Hochschule für Technik FHNW

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13-month climatology of the aerosol hygroscopicity at the free tropospheric site Jungfraujoch (3580 m a.s.l.)
(Copernicus, 16.11.2010) Kammermann, Lukas; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
A hygroscopicity tandem differential mobility analyzer (HTDMA) was operated at the high-alpine site Jungfraujoch in order to characterize the hygroscopic diameter growth factors of the free tropospheric Aitken and accumulation mode aerosol. More than ~5000 h of valid data were collected for the dry diameters D0 = 35, 50, 75, 110, 165, and 265 nm during the 13-month measurement period from 1 May 2008 through 31 May 2009. No distinct seasonal variability of the hygroscopic properties was observed. Annual mean hygroscopic diameter growth factors (D/D0) at 90% relative humidity were found to be 1.34, 1.43, and 1.46 for D0 = 50, 110, and 265 nm, respectively. This size dependence can largely be attributed to the Kelvin effect because corresponding values of the hygroscopicity parameter κ are nearly independent of size. The mean hygroscopicity of the Aitken and accumulation mode aerosol at the free tropospheric site Jungfraujoch was found to be κ≈0.24 with little variability throughout the year. The impact of Saharan dust events, a frequent phenomenon at the Jungfraujoch, on aerosol hygroscopicity was shown to be negligible for D0<265 nm. Thermally driven injections of planetary boundary layer (PBL) air, particularly observed in the early afternoon of summer days with convective anticyclonic weather conditions, lead to a decrease of aerosol hygroscopicity. However, the effect of PBL influence is not seen in the annual mean hygroscopicity data because the effect is small and those conditions (weather class, season and time of day) with PBL influence are relatively rare. Aerosol hygroscopicity was found to be virtually independent of synoptic wind direction during advective weather situations, i.e. when horizontal motion of the atmosphere dominates over thermally driven convection. This indicates that the hygroscopic behavior of the aerosol observed at the Jungfraujoch can be considered representative of the lower free troposphere on at least a regional if not continental scale.
01A - Beitrag in wissenschaftlicher Zeitschrift
18HLT02 AeroToX: Measurements for mitigating adverse health effects from atmospheric particulate pollutants
2D-3D-Modellerzeuger
40 Gb/s optical receivers
(2003) Huber, Alexander
04B - Beitrag Konferenzschrift
40 Gb/s quarter rate CDR with data rate selection in 90\,nm CMOS
(2010) Huber, Alexander; Schmatz, Martin; Toifl, Thomas; Menolfi, Christian; Kossel, Marcel; von Bueren, Georg; Rodoni, Lucio; Jäckel, Heinz; Morf, Thomas
04B - Beitrag Konferenzschrift
4D4SBB
4uComputing
A 17 month climatology of the cloud condensation nuclei number concentration at the high alpine site Jungfraujoch
(Wiley, 24.05.2011) Jurányi, Zsófia; Gysel, Martin; Weingartner, Ernest; Bukowiecki, Nicolas; Kammermann, Lorenz; Baltensperger, Urs [in: Journal of Geophysical Research: Atmospheres]
Between May 2008 and September 2009 the cloud condensation nuclei (CCN) number concentration, NCCN, was measured at the high alpine site Jungfraujoch, which is located in the free troposphere most of the time. Measurements at 10 different supersaturations (0.12%–1.18%) were made using a CCN counter (CCNC). The monthly median NCCN values show a distinct seasonal variability with ∼5–12 times higher values in summer than in winter. The major part of this variation can be explained by the seasonal amplitude of total aerosol number concentration (∼4.5 times higher values in summer), but it is further amplified (factor of ∼1.1–2.6) by a shift of the particle number size distribution toward slightly larger sizes in summer. In contrast to the extensive properties, the monthly median of the critical dry diameter, above which the aerosols activate as CCN, does not show a seasonal cycle (relative standard deviations of the monthly median critical dry diameters at the different supersaturations are 4–9%) or substantial variability (relative standard deviations of individual data points at the different supersaturations are less than 18–37%). The mean CCN-derived hygroscopicity of the aerosol corresponds to a value of the hygroscopicity parameter κ of 0.20 (assuming a surface tension of pure water) with moderate supersaturation dependence. NCCN can be reliably predicted throughout the measurement period with knowledge of the above-mentioned averaged κ value and highly time-resolved (∼5 min) particle number size distribution data. The predicted NCCN was within 0.74 to 1.29 times the measured value during 80% of the time (94,499 data points in total at 10 different supersaturations).
01A - Beitrag in wissenschaftlicher Zeitschrift
A 300 Hz 19 b DR capacitive accelerometer based on a versatile front end in a 5th-order DeltaSigma loop
(2009) Pastre, Marc; Kayal, Maher; Schmid, Hanspeter; Huber, Alexander; Zwahlen, Pascal; Nguyen, Anne-Marie; Dong, Yufeng [in: Proc. ESSCIRC]
04B - Beitrag Konferenzschrift
A 5.75 to 44\,Gb/s quarter rate CDR with data rate selection in 90nm bulk CMOS
(2008) Rodoni, Lucio; von Buren, Georg; Huber, Alexander; Schmatz, Martin; Jäckel, Heinz [in: Proc. ESSCIRC]
04B - Beitrag Konferenzschrift
A broadband FFT spectrometer for radio and millimeter astronomy
(EDP Sciences, 2005) Stuber, Bruno; Zardet, Dino [in: Astronomy and Astrophysics]
01A - Beitrag in wissenschaftlicher Zeitschrift
A Combined Dynamic and Static Frequency Divider for a 40\,GHz PLL in 80\,nm CMOS
(2006) von Bueren, Georg; Kromer, Christian; Ellinger, Frank; Huber, Alexander; Schmatz, Martin; Jäckel, Heinz [in: Proc. ISSCC]
04B - Beitrag Konferenzschrift
A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles
(Copernicus, 19.09.2008) Zardini, Alessandro A.; Sjogren, S.; Marcolli, Claudia; Krieger, Ulrich K.; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Peter, Thomas [in: Atmospheric Chemistry and Physics]
Atmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/glutaric acid system; deviations up to 10% in mass growth factor (corresponding to deviations up to 3.5% in size growth factor) are observed for the ammonium sulfate/citric acid 1:1 mixture at 80% RH. We observe even more significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces.
01A - Beitrag in wissenschaftlicher Zeitschrift
A compact and portable deposition chamber to study nanoparticles in air-exposed tissue
(Mary Ann Liebert, 2013) Mertes, Peter; Praplan, Arnaud P.; Künzi, Lisa; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; Weingartner, Ernest; Ricka, Jaroslav; Fierz, Martin; Kalberer, Markus [in: Journal of Aerosol Medicine and Pulmonary Drug Delivery]
01A - Beitrag in wissenschaftlicher Zeitschrift
A comprehensive dynamic model of the diamond wire sawing process
(WIP, 2017) Treyer, Daniel; Gaulocher, Sebastian; Niederberger, Stefan; Rafael, Helge; Ams, Alfons; Smets, A.; Helm, P.; Taylor, N. [in: Proc. 33rd European Photovoltaic Solar Energy Conf. and Exhibition EUPVSEC]
04B - Beitrag Konferenzschrift
A dual-wavelength photothermal aerosol absorption monitor. Design, calibration and performance
(Copernicus, 2022) Drinovec, Luka; Jagodič, Uroš; Pirker, Luka; Škarabot, Miha; Kurtjak, Mario; Vidović, Kristijan; Ferrero, Luca; Visser, Bradley; Röhrbein, Jannis; Weingartner, Ernest; Kalbermatter, Daniel M.; Vasilatou, Konstantina; Bühlmann, Tobias; Pascale, Celine; Müller, Thomas; Wiedensohler, Alfred; Močnik, Griša [in: Atmospheric Measurement Techniques]
There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology - 1. physical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe
(Elsevier, 05/2004) Van Dingenen, Rita; Raes, Frank; Putaud, Jean-Philippe; Baltensperger, Urs; Charron, Aurélie; Facchini, Maria Cristina; Decesari, Stefano; Fuzzi, Sandro; Gehrig, Robert; Hansson, Hans-Christen; Harrison, Roy M.; Hüglin, Cristoph; Jones, Alan M.; Laj, Paolo; Lorbeer, Gundi; Maenhaut, Willy; Palmgren, Finn; Querol, Xavier; Rodriguez, Sergio; Schneider, Jürgen; ten Brink, Harry; Tunved, Peter; Tørseth, Kjetil; Wehner, Birgit; Weingartner, Ernest; Wiedensohler, Alfred; Wåhlin, Peter [in: Atmospheric Environment]
This paper synthesizes data on aerosol (particulate matter, PM) physical characteristics, which were obtained in European aerosol research activities at free-troposphere, natural, rural, near-city, urban, and kerbside sites over the past decade. It covers only two sites in the semi-arid Mediterranean area, and lacks data from Eastern Europe. The data include PM10 and/or PM2.5 mass concentrations, and aerosol particle size distributions. Such data sets are more comprehensive than those currently provided by air quality monitoring networks (e.g. EMEP, EUROAIRNET). Data available from 31 sites in Europe (called “The Network”) were reviewed. They were processed and plotted to allow comparisons in spite of differences in the sampling and analytical techniques used in various studies. A number of conclusions are drawn as follows: Background annual average PM10 and PM2.5 mass concentrations for continental Europe are 7.0±4.1 and 4.8±2.4 μg mˉ³, respectively. The EU 2005 annual average PM10 standard of 40 μg mˉ³ is exceeded at a few sites in The Network. At all near city, urban and kerbside sites, the EU 2010 annual average PM10 standard of 20 μg mˉ³, as well as the US-EPA annual average PM2.5 standard of 15 μg mˉ³ are exceeded. In certain regions, PM10 and PM2.5 in cities are strongly affected by the regional aerosol background. There is no “universal” (i.e. valid for all sites) ratio between PM2.5 and PM10 mass concentrations, although fairly constant ratios do exist at individual sites. There is no universal correlation between PM mass concentration on the one hand, and total particle number concentration on the other hand, although a ‘baseline’ ratio between number and mass is found for sites not affected by local emissions. This paper is the first part of two companion papers of which the second part describes chemical characteristics.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology-5. Climatology of black carbon optical properties at 9 regional background sites across Europe
(Elsevier, 2016) Zanatta, Marco; Gysel, Martin; Bukowiecki, Nicolas; Müller, Thomas; Weingartner, Ernest; Areskoug, Hans; Fiebig, Markus; Yttri, Karl Espen; Mihalopoulos, Nikolaos; Kouvarakis, Giorgos; Beddows, David; Harrison, Roy; Cavalli, Fabrizia; Putaud, Jean; Spindler, Gerald; Wiedensohler, Alfred; Alastuey, Andrés; Pandolfi, Marco; Sellegri, Karine; Swietlicki, Erik; Jaffrezo, Jean-Luc; Baltensperger, Urs; Laj, Paolo [in: Atmospheric Environment]
01A - Beitrag in wissenschaftlicher Zeitschrift
A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties
(Copernicus, 2021) Titos, Gloria; Burgos, María A.; Zieger, Paul; Alados-Arboledas, Lucas; Baltensperger, Urs; Jefferson, Anne; Sherman, James; Weingartner, Ernest; Henzing, Bas; Luoma, Krista; O'Dowd, Colin; Wiedensohler, Alfred; Andrews, Elisabeth [in: Atmospheric Chemistry and Physics]
The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower than f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω0 and scattering Ångström exponent, αsp) to parameterize f(RH). The majority of sites (75 %) showed a consistent trend with ω0 (higher f(RH = 85 %) for higher ω0), while no clear pattern was observed between f(RH = 85 %) and αsp. This suggests that aerosol ω0 is more promising than αsp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω0 and f(RH) could serve as a constraint on global model simulations.
01A - Beitrag in wissenschaftlicher Zeitschrift
A mobile pollutant measurement laboratory - measuring gas phase and aerosol ambient concentrations with high spatial and temporal resolution
(Elsevier, 12/2002) Bukowiecki, Nicolas; Dommen, Josef; Prévôt, André S.H.; Richter, Rene; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Environment]
A mobile pollutant measurement laboratory was designed and built at the Paul Scherrer Institute (Switzerland) for the measurement of on-road ambient concentrations of a large set of trace gases and aerosol parameters with high time resolution (<15 s for most instruments), along with geographical and meteorological information. This approach allowed for pollutant level measurements both near traffic (e.g. in urban areas or on freeways/main roads) and at rural locations far away from traffic, within short periods of time and at different times of day and year. Such measurements were performed on a regular base during the project year of gas phase and aerosol measurements (YOGAM). This paper presents data measured in the Zürich (Switzerland) area on a late autumn day (6 November) in 2001. The local urban particle background easily reached 50 000 cmˉ³, with additional peak particle number concentrations of up to 400 000 cmˉ³. The regional background of the total particle number concentration was not found to significantly correlate with the distance to traffic and anthropogenic emissions of carbon monoxide and nitrogen oxides. On the other hand, this correlation was significant for the number concentration of particles in the size range 50–150 nm, indicating that the particle number concentration in this size range is a better traffic indicator than the total number concentration. Particle number size distribution measurements showed that daytime urban ambient air is dominated by high number concentrations of ultrafine particles (nanoparticles) with diameters < 50 nm, which are immediately formed by traffic exhaust and thus belong to the primary emissions. However, significant variation of the nanoparticle mode was also observed in number size distributions measured in rural areas both at daytime and nighttime, suggesting that nanoparticles are not exclusively formed by primary traffic emissions. While urban daytime total number concentrations were increased by a factor of 10 compared to the nighttime background, corresponding factors for total surface area and total volume concentrations were 2 and 1.5, respectively.
01A - Beitrag in wissenschaftlicher Zeitschrift

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