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Optical properties and aging of light-absorbing secondary organic aerosol

Light absorbing organic aerosols (BrC) absorb sunlight thereby influencing climate; however, understanding of the link between their optical properties and environmental variables remains limited. Our chamber experiment results suggest that variables including NO_xconcentration, RH level, and photolysis time have considerable influence on secondary BrC optical properties. The results contribute to a more accurate characterization of the impacts of aerosols on climate, especially in urban areas.

Screening of cloud microorganisms isolated at the Puy de Dôme (France) station for the production of biosurfactants

A total of 480 microorganisms collected from 39 clouds sampled in France were isolated and identified. This unique collection was screened for biosurfactant production by measuring the surface tension. 41 % of the tested strains were active producers.Pseudomonas, the most frequently detected genus in clouds, was the dominant group for the production of biosurfactants. Further, the potential impact of the production of biosurfactants by cloud microorganisms on atmospheric processes is discussed.

Long-term visibility variation in Athens (1931–2013): a proxy for local and regional atmospheric aerosol loads

Historical time series are unique sources of information for past climate and atmospheric composition change. The 82-year time series of visibility data collected at the National Observatory of Athens (NOA) was an excellent proxy for the long-term evolution of particulate pollution in the eastern Mediterranean, at times when direct aerosol measurements were missing. Evolution of particulate pollution of both local and regional origin is nicely reflected on visibility records of NOA.

Impacts of aviation fuel sulfur content on climate and human health

Using a coupled tropospheric chemistry-aerosol microphysics model this research paper investigates the effect of variations in aviation fuel sulfur content (FSC) on surface PM_2.5 concentrations, increases in aviation-induced premature mortalities, low-level cloud condensation nuclei and radiative effect. When investigating the climatic impact of variations in FSC the ozone direct radiative effect, aerosol direct radiative effect and aerosol cloud albedo effect are quantified.

Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations

HF, the dominant stratospheric fluorine reservoir, results from the atmospheric degradation of anthropogenic species such as CFCs, HCFCs, and HFCs. All are strong greenhouse gases, and CFCs and HCFCs deplete stratospheric ozone. We report the comparison of HF global distributions and trends measured by the ACE-FTS and HALOE satellite instruments with the output of SLIMCAT, a chemical transport model. The global HF trends reveal a slowing down in the rate of increase of HF since the 1990s.

SLIMCAT calculations">Read more

Large gain in air quality compared to an alternative anthropogenic emissions scenario

Three 30-year simulations of past atmospheric composition changes were performed using different anthropogenic emissions of pollutants accounting or not for the applied air quality legislation and accounting for the year–to–year observed climate and natural emissions variability. The actual benefit of applied legislation along with technological advances is higher than what is usually calculated by a simple comparison of today’s atmosphere against a constant anthropogenic emissions simulation.

Growth of nucleation mode particles in the summertime Arctic: a case study

We present a case study focused on an aerosol growth event observed in the Canadian High Arctic during summer. Using measurements of aerosol chemical and physical properties we find evidence for aerosol growth into cloud condensation nuclei-active sizes, through marine-influenced secondary organic aerosol formation. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties, and therefore radiative balance and climate.

Will a perfect model agree with perfect observations? The impact of spatial sampling

We show that evaluating global aerosol model data with observations of very different spatial scales (200 vs. 10 km) can lead to large discrepancies, solely due to different spatial sampling. Strategies for reducing these sampling errors are developed and tested using a set of high-resolution model simulations.

Aura OMI observations of regional SO2 and NO2 pollution changes from 2005 to 2015

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.

OMI observations of regional SO2 and NO2 pollution changes from 2005 to 2015">Read more

Kinetic isotope effects of ¹³CH₃D + OH and ¹³CH₃D + OH from 278 to 313 K

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.

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