Organic material found in ambient aerosol is mostly formed through the oxidation of gaseous precursors. It is semi-volatile under atmospheric conditions, and it continuously partitions between the gas and particle phases. At the same time, it is also highly water soluble. We show that wet and especially dry deposition of semi-volatile organic compounds in the gas phase are major indirect removal pathways for the particle phase, and hence need to be accurately accounted for in modeling studies.

(1) NR-PM1 at the HKUST Supersite was highly aged, with a high sulfate content and highly oxygenated organics. (2) Seasonal variation in NR-PM1 concentration was not obvious, but the relative fractions of different species showed strong seasonal dependence. (3) Both NR-PM1 concentrations and the relative fractions showed a strong dependence on air mass origin. (4) Both locally produced and regionally transported organic aerosols contribute to the organic content of PM at this site.

We used an ion mass spectrometer at CERN's CLOUD chamber to investigate the detailed composition of ammonia--sulfuric acid ion clusters (of both polarities) as they initially form and then grow into aerosol particles, at atmospherically relevant conditions. We found that these clusters’ composition is mainly determined by the ratio of the precursor vapors and ranges from ammonia-free clusters to clusters containing > 1 ammonia per sulfuric acid. Acid--base bindings are a key formation mechanism.

Recent research suggests the Antarctic ozone hole has started to shrink due to decreasing ozone-depleting substances. Because it could be questioned how robust these results are, we provide an assessment of uncertainties in both the underlying ozone observational records and the detection-attribution method. Although Antarctic ozone concentrations are definitely increasing slowly, the formal identification of recovery is not yet justified, although this will likely become possible this decade.

We use satellite measurements of O3, CO and NO2 from TES, MOPITT and OMI to quantify O3 precursor emissions for 2006 and their impact on free tropospheric O3 over northeastern Asia. Using the adjoint of GEOS-Chem, we found that Chinese emissions have the largest influence on the free tropospheric O3. The contributions from lightning NOx in summer and India and southeastern Asia emissions in winter are sizable, comparable with Chinese emissions.

This paper uses numerical model simulations to investigate the meteorological characteristics of the 31 January–6 February 2013 cold-air pool (also know as a temperature 'inversion') in the Uintah Basin, Utah, and the resulting high ozone concentrations. A number of factors that influence cold pools and pollutant concentrations in the Uintah Basin are discussed, including snow cover, ice fog, and thermally driven flows.

Simulations from a group of GCMs, forecast models, and regional models are compared with aircraft and ship observations of the marine boundary layer (MBL) in the southeast Pacific region during the VOCALS-REx field campaign of October-November 2008. Gradients of cloud, aerosol, and chemical properties in and above the MBL extending from the Peruvian coast westward along 20 degrees south are compared during the period.

Data collected in the eastern US between 1990 and 2009 at 34 paired dry and wet monitoring sites are examined. A goal is to evaluate the air quality impacts occurring over four 5-year periods between 1990 and 2009 that are associated with concurrent legislatively mandated changes in emissions. Results suggest that legislatively mandated air pollution mitigation strategies have been successful in improving air quality and reducing atmospheric deposition in the eastern US.

This study aims to quantify the effect of severe dust events on radiation fluxes and regional climate characteristics over the Arabian Peninsula. We simulated the storm that occurred from 18 to 20 March 2012 and swept over a remarkably large area affecting the entire Middle East, North-Eastern Africa, Afghanistan, and Pakistan. We estimate that this storm generated over 94 Mt of dust and deposited approximately 1.2 Mt of dust into the Red Sea, bringing nutrients to marine ecosystems.

Glyoxal and methylglyoxal are short-lived organic trace gases and important precursors of secondary organic aerosol. Measurements over oceans are sparse. We present the first in situ glyoxal and methylglyoxal observations over remote temperate oceans, alongside observations of precursor gases. Precursor gases cannot explain observed mixing ratios, highlighting an unknown source. We show a large discrepancy between calculated vertical column densities of glyoxal and those retrieved by satellite.

Atomic oxygen-to-carbon (O:C), hydrogen-to-carbon (H:C), and organic mass-to-organic carbon (OM:OC) ratios of ambient organic aerosol (OA) species provide key constraints for understanding their sources and impacts. Here an improved method for obtaining accurate O:C, H:C, and OM:OC with a widely used aerosol mass spectrometer is developed. These results imply that OA is more oxidized than previously estimated and indicate the need for new chemical mechanisms that simulate ambient oxidation.

Global concentration fields of Mg and Mg+ in the Earth's upper mesosphere and lower thermosphere (70-150km) are presented. These are retrieved from SCIAMACHY/Envisat satellite grating spectrometer measurements in limb viewing geometry between 2008 and 2012. These were compared with WACCM-Mg model results and a large fraction of the available measurement results for these species, and an interpretation of the results is done. The variation of these species during NLC presence is discussed.

The dynamical coupling process between stratosphere and troposphere in the tropical tropopause layer (TTL) during stratospheric sudden warming (SSW) was investigated using simulation data of global non-hydrostatic model (NICAM) that does not use cumulus parameterization. The results suggested that increased stratospheric tropical upwelling associated with SSW induced decreased static stability in TTL, which contributes to increased convective activity and changes in its large-scale organizations

The paper compares methane observations at Cape Grim, Tasmania, with model-simulated methane to better constrain methane fluxes from southeastern Australia. Inventory estimates of anthropogenic methane emissions appear to be supported by observed atmospheric methane. A missing methane source in springtime (October to November) is tentatively attributed to wetland emissions.

The estimation of PM10 from optical measurement of AERONET and MODIS by various empirical models was evaluated for the DRAGON-Asia campaign. The results showed the importance of boundary layer height (BLH) and effective radius (Reff) in estimating PM10. The highest correlation between the estimated and measured values was found to be 0.81 in winter due to the stagnant air mass and low BLH, while the poorest values were 0.54 in spring due to the influence of long-range transport above BLH.

In this study, we simulated the regional transport and evolution of biomass burning occurring in Indonesia during the high fire event in 2006. We studied and quantified the contribution of those fires to the Singapore pollution levels. This high resolution modelling study showed that about half of the particulate pollution events in Singapore were mainly due to fires occurring in Sumatra (Indonesia), while the other half were due to local pollution.

This paper develops two models for the reconstruction of ultraviolet erythemal radiation (UVER). The models are based on shortwave radiation (SW) and sunshine duration measurements. Both models are used to reconstruct UVER irradiation at nine Spanish places from 1950 to 2011. The trends of UVER are calculated at different periods. UVER presented a brightening phenomenon, but not dimming, due to the ozone depletion until the mid-1990s.

Laboratory and field data are used together to develop an empirical relation between the concentrations of mineral dust particles at sizes above 0.5 microns, approximated as a single compositional type, and ice nucleating particle concentrations measured versus temperature. This should be useful in global modeling of ice cloud formation. The utility of laboratory data for parameterization development is reinforced, and the need for careful interpretation of ice nucleation data is emphasized.

High 2013 wintertime O3 pollution events associated with oil/gas production within the Uinta Basin are studied using a 3D model. It's able quantitatively to reproduce these events using emission estimates of O3 precursors based on ambient measurements (top-down approach), but unable to reproduce them using a recent bottom-up emission inventory for the oil/gas industry. The role of various physical and meteorological processes, chemical species and pathways contributing to high O3 are quantified.

This study presents a new, improved parameterisation of the temperature dependence of activity coefficients implemented in the AIOMFAC group-contribution model. The AIOMFAC model with the improved parameterisation is applicable for a large variety of aqueous organic as well as water-free organic solutions of relevance for atmospheric aerosols. The new model parameters were determined based on published and new thermodynamic equilibrium data covering a temperature range from ~190 to 440 K.

In this work, a satellite-based approach to derive the aerosol direct shortwave (SW) radiative effect (ADRE) is studied. The method is based on using coincident satellite observations of SW fluxes and aerosol optical depths (AODs). The key findings of this study are that using normalized values of observed fluxes improves the estimates of ADRE and aerosol-free TOA fluxes as compared to a model. The method was applied over eastern China where the satellite-based mean ADRE of -5Wm-2 was obtained.

The main purpose of this study was to build a framework in the Community Atmosphere Models version 4 and 5 within the Community Earth System Model to simulate dust aerosols as their component minerals. With this framework, we investigate the direct radiative forcing that results from the mineral speciation. We find that adding mineralogy results in a small positive forcing at the top of the atmosphere, while simulations without mineralogy have a small negative forcing.