrected aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer and the Advanced Very High Resolution Radiometer instruments. Additionally, MERRA-2 assimilates (non bias corrected) AOD from the Multiangle Imaging SpectroRadiometer over bright surfaces and AOD from Aerosol Robotic Network sunphotometer stations. This paper, the second of a pair, summarizes the efforts to assess the quality of the MERRA-2 aerosol products. First, MERRA-2 aerosols are evaluated using independent observations. It is shown that the MERRA-2 absorption aerosol optical depth (AAOD) and ultraviolet aerosol index (AI) compare well with Ozone Monitoring Instrument observations. Next, aerosol vertical structure and surface fine particulate matter (PM2.5) are evaluated using available satellite, aircraft, and ground-based observations. While MERRA-2 generally compares well to these observations, the assimilation cannot correct for all deficiencies in the model (e.g., missing emissions). Such deficiencies can explain many of the biases with observations. Finally, a focus is placed on several major aerosol events to illustrate successes and weaknesses of the AOD assimilation: the Mount Pinatubo eruption, a Saharan dust transport episode, the California Rim Fire, and an extreme pollution event over China. The article concludes with a summary that points to best practices for using the MERRA-2 aerosol reanalysis in future studies. [ABSTRACT FROM AUTHOR]

Urban air pollution is one of the most widespread global sustainability problems. Previous research has studied growth or fall of particulate matter (PM) levels using on-ground monitoring stations in urban regions. However, studying this worldwide is difficult because most cities do not have sufficient infrastructure to monitor air quality. Thus, satellite data is increasingly being employed to solve this limitation. In this paper, we use 16 years (2001-2016) of aerosol optical depth (AOD) and Angstrom exponent (α) datasets, retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) sensors on the National Aeronautics and Space Administration's (NASA) Terra satellite to study air quality over 60 locations globally. We propose a novel technique, called AirRGB decomposition, to characterize urban air quality by decomposing AOD and α retrievals into 'components' of three distinct scenarios. In the AirRGB decomposition method, using AOD and α dataset three scenarios were investigated: 'R'--high α and high AOD, 'G'--high α and low AOD, and 'B'--low α and low AOD values. These scenarios were mapped and quantified over a triangular red, green and blue color scale. This visualization easily segregates regions having a high concentration of industrial aerosol from only natural aerosols. Our analysis indicates that a sharp divide exists between North American and European cities and Asian cities in terms of baseline pollution and slopes of R and G trends. We found that while pollution in cities in China has started to decrease (e.g., since 2011 for Beijing), it continues to increase in South Asia and Southeast Asia. e.g., R offset of Beijing and New Delhi was 54.98 and 50.43 respectively but R slope was -0.04 and 0.08 respectively. High offset (≥45) and slope (≥0.025) of B for New York, Tokyo, Sydney and Sao Paolo shows that they have clean air, which is still getting better. [ABSTRACT FROM AUTHOR]

Aerosol pollution in urban environments has been recognized to be responsible for important pathologies of the cardiovascular and respiratory systems. In this perspective, great attention has been addressed to Ultra Fine Particles (UFPs < 100 nm), because they efficiently penetrate into the respiratory system and are capable of translocating from the airways into the blood circulation. This paper describes the aerosol regional doses deposited in the human respiratory system in a high-traffic urban area. The aerosol measurements were carried out on a curbside in downtown Rome, on a street characterized by a high density of autovehicular traffic. Aerosol number-size distributions were measured by means of a Fast Mobility Particle Sizer in the range from 5.6 to 560 nm with a 1 s time resolution. Dosimetry estimates were performed with the Multiple-Path Particle Dosimetry model by means of the stochastic lung model. The exposure scenario close to traffic is represented by a sequence of short-term peak exposures: about 6.6 × 10 particles are deposited hourly into the respiratory system. After 1 h of exposure in proximity of traffic, 1.29 × 10, 1.88 × 10, and 3.45 × 10 particles are deposited in the head, tracheobronchial, and alveolar regions. More than 95 % of such doses are represented by UFPs. Finally, according to the greater dose estimated, the right lung lobes are expected to be more susceptible to respiratory pathologies than the left lobes. [ABSTRACT FROM AUTHOR]

This paper studies the feasibility of retrieving aerosol concentrations in the planetary boundary layer (PBL) with a variational data assimilation (VDA) algorithm using dual-wavelength lidar returns and visual range simulated at multiple times. Aerosols are assumed to consist of nucleation, accumulation, and coarse modes, with each mode distributed in a gamma distribution. The VDA algorithm retrieves initial vertical profiles of aerosol concentrations of the three modes, which are predicted by a 1D PBL model. The accuracy of retrieved aerosol concentrations of the three modes is examined through a series of identical twin numerical experiments. For the VDA algorithm that uses data from a lidar wavelength pair (0.289, 11.15 μm), results show that 1) if both random and systematic errors in the observed data are less than 1.0 dB and the number densities of accumulation and coarse modes are, respectively, 0.025-0.25 and 0-1.25 X 10[sup-3] times that of the nucleation mode, relative errors in the retrieved aerosol concentrations are 12%-110% for the nucleation mode, 9%-40% for the accumulation, and 3%-25% for the coarse mode; 2) the accuracy of retrieved aerosol concentrations is slightly (greatly) affected by the errors in relative humidity (RH) if RH is less (greater) than 95%, and moderately by the vertical scales of initial aerosol concentration fields; 3) systematic errors in the observed data can severely reduce the accuracy of retrieved aerosol concentrations; and 4) the VDA algorithm is more accurate than traditional methods that use single-time data. Moreover, a method is developed to retrieve systematic errors in the observed data. Results show that if systematic errors in lidar returns are less than about 2 dB, retrieving systematic errors can increase the accuracy of retrieved aerosol concentrations, especially for the accumulation mode. The method to retrieve systematic errors in the observed data can find applications in other retrieval problems... [ABSTRACT FROM AUTHOR]

Conventional methods for Aerosol Optical Depth (AOD) retrieval are limited to areas with low reflectance such as water or vegetated areas because the satellite signals from the aerosols in these areas are more obvious than those in areas with higher reflectance such as urban and sandy areas. Land Surface Reflectance (LSR) is the key parameter that must be estimated accurately. Most current methods used to estimate AOD are applicable only in areas with low reflectance. It has historically been difficult to estimate the LSR for bright surfaces because of their complex structure and high reflectance. This paper provides a method for estimating LSR for AOD retrieval in bright areas, and the method is applied to AOD retrieval for Landsat 8 Operational Land Imager (OLI) images at 500 m spatial resolution. A LSR database was constructed with the MODerate-resolution Imaging Spectroradiometer (MODIS) surface reflectance product (MOD09A1), and this database was also used to estimate the LSR of Landsat 8 OLI images. The AOD retrieved from the Landsat 8 OLI images was validated using the AOD measurements from four AErosol RObotic NETwork (AERONET) stations located in areas with bright surfaces. The MODIS AOD product (MOD04) was also compared with the retrieved AOD. The results demonstrate that the AOD retrieved with the new algorithm is highly consistent with the AOD derived from ground measurements, and its precision is better than that of MOD04 AOD products over bright areas. [ABSTRACT FROM AUTHOR]

Acoustic radiation sources are successfully applied to cleaning rooms from dust of fairly large particle sizes (ten micrometers and larger). The sedimentation of fine aerosols (particle diameter of 1-10 microns) is a more complicated challenge. The paper is devoted to the substantiation of the acoustic sedimentation method for such aerosols. On the basis of the mathematical model analysis for aerosol sedimentation by the acoustic field the mechanisms of this process have been determined and include the particle coagulation acceleration and radiation pressure effect. The experimental results of the acoustic sedimentation of a model aerosol (NaCl) are shown. The calculation results according to the mathematical model for coagulation and sedimentation, on the basis of the Smolukhovsky's equation taking into account various mechanisms of aerosol sedimentation by sound depending on the particle sizes and sound intensity, are given. The necessity to use intensive sources of high-frequency sound has been confirmed, suggesting that these sources must be located above dust clouds. [ABSTRACT FROM AUTHOR]

Aerosols affect the atmosphere through direct interaction with short-wave and long-wave radiation and the microphysical properties of clouds. In this paper we report in detail on several mechanisms by which the short-term impact of dust on surface radiative fluxes can affect the dust loading of the atmosphere via modification of boundary-layer meteorology. This in turn affects the aerosol radiative forcing itself. Examples of these feedbacks between dust and boundary layer meteorology were observed during a series of dust storms in the Sahara and the eastern Mediterranean in April 2012. These case studies have been analysed using the Monitoring Atmospheric Composition and Climate - Interim Implementation (MACC-II) system. The radiative fluxes in the short-wave and long-wave spectra were both significantly affected by the prognostic aerosol-radiation interaction, which in turn impacted the meteorological simulation. Reduced incoming solar radiation below the aerosol layers led to a decrease in maximum surface temperatures and to a more stable thermal stratification of the lower atmosphere. This in turn forced weaker surface wind speeds and eventually smaller dust emissions. Moreover, we also observed a secondary impact of the aerosol radiative forcing, whereby horizontal gradients of surface temperature were increased at the edge of the dust plume, which led to local increases of surface wind speeds due to the thermal wind effect. The differentiated impact of the aerosol layer on surface pressure also contributed to the increase in surface wind speed and dust production in the same area. Enhanced long-wave radiative fluxes by the dust mass were associated with opposite processes. Less stable thermal stratification at night, brought mainly by higher minimum temperatures at the surface, caused stronger surface winds. At the edge of the dust storm, weaker horizontal temperature and pressure gradients forced lower winds and reduced dust production. Regarding dust emissions, short-wave radiative forcing had a larger impact than long-wave radiative forcing, corroborating several previous studies. For surface temperature, short-wave and long-wave contribution were close in intensity. These feedbacks were amplified when using data assimilation to build the aerosol analysis of the MACC-II global system. This led to an improvement in the short-term forecasts of thermal radiative fluxes and surface temperatures. [ABSTRACT FROM AUTHOR]

As part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) conducted under the Geosphere Biosphere Programme of Indian Space Research Organisation, ship-based aerosol sampling was carried out over the marine environment of Bay of Bengal (BoB) during the northern winter months of December 2008 to January 2009. About 101 aerosol samples were collected, covering the region from 3.4° to 21° N latitude and 76° to 98° E longitude-the largest area covered-including the south east (SE) BoB for the first time. These samples were subjected to gravimetric and chemical analysis and the total aerosol loading as well the mass concentration of the ionic species namely F, Cl, Br, NO, NO, PO, SO, NH, etc. and the metallic species, Na, Mg, Ca, K, Al, Fe, Mn, Zn, and Pb were estimated for each sample. Based on the spatial distribution of individual chemical species, the air flow pattern, and airmass back trajectory analysis, the source characteristics of aerosols for different regions of BoB were identified. Significant level of continental pollution was noticed over BoB during winter. While transport of pollution from Indo-Gangetic Plain (IGP) contributed to aerosols over north BoB, those over SE BoB were influenced by SE Asia. A quantitative study on the wind-induced production of sea salt aerosols and a case study on the species dependent effect of rainfall are also presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper the Secondary Organic Aerosol Processor (SOAP v1.0) model is presented. This model determines the partitioning of organic compounds between the gas and particle phases. It is designed to be modular with different user options depending on the computation time and the complexity required by the user. This model is based on the molecular surrogate approach, in which each surrogate compound is associated with a molecular structure to estimate some properties and parameters (hygroscopicity, absorption into the aqueous phase of particles, activity coefficients and phase separation). Each surrogate can be hydrophilic (condenses only into the aqueous phase of particles), hydrophobic (condenses only into the organic phases of particles) or both (condenses into both the aqueous and the organic phases of particles). Activity coefficients are computed with the UNIFAC (UNIversal Functional group Activity Coefficient; Fredenslund et al., 1975) thermodynamic model for short-range interactions and with the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) parameterization for medium- and long-range interactions between electrolytes and organic compounds. Phase separation is determined by Gibbs energy minimization. The user can choose between an equilibrium representation and a dynamic representation of organic aerosols (OAs). In the equilibrium representation, compounds in the particle phase are assumed to be at equilibrium with the gas phase. However, recent studies show that the organic aerosol is not at equilibrium with the gas phase because the organic phases could be semi-solid (very viscous liquid phase). The condensation–evaporation of organic compounds could then be limited by the diffusion in the organic phases due to the high viscosity. An implicit dynamic representation of secondary organic aerosols (SOAs) is available in SOAP with OAs divided into layers, the first layer being at the center of the particle (slowly reaches equilibrium) and the final layer being near the interface with the gas phase (quickly reaches equilibrium). Although this dynamic implicit representation is a simplified approach to model condensation–evaporation with a low number of layers and short CPU (central processing unit) time, it shows good agreements with an explicit representation of condensation–evaporation (no significant differences after a few hours of condensation). [ABSTRACT FROM AUTHOR]

A study of the assessment and management of air quality was carried out at 11 coal mines in India. Long-term observations (about 13 years, March 2000-December 2012) and modeling of aerosol loading over coal mines in India are analyzed in the present study. In this respect, the Box-Jenkins popular autoregressive integrated moving average (ARIMA) model was applied to simulate the monthly mean Terra Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) over 11 sites in the coal mines region. The ARIMA model was found as the most suitable model with least normalized Bayesian information criterion (BIC) and root mean square error and high value of R. Estimation was done with the Ljung-Box test. Finally, a forecast for a 3-year period from January 2013 to December 2015 was calculated which showed that the model forecasted values are following the observed trend quite well over all mining areas in India. The average values of AOD for the next 3 years (2013-2015) at all sites are found to be 0.575 ± 0.13 (Raniganj), 0.452 ± 0.12 (Jharia), 0.339 ± 0.13 (Bokaro), 0.280 ± 0.09 (Bishrampur), 0.353 ± 0.13 (Korba), 0.308 ± 0.08 (Talcher), 0.370 ± 0.11 (Wardha), 0.35 ± 0.10 (Adilabad), 0.325 ± 0.09 (Warangal), 0.467 ± 0.09 (Godavari Valley), and 0.236 ± 0.07 (Cuddapah), respectively. In addition, long-term lowest monthly mean AOD values are observed over Bishrampur followed by Cuddapah, Talcher, Warangal, Adilabad, Korba, Wardha, Godavari Valley, Jharia, and Raniganj. Raniganj and Jharia exhibit the highest AOD values due to opencast mines and extensive mining activities as well as a large number of coal fires. Similarly, the highest AOD values are observed during the monsoon season among all four seasons over all the mining sites. Raniganj exhibits the highest AOD value at all seasons and at all sites. In contrast, the lowest seasonal AOD values are observed during the post-monsoon season over Raniganj, Talcher, Wardha, Adilabad, Warangal, and Godavari Valley. Similarly, over Jharia, Bokaro, Bishrampur, Korba, and Cuddapah, the lowest AOD values are found in the winter season. Increasing trends in AOD have been observed over Raniganj, Bokaro, Bishrampur, Korba, Talcher, and Wardha as well as over Adilabad and Godavari Valley, which is in agreement with previous works. Negative or decreasing AOD trend is found only over Jharia, Warangal, and Cuddapah without being statistically significant. Seasonal trends in AODs have also been studied in the present paper. [ABSTRACT FROM AUTHOR]

This paper deals with recent improvements to the global chemical transport model of Météo-France MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle) that consists of updates to different aerosol parameterizations. MOCAGE only contains primary aerosol species: desert dust, sea salt, black carbon, organic carbon, and also volcanic ash in the case of large volcanic eruptions. We introduced important changes to the aerosol parameterization concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant source function is introduced for sea salt aerosols. Wet deposition is modified toward a more physically realistic representation by introducing re-evaporation of falling rain and snowfall scavenging and by changing the in-cloud scavenging scheme along with calculations of precipitation cloud cover and rain properties. The sedimentation scheme update includes changes regarding the stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI), the ground (AERONET, EMEP), and a model inter-comparison project (AeroCom) are compared with MOCAGE simulations and show that the introduced changes brought a significant improvement on aerosol representation, properties and global distribution. Emitted quantities of desert dust and sea salt, as well their lifetimes, moved closer towards values of AeroCom estimates and the multimodel average. When comparing the model simulations with MODIS aerosol optical depth (AOD) observations over the oceans, the updated model configuration shows a decrease in the modified normalized mean bias (MNMB; from 0.42 to 0.10) and a better correlation (from 0.06 to 0.32) in terms of the geographical distribution and the temporal variability. The updates corrected a strong positive MNMB in the sea salt representation at high latitudes (from 0.65 to 0.16), and a negative MNMB in the desert dust representation in the African dust outflow region (from 􀀀1:01 to 􀀀0:22). The updates in sedimentation produced a modest difference; the MNMB with MODIS data from 0.10 in the updated configuration went to 0.11 in the updated configuration only without the sedimentation updates. Yet, the updates in the emissions and the wet deposition made a stronger impact on the results; the MNMB was 0.27 and 0.21 in updated configurations only without emission, and only without wet deposition updates, respectively. Also, the lifetime, the extent, and the strength of the episodic aerosol events are better reproduced in the updated configuration. The wet deposition processes and the differences between the various configurations that were tested greatly influence the representation of the episodic events. However, wet deposition is not a continuous process; it has a local and episodic signature and its representation depends strongly on the precipitation regime in the model. [ABSTRACT FROM AUTHOR]

Air pollution is one of the grave concerns of the modern era, claiming millions of lives and adversely impacting the economy. Aerosols have been observed to play a significant role in negatively influencing climatological variables and human health in given areas. The current study aimed to study the trend of aerosols and particulates on daily, monthly, seasonal, and annual levels using a 20-year (2002-2021) daily mean aerosol optical depth (AOD) product released by moderate resolution imaging spectrometer (MODIS) sensors for the Hyderabad district in India. The results of the daily mean analysis revealed a rising trend in the number of days with severe AOD (>1), whereas examinations of the seasonal and monthly mean data from 2017 through 2022 showed that peak AOD values alternated between the summer, autumn, and winter seasons over the years. Trend analysis using Mann-Kendall, modified Mann-Kendall, and innovative trend analysis (ITA) tests revealed that AOD increased significantly from 2002 through 2021 (p < 0.05; Z > 0). Furthermore, correlation analysis was performed to check for correlations between AOD levels and certain meteorological factors for the Charminar and Secunderabad regions; it was noticed that temperature had a weak positive correlation with AOD (p < 0.05; r = 0.283 [Secunderabad] - p < 0.05; r = 0.301 [Charminar]), whereas relative humidity developed a very weak negative correlation with AOD (p < 0.05; r = -0.079 [Secunderabad] - p < 0.05; r = -0.109 [Charminar]). [ABSTRACT FROM AUTHOR]

Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in total forcing result in increases in global average temperature. Non-Kyoto forcing modeling is a relatively new component of climate management scenarios. This paper describes and assesses current non-Kyoto radiative forcing modeling within five integrated assessment models. The study finds negative forcing from aerosols masking (offsetting) approximately 25 % of positive forcing in the near-term in reference non-climate policy projections. However, masking is projected to decline rapidly to 5-10 % by 2100 with increasing Kyoto emissions and assumed reductions in air pollution-with the later declining to as much as 50 % and 80 % below today's levels by 2050 and 2100 respectively. Together they imply declining importance of non-Kyoto forcing over time. There are however significant uncertainties and large differences across models in projected non-Kyoto emissions and forcing. A look into the modeling reveals differences in base conditions, relationships between Kyoto and non-Kyoto emissions, pollution control assumptions, and other fundamental modeling. In addition, under climate policy scenarios, we find air pollution and resulting non-Kyoto forcing reduced to levels below those produced by air pollution policies alone-e.g., China sulfur emissions fall an additional 45-85 % by 2050. None of the models actively manage non-Kyoto forcing for climate implications. Nonetheless, non-Kyoto forcing may be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited. [ABSTRACT FROM AUTHOR]

Recent scientific findings and legislations have clearly highlighted the need for comprehensive approaches and methods to evaluate natural dust contributions to an urban atmosphere. The evaluation of chemical compositions of airborne aerosols is of these methods that may employ several advanced analytical techniques and processes. In this paper, an episodic appearance of Saharan dust incursion over a megacity (Istanbul, Turkey) was investigated using size segregated particulate matter (PM) samples in fine and coarse fractions collected between February 27 and March 8, 2009. The Saharan impact was investigated using satellite observations, backward air trajectory statistics, and chemical analyses of the collected samples. In the chemical analyses, Fourier transform infrared coupled with attenuated total reflectance (ATR-FTIR) spectroscopic method was used to determine the functional groups, namely, alcohols, ammonium, aliphatic carbons, carbonyls, organonitrates, nitrate, silicate, silica, kaolinite, and calcium carbonate. Among all the measured functional groups, it was clearly seen that the intensities of IR peaks related to silicate, silica, kaolinite, and calcium carbonate were associated with the increased mass concentrations during the impact period. The observed IR peaks at 1,030 and 800 cm for silicate ions in the samples can be used as an indicator of the large dust incursion into the atmosphere (e.g., Saharan dust episodes observed in Istanbul). This study showed that the ATR-FTIR spectroscopic method is a fast and convenient method to identify these peaks and the IR method in general is useful for identifying a large dust incursion into the atmosphere. [ABSTRACT FROM AUTHOR]

The height of desert dust and carbonaceous aerosols layers and, to a lesser extent, the difficulty in determining the predominant size mode of these absorbing aerosol types, are sources of uncertainty in the retrieval of aerosol properties from near-UV satellite observations. The availability of independent, near-simultaneous measurements of aerosol layer height, and aerosol-type related parameters derived from observations by other A-train sensors, makes possible the use of this information as input to the OMI (ozone monitoring instrument) near-UV aerosol retrieval algorithm (OMAERUV). A monthly climatology of aerosol layer height derived from observations by the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) sensor, and real-time AIRS (Atmospheric Infrared Sounder) carbon monoxide (CO) observations are used in an upgraded version of the OMAERUV algorithm. AIRS CO measurements are used as an adequate tracer of carbonaceous aerosols, which allows the identification of smoke layers in regions and seasons when the dust-smoke differentiation is difficult in the near-UV. The use of CO measurements also enables the identification of high levels of boundary layer pollution undetectable by near-UV observations alone. In this paper we discuss the combined use of OMI, CALIOP and AIRS observations for the characterization of aerosol properties, and show an improvement in OMI aerosol retrieval capabilities. [ABSTRACT FROM AUTHOR]

Studies describing the chemical composition of fine aerosol (PM2.5) in urban areas are often conducted for a few weeks only and at one sole site, giving thus a narrow view of their temporal and spatial characteristics. This paper presents a one-year (11 September 2009-10 September 2010) survey of the daily chemical composition of PM2.5 in the region of Paris, which is the second most populated "Larger Urban Zone" in Europe. Five sampling sites representative of suburban (SUB), urban (URB), northeast (NER), northwest (NWR) and south (SOR) rural backgrounds were implemented. The major chemical components of PM2.5 were determined including elemental carbon (EC), organic carbon (OC), and the major ions. OC was converted to organic matter (OM) using the chemical mass closure methodology, which leads to conversion factors of 1.95 for the SUB and URB sites, and 2.05 for the three rural ones. On average, gravimetrically determined PM2.5 annual mass concentrations are 15.2, 14.8, 12.6, 11.7 and 10.8 μgm-3 for SUB, URB, NER, NWR and SOR sites, respectively. The chemical composition of fine aerosol is very homogeneous at the five sites and is composed of OM (38-47 %), nitrate (17-22 %), non-sea-salt sulfate (13-16 %), ammonium (10-12 %), EC (4-10 %), mineral dust (2-5 %) and sea salt (3-4 %). This chemical composition is in agreement with those reported in the literature for most European environments. On an annual scale, Paris (URB SUB sites) exhibits its highest PM2.5 concentrations during late autumn, winter and early spring (higher than 15 μgm-3 on average, from December to April), intermediates during late spring and early autumn (between 10 and 15 μgm-3 during May, June, September, October, and November) and the lowest during summer (below 10 μgm-3 during July and August). PM levels are mostly homogeneous on a regional scale, during the whole project (e.g. for URB plotted against NER sites: slope=1.06, r2 = 0.84, n = 330), suggesting the importance of mid- or long-range transport, and regional instead of local scale phenomena. During this one-year project, two thirds of the days exceeding the PM2.5 2015 EU annual limit value of 25 μgm-3 were due to continental import from countries located northeast, east of France. This result questions the efficiency of local, regional and even national abatement strategies during pollution episodes, pointing to the need for a wider collaborative work with the neighbouring countries on these topics. Nevertheless, emissions of local anthropogenic sources lead to higher levels at the URB and SUB sites compared to the others (e.g. 26% higher on average at the URB than at the NWR site for PM2.5, during the whole campaign), which can even be emphasised by specific meteorological conditions such as low boundary layer heights. OM and secondary inorganic species (nitrate, non-sea-salt sulfate and ammonium, noted SIA) are mainly imported by mid- or long-range transport (e.g. for NWR plotted against URB sites: slope=0.79, r2 = 0.72, n = 335 for OM, and slope=0.91, r2 = 0.89, n = 335 for SIA) whereas EC is primarily locally emitted (e.g. for SOR plotted against URB sites: slope=0.27; r2 = 0.03; n = 335). This database will serve as a basis for investigating carbonaceous aerosols, metals as well as the main sources and geographical origins of PM in the region of Paris. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the development and evaluation of an environmental turbulent reacting flow model, the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model. CTAG is designed to simulate transport and transformation of multiple air pollutants, e.g., from emission sources to ambient background. For the on-road and near-road applications, CTAG explicitly couples the major turbulent mixing processes, i.e., vehicle-induced turbulence (VIT), road-induced turbulence (RIT) and atmospheric boundary layer turbulence with gas-phase chemistry and aerosol dynamics. CTAG''s transport model is referred to as CFD-VIT-RIT. This paper presents the evaluation of the CTAG model in simulating the dynamics of individual plumes in the “tailpipe-to-road” stage, i.e., VIT behind a moving van and aerosol dynamics in the wake of a diesel car by comparing the modeling results against the respective field measurements. Combined with sensitivity studies, we analyze the relative roles of VIT, sulfuric acid induced nucleation, condensation of organic compounds and presence of soot-mode particles in capturing the dynamics of exhaust plumes as well as their implications in vehicle emission controls. [Copyright &y& Elsevier]

The Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm makes aerosol retrievals from MODIS data at 1 km resolution providing information about the fine scale aerosol variability. This information is required in different applications such as urban air quality analysis, aerosol source identification etc. The quality of high-resolution aerosol data is directly linked to the quality of cloud mask, in particular detection of small (sub-pixel) and low clouds. This work continues research in this direction, describing a technique to detect small clouds and introducing the "smoke test" to discriminate the biomass burning smoke from the clouds. The smoke test relies on a relative increase of aerosol absorption at MODIS wavelength 0.412 µm as compared to 0.47-0.67 µm due to multiple scattering and enhanced absorption by organic carbon released during combustion. This general principle has been successfully used in the OMI detection of absorbing aerosols based on UV measurements. This paper provides the algorithm detail and illustrates its performance on two examples of wildfires in US Pacific North-West and in Georgia/Florida of 2007. [ABSTRACT FROM AUTHOR]