Search results for "C1"
showing 10 items of 3475 documents
Sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes
2017
We present a sensitivity study on transatlantic dust transport, a process which has many implications for the atmosphere, the ocean and the climate. We investigate the impact of key processes that control the dust outflow, i.e., the emission flux, convection schemes and the chemical aging of mineral dust, by using the EMAC model following Abdelkader et al. (2015). To characterize the dust outflow over the Atlantic Ocean, we distinguish two geographic zones: (i) dust interactions within the Intertropical Convergence Zone (ITCZ), or the dust–ITCZ interaction zone (DIZ), and (ii) the adjacent dust transport over the Atlantic Ocean (DTA) zone. In the latter zone, the dust loading shows a steep …
Suppression of new particle formation from monoterpene oxidation by NOx
2014
The impact of nitrogen oxides (NOx = NO + NO2) on new particle formation (NPF) and on photochemical ozone production from real plant volatile organic compound (BVOC) emissions was studied in a laboratory setup. At high NOx conditions ([BVOC] / [NOx] x] > 23 ppb) new particle formation was suppressed. Instead, photochemical ozone formation was observed resulting in higher hydroxyl radical (OH) and lower nitrogen monoxide (NO) concentrations. When [NO] was reduced back to levels below 1 ppb by OH reactions, NPF was observed. Adding high amounts of NOx caused NPF to be slowed by orders of magnitude compared to analogous experiments at low NOx conditions ([NOx] ~300 ppt), although OH concentrat…
Particulate trimethylamine in the summertime Canadian high Arctic lower troposphere
2017
Size-resolved and vertical profile measurements of single particle chemical composition (sampling altitude range 50–3000 m) were conducted in July 2014 in the Canadian high Arctic during an aircraft-based measurement campaign (NETCARE 2014). We deployed the single particle laser ablation aerosol mass spectrometer ALABAMA (vacuum aerodynamic diameter range approximately 200–1000 nm) to identify different particle types and their mixing states. On the basis of the single particle analysis, we found that a significant fraction (23 %) of all analyzed particles (in total: 7412) contained trimethylamine (TMA). Two main pieces of evidence suggest that these TMA-containing particles originated from…
The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe
2018
A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust–cloud and dust–radiation interactions of the simulated dust plume. We evaluate model results with ground-based and spaceborne remote sensing measurements of aerosol and cloud properties, as well as the in situ meas…
Sub-micrometer refractory carbonaceous particles in the polar stratosphere
2017
Eleven particle samples collected in the polar stratosphere during SOLVE (SAGE III Ozone loss and validation experiment) from January until March 2000 were characterized in detail by high-resolution transmission and scanning electron microscopy (TEM/SEM) combined with energy-dispersive X-ray microanalysis. A total of 4202 particles (TEM = 3872; SEM = 330) were analyzed from these samples, which were collected mostly inside the polar vortex in the altitude range between 17.3 and 19.9 km. Particles that were volatile in the microscope beams contained ammonium sulfates and hydrogen sulfates and dominated the samples. Some particles with diameters ranging from 20 to 830 nm were refractory i…
Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models
2016
Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available ae…
Variability of aerosol, gaseous pollutants and meteorological characteristics associated with changes in air mass origin at the SW Atlantic coast of …
2012
Measurements of the ambient aerosol were performed at the Southern coast of Spain, within the framework of the DOMINO (<b>D</b>iel <b>O</b>xidant <b>M</b>echanisms <b>I</b>n relation to <b>N</b>itrogen <b>O</b>xides) project. The field campaign took place from 20 November until 9 December 2008 at the atmospheric research station "El Arenosillo" (37°5'47.76" N, 6°44'6.94" W). As the monitoring station is located at the interface between a natural park, industrial cities (Huelva, Seville) and the Atlantic Ocean, a variety of physical and chemical parameters of aerosols and gas phase could be characterized in dependency on…
Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016
2019
Activated chlorine compounds in the polar winter stratosphere drive catalytic cycles that deplete ozone and methane, whose abundances are highly relevant to the evolution of global climate. The present work introduces a novel dataset of in situ measurements of relevant chlorine species in the lowermost Arctic stratosphere from the aircraft mission POLSTRACC–GW-LCYCLE–SALSA during winter 2015/2016. The major stages of chemical evolution of the lower polar vortex are presented in a consistent series of high-resolution mass spectrometric observations of HCl and ClONO2. Simultaneous measurements of CFC-12 are used to derive total inorganic chlorine (Cly) and active chlorine (ClOx). The new data…
Impact of surface and near-surface processes on ice crystal concentrations measured at mountain-top research stations
2017
In situ cloud observations at mountain-top research stations regularly measure ice crystal number concentrations (ICNCs) orders of magnitudes higher than expected from measurements of ice nucleating particle (INP) concentrations. Thus, several studies suggest that mountain-top in situ cloud microphysical measurements are influenced by surface processes, e.g., blowing snow, hoar frost or riming on snow-covered trees, rocks and the snow surface. This limits the relevance of such measurements for the study of microphysical properties and processes in free-floating clouds. This study assesses the impact of surface processes on in situ cloud observations at the Sonnblick Observatory in the Hohen…
Historic records of organic compounds from a high Alpine glacier: influences of biomass burning, anthropogenic emissions, and dust transport
2016
Historic records of α-dicarbonyls (glyoxal, methylglyoxal), carboxylic acids (C6–C12 dicarboxylic acids, pinic acid, p-hydroxybenzoic acid, phthalic acid, 4-methylphthalic acid), and ions (oxalate, formate, calcium) were determined with annual resolution in an ice core from Grenzgletscher in the southern Swiss Alps, covering the time period from 1942 to 1993. Chemical analysis of the organic compounds was conducted using ultra-high-performance liquid chromatography (UHPLC) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) for dicarbonyls and long-chain carboxylic acids and ion chromatography for short-chain carboxylates. Long-term records of the carboxylic acid…