Climatology of the aerosol optical depth by components from the Multiangle Imaging SpectroRadiometer (MISR) and a high-resolution chemistry transport model
Summary: The Multi-angle Imaging SpectroRadiometer (MISR) on NASA’s TERRA satellite provides a global distribution of aerosol amount and type information for each month between March 2000 and the present. This study analyzes, for the first time, characteristics of observed and simulated distributions of aerosols for three broad classes of aerosols: non-absorbing, absorbing, and non-spherical - near or downwind of their major source regions.
Atmos. Chem. Phys. Discuss., 15, 33897-33929, doi:10.5194/acpd-15-33897-2015, 2015
Aqueous phase oxidation of sulphur dioxide by ozone in cloud droplets
Summary: A significant portion of sulphate, an important constituent of atmospheric aerosols, is formed via the aqueous phase oxidation of sulphur dioxide by ozone. The rate of this reaction has previously only been measured over a relatively small temperature range. Here, we use the state of the art CLOUD chamber at CERN to perform the first measurements of this reaction rate in super-cooled droplets, confirming that the existing extrapolation of the reaction rate to sub-zero temperatures is accurate.
Atmos. Chem. Phys. Discuss., 15, 33843-33896, doi:10.5194/acpd-15-33843-2015, 2015
Evaluation and application of multi-decadal visibility data for trend analysis of atmospheric haze
Summary: We comprehensively screen and process global hourly visibility data to construct a more reliable monthly inverse visibility (1/Vis) dataset, and to infer trends in atmospheric haze. Consistency is found for the inferred 1/Vis seasonality and trends with other collocated in situ aerosol measurements over the US and Europe. Trends of 1/Vis over 1945-1996 for the eastern US, and over 1973-2013 for Europe and Eastern Asia are significantly associated with the variation of SO2 emission.
Atmos. Chem. Phys. Discuss., 15, 33789-33841, doi:10.5194/acpd-15-33789-2015, 2015
Vehicular emissions of organic particulate matter in Sao Paulo, Brazil
Summary: Vehicular emissions have a strong impact on air pollution in big cities, therefore the study was performed in Sao Paulo city, where light duty (LDV) and heavy duty vehicles (HDV) run on different fuels. Our results shows that OA emission from LDV and HDV is a complex process involving oxidation of fuel constituents, NOx chemistry, and condensation of unburned fuel hydrocarbons on new or existing particles. The obtained emission patterns can be used to study processing of young aerosol in Brazil
Atmos. Chem. Phys. Discuss., 15, 33755-33788, doi:10.5194/acpd-15-33755-2015, 2015
Vortex-wide chlorine activation by a mesoscale PSC event in the Arctic winter of 2009/10
Summary: Satellite observations are used to constrain areas with large backscatter values areas inside the polar vortex. Surface area is derived from these observations and used in heterogeneous modeling. Satellite gas species observations show a decrease in HCl downwind of areas with large surface area density indicating heterogeneous processing inside these areas. This decrease can only be simulated if a realistic surface area is assumed demonstrating the importance of polar stratospheric cloud.
Atmos. Chem. Phys. Discuss., 15, 33731-33754, doi:10.5194/acpd-15-33731-2015, 2015
Optical properties of atmospheric fine particles near Beijing during the HOPE-J3A Campaign
Summary: Comprehensive studies of intensive optical properties and light apportionment are necessary for a better understanding of the evolution of aerosol physical and optical properties in the North China Plain (NCP). In this work, we report the field measurement of the optical properties, particle size distributions, and chemical components of the submicron aerosol at a suburban site in Beijing during the winter coal heating season.
Atmos. Chem. Phys. Discuss., 15, 33675-33730, doi:10.5194/acpd-15-33675-2015, 2015
Technical Note: Development of chemoinformatic tools to enumerate functional groups in molecules for organic aerosol characterization
Summary: We present a set of tools for mapping molecular information to functional group composition that will be useful for reducing the complex representation of organic aerosol mixtures consisting of hundreds or thousands of molecule types. We describe the tools and methods for validation, and demonstrate several applications in which this tool can facilitate measurement intercomparisons and chemical modeling of aerosol chemistry.
Atmos. Chem. Phys. Discuss., 15, 33631-33674, doi:10.5194/acpd-15-33631-2015, 2015
Observationally-constrained carbonaceous aerosol source estimates for the Pearl River Delta area of China
Atmos. Chem. Phys. Discuss., 15, 33583-33629, doi:10.5194/acpd-15-33583-2015, 2015
Quantification of black carbon mixing state from traffic: implications for aerosol optical properties
Atmos. Chem. Phys. Discuss., 15, 33555-33582, doi:10.5194/acpd-15-33555-2015, 2015
Aerosol water parameterization: a single parameter framework
Summary: We introduce an unique single parameter framework to efficiently parameterize the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, being entirely based on the single solute specific coefficient introduced in Metzger et al. (2012).
Atmos. Chem. Phys. Discuss., 15, 33493-33553, doi:10.5194/acpd-15-33493-2015, 2015
Comprehensive tool for calculation of radiative fluxes: illustration of shortwave aerosol radiative effect sensitivities to the details in aerosol and underlying surface characteristics
Summary: The study presents a comprehensive tool for accurate calculation of solar flux as part of a novel algorithm GRASP (Generalized Retrieval of Aerosol and Surface Properties). We show that simplification of details in directional properties of atmospheric aerosol scattering and reflectance of underlying surface causes systematic biases in evaluation of aerosol radiative effect. Presented application for satellite data is one more step in the measurement-based estimate of aerosol effect on climate.
Atmos. Chem. Phys. Discuss., 15, 33445-33492, doi:10.5194/acpd-15-33445-2015, 2015
Characteristics of aerosol pollution during heavy haze events in Suzhou, China
Summary: The discussion were based on high time resolution data which could provide detailed insight into shorter haze periods; The dominant species in PM2.5 and responsible for the visibility reduction were identified in Suzhou; The formation mechanism of sulfate and nitrate were explored as high secondary aerosol contributions to particulate pollution during haze events; The impact of local and transport sources on the origin of aerosol pollution in urban Suzhou was discussed.
Atmos. Chem. Phys. Discuss., 15, 33407-33443, doi:10.5194/acpd-15-33407-2015, 2015
Observations and implications of liquid–liquid phase separation at high relative humidities in secondary organic material produced by α-pinene ozonolysis without inorganic salts
Atmos. Chem. Phys. Discuss., 15, 33379-33405, doi:10.5194/acpd-15-33379-2015, 2015
Vertical and horizontal variability of PM10 source contributions in Barcelona during SAPUSS
Atmos. Chem. Phys. Discuss., 15, 33331-33378, doi:10.5194/acpd-15-33331-2015, 2015
Modelled thermal and dynamical responses of the middle atmosphere to EPP-induced ozone changes
Atmos. Chem. Phys. Discuss., 15, 33283-33329, doi:10.5194/acpd-15-33283-2015, 2015
Time-resolved characterization of primary and secondary particle emissions of a modern gasoline passenger car
Summary: We characterized primary and secondary particulate emissions of a modern gasoline passenger car. In mass terms, the amount of secondary particles was 13 times the amount of primary particles. The highest emissions were observed after a cold start when the engine and catalyst performance were suboptimal. The key parameter for secondary particle formation was the amount of gaseous hydrocarbons in the exhaust. In future legislation, attention should be directed into the reduction of hydrocarbons.
Atmos. Chem. Phys. Discuss., 15, 33253-33282, doi:10.5194/acpd-15-33253-2015, 2015
The impact of monthly variation of the Pacific-North America (PNA) teleconnection pattern on wintertime surface-layer aerosol concentrations in the United States
Summary: We examine the impacts of monthly variations in Pacific-North America (PNA) teleconnection phase on aerosol concentrations in the United States during wintertime, by analyzing observations from the EPA-AQS and the model results from the GEOS-Chem model. We find that surface-layer PM2.5 concentrations in the PNA positive phases were higher by about 13% relative to the PNA negative phases, which have important implications for understanding and prediction of air quality in the United States.
Atmos. Chem. Phys. Discuss., 15, 33209-33251, doi:10.5194/acpd-15-33209-2015, 2015
SOA formation from the photooxidation of α-pinene: systematic exploration of the simulation of chamber data
Summary: We examine secondary organic aerosol formation from the biogenic hydrocarbon alpha-pinene and observe unexpected experimental results that run contrary to model predictions. Various processes are explored via modelling to rationalize the observations. The paper identifies the importance of further constraining via experiments various steps in the chemical mechanism.
Atmos. Chem. Phys. Discuss., 15, 33161-33207, doi:10.5194/acpd-15-33161-2015, 2015
Simulating the SOA formation of isoprene from partitioning and aerosol phase reactions in the presence of inorganics
Summary: The secondary organic aerosol (SOA) produced by the photooxidation of isoprene with and without inorganic seed is simulated using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model, assuming a single homogenously mixed organic-inorganic phase. UNIPAR is used to determine the sensitivity of isoprene SOA formation to NOx, aerosol acidity and aerosol liquid water content. Isoprene SOA is found to be most sensitive to aerosol acidity, but dynamically related to all three parameters.
Atmos. Chem. Phys. Discuss., 15, 33121-33159, doi:10.5194/acpd-15-33121-2015, 2015
High concentrations of sub-3 nm clusters and frequent new particle formation observed in the Po Valley, Italy, during the PEGASOS 2012 campaign
Atmos. Chem. Phys. Discuss., 15, 33077-33119, doi:10.5194/acpd-15-33077-2015, 2015
North Atlantic Oscillation model projections and influence on tracer transport
Summary: We investigate the temporal variability of the North Atlantic Oscillation (NAO) pattern and its relation to the atmospheric dispersion of pollutants in the near past and in the future. We use a global climate circulation model in order to analyze the NAO signal and its correlation with pollutant concentrations. We find that the NAO is influenced by natural climate variability and that the NAO Indices may be used as indicators of (future) pollutant transport over Europe.
Atmos. Chem. Phys. Discuss., 15, 33049-33075, doi:10.5194/acpd-15-33049-2015, 2015
Analysis of the potential of near ground measurements of CO2 and CH4 in London, UK for the monitoring of city-scale emissions using an atmospheric transport model
Summary: We measured carbon dioxide and methane concentrations at four near ground sites located in London, 2012. We investigated the potential for using these measurements, alongside numerical modelling, to help us to understand urban greenhouse gas emissions. Low level sites were highly sensitive to local emissions, which questions our ability to use measurements from near ground sites in cities in some modelling applications. A gradient approach was found to be beneficial to reduce model-data errors.
Atmos. Chem. Phys. Discuss., 15, 33003-33048, doi:10.5194/acpd-15-33003-2015, 2015
Effect of varying experimental conditions on the viscosity of α-pinene derived secondary organic material
Summary: The effect of several experimental parameters on the viscosity of secondary organic material (SOM) generated from the ozonolysis of α-pinene has been studied. The results demonstrate that the viscosity of SOM depends on the particle mass concentration at which SOM is produced, and the relative humidity (RH) at which the SOM is studied. Hence, particle mass concentration and RH should be considered when comparing experimental results for SOM, or extrapolating laboratory results to the atmosphere.
Atmos. Chem. Phys. Discuss., 15, 32967-33002, doi:10.5194/acpd-15-32967-2015, 2015
Atmospheric speciated mercury concentrations on an island between China and Korea: sources and transport pathways
Summary: This study was initiated to identify the sources affecting speciated mercury concentrations measured on the island located between mainland Korea and China. The results from various approaches consistently show that Korean sources are most important for gaseous oxidized form while for other Hg species regional transport were also important. It is also suggested that the secondary formation of particulate Hg becomes more important as the significance of long-range transport increased.
Atmos. Chem. Phys. Discuss., 15, 32931-32966, doi:10.5194/acpd-15-32931-2015, 2015
Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review
Atmos. Chem. Phys. Discuss., 15, 32889-32929, doi:10.5194/acpd-15-32889-2015, 2015
Profiling of aerosol microphysical properties at several EARLINET/AERONET sites during July 2012 ChArMEx/EMEP campaign
Summary: This study provides a detailed overview of the Mediterranean base state regarding aerosol microphysical properties during the ChArMEx/EMEP campaign in July 2012. A detailed analysis on the horizontal, vertical and temporal dimensions is performed using LIRIC, proving the algorithm capability for the automated retrieval of microphysical properties profiles. In addition, a validation of four dust models is included, obtaining a fair good agreement, especially in the location of the aerosol layers.
Atmos. Chem. Phys. Discuss., 15, 32831-32887, doi:10.5194/acpd-15-32831-2015, 2015
Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget
Summary: Blarck carbon aging significantly affects its global distribution and thus climatic effects. This study develops a microphysics-based BC aging scheme in a global model, which substantially improves model simulations of BC. The microphysical scheme shows very fast aging over source regions and much slower aging in remote regions. The microphysical aging significantly reduces global BC burden and lifetime, showing important implications for the estimate of BC radiative effects.
Atmos. Chem. Phys. Discuss., 15, 32779-32829, doi:10.5194/acpd-15-32779-2015, 2015
Comparison of eddy covariance and modified Bowen ratio methods for measuring gas fluxes and implications for measuring fluxes of persistent organic pollutants
Summary: Our article confronts the question of how to accurately measure fluxes of volatile chemicals between the earth's surface and the atmosphere when the possibility of using high frequency analyzers such as with eddy covariance techniques, is nonexistent. By sub-sampling and averaging publically available data from FLUXNET and applying the modified Bowen ratio method (MBR), we have determined that the MBR can work when using prolonged sampling times and single average estimates of eddy diffusivity.
Atmos. Chem. Phys. Discuss., 15, 32759-32777, doi:10.5194/acpd-15-32759-2015, 2015
Temporal consistency of lidar observables during aerosol transport events in the framework of the ChArMEx/ADRIMED campaign at Menorca Island in June 2013
Summary: We performed synergetic active and passive remote sensing observations at Menorca (Spain), over more than 3 weeks in spring 2013. We characterized the aerosol optical properties and type using a combination of Rayleigh-Mie-Raman lidar and sun-photometer data. Results show a high variability due to changing atmospheric transport regimes and aerosol sources. Such variability significantly influences the radiative balance through the entire atmosphere and then the climate of the Mediterranean area.
Atmos. Chem. Phys. Discuss., 15, 32723-32757, doi:10.5194/acpd-15-32723-2015, 2015
A numerical study of back-building process in a quasi-stationary rainband with extreme rainfall over northern Taiwan during 11–12 June 2012
Summary: In this study, the back-building process of a quasi-stationary convective line with extreme rainfall is investigated using a cloud model. At the initiation stage of new cells, thermodynamic processes of near-surface latent heating coupled with adiabatic cooling above along the convergence line, rather than dynamic pressure perturbations, are found to be important. The stronger uplift and cooling aloft provided by old cells made their upstream areas more favorable for new cell development.
Atmos. Chem. Phys. Discuss., 15, 32679-32722, doi:10.5194/acpd-15-32679-2015, 2015
Characteristics of gravity waves generated in a baroclinic instability simulation
Summary: We investigated the characteristics of atmospheric gravity waves that are generated in a baroclinic life cycle simulation using a high-resolution global model. We analysed the spatiotemporal scales, vertical-propagation aspects, and sources of the gravity waves as well as their phase-velocity spectrum. The wave characteristics investigated in this study are the crucial information for parameterizing gravity waves in large-scale models.
Atmos. Chem. Phys. Discuss., 15, 32639-32678, doi:10.5194/acpd-15-32639-2015, 2015
Limitations of passive satellite remote sensing to constrain global cloud condensation nuclei
Summary: Cloud droplets form on suitable nuclei from aerosol emissions. Clouds with more droplets have higher reflectance so that aerosol emissions have a cooling climate effect. Numerous publications of these effects rely on passive satellite remote sensing. In this work I use a self consistent global aerosol model to show that a commonly used assumption (passively retrieved aerosol extinction is a suitable proxy for cloud condensation nuclei) is violated for a significant fraction of the Earth.
Atmos. Chem. Phys. Discuss., 15, 32607-32637, doi:10.5194/acpd-15-32607-2015, 2015
Insights into a historic severe haze weather in Shanghai: synoptic situation, boundary layer and pollutants
Summary: Meteorological conditions, local anthropogenic emissions and aerosol properties played the major roles in this historic winter haze weather formation. Aerosols in size of 600-1400nm are mostly responsible for the impairment of atmospheric visibility. This study was performed by combining many on-line measurement techniques which were calibrated regularly to ensure reliability, and can act as a reference for forecasting and eliminating the occurrences of regional atmospheric pollutions in China.
Atmos. Chem. Phys. Discuss., 15, 32561-32605, doi:10.5194/acpd-15-32561-2015, 2015
Effects of aerosols on solar radiation in the ALADIN-HIRLAM NWP system
Summary: We examined the direct shortwave (SW) effect of aerosols in the ALADIN-HIRLAM numerical weather prediction system using 3 radiation schemes of varying complexity, and observed, climatological and no aerosols. Each scheme accurately simulates the direct SW effect when observed aerosols are used, particularly for heavy pollution scenarios. The purpose of this work was to evaluate the strengths and weaknesses of the model in order to prepare it for eventual use of real-time aerosol data.
Atmos. Chem. Phys. Discuss., 15, 32519-32560, doi:10.5194/acpd-15-32519-2015, 2015
Mapping pan-Arctic methane emissions at high spatial resolution using an adjoint atmospheric transport and inversion method and process-based wetland and lake biogeochemical models
Atmos. Chem. Phys. Discuss., 15, 32469-32518, doi:10.5194/acpd-15-32469-2015, 2015
Rethinking the global secondary organic aerosol (SOA) budget: stronger production, faster removal, shorter lifetime
Summary: The global budget and spatial distribution of secondary organic aerosol (SOA) are highly uncertain in chemistry-climate models, which reflects our inability to characterize all phases of the OA lifecycle. We have performed global model simulations with the newly proposed formation and removal processes (photolysis and heterogeneous chemistry), and shown that SOA is a far more dynamic system, with four times stronger production rates and more efficient removal mechanisms, than assumed in models.
Atmos. Chem. Phys. Discuss., 15, 32413-32468, doi:10.5194/acpd-15-32413-2015, 2015
Modeling of the anthropogenic heat flux and its effect on air quality over the Yangtze River Delta region, China
Summary: The spatial and temporal distribution of anthropogenic heat emissions over the YRD region was developed. These gridded AH emissions were incorporated into the modified WRF/Chem model with the seasonal and diurnal variation. The impacts of AH on meteorology and chemical variables were evaluated. The results show that the anthropogenic heat inputs improved the meteorology and air pollution predictions from WRF/Chem in and around large urban areas.
Atmos. Chem. Phys. Discuss., 15, 32367-32412, doi:10.5194/acpd-15-32367-2015, 2015
Long range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the Western Mediterranean basin
Summary: A multi-lidar analysis conducted in the Mediterranean basin compares the impact of the long range transport of North American biomass burning aerosols with the role of frequently observed Saharan dust outbreaks. This paper provides a detailed analysis of the potential North American aerosol sources, their transport to Europe and the mixing of different aerosol sources, using simulations of a particle dispersion model and lidar measurements of the aerosol optical properties.
Atmos. Chem. Phys. Discuss., 15, 32323-32365, doi:10.5194/acpd-15-32323-2015, 2015
On the climatological probability of the vertical propagation of stationary planetary waves
Summary: We introduce a diagnostic tool to assess in a climatological framework the optimal propagation conditions for stationary planetary waves. Analyzing 50 winters using NCEP/NCAR reanalysis data we demonstrate several problematic features of the refractive index of Rossby waves. We introduced the Rossby waves membership Value Function to calculate the optimal propagation conditions for Rossby waves. Sensitivity of our diagnostic tool to strong and weak vortex regimes are examined.
Atmos. Chem. Phys. Discuss., 15, 32289-32321, doi:10.5194/acpd-15-32289-2015, 2015
Implementation of warm-cloud processes in a source-oriented WRF/Chem model to study the effect of aerosol mixing state on fog formation in the Central Valley of California
Summary: A source-oriented CCN module was implemented into a source-oriented chemistry model to study the effect of aerosol mixing state on fog formation. The fraction of aerosols activating into CCN at a supersaturation of 0.5% in the Central Valley decreased from 94% in the internal mixture model to 80% in the source-oriented model. The internal mixture model predicted greater CCN activation than the source-oriented model due to artificial coating of hydrophobic particles with hygroscopic components.
Atmos. Chem. Phys. Discuss., 15, 32239-32288, doi:10.5194/acpd-15-32239-2015, 2015
Temporal variations in CO2 and CO at Ahmedabad in western India
Summary: About 70% of the man-made CO2 is emitted from the urban areas of the world. Measurements of CO2 and CO are carried out at an urban site Ahmedabad, India. The observed time series are analysed using a global chemistry-transport model, and correlations between the two species. We have identified the roles of land ecosystem, man-made emissions and atmospheric transport on CO2 variations. This study is aimed at drawing effective emission mitigation policy for combating future climate change.
Atmos. Chem. Phys. Discuss., 15, 32185-32238, doi:10.5194/acpd-15-32185-2015, 2015
Single particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium
Summary: Single particle measurements from a soot-particle aerosol mass spectrometer were performed to examine the mixing state of aerosol particles in an air mass influenced by aged biomass burning. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and potassium content and illustrate that high molecular weight organic compounds can be a key contributor to low-volatility BrC observed in biomass burning organic aerosols.
Atmos. Chem. Phys. Discuss., 15, 32157-32183, doi:10.5194/acpd-15-32157-2015, 2015
On the long term impact of emissions from central European cities on regional air-quality
Summary: We introduce a study dealing with the present day air-quality impacts of the urban emissions, focusing on central Europe. Using a coupled regional climate/chemistry model we showed that urban centres impact largely (by up to 10-20%) the regional air quality but the urban air-quality itself is affected by local emission by only 50% and the rural (non-urban) emission play an important role in urban air-pollution. This has to be taken into account in air-quality control measures.
Atmos. Chem. Phys. Discuss., 15, 32101-32155, doi:10.5194/acpd-15-32101-2015, 2015
Summertime nitrate aerosol in the upper troposphere and lower stratosphere over the Tibetan Plateau and the South Asian summer monsoon region
Summary: This is the first study to examine nitrate aerosol in the upper troposphere and lower stratosphere (UTLS) over the Tibetan Plateau (TP) and the South Asian summer monsoon (SASM) region in summer. Nitrate aerosol is simulated to be the most dominant aerosol species in the UTLS over the studied region. The mechanisms for the accumulation of nitrate in the UTLS over the TP/SASM region include vertical transport and the gas-to-aerosol conversion of nitric acid to form nitrate.
Atmos. Chem. Phys. Discuss., 15, 32049-32099, doi:10.5194/acpd-15-32049-2015, 2015
Aqueous-phase mechanism for secondary organic aerosol formation from isoprene: application to the Southeast United States and co-benefit of SO2 emission controls
Summary: Isoprene secondary organic aerosol (SOA) is a large aerosol component in the Southeast US, but models underestimate isoprene SOA mass with traditional schemes based on chamber studies operated under conditions dissimilar from isoprene emitting forests. We find that our mechanism can reproduce isoprene SOA yields (3.3%) and composition in the Southeast US, and so will lead to improved understanding of the impact of isoprene on climate and human health in the Southeast US.
Atmos. Chem. Phys. Discuss., 15, 32005-32047, doi:10.5194/acpd-15-32005-2015, 2015
Ozone changes under solar geoengineering: implications for UV exposure and air quality
Summary: Various forms of solar geoengineering have been proposed, i.e. alternative measures of counteracting man-made climate change if CO2 emissions are not reduced. However, every such countermeasure would have unintended side-effects. Here, we add a novel perspective to this discussion by showing how changes in atmospheric ozone under solar geoengineering could affect air pollution as well as the intensity of UV radiation reaching the surface, with important implications for human health and ecology.
Atmos. Chem. Phys. Discuss., 15, 31973-32004, doi:10.5194/acpd-15-31973-2015, 2015
Significant increase of surface ozone at a regional background station in the eastern China
Summary: In this paper, we find that the daily maximum 8-h O3 in the eastern China has undergone a significant increase during 2003-2015, with a rate of 1.1ppb/yr. The increase of surface ozone was mainly induced by the emission changes and the meteorological factors just played a tiny negative influence. Our result also indicates that VOCs seem to play more important role in the ozone increase than the effect of NO titration.
Atmos. Chem. Phys. Discuss., 15, 31951-31972, doi:10.5194/acpd-15-31951-2015, 2015
Tropospheric Ozone Variability during the East Asian Summer Monsoon as Observed by Satellite (IASI), Aircraft (MOZAIC) and Ground Stations
Summary: The Asian Summer Monsoon has implication on the weather and climate system as well as pollutants concentration over the monsoon regions leading to effects on the global air quality. Our results, combining satellite, aircraft and ground station data, show that the tropospheric ozone, the 3rd most important green house gas, decrease during the period May-August over East and South Asia due to the Monsoon. The magnitude of this drop depends largely on meteorology and geographic location.
Atmos. Chem. Phys. Discuss., 15, 31925-31950, doi:10.5194/acpd-15-31925-2015, 2015
A new source of methyl glyoxal in the aqueous phase
Summary: The study highlights methyl ethyl ketone as a new and unknown source for methyl glyoxal in the aqueous phase that is important for aqueous secondary organic aerosol (aqSOA) formation. Besides 2,3-butanedione (29.5%) and hydroxyacetone (3.0%) methyl glyoxal was formed with a molar yield of 9.5%. According to the detected products a reaction mechanism was developed and evaluated. The comparison of the model and experimental data showed excellent agreements, in particular for methyl glyoxal.
Atmos. Chem. Phys. Discuss., 15, 31891-31924, doi:10.5194/acpd-15-31891-2015, 2015
An approximation for homogeneous freezing temperature of water droplets
Summary: In this work, based on the well-known formulae of classical nucleation theory (CNT), a new approximation for homogeneous freezing temperature of water droplets is derived. Without consideration of time dependence and stochastic nature of the ice nucleation process, the approximation is able to reproduce the dependence of homogeneous freezing temperature on drop size and water activity of aqueous drops observed in a wide range of experimental studies.
Atmos. Chem. Phys. Discuss., 15, 31867-31889, doi:10.5194/acpd-15-31867-2015, 2015
Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic
Summary: We analyze interactions of arctic clouds with pollution plumes that have been transported long distances from mid-latitudes. Constraining for meteorological state, we find that pollution decreases cloud droplet effective radius and increases cloud optical depth. The impact is highest when the atmosphere is particularly humid and/or stable suggesting that aerosol-cloud interactions depend on the Arctic's climate.
Atmos. Chem. Phys. Discuss., 15, 31823-31866, doi:10.5194/acpd-15-31823-2015, 2015
Estimates of free-tropospheric NO2 and HCHO mixing ratios derived from high-altitude mountain MAX-DOAS observations in the mid-latitudes and tropics
Summary: Mixing ratios of NO2 and HCHO in the free troposphere are obtained from MAX-DOAS measurements at two mountain stations in the mid-latitudes and tropics using a modified geometrical approach. The method is applied in the UV wavelength range and thus, allows the detection of HCHO mixing ratios, in addition to NO2. We find that mixing ratios of both species are increased in the tropical free troposphere due to biomass burning.
Atmos. Chem. Phys. Discuss., 15, 31781-31821, doi:10.5194/acpd-15-31781-2015, 2015
On the vertical distribution of smoke in the Amazonian atmosphere during the dry season
Summary: A widespread and persistent smoke layer was observed in the Amazon region during the biomass burning season, spanning a distance of 2200km and a period of 14 days. The larger smoke content was typically found in elevated layers, from 1-1.5km to 4-6km. Measurements have been compared to model predictions, and the latter were able to reproduce the general features of the smoke layer, but with some differences which are analysed and described in the paper.
Atmos. Chem. Phys. Discuss., 15, 31739-31780, doi:10.5194/acpd-15-31739-2015, 2015
Anvil microphysical signatures associated with lightning-produced NOx
Summary: Lightning-produced NOx and ice particles were studied using airborne measurements in thunderstorm anvil clouds during the Deep Convective Clouds and Chemistry experiment (DC3). These data were compared with radar and Lightning Mapping Array (LMA) measurements. A characteristic signature was found in three anvils that relates the occurrence of frozen cloud droplets and aggregates of frozen droplets to the presence of lightning-produced NOx in these storms.
Atmos. Chem. Phys. Discuss., 15, 31705-31737, doi:10.5194/acpd-15-31705-2015, 2015
Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission
Atmos. Chem. Phys. Discuss., 15, 31665-31703, doi:10.5194/acpd-15-31665-2015, 2015
Understanding isoprene photo-oxidation using observations and modelling over a subtropical forest in the Southeast US
Atmos. Chem. Phys. Discuss., 15, 31621-31663, doi:10.5194/acpd-15-31621-2015, 2015
Formaldehyde production from isoprene oxidation across NOx regimes
Summary: This study uses airborne trace gas observations acquired over the Southeast US to examine how both natural (isoprene) and manmade (NOx) emissions influence the production of formaldehyde (HCHO). We find a 3-fold increase in HCHO yield between rural and polluted environments. Furthermore, state-of-the-science chemical mechanisms are generally able to reproduce this behavior. These results add confidence to global hydrocarbon emission inventories constrained by space-borne HCHO observations.
Atmos. Chem. Phys. Discuss., 15, 31587-31620, doi:10.5194/acpd-15-31587-2015, 2015
A microphysics guide to cirrus clouds – Part 1: Cirrus types
Atmos. Chem. Phys. Discuss., 15, 31537-31586, doi:10.5194/acpd-15-31537-2015, 2015
In situ measurements and modeling of reactive trace gases in a small biomass burning plume
Atmos. Chem. Phys. Discuss., 15, 31501-31536, doi:10.5194/acpd-15-31501-2015, 2015
Aerosol optical properties in the southeastern United States in summer – Part 2: Sensitivity of aerosol optical depth to relative humidity and aerosol parameters
Summary: Two research aircraft made dozens of vertical profiles over rural areas in the southeastern U.S. in summer 2013. These measurements show that, in addition to how much pollution was present and how moist the atmosphere was, the size of the pollutant particles affected how much sunlight was reflected back to space. These measurements will help climate modelers determine which characteristics of pollution are important to predict with accuracy.
Atmos. Chem. Phys. Discuss., 15, 31471-31499, doi:10.5194/acpd-15-31471-2015, 2015
Discrimination of water, ice and aerosols by light polarisation in the CLOUD experiment
Summary: Atmospheric processes and mechanisms are often governed by the physico-chemical properties of small particles. Ice and mixed clouds were formed in an expansion chamber at CERN. We show a link between cloud particle properties and their unique light polarisation fingerprints. The classification map presented here allows to discriminate between various particles such as viscous organic aerosol, salt, ice and liquid. We report a viscous to liquid to viscous transition of organic aerosol particles.
Atmos. Chem. Phys. Discuss., 15, 31433-31469, doi:10.5194/acpd-15-31433-2015, 2015
Potential impact of a US climate policy and air quality regulations on future air quality and climate change
Summary: We investigated the impact of US air quality regulations and hypothetical CO2 reduction policy on public health and climate change. We find that the air quality regulations are projected to have a strong beneficial impact on US public health in year 2030 and 2055 but result in a strong positive radiative forcing (RF), ~0.8W m-2 over the US. Under the US CO2 reduction policy, we find air quality co-benefits, but it leads to climate dis-benefits over the US (+0.22W m-2 over the US in 2055).
Atmos. Chem. Phys. Discuss., 15, 31385-31432, doi:10.5194/acpd-15-31385-2015, 2015
Synergistic use of Lagrangian dispersion modelling, satellite and surface remote sensing measurements for the investigation of volcanic plumes: the Mount Etna eruption of 25–27 October 2013
Summary: In this study, we combine SO2/ash plume dispersion modelling, satellite and surface remote sensing observations to study the regional influence of a relatively weak volcanic eruption from Mount Etna (25-27 October 2013) on the optical and micro-physical properties of Mediterranean aerosols. Our results indicate that even relatively weak volcanic eruptions may produce an observable effect on the aerosol properties at the regional scale, with a significant impact on the regional radiative balance
Atmos. Chem. Phys. Discuss., 15, 31335-31383, doi:10.5194/acpd-15-31335-2015, 2015
Diurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Summary: The long-term evolution of HCHO in the remote troposphere is characterized, using a 27-year time series of total column from high-resolution FTIR solar spectra recorded at Jungfraujoch. A parametric model is used to remove the effect of the HCHO diurnal variations for improving the trend determination and the comparison with columns simulated by GEOS-Chem. Sensitivity tests are performed to identify the main drivers of the HCHO seasonal and inter-annual variations, as well as their contribution.
Atmos. Chem. Phys. Discuss., 15, 31287-31333, doi:10.5194/acpd-15-31287-2015, 2015
Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production
Atmos. Chem. Phys. Discuss., 15, 31247-31286, doi:10.5194/acpd-15-31247-2015, 2015
CALIPSO climatological products: evaluation and suggestions from EARLINET
Summary: Satellite-derived products must undergo data evaluation with reference data sets in order to identify any possible reasons of discrepancy or assess their representativity. In that direction, data coming from CALIPSO satellite were compared with observations from the ground. We identified a CALIPSO underestimation that could be linked to an assumption in the satellites’ algorithms. The proposed correction improves the performance and could enhance aerosol modeling.
Atmos. Chem. Phys. Discuss., 15, 31197-31246, doi:10.5194/acpd-15-31197-2015, 2015
Role of methyl group number on SOA formation from aromatic hydrocarbons photooxidation under low NOx conditions
Summary: Substitution of methyl groups onto the aromatic ring determines the SOA formation from the aromatic hydrocarbon precursor. This study links the number of methyl groups on the aromatic ring to SOA formation from aromatic hydrocarbons photooxidation under low NOx conditions (HC/NO>10 ppbC:ppb). Aromatics are determined to be less oxidized per mass/carbon as the number of methyl groups on aromatic ring increase based on SOA yield, SOA chemical composition and SOA physical characteristics.
Atmos. Chem. Phys. Discuss., 15, 31153-31196, doi:10.5194/acpd-15-31153-2015, 2015
Global dimming and urbanization: did stronger negative SSR trends collocate with regions of population growth?
Summary: Systematic measurements of surface solar radiation revealed a worldwide decrease from the 1960s to the mid-1980s. The role of urbanization for this so called global dimming is still under debate. We developed a set of population-data based urbanization indicators and found no correlation between urbanization and global dimming for Europe and Japan, while an urbanization impact can't be precluded for Asia. It is thus called into question whether the global dimming was mainly a local phenomenon.
Atmos. Chem. Phys. Discuss., 15, 31133-31151, doi:10.5194/acpd-15-31133-2015, 2015
A modelling case study of a large-scale cirrus in the tropical tropopause layer
Summary: The Weather Research and Forecast model is used to simulate a large-scale tropical tropopause layer (TTL) cirrus. Validated with satellite observations, the simulation shows that several clouds successively form due to a large-scale uplift initiated by the intrusion of air from the midlatitudes. The simulated cloud field is found as sensitive to the initial condition as it is to the choice of the microphysics parametrisation. The cloud impacts on the radiative and water budgets are estimated.
Atmos. Chem. Phys. Discuss., 15, 31089-31131, doi:10.5194/acpd-15-31089-2015, 2015
Evaluation of size segregation of elemental carbon emission in Europe: influence on atmospheric long-range transportation
Summary: We evaluated the EC point sources in Germany with high resolution simulation by WRF-Chem, and find out that point sources contribute too much EC in the coarse mode aerosol mass. The area emissions in Eastern Europe and Russia also allocate too much EC emission in coarse mode in the EUCAARI EC emission inventory. Because of the shorter life time of coarse mode EC, about 20-40% less EC can be transported to Melpitz from Eastern Europe. Size segregation information is important for EC inventories.
Atmos. Chem. Phys. Discuss., 15, 31053-31087, doi:10.5194/acpd-15-31053-2015, 2015
A Joint data record of tropospheric ozone from Aura-TES and MetOp-IASI
Atmos. Chem. Phys. Discuss., 15, 31025-31051, doi:10.5194/acpd-15-31025-2015, 2015
Long-term trends of surface ozone and its influencing factors at the Mt. Waliguan GAW station, China – Part 1: Overall trends and characteristics
Summary: Long-term characteristics and trends of baseline surface ozone concentration at Waliguan station in western China for the period of 1994 to 2013 were analysed, using a modified Mann-Kendall test and the Hilbert Huang Transform analysis for the trend and periodicity analysis, respectively. Significant increasing trends were detected in all seasons, except for summer. The non-linearity caused by the interannual variation of ozone concentrations is evident, showing a 2-4, 7 and 11 year periodicity.
Atmos. Chem. Phys. Discuss., 15, 30987-31024, doi:10.5194/acpd-15-30987-2015, 2015
Contribution of ship emissions to the concentration and deposition of air pollutants in Europe
Summary: As least regulated source, ship emissions contribute significantly to air pollution. We used an air quality model to determine the effects of international shipping on the annual and seasonal concentrations of ozone, primary and secondary components of PM2.5 and dry and wet deposition of N and S compounds in Europe. The results presented in this paper suggest that evolution of NOx emissions from ships and land-based NH3 emissions will play a significant role in the future European air quality.
Atmos. Chem. Phys. Discuss., 15, 30959-30986, doi:10.5194/acpd-15-30959-2015, 2015
Atmospheric methane evolution the last 40 years
Atmos. Chem. Phys. Discuss., 15, 30895-30957, doi:10.5194/acpd-15-30895-2015, 2015
PCBs in the Arctic atmosphere: determining important driving forces using a global atmospheric transport model
Summary: We present a new global model to simulate the atmospheric transport of toxic contaminants (PCBs). We evaluate the model against PCB observations in the northern hemisphere mid-latitude and Arctic atmosphere. We then use the model to calculate global budgets of PCBs and to examine the influence of climate- and emissions-driven processes on Arctic atmospheric concentrations. We find that processes occurring outside the Arctic have a greater influence on Arctic PCBs than those occurring within.
Atmos. Chem. Phys. Discuss., 15, 30857-30894, doi:10.5194/acpd-15-30857-2015, 2015
Comparison of VLT/X-shooter OH and O2 rotational temperatures with consideration of TIMED/SABER emission and temperature profiles
Summary: We compare temperatures derived from simultaneous observations of 25 OH and two O2 mesospheric airglow bands taken with the X-shooter spectrograph at the Very Large Telescope in Chile. Considering emission and temperature profile data from the radiometer SABER on the TIMED satellite, we find significant time-dependent non-thermal contributions to the OH-based temperatures, especially for bands originating from high vibrational levels. Many studies of the mesopause region are affected.
Atmos. Chem. Phys. Discuss., 15, 30793-30856, doi:10.5194/acpd-15-30793-2015, 2015
Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the Eastern Caribbean Sea
Summary: We have investigated the cloud condensation nuclei (CCN) properties in the marine boundary layer of the Eastern Caribbean during the dust season. Little is known about the CCN influencing cloud optical properties in that region. High mass concentrations of mineral dust were observed, but the number concentrations of mineral dust and sea salt were not high enough to influence CCN properties, and the CCN were likely to be dominated by a mixture of sulfates and organic species.
Atmos. Chem. Phys. Discuss., 15, 30757-30791, doi:10.5194/acpd-15-30757-2015, 2015
Atmospheric inversion for cost effective quantification of city CO2 emissions
Summary: This paper advances atmospheric inversion of city CO2 emissions as follows: 1) Illustrate how inversion methodology can be tailored to deal with very large urban networks of sensors measuring CO2 concentrations; 2) Demonstrate that atmospheric inversion could be a relevant tool of Monitoring, Reporting and Verification (MRV) of city CO2 emissions; 3) Clarify the theoretical potential of inversion for reducing uncertainties in the estimates of citywide total and sectoral CO2 emissions.
Atmos. Chem. Phys. Discuss., 15, 30693-30756, doi:10.5194/acpd-15-30693-2015, 2015
Drivers of changes in stratospheric and tropospheric ozone between year 2000 and 2100
Atmos. Chem. Phys. Discuss., 15, 30645-30691, doi:10.5194/acpd-15-30645-2015, 2015
Oxidative potential of ambient water-soluble PM2.5 measured by Dithiothreitol (DTT) and Ascorbic Acid (AA) assays in the southeastern United States: contrasts in sources and health associations
Summary: Dithiothreitol (DTT) and Ascorbic Acid (AA) assay measures of water-soluble PM2.5 oxidative potential (OP) are compared in terms of spatiotemporal trends, chemical selectivity, sources, and health impacts based on an epidemiological study with backcast estimated OP. Both assays point to metals from brake/tire wear, but only the DTT assay also identifies organics from combustion. DTT is associated with emergency department visits for asthma/wheeze and congestive heart failure, whereas AA is not.
Atmos. Chem. Phys. Discuss., 15, 30609-30644, doi:10.5194/acpd-15-30609-2015, 2015
Summertime ozone formation in Xi'an and surrounding areas, China
Atmos. Chem. Phys. Discuss., 15, 30563-30608, doi:10.5194/acpd-15-30563-2015, 2015
Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds
Atmos. Chem. Phys. Discuss., 15, 30511-30561, doi:10.5194/acpd-15-30511-2015, 2015
Precipitation regime and stable oxygen isotopes at Dome C, East Antarctica – a comparison of two extreme years 2009 and 2010
Summary: Striking difference in the atmospheric flow and thus weather conditions in 2009 and 2010 at the Antarctic deep ice core drilling site Dome C were investigated using a mesoscale atmospheric model and precipitation measurements, including stable isotope ratios of the precipitation samples. Stable isotope ratios are commonly used to derive paleotemperatures and are strongly influenced by the prevailing atmospheric flow regime, namely a strong zonal flow or a highly meriodional flow.
Atmos. Chem. Phys. Discuss., 15, 30473-30509, doi:10.5194/acpd-15-30473-2015, 2015
In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor
Summary: Ambient pine forest air was oxidized by OH radicals in a PAM oxidation flow reactor during the BEACHON-RoMBAS campaign to study secondary organic aerosol formation. Approximately 6 times more secondary organic aerosol was formed in the reactor than could be explained by the volatile organic gases (VOCs) measured in ambient air. The organic aerosol formation could be explained by including an SOA yield from typically unmeasured semi- and intermediate-volatility organic gases (S/IVOCs).
Atmos. Chem. Phys. Discuss., 15, 30409-30471, doi:10.5194/acpd-15-30409-2015, 2015
Semi-annual oscillation (SAO) of the nighttime ionospheric D-region as detected through ground-based VLF receivers
Summary: We report for the first time that the semi-annual oscillation (SAO) is one of the dominant oscillations in the nighttime lower ionosphere, using ground-based measurements of VLF signals reflected off the lower part of the ionosphere. We conclude that the origins of this oscillation are oscillatory changes of the D-region's electrical characteristics, driven by NOx transport from the lower thermosphere. This oscillation should be considered in lower ionospheric and VLF wave propagation models.
Atmos. Chem. Phys. Discuss., 15, 30383-30407, doi:10.5194/acpd-15-30383-2015, 2015
Theoretical analysis of mixing in liquid clouds – Part 3: Inhomogeneous mixing
Summary: An idealized diffusion-evaporation model of time-dependent mixing between cloud and non-cloud volumes is analyzed. It is shown that the evolution of microphysical variables and the final equilibrium stage are unambiguously determined by two non-dimensional parameters. Delimitation between the types of mixing on the plane of these parameters is carried out. The definitions of homogeneous and inhomogeneous mixings are reconsidered and clarified. Results are compared with the classical concept.
Atmos. Chem. Phys. Discuss., 15, 30321-30381, doi:10.5194/acpd-15-30321-2015, 2015
Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing
Summary: The evolution of monodisperse and polydisperse droplet size distributions (DSDs) during homogeneous mixing is analyzed. It is shown that the classic conceptual scheme, according to which homogeneous mixing leads to a decrease in the droplet mass under constant droplet concentration, is valid only in cases of initially very narrow DSDs. In cases of wide DSDs a decrease of both mass and concentration take place such that the characteristic droplet sizes remain nearly constant.
Atmos. Chem. Phys. Discuss., 15, 30269-30320, doi:10.5194/acpd-15-30269-2015, 2015
Theoretical study of mixing in liquid clouds – Part 1: Classical concept
Summary: Relationships between basic microphysical parameters are studied within the framework of homogeneous and extreme inhomogeneous mixing. Analytical expressions and numerical simulations of relationships between droplet concentration, extinction coefficient, liquid water content, and mean volume droplet size are presented. The obtained relationships between moments are used to identify type of mixing for in-situ observations obtained in convective clouds.
Atmos. Chem. Phys. Discuss., 15, 30211-30267, doi:10.5194/acpd-15-30211-2015, 2015
Introduction: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5)
Atmos. Chem. Phys. Discuss., 15, 30175-30210, doi:10.5194/acpd-15-30175-2015, 2015
New insights into PM2.5 chemical composition and sources in two major cities in China during extreme haze events using aerosol mass spectrometry
Summary: This work represents the first online chemical characterization of the PM2.5 using a high resolution time-of flight aerosol mass spectrometer during extreme haze events China. The application of novel source apportionment techniques allowed for an improved identification and quantification of the sources of organic aerosols. The main sources and processes driving the extreme haze events are assessed.
Atmos. Chem. Phys. Discuss., 15, 30127-30174, doi:10.5194/acpd-15-30127-2015, 2015
Simulating secondary organic aerosol in a regional air quality model using the statistical oxidation model – Part 2: Assessing the influence of vapor wall losses
Summary: Losses of vapors to walls of chambers can negatively bias SOA formation measurements, consequently leading to low predicted SOA concentrations in air quality models. Here, we show that accounting for such vapor losses leads to substantial increases in the predicted amount of SOA formed from VOCs and to notable increases in the O:C atomic ratio in two US regions. Comparison with a variety of observational data suggests generally improved model performance when vapor wall losses are accounted for.
Atmos. Chem. Phys. Discuss., 15, 30081-30126, doi:10.5194/acpd-15-30081-2015, 2015
Climatic impacts of stratospheric geoengineering with sulfate, black carbon and titania injection
Summary: In this paper we assess the potential climatic impacts of geoengineering with sulfate, black carbon and titania injection strategies. We find that black carbon injection results in severe stratospheric warming and precipitation impacts, and therefore black carbon is unsuitable for geoengineering purposes. As the injection rates for titania are close to those for sulfate, there appears little benefit of using titania when compared to injection of sulfur dioxide.
Atmos. Chem. Phys. Discuss., 15, 30043-30079, doi:10.5194/acpd-15-30043-2015, 2015
Hydroxyl radicals from secondary organic aerosol decomposition in water
Summary: Here we provide experimental evidence that SOA form substantial amounts of OH radicals upon interaction with liquid water and iron. Our measurements and model results imply that the chemical reactivity of SOA in the atmosphere, particularly in clouds, can be faster than previously thought. Inhalation and deposition of SOA particles in the human respiratory tract may lead to a substantial release of OH radicals in vivo, causing oxidative stress and adverse aerosol health effects.
Atmos. Chem. Phys. Discuss., 15, 30017-30042, doi:10.5194/acpd-15-30017-2015, 2015
Ammonia in the summertime Arctic marine boundary layer: sources, sinks and implications
Summary: Air near the surface in the summertime Arctic is extremely clean and typically has very low concentrations of both gases and particles. However, atmospheric measurements taken throughout the Canadian Arctic in the summer of 2014 revealed higher-than-expected amounts of gaseous ammonia. It is likely the majority of this ammonia is coming from migratory seabird colonies throughout the Arctic. Seabird guano (dung) releases ammonia which could impact climate and sensitive Arctic ecosystems.
Atmos. Chem. Phys. Discuss., 15, 29973-30016, doi:10.5194/acpd-15-29973-2015, 2015
Kinematic and diabatic vertical velocity climatologies from a chemistry climate model
Atmos. Chem. Phys. Discuss., 15, 29939-29971, doi:10.5194/acpd-15-29939-2015, 2015
Carbon monoxide climatology derived from the trajectory mapping of global MOZAIC-IAGOS data
Summary: A new 3D gridded climatology of CO has been developed by trajectory mapping of global MOZAIC-IAGOS in situ aircraft measurements. The dataset is archived monthly from 2001-2012 on a grid of 5×5deg×1 km altitude. The dataset facilitates comparison of different years and seasons and offers insight into the global variation and trends of CO. Major CO sources are clearly visible. The dataset can be used as an a priori data for satellite retrieval and for air quality model validation & initialization
Atmos. Chem. Phys. Discuss., 15, 29871-29937, doi:10.5194/acpd-15-29871-2015, 2015
Turbulence Kinetic Energy budget during the afternoon transition – Part 2: A simple TKE model
Summary: A new simple model for turbulence kinetic energy (TKE) and its budget is presented for sheared convective atmospheric boundary layer. It is used to study effects of buoyancy and shear on TKE evolution during the afternoon transition, especially near the surface. We find a region of weak turbulence during unstable afternoon conditions below the inversion top which we refer to as a ‘pre-residual layer’ .
Atmos. Chem. Phys. Discuss., 15, 29807-29869, doi:10.5194/acpd-15-29807-2015, 2015
Turbulence Kinetic Energy budget during the afternoon transition – Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days
Summary: The evolution of near surface turbulence kinetic energy (TKE) and its budget in the afternoon transition has been studied based on field measurements. The study shows that TKE transport is an important budget term that needs to be taken into account in modeling of TKE. A non-local parametrization of dissipation using a TKE length scale model which takes into account of boundary layer depth also gave improved results compared to a local parametrization
Atmos. Chem. Phys. Discuss., 15, 29747-29805, doi:10.5194/acpd-15-29747-2015, 2015
Sensitivity of modeled atmospheric nitrogen species to variations in sea salt emissions in the North and Baltic Sea regions
Summary: The impact of sea salt on nitrate, ammonium, and sulfate in the North and Baltic Sea region is assessed. Sea salt has a low effect on nitrate concentrations and does not improve them. The region’s air is rich in ammonia which neutralizes nitric acid and enables nitrate formation. In the absence of ammonia, hydrochloric acid would evaporate from salt particles to neutralize particle water pH. In that situation, prevailing in some other studies, sea salt considerably impacted nitrate.
Atmos. Chem. Phys. Discuss., 15, 29705-29745, doi:10.5194/acpd-15-29705-2015, 2015
Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation
Summary: The chemical evolution of SOA formed during aqueous reactions of phenolic compounds is investigated. Based on the bulk and molecular results, we found that phenolic SOA evolves dynamically during photochemical aging, with different reaction mechanisms (oligomerization, fragmentation, and functionalization) leading to different generations of products that span an enormous range in volatilities and a large range in oxidation state and composition.
Atmos. Chem. Phys. Discuss., 15, 29673-29704, doi:10.5194/acpd-15-29673-2015, 2015
The immersion freezing behavior of mineral dust particles mixed with biological substances
Atmos. Chem. Phys. Discuss., 15, 29639-29671, doi:10.5194/acpd-15-29639-2015, 2015
Toward consistency between bottom-up CO2 emissions trends and top-down atmospheric measurements in the Los Angeles megacity
Summary: Combining 14C and 13C data from the Los Angeles, CA megacity with background data allows source attribution of CO2 emissions among biosphere, natural gas, and gasoline. The 8-year record of CO2 emissions from fossil fuel burning is consistent with "The Great Recession" of 2008-2010. The long-term trend and source attribution are consistent with government inventories. Seasonal patterns agree with the high-resolution Hestia-LA emission data product, when seasonal wind directions are considered.
Atmos. Chem. Phys. Discuss., 15, 29591-29638, doi:10.5194/acpd-15-29591-2015, 2015
Characterization of polar organosulfates in secondary organic aerosol from the unsaturated aldehydes 2-E-pentenal, 2-E-hexenal, and 3-Z-hexenal
Summary: Evidence is provided that the green leaf aldehydes 2-E-pentenal, 2-E-hexenal and 3-Z-hexenal are precursors for secondary organic aerosol, namely, organosulfates with MWs 230, 214, and 170. The structures were elucidated with liquid chromatography/(-)electrospray ionization mass spectrometry (MS), involving accurate mass measurements and ion trap MS. It is shown that the MW 214 isomer with the sulfate group at the C-2 position is unstable and decarboxylates to a MW 170 organosulfate.
Atmos. Chem. Phys. Discuss., 15, 29555-29590, doi:10.5194/acpd-15-29555-2015, 2015
Particle water and pH in the Eastern Mediterranean: sources variability and implications for nutrients availability
Summary: Atmospheric aerosols and relevant parameters were measured in the eastern Mediterranean during summer and fall 2012. Submicron aerosol was by up to 33% of aerosol water from which 27.5% was due to the organic compounds present in aerosol. Using these data the pH of the submicron aerosols were calculated to be highly acidic varying from 0.5 to 2.8 and independently of air masses origin. Such pH values could increase nutrient availability and thus sea water productivity of the Mediterranean Sea.
Atmos. Chem. Phys. Discuss., 15, 29523-29554, doi:10.5194/acpd-15-29523-2015, 2015
Upper-tropospheric humidity changes under constant relative humidity
Summary: Upper Tropospheric Humidity (UTH) is a weighted mean of the relative humidity (RH) in the upper troposphere. It can change due to climate change even when the relative humidity would stay unchanged because the weighting functions will alter. We show that changes of UTH expected during 30 years of tropospheric warming are typically less than 1% in magnitude and mostly negative. Larger positive changes of UTH (as found in an analysis of 30 years of satellite data) point thus to an increase of RH.
Atmos. Chem. Phys. Discuss., 15, 29497-29521, doi:10.5194/acpd-15-29497-2015, 2015
Resolving ice cloud optical thickness biases between CALIOP and MODIS using infrared retrievals
Atmos. Chem. Phys. Discuss., 15, 29455-29495, doi:10.5194/acpd-15-29455-2015, 2015
Exploring the variability of aerosol particle composition in the Arctic: a study from the springtime ACCACIA campaign
Atmos. Chem. Phys. Discuss., 15, 29403-29453, doi:10.5194/acpd-15-29403-2015, 2015
Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime
Summary: A recent field campaign (CARDEX) in the northern Indian Ocean concurrently measured cloud and aerosol properties, and atmospheric structure and dynamics from a ground-based observatory and Unmanned Aerial Vehicles (UAVs). These new measurements show a correlation between highly-polluted conditions and increased cloud water content, concurrent with higher atmospheric temperature and humidity. Such correlations may be of interest in future studies of the effects of pollution on cloud properties.
Atmos. Chem. Phys. Discuss., 15, 29347-29402, doi:10.5194/acpd-15-29347-2015, 2015
Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States
Summary: Land use and land cover changes driven by anthropogenic activities or natural causes (e.g. forestry management, agriculture, wildfires) can impact climate and air quality in many complex ways. Using a state-of-the-art chemistry model, we investigate how tree mortality in the US due to insect infestation and disease outbreak may impact atmospheric composition. We find that the concentrations of major smog constituents can be altered due to changing background emissions and loss processes.
Atmos. Chem. Phys. Discuss., 15, 29303-29345, doi:10.5194/acpd-15-29303-2015, 2015
The incorporation of an organic soil layer in the Noah-MP Land Surface Model and its evaluation over a Boreal Aspen Forest
Summary: This work is for the first time that Noah-MP is used to investigate impact of parameterizing organic soil at a boreal forest site. Including an organic-soil parameterization - Significantly improved performance of the model in surface energy and hydrology simulation due to the lower thermal conductivity and greater porosity of the organic soil. - Substantially modified the partition between direct soil evaporation and vegetation transpiration in the simulation.
Atmos. Chem. Phys. Discuss., 15, 29265-29302, doi:10.5194/acpd-15-29265-2015, 2015
Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy
Summary: Volatile organic compounds (VOCs) represent a large source of reactive carbon into the atmosphere and hence have a significant impact on air quality. It is therefore important that we can accurately quantify their emission. In this paper we use three methods to determine the fluxes of reactive VOCs from a woodland canopy. We show that two different canopy scale measurement methods give good agreement whereas estimates based on leaf level based emission underestimate isoprene fluxes.
Atmos. Chem. Phys. Discuss., 15, 29213-29264, doi:10.5194/acpd-15-29213-2015, 2015
Airborne observation of mixing across the entrainment zone during PARADE 2011
Summary: We presented airborne measurements of CO2 and O3 across the entrainment zone over a semi-remote environment in southwestern Germany in late summer 2011 . For the first time CO2 and O3 were used as tracer to identify mixing through this transport barrier. We demonstrated that the tracer-tracer correlation of CO2 and O3 is a powerful tool to identify entrainment and mixing.
Atmos. Chem. Phys. Discuss., 15, 29171-29212, doi:10.5194/acpd-15-29171-2015, 2015
Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea-ice
Summary: This work represents the first observational study of atmospheric sub-micron aerosols in the East Antarctic pack ice region and found spring-time aerosol concentrations were higher than any observed elsewhere in the Antarctic and Southern Ocean region. Further analysis suggested these aerosols formed in the Antarctic free troposphere. Their subsequent transport to the Southern Ocean, as suggest by trajectory analyses, could help to reduce the discrepancy in the radiative budget in the region.
Atmos. Chem. Phys. Discuss., 15, 29125-29170, doi:10.5194/acpd-15-29125-2015, 2015
Processes controlling the seasonal cycle of Arctic aerosol number and size distributions
Atmos. Chem. Phys. Discuss., 15, 29079-29124, doi:10.5194/acpd-15-29079-2015, 2015
Environmental controls on pyrocumulus and pyrocumulonimbus initiation and development
Summary: Lidar and radiosonde observations obtained during large wildfires shed new light on the initiation and development of pyrocumulus and pyrocumulonimbus clouds. Lidar data show, for example, that the condensation level in these towering convective plumes can significantly exceed the condensation level in the ambient environment. Above the condensation level the subsequent cloud development is shown to be sensitive to shear and dry air entrainment, which limit vertical growth.
Atmos. Chem. Phys. Discuss., 15, 29047-29077, doi:10.5194/acpd-15-29047-2015, 2015
Pre-activation of ice nucleating particles by the pore condensation and freezing mechanism
Summary: We have investigated the enhancement of the ice nucleation ability of well-known and abundant ice nucleating particles like dust grains due to pre-activation. Temporary exposure to a low temperature (228 K) provokes that pores and surface cracks of the particles are filled with ice, which makes them better nuclei for the growth of macroscopic ice crystals at high temperatures (245 – 260 K).
Atmos. Chem. Phys. Discuss., 15, 28999-29046, doi:10.5194/acpd-15-28999-2015, 2015
Properties of young contrails – a parametrisation based on large eddy simulations
Summary: A large comprehensive data set of 3D Large Eddy Simulation (LES) of young contrails has been analysed. Parametrisations of the most important properties of young contrails, namely the ice crystal number and geometric depth, are provided taking into account the effect of many environmental and aircraft parameters. The parametrisation is suited to be incorporated in larger scale models like GCMs.
Atmos. Chem. Phys. Discuss., 15, 28939-28997, doi:10.5194/acpd-15-28939-2015, 2015
Climate modulation of the Tibetan Plateau on haze in China
Summary: We study the climate modulation of Tibetan Plateau (TP) on atmospheric environment in China with three key points: 1) A large-scale "susceptible region" for haze is climatologically identified over central-eastern China (CEC) harbored by the TP. 2) Thermal anomalies of the TP induce the changes in meteorological drivers downstream for frequent haze events in CEC. 3) Implications of the TP for atmospheric environment will be having potential utility for development planning in China.
Atmos. Chem. Phys. Discuss., 15, 28915-28937, doi:10.5194/acpd-15-28915-2015, 2015
Seasonality of isoprenoid emissions from a primary rainforest in central Amazonia
Summary: For a long time, it was thought that tropical rainforests are everygreen forests and the processes involved in these ecosystems remain similar all year long. However, some satellite retrievals have suggested that ecophysiological processes may present seasonal variations mainly due to variation in light and leaf phenology in Amazonia. These in situ measurements are the first showing a seasonal trend of volatile organic compound emissions, correlating with light and leaf phenology in Amazonia.
Atmos. Chem. Phys. Discuss., 15, 28867-28913, doi:10.5194/acpd-15-28867-2015, 2015
Direct measurements of OH and other product yields from the HO2 + CH3C(O)O2 reaction
Summary: OH radicals are important intermediates in the atmosphere and the high concentrations observed in tropical regions are yet to be fully explained. Radical-radical reactions such as the title reaction can contribute to OH formation. This is the most fully comprehensive study of the CH3C(O)O2 + HO2 reaction with direct observation of products in all reaction channels. The implications of the new measurements on OH, PAN and NOx concentrations are considered via global models.
Atmos. Chem. Phys. Discuss., 15, 28815-28866, doi:10.5194/acpd-15-28815-2015, 2015
Dominance of brown carbon in aerosol emissions from burning of boreal peatlands
Summary: Microphysical properties of aerosols emitted from smoldering peat land samples collected from interior Alaska and western Siberia were investigated. Emitted aerosols were brown carbon in nature with very little (negligible) amount of black carbon mixing. They had very strong absorption in the shorter visible wavelengths, characterized by a mean Ångström coefficient of ≈9. The impact of these aerosols on top-of-atmosphere direct radiative forcing is positive over bright surfaces, such as snow.
Atmos. Chem. Phys. Discuss., 15, 28793-28813, doi:10.5194/acpd-15-28793-2015, 2015
Oil and gas impacts on air quality in federal lands in the Bakken region: an overview of the Bakken Air Quality Study and first results
Summary: The Bakken formation contains billions of barrels of oil and gas trapped in rock and shale. Horizontal drilling and hydraulic fracturing methods have allowed for extraction of these resources, leading to exponential growth of oil production in the region. Along with this development has come an increase in associated emissions to the atmosphere. This paper describes a field study (BAQS) aimed at better understanding the impacts of these emissions on air quality in nearby federal lands.
Atmos. Chem. Phys. Discuss., 15, 28749-28792, doi:10.5194/acpd-15-28749-2015, 2015
Interferences in photolytic NO2 measurements: explanation for an apparent missing oxidant?
Summary: The self cleaning capacity of the atmosphere in places like Antarctica can be measured by quantifying very low amounts of combustion products that exist in a well known ratio. When this ratio deviates from 1 it points to the existence of unknown compounds. Several unknown compounds have been theorized to exist but never measured. We have found the method for measuring the ratio of combustion products suffers a bias in remote places, which when taken into account disproves any unknown compounds.
Atmos. Chem. Phys. Discuss., 15, 28699-28747, doi:10.5194/acpd-15-28699-2015, 2015
Secondary formation of nitrated phenols: insights from observations during the Uintah Basin Winter Ozone Study (UBWOS) 2014
Summary: We describe high resolution measurements of nitrated phenols using a time of flight chemical ionization mass spectrometer (ToF-CIMS). Strong diurnal profiles were observed for nitrated phenols, with concentration maxima at night. Box model simulations were able to reproduce the measured nitrated phenols.
Atmos. Chem. Phys. Discuss., 15, 28659-28697, doi:10.5194/acpd-15-28659-2015, 2015
Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling
Summary: Mixed-phase clouds are ubiquitous. Process-level understanding is needed to address the complexity of mixed-phase clouds and to improve their representation in models. This study illustrates steps to identify the impact of a microphysical process (riming) on cloud Doppler radar observations. It suggests that in-situ observations of key ice properties are needed to complement radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations in models.
Atmos. Chem. Phys. Discuss., 15, 28619-28658, doi:10.5194/acpd-15-28619-2015, 2015
Observation of viscosity transition in α-pinene secondary organic aerosol
Atmos. Chem. Phys. Discuss., 15, 28575-28617, doi:10.5194/acpd-15-28575-2015, 2015
Developing and bounding ice particle mass- and area-dimension expressions for use in atmospheric models and remote sensing
Summary: - Ice particle projected area- and mass-dimension expressions are developed and validated. - Uncertainties for power laws derived from these expressions are determined.
Atmos. Chem. Phys. Discuss., 15, 28517-28573, doi:10.5194/acpd-15-28517-2015, 2015
Impact of an improved WRF-urban canopy model on diurnal air temperature simulation over northern Taiwan
Atmos. Chem. Phys. Discuss., 15, 28483-28516, doi:10.5194/acpd-15-28483-2015, 2015
Light absorption of brown carbon aerosol in the PRD region of China
Atmos. Chem. Phys. Discuss., 15, 28453-28482, doi:10.5194/acpd-15-28453-2015, 2015
Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations
Summary: Observed and projected trends in large scale wind speed over the oceans prompt the question: How might marine stratocumulus clouds and their radiative properties respond to future changes in large scale wind speed? We present an investigation of the dynamical response of marine stratocumulus clouds to different wind speeds. We find that higher wind speed leads to faster boundary layer growth and stronger entrainment, and changes cloud radiative properties.
Atmos. Chem. Phys. Discuss., 15, 28395-28452, doi:10.5194/acpd-15-28395-2015, 2015
Using proxies to explore ensemble uncertainty in climate impact studies: the example of air pollution
Summary: Because of its sensitivity to unfavorable weather patterns, air pollution is sensitive to climate change. Its impact is typically assessed using deterministic chemistry-transport models forced by an ensemble of climate projection. Because of the high computational cost of such initiative, elaborated techniques are required to optimize the exploration of ensemble of future projections. We develop such a technique, which also allows quantifying uncertainties in climate and air quality projections.
Atmos. Chem. Phys. Discuss., 15, 28361-28393, doi:10.5194/acpd-15-28361-2015, 2015
Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US
Atmos. Chem. Phys. Discuss., 15, 28317-28360, doi:10.5194/acpd-15-28317-2015, 2015
Constraining condensed-phase formation kinetics of secondary organic aerosol components from isoprene epoxydiols
Atmos. Chem. Phys. Discuss., 15, 28289-28316, doi:10.5194/acpd-15-28289-2015, 2015
Mixing layer height and the implications for air pollution over Beijing, China
Summary: This is the first paper to validate and characterize mixing layer height and discuss its relationship with air pollution, using a ceilometer in Beijing. The novelty, originality, and importance of this paper are as follows: (1) the applicable conditions of the ceilometer; (2) the variations of mixing layer height; (3) thermal/dynamic structure inside mixing layers with different degrees of pollution; and (4) critical meteorological conditions for the formation of heavy air pollution.
Atmos. Chem. Phys. Discuss., 15, 28249-28288, doi:10.5194/acpd-15-28249-2015, 2015
Tropospheric mercury vertical profiles between 500 and 10 000 m in central Europe
Summary: We show first mercury profile measurements over Europe since 1996. Beside gaseous mercury species, CO, SO2, NOx, and O3 was measured from board a research aircraft over four European locations. Compared to the boundary layer, in the free troposphere the concentration of gaseous elemental mercury and gaseous oxidized mercury was lower and higher, respectively. Inside the individual layers no gradient was apparent. The combination with CARIBIC data provides a unique profile from 0.4 to 10.5 km.
Atmos. Chem. Phys. Discuss., 15, 28217-28247, doi:10.5194/acpd-15-28217-2015, 2015
Variational data assimilation for the optimized ozone initial state and the short-time forecasting
Atmos. Chem. Phys. Discuss., 15, 28167-28216, doi:10.5194/acpd-15-28167-2015, 2015
Organic peroxides gas-particle partitioning and rapid heterogeneous decomposition on secondary organic aerosol
Atmos. Chem. Phys. Discuss., 15, 28133-28165, doi:10.5194/acpd-15-28133-2015, 2015
Development of the Ensemble Navy Aerosol Analysis Prediction System (ENAAPS) and its application of the Data Assimilation Research Testbed (DART) in support of aerosol forecasting
Summary: This work tests the use of an ensemble prediction system for aerosol forecasting, including an Ensemble Adjustment Kalman Filter for MODIS AOT assimilation. Key findings include: 1) meteorology and source-perturbed ensembles are needed to capture long-range transport and near-source aerosol events 2) adaptive covariance inflation is recommended for assimilating spatially heterogenous observations and 3) the ensemble system captures sharp gradients relative to a deterministic/variational system.
Atmos. Chem. Phys. Discuss., 15, 28069-28132, doi:10.5194/acpd-15-28069-2015, 2015
A Lagrangian description on the troposphere-to-stratosphere transport changes associated with the stratospheric water drop around the year 2000
Summary: This paper tries to answer the long-lasting question in middle atmosphere science on the mechanism of the sudden drop in stratospheric water vapor around the year 2000, which could have slowed down the global surface warming by about 25%. Our findings suggest a possible role of the eastward expansion of warm water in the tropical Pacific during the northern summer of 2000. The circulation pattern may have been modified due to the interaction of the heating from Pacific Ocean and Tibetan Plateau.
Atmos. Chem. Phys. Discuss., 15, 28037-28068, doi:10.5194/acpd-15-28037-2015, 2015
Substantial secondary organic aerosol formation in a coniferous forest: observations of both day and night time chemistry
Summary: Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region at Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment. In particular, our observations provide insights into the relative importance of different oxidation mechanisms between day and night.
Atmos. Chem. Phys. Discuss., 15, 28005-28035, doi:10.5194/acpd-15-28005-2015, 2015
PollyNET: a global network of automated Raman-polarization lidars for continuous aerosol profiling
Summary: The findings from more than 10 years of global aerosol lidar measurements with Polly systems are summarized. A data base of optical properties for specific aerosol types is given. Furthermore, an automated data retrieval algorithm for continuous lidar observations is presented and discussed by means of a case study of Saharan dust advection in Germany. Finally, a statistics of vertical aerosol profiles at 20 locations worldwide including seasonal variations is presented for the first time.
Atmos. Chem. Phys. Discuss., 15, 27943-28004, doi:10.5194/acpd-15-27943-2015, 2015
Photolysis of frozen iodate salts as a source of active iodine in the polar environment
Summary: Reactive iodine species play a key role in the oxidation capacity of the polar troposphere, although sources and mechanisms are poorly understood. In this paper, the photolysis of frozen iodate salt has been studied, confirming that under near-UV/Vis radiation iodate is photolyzed. Incorporating this result into an Antarctic atmospheric model, we have showed that it could increase the atmospheric IO levels and it could constitute a pathway for the release of active iodine to the polar atmosphere
Atmos. Chem. Phys. Discuss., 15, 27917-27942, doi:10.5194/acpd-15-27917-2015, 2015
Molecular corridors and parameterizations of volatility in the evolution of organic aerosols
Atmos. Chem. Phys. Discuss., 15, 27877-27915, doi:10.5194/acpd-15-27877-2015, 2015
Development of a new methane tracer: kinetic isotope effect of 13CH3D + OH from 278 to 313 K
Summary: We present experimental kinetic isotope effects (KIE) for the OH oxidation of CH3D and 13CH3D and their temperature dependence. Our determination of the 13CH3D+OH KIE is novel and we find no "clumped" isotope effect within the experimental uncertainty.
Atmos. Chem. Phys. Discuss., 15, 27853-27875, doi:10.5194/acpd-15-27853-2015, 2015
A global simulation of brown carbon: implications for photochemistry and direct radiative effect
Summary: We develop a new approach to estimate global emission of primary brown carbon from biomass burning and biofuel use and explicitly simulate brown carbon aerosol that has not been considered in climate and air quality models despite of its importance for solar absorption at UV and short visible wavelengths. Using our best simulation results, we estimate radiative effects of brown carbon aerosol for climate and photochemistry.
Atmos. Chem. Phys. Discuss., 15, 27805-27852, doi:10.5194/acpd-15-27805-2015, 2015
Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis datasets
Summary: We report a comparison of the stratospheric mean-meridional circulation and eddy mixing in the stratospheric Brewer-Dobson circulation (BDC) among the six reanalysis products. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments into these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.
Atmos. Chem. Phys. Discuss., 15, 27749-27803, doi:10.5194/acpd-15-27749-2015, 2015
Mediterranean desert dust outbreaks and their vertical structure based on remote sensing data
Summary: This study presents the intense Mediterranean desert dust outbreaks’ 3D structure, over the period Mar2000–Feb2013. The desert dust (DD) episodes are identified through an objective and dynamic algorithm, which uses satellite retrievals (MODIS, TOMS and OMI) as inputs. The performance of the satellite algorithm is evaluated versus AERONET and PM10 data. The geometrical characteristics of the identified DD episodes are analyzed using the collocated CALIOP profiles as a complementary tool.
Atmos. Chem. Phys. Discuss., 15, 27675-27748, doi:10.5194/acpd-15-27675-2015, 2015
Characterization of total ecosystem scale biogenic VOC exchange at a Mediterranean oak-hornbeam forest
Summary: We present ecosystem exchange fluxes from a mixed oak-hornbeam forest in the Po Valley, Italy. Detectable fluxes were observed for twelve compounds, dominated by isoprene, which comprised over 65% of the total flux emission. Methanol seemed to be deposited to dew, as the deposition happened in the early morning. We estimated that up to 27% of the upward flux of methyl vinyl ketone and methacrolein originated from atmospheric oxidation of isoprene.
Atmos. Chem. Phys. Discuss., 15, 27627-27673, doi:10.5194/acpd-15-27627-2015, 2015
Ozone variability in the troposphere and the stratosphere from the first six years of IASI observations (2008–2013)
Atmos. Chem. Phys. Discuss., 15, 27575-27625, doi:10.5194/acpd-15-27575-2015, 2015
Controlled meteorological (CMET) balloon profiling of the Arctic atmospheric boundary layer around Spitsbergen compared to a mesoscale model
Summary: We present five Controlled Meteorological (CMET) balloon flights in the Arctic. CMETs are a novel type of balloon that can be controlled (via satellite link) to rise or fall in altitude during flight, and can remain in the troposphere up to several days to probe remote regions. We performed automated repeated soundings into the Arctic Boundary Layer during the flight. We compare and interpret the CMET observations (temperature, humidity) with output from a regional atmospheric model.
Atmos. Chem. Phys. Discuss., 15, 27539-27573, doi:10.5194/acpd-15-27539-2015, 2015
First comprehensive modelling study on observed new particle formation at the SORPES station in Nanjing, China
Atmos. Chem. Phys. Discuss., 15, 27501-27538, doi:10.5194/acpd-15-27501-2015, 2015
Aerosol–radiation–cloud interactions in a regional coupled model: the effects of convective parameterisation and resolution
Summary: The response of the Weather Research and Forecasting model with Chemistry to forcings by biomass burning aerosol were investigated in high-resolution nested domains over Brazil. The aerosol-layer was found to have a negative direct effect at the top of atmosphere, but this was largely cancelled by a semi-direct effect which inhibited afternoon cloud formation. The cloud-response to the aerosol was found to be highly sensitive to model resolution and use of convective parameterisation.
Atmos. Chem. Phys. Discuss., 15, 27449-27499, doi:10.5194/acpd-15-27449-2015, 2015
Interpreting the Ultraviolet Aerosol Index observed with the OMI satellite instrument to understand absorption by organic aerosols: implications for atmospheric oxidation and direct radiative effects
Summary: We interpret satellite observations to infer the global absorption properties of brown carbon (BrC) aerosols. We incorporate these BrC absorption properties into a chemical transport model to estimate global direct radiative effects and changes in hydroxyl radical (OH) concentrations. To our knowledge, this is the first time the effect of BrC absorption on atmospheric photochemistry has been considered in a global chemical transport model.
Atmos. Chem. Phys. Discuss., 15, 27405-27447, doi:10.5194/acpd-15-27405-2015, 2015
The impact of observation nudging on simulated meteorology and ozone concentrations during DISCOVER-AQ 2013 Texas campaign
Atmos. Chem. Phys. Discuss., 15, 27357-27404, doi:10.5194/acpd-15-27357-2015, 2015
How skillfully can we simulate drivers of aerosol direct climate forcing at the regional scale?
Atmos. Chem. Phys. Discuss., 15, 27311-27355, doi:10.5194/acpd-15-27311-2015, 2015
Baseline carbon monoxide and ozone in the northeast US over 2001–2010
Summary: Baseline carbon monoxide (CO) and ozone (O3) were studied at seven rural sites in the Northeast U.S. during varying periods over 2001 – 2010. Baseline CO at all sites decreased significantly at a rate between -4.3 – -2.3 ppbv yr-1, while baseline O3 was relatively constant. Interannual and seasonal variations of baseline CO and O3 were related to increasing Asian emissions, NOx emissions reduction in urban areas, global biomass burning emissions, and meteorological conditions.
Atmos. Chem. Phys. Discuss., 15, 27253-27309, doi:10.5194/acpd-15-27253-2015, 2015
Detecting moisture transport pathways to the subtropical North Atlantic free troposphere using paired H2O-δ D in situ measurements
Atmos. Chem. Phys. Discuss., 15, 27219-27251, doi:10.5194/acpd-15-27219-2015, 2015
Atmospheric salt deposition in a tropical mountain rain forest at the eastern Andean slopes of South Ecuador – Pacific or Atlantic origin?
Summary: In this article we have analyzed the atmospheric deposition of salt and its sources in a bio-diverse tropical mountain forest characterized by a very complex terrain in the South of Ecuador. We found that, given the location of the study area in a topographic depression close to the Pacific and to the seasonal west shifts in the atmospheric synoptic circulation, the additional contribution of salt from Pacific sources in part alleviates from salt scarcity seen in other similar ecosystems.
Atmos. Chem. Phys. Discuss., 15, 27177-27218, doi:10.5194/acpd-15-27177-2015, 2015
Future vegetation–climate interactions in Eastern Siberia: an assessment of the competing effects of CO2 and secondary organic aerosols
Summary: We study the potentially contrasting effects of enhanced ecosystem CO2 release in response to warmer temperatures vs. emissions of biogenic volatile organic compounds and their formation of secondary organic aerosol through a combination of measurements and modelling at a remote location in Eastern Siberia. The study aims to highlight the number of potentially opposing processes and complex interactions between vegetation physiology, soil processes and trace-gas exchanges in the climate system.
Atmos. Chem. Phys. Discuss., 15, 27137-27175, doi:10.5194/acpd-15-27137-2015, 2015
On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol
Atmos. Chem. Phys. Discuss., 15, 27087-27136, doi:10.5194/acpd-15-27087-2015, 2015
Mid-21st century air quality at the urban scale under the influence of changed climate and emissions: case studies for Paris and Stockholm
Summary: - Overall climate benefit at both cities and pollutants (-2 to -10% depending on metric). - Over the city of Paris local mitigation of NOx emissions increases future ozone due to titration inhibition. - Climate is the most influential factor for maximum ozone in Paris which is particularly interesting in a health impact perspective. - Over urban areas with major regional contribution (e.g., Stockholm) the bias due to coarse emission inventory may lead to policy misclassification.
Atmos. Chem. Phys. Discuss., 15, 27041-27085, doi:10.5194/acpd-15-27041-2015, 2015
Evaluating the spatio-temporal performance of sky imager based solar irradiance analysis and forecasts
Summary: We performed an irradiance forecast experiment based on analysis of hemispheric sky images and evaluated results on a large dataset of 99 pyranometers distributed over 10 x 12 km. We developed a surface irradiance retrieval from cloud information derived from the images. Very high-resolution forecasts were processed up to 25 minutes. A main finding is that forecast skill is enhanced in complex cloud conditions leading to high variability in surface irradiance.
Atmos. Chem. Phys. Discuss., 15, 26997-27039, doi:10.5194/acpd-15-26997-2015, 2015
High-resolution ammonia emissions inventories in China from 1980–2012
Summary: The multi-year (1980–2012) comprehensive ammonia emissions inventories were compiled for China on 1km × 1km grid. Various realistic parameters (ambient temperature, wind speed, soil acidity, synthetic fertilizer types, etc.) were considered in these inventories to synthetically refine the emission factors of ammonia volatilization according to local agricultural practice. This paper shows the interannual trend and spatial distribution of ammonia emissions in details over recent decades.
Atmos. Chem. Phys. Discuss., 15, 26959-26995, doi:10.5194/acpd-15-26959-2015, 2015
Decadal-scale relationship between measurements of aerosols, land-use change, and fire over Southeast Asia
Summary: Analyzing 13 years of land cover, fire, precipitation, and aerosol measurements over Southeast Asia leads to definitive patterns inter and intra-annually. Both anthropogenic and climate influences are essential to match the patterns. While fires occur annually, there is much variance in the onset, duration, and intensity, in time, although the sources are unique and distinct in space. Our model robustly represents AOD in terms of timing and intensity, even when fires are obscured by cloud-cover.
Atmos. Chem. Phys. Discuss., 15, 26895-26957, doi:10.5194/acpd-15-26895-2015, 2015
Origin of oxidized mercury in the summertime free troposphere over the southeastern US
Summary: We present airborne observations of mercury over the southeastern USA during summer. Higher concentrations of oxidized mercury were observed in clean, dry air masses descending in the subtropical anti-cyclones. We used an atmospheric model to simulate the chemistry and transport of mercury. We found reasonable agreement with the observations when the modeled oxidation of elemental mercury was increased, suggesting fast cycling between elemental and oxidized mercury.
Atmos. Chem. Phys. Discuss., 15, 26839-26893, doi:10.5194/acpd-15-26839-2015, 2015
Understanding sources of organic aerosol during CalNex-2010 using the CMAQ-VBS
Atmos. Chem. Phys. Discuss., 15, 26745-26793, doi:10.5194/acpd-15-26745-2015, 2015
Aura OMI observations of regional SO2 and NO2 pollution changes from 2005 to 2014
Summary: We examine changes in SO2 and NO2 over the world’s most polluted regions during the first decade of Aura OMI observations. Over the eastern US, both NO2 and SO2 levels decreased by 40% and 80%, respectively. OMI confirmed large reductions in SO2 over eastern Europe’s largest coal power plants. The North China Plain has the world’s most severe SO2 pollution, but a decreasing trend been observed since 2011, with a 50% reduction in 2012-2014. India’s SO2 and NO2 levels are growing at a fast pace. S
Atmos. Chem. Phys. Discuss., 15, 26555-26607, doi:10.5194/acpd-15-26555-2015, 2015
Dicarboxylic acids, oxoacids, benzoic acid, α-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes
Atmos. Chem. Phys. Discuss., 15, 26509-26554, doi:10.5194/acpd-15-26509-2015, 2015
Can we use modelling methodologies to assess airborne benzo[a]pyrene from biomonitors? A comprehensive evaluation approach
Summary: This original interpretation and application of environmental databases combines biomonitoring and atmospheric field data and state-of-the-art chemistry transport models to study one of the most carcinogenic atmospheric pollutants, benzo(a)pyrene (BaP). A comparison of ways to estimate air concentrations of BaP from its levels in vegetation is also a strong asset of this study. The whole methodology proposed here is versatile and can easily be applied to other regions and chemicals of interest.
Atmos. Chem. Phys. Discuss., 15, 26481-26507, doi:10.5194/acpd-15-26481-2015, 2015
Meteorological-gaseous influences on seasonal PM2.5 variability in the Klang Valley urban-industrial environment
Summary: This study investigate the PM2.5 variability in the Klang Valley urban-industrial environment. Source apportionment analysis reveal two major contributors of PM2.5 in the study area i.e. secondary inorganic aerosols and biomass burning. The chemical constituents and sources of PM2.5 in this study area were greatly influenced and characterised by meteorological and gaseous parameters which largely varies with season.
Atmos. Chem. Phys. Discuss., 15, 26423-26479, doi:10.5194/acpd-15-26423-2015, 2015
Fossil and non-fossil source contributions to atmospheric carbonaceous aerosols during extreme spring grassland fires in Eastern Europe
Summary: In early spring the Baltic region is frequently affected by high pollution events due to biomass burning in that area. Here we present a comprehensive study to investigate the impact of biomass/grass burning (BB) on the evolution and composition of aerosol in Preila, Lithuania, during springtime open fires.
Atmos. Chem. Phys. Discuss., 15, 26315-26355, doi:10.5194/acpd-15-26315-2015, 2015
Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan
Summary: Detailed understandings of light absorption property of black carbon (BC) particles and its relation to the mixing state and morphology are important. In this study, the enhancement of light absorption of BC due to coating (lensing effect) in a well-aged air mass was observed at an East Asian outflow site in Japan using a photoacoustic spectrometer and its relation with mixing state and morphology of individual particles was examined based on transmission electron microscope analyses.
Atmos. Chem. Phys. Discuss., 15, 25089-25138, doi:10.5194/acpd-15-25089-2015, 2015
Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley
Summary: First deployment of PTR-TOF-MS in South Asia. High acetaldehyde and biogenic isoprene concentrations detected even in winter in the Kathmandu Valley. Isocyanic acid, formamide, acetamide, naphthalene and nitromethane, were detected for the first time in South Asian air. Oxygenated VOCs & isoprene dominated OH reactivity and ozone production potentials (>68% OPP). Mitigation of emissions from biomass co-fired brick kilns' by cleaner technology would improve air quality of the Valley.
Atmos. Chem. Phys. Discuss., 15, 25021-25087, doi:10.5194/acpd-15-25021-2015, 2015
Comparisons of urban and rural PM10−2.5 and PM2.5 mass concentrations and semi-volatile fractions in Northeastern Colorado
Atmos. Chem. Phys. Discuss., 15, 24587-24622, doi:10.5194/acpd-15-24587-2015, 2015
Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models
Atmos. Chem. Phys. Discuss., 15, 24513-24585, doi:10.5194/acpd-15-24513-2015, 2015
Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign
Atmos. Chem. Phys. Discuss., 15, 24041-24083, doi:10.5194/acpd-15-24041-2015, 2015
AIRUSE-LIFE+: a harmonized PM speciation and source apportionment in 5 Southern European cities
Summary: PM10/PM2.5 source apportionment at 5 EU cities (Barcelona, Florence, Milan, Athens and Porto) reveals that vehicle exhaust (excluding nitrate) and non-exhaust contributes 16-32% to PM10 and 15-36% to PM2.5. Secondary PM represents 37-82% of PM2.5. Biomass burning varies from <2 to 24% of PM10, depending on the residential heating fuel. Other sources are local dust (7-19% of PM10), industries (4-11% of PM10, 5-12% of PM2.5), shipping, sea salt and Saharan dust.
Atmos. Chem. Phys. Discuss., 15, 23989-24039, doi:10.5194/acpd-15-23989-2015, 2015
Charging and coagulation of radioactive and nonradioactive particles in the atmosphere
Summary: Three microphysical approaches are proposed to incorporate mutual effects of particle charging and coagulation in predictions of transient charge and size distributions of atmospheric particles, including radioactive aerosols. The three approaches have different levels of complexities and are applicable to various laboratory and field atmospheric studies. Also, these approaches can be easily incorporated into aerosol transport models at different scales to account for particle charging effects.
Atmos. Chem. Phys. Discuss., 15, 23795-23840, doi:10.5194/acpd-15-23795-2015, 2015
Pesticides in the atmosphere: a comparison of gas-particle partitioning and particle size distribution of legacy and current-use pesticides
Summary: We examined gas-particle partitioning and size-fraction specific particle phase distributions for 27 current use pesticides, identifying seasonal and source-related trends, and contrasting with legacy organochlorine pesticides. The timing of pesticide use, seasonal air concentration trends, and particle size distributions were related. This informs our understanding of the atmospheric fate and transport of current use pesticides.
Atmos. Chem. Phys. Discuss., 15, 23651-23681, doi:10.5194/acpd-15-23651-2015, 2015
Emissions factors for gaseous and particulate pollutants from offshore diesel engine vessels in China
Summary: In this study, on-board test of three offshore vessels in China have been carried out for the first time. Emission factors for gaseous species, PM and relevant chemical components (OC, EC, metal elements and water soluble ions) in different operating modes are given which means a lot for estimating contribution of ships to atmosphere and calculating emission inventories of ships. Besides, impacts of engine speed on NOx emission factors also have been discussed for the first time.
Atmos. Chem. Phys. Discuss., 15, 23507-23541, doi:10.5194/acpd-15-23507-2015, 2015
Observation of a tidal effect on the Polar Jet Stream
Summary: This paper demonstrates for the first time a direct link between atmospheric tides and the Polar Jet Stream flow. The authors have identified an anti-correlation of the Arctic Oscillation with the horizontal (‘tractional’) tidal force acting at high latitudes, particularly during winter months. The tractional force varies strongly during the lunar month and with the 18.6 year precession cycle of the lunar orbit. Changes in Jet Stream flow have a large effect on winter weather.
Atmos. Chem. Phys. Discuss., 15, 22701-22713, doi:10.5194/acpd-15-22701-2015, 2015
Influence of biomass burning on CCN number and hygroscopicity during summertime in the eastern Mediterranean
Summary: BBOA from long-range transport exhibits increased CCN concentrations for particles larger than 100 nm. At the same time the hygroscopicity parameter decreased for all particle sizes, as sub-100 nm particles appear to be richer in less hygroscopic, organic material while larger particles become less hygroscopic due to condensation of less hygroscopic gaseous compounds. Finally, atmospheric processing of freshly-emitted BBOA to more oxidized organic aerosol can result in a 2-fold increase of κ_org
Atmos. Chem. Phys. Discuss., 15, 21539-21582, doi:10.5194/acpd-15-21539-2015, 2015
Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition
Atmos. Chem. Phys. Discuss., 15, 19367-19403, doi:10.5194/acpd-15-19367-2015, 2015
PLAM – a meteorological pollution index for air quality and its applications in fog-haze forecasts in north China
Summary: On the basis of parameterized meteorological condition principle method, this paper discussed the mutual impact of emission and meteorological condition, and studied the structure and function of meteorological conditions PLAM index in quantitatively identifying, diagnosing and forecasting large scope of fog-haze weather. A new model of PLAM/h – the meteorological pollution Index for air quality has been developed and used in NRT air quality forecasts, by considering both meteorology and polluta
Atmos. Chem. Phys. Discuss., 15, 9077-9106, doi:10.5194/acpd-15-9077-2015, 2015