Auflistung nach Autor:in "Schwikowski, Margit"
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Publikation Aerosol climatology at the high‐alpine site Jungfraujoch, Switzerland(Wiley, 01.08.1997) Baltensperger, Urs; Gäggeler, Heinz W.; Jost, Dieter T.; Lugauer, Matthias; Schwikowski, Margit; Weingartner, Ernest; Seibert, PetraContinuous aerosol measurements have been performed at the high-alpine site Jungfraujoch (3450 m above sea level) since 1988 by means of an epiphaniometer. The instrument, which determines the Fuchs surface area of the aerosol particles, was operated with a time resolution of 30 min. High correlation coefficients (r>0.8) were found between the epiphaniometer signal and other aerosol parameters, which could be attributed to a rather constant size distribution of the Jungfraujoch aerosol in the accumulation range (0.101A - Beitrag in wissenschaftlicher ZeitschriftPublikation Characterization of size-fractionated aerosol from the Jungfraujoch (3580 m asl) using total reflection x-ray fluorescence (TXRF)(Taylor & Francis, 22.09.2000) Streit, Niklaus; Weingartner, Ernest; Zellweger, Christoph; Schwikowski, Margit; Gäggeler, Heinz W.; Baltensperger, UrsDuring three field campaigns at the Jungfraujoch High Alpine Research Station, Switzerland, size-fractionated aerosol was collected using a cascade impactor. The particles were impacted on silicon oil-coated quartz sampling substrates. The actual analysis was then performed directly on these quartz sampling substrates using total reflection X-ray fluorescence. The resulting size distributions of 16 elements (S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Se, Br, Rb, Sr, Y, Zr, Pb) were investigated to determine the best cut-off diameter to distinguish between geogenic and anthropogenic particles. The obtained cut-off diameter of 1 μm is an important parameter in the current world-wide measurements under the auspices of the World Meteorological Organization's Global Atmosphere Watch aerosol project.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Ground-based and airborne in-situ measurements of the Eyjafjallajökull volcanic aerosol plume in Switzerland in spring 2010(Copernicus, 04.10.2011) Bukowiecki, Nicolas; Zieger, Paul; Weingartner, Ernest; Jurányi, Zsófia; Gysel, Martin; Neininger, Bruno; Schneider, Boris; Hueglin, Christoph; Ulrich, Andrea; Wichser, Adrian; Henne, Stephan; Brunner, Dominik; Kaegi, Ralf; Schwikowski, Margit; Tobler, Leonhard; Wienhold, Frank G.; Engel, Ilana; Buchmann, Brigitte; Peter, Thomas; Baltensperger, UrsThe volcanic aerosol plume resulting from the Eyjafjallajökull eruption in Iceland in April and May 2010 was detected in clear layers above Switzerland during two periods (17–19 April 2010 and 16–19 May 2010). In-situ measurements of the airborne volcanic plume were performed both within ground-based monitoring networks and with a research aircraft up to an altitude of 6000 m a.s.l. The wide range of aerosol and gas phase parameters studied at the high altitude research station Jungfraujoch (3580 m a.s.l.) allowed for an in-depth characterization of the detected volcanic aerosol. Both the data from the Jungfraujoch and the aircraft vertical profiles showed a consistent volcanic ash mode in the aerosol volume size distribution with a mean optical diameter around 3 ± 0.3 μm. These particles were found to have an average chemical composition very similar to the trachyandesite-like composition of rock samples collected near the volcano. Furthermore, chemical processing of volcanic sulfur dioxide into sulfate clearly contributed to the accumulation mode of the aerosol at the Jungfraujoch. The combination of these in-situ data and plume dispersion modeling results showed that a significant portion of the first volcanic aerosol plume reaching Switzerland on 17 April 2010 did not reach the Jungfraujoch directly, but was first dispersed and diluted in the planetary boundary layer. The maximum PM10 mass concentrations at the Jungfraujoch reached 30 μgm−3 and 70 μgm−3 (for 10-min mean values) duri ng the April and May episode, respectively. Even low-altitude monitoring stations registered up to 45 μgm−3 of volcanic ash related PM10 (Basel, Northwestern Switzerland, 18/19 April 2010). The flights with the research aircraft on 17 April 2010 showed one order of magnitude higher number concentrations over the northern Swiss plateau compared to the Jungfraujoch, and a mass concentration of 320 (200–520) μgm−3 on 18 May 2010 over the northwestern Swiss plateau. The presented data significantly contributed to the time-critical assessment of the local ash layer properties during the initial eruption phase. Furthermore, dispersion models benefited from the detailed information on the volcanic aerosol size distribution and its chemical composition.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Saharan dust events at the Jungfraujoch. detection by wavelength dependence of the single scattering albedo and first climatology analysis(Copernicus, 08.12.2004) Collaud Coen, Martine; Weingartner, Ernest; Schaub, D.; Hueglin, Christoph; Corrigan, C.; Henning, Silvia; Schwikowski, Margit; Baltensperger, UrsScattering and absorption coefficients have been measured continuously at several wave-lengths since March 2001 at the high altitude site Jungfraujoch (3580ma.s.l.). From these data, the wavelength dependences of the Ångström exponent and particularly of the single scattering albedo are determined. While the exponent of the single scattering albedo usually increases with wavelength, it decreases with wavelength during Saharan dust events (SDE) due to the greater size of the mineral aerosol particles and their different chemical composition. This change in the sign of the single scattering exponent turns out to be a sensitive means for detecting Saharan dust events. The occurrence of SDE detected by this new method was confirmed by visual in-spection of filter colors and by studying long-range back-trajectories. An examination of SDE over a 22-month period shows that SDE are more frequent during the March-June period as well as during October and November. The trajectory analysis indicated a mean traveling time of 96.5h, with the most important source countries situated in the northern and north-western part of the Saharan desert. Most of the SDE do not lead to a detectable increase of the 48-h total suspended particulate matter (TSP) concentration at the Jungfraujoch. During Saharan dust events, the average contribution of this dust to hourly TSP at the Jungfraujoch is 16µg/m³, which corresponds to an annual mean of 0.8µg/m³ or 24% of TSP.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Seasonal variation of water‐soluble ions of the aerosol at the high‐alpine site Jungfraujoch (3580 m asl)(Wiley, 15.01.2003) Henning, Silvia; Weingartner, Ernest; Schwikowski, Margit; Gäggeler, Heinz W.; Gehrig, Robert; Hinz, Klaus-Peter; Trimborn, Achim; Spengler, Bernhard; Baltensperger, UrsWithin the Global Atmosphere Watch (GAW) Aerosol Program of the World Meteorological Organization (WMO), the aerosol chemical composition has been continuously measured since July 1999 at the Jungfraujoch (JFJ) of which the first 1.5-year data set is presented. Sampling is performed in two size classes (total suspended particles (TSP) and particles with aerodynamic diameters smaller than 1 μm). The filters are analyzed for major ions, which constitute 30% of the total dry aerosol mass collected at this site. As annual mean, a total ion mass concentration of 1.04 μg mˉ³ was observed. Sulfate, ammonium, and nitrate were the major components of the fine aerosol fraction, while calcium and nitrate were two major water-soluble components in the coarse mode. Single particle analysis confirmed the internal mixture of calcium and nitrate in the coarse mode. The total ion mass concentration showed strong seasonal differences, with 1.25, 1.62, 0.70, and 0.25 μg mˉ³ for spring, summer, fall, and winter, respectively. The variability was stronger for sulfate, ammonium, and nitrate than for calcium. The reason for this is believed to be local sources of calcium, which do not require vertical transport, along with Sahara dust episodes, which occur occasionally over the whole year, independent from the season.01A - Beitrag in wissenschaftlicher Zeitschrift