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Author: Tuch, Thomas × Author: Wiedensohler, Alfred × End date: 2019 × Start date: 1990 ×

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Now showing 1 - 5 of 5
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    Measuring soot particles from automotive exhaust emissions
    (Les Ulis : EDP Sciences, 2014) Andres, Hanspeter; Lüönd, Felix; Schlatter, Jürg; Auderset, Kevin; Jordan-Gerkens, Anke; Nowak, Andreas; Ebert, Volker; Buhr, Egbert; Klein, Tobias; Tuch, Thomas; Wiedensohler, Alfred; Mamakos, Athanasios; Riccobono, Francesco; Discher, Kai; Högström, Richard; Yli-Ojanperä, Jaakko; Quincey, Paul
    The European Metrology Research Programme participating countries and the European Union jointly fund a three year project to address the need of the automotive industry for a metrological sound base for exhaust measurements. The collaborative work on particle emissions involves five European National Metrology Institutes, the Tampere University of Technology, the Joint Research Centre for Energy and Transport and the Leibniz Institute for Tropospheric Research. On one hand, a particle number and size standard for soot particles is aimed for. Eventually this will allow the partners to provide accurate and comparable calibrations of measurement instruments for the type approval of Euro 5b and Euro 6 vehicles. Calibration aerosols of combustion particles, silver and graphite proof partially suitable. Yet, a consensus choice together with instrument manufactures is pending as the aerosol choice considerably affects the number concentration measurement. Furthermore, the consortium issued consistent requirements for novel measuring instruments foreseen to replace today’s opacimeters in regulatory periodic emission controls of soot and compared them with European legislative requirements. Four partners are conducting a metrological validation of prototype measurement instruments. The novel instruments base on light scattering, electrical, ionisation chamber and diffusion charging sensors and will be tested at low and high particle concentrations. Results shall allow manufacturers to further improve their instruments to comply with legal requirements.
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    Significant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area
    (Amsterdam : Elsevier, 2015) Kecorius, Simonas; Kivekäs, Niku; Kristensson, Adam; Tuch, Thomas; Covert, David S.; Birmili, Wolfram; Lihavainen, Heikki; Hyvärinen, Antti-Pekka; Martinsson, Johan; Sporre, Moa K.; Swietlicki, Erik; Wiedensohler, Alfred; Ulevicius, Vidmantas
    In this study, we evaluated 10 months data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden), Utö (upwind, Finland), and Preila (downwind, Lithuania). Differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, were used to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50–400 nm) in the Lithuanian background coastal environment. A clear increase in particle number concentration could be noticed, by a factor of 1.9 from Utö to Preila (the average total number concentration at Utö was 791 cm−3), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm−3). The simultaneous measurements of absorption Ångström exponents close to unity at Preila supported our conclusion that ship emissions in the Baltic Sea contributed to the increase in particle number concentration at Preila.
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    Arctic haze over Central Europe
    (Milton Park : Taylor & Francis, 2017) Heintzenberg, Jost; Tuch, Thomas; Wehner, Birgit; Wiedensohler, Alfred; Wex, Heike; Ansmann, Albert; Mattis, Ina; Müller, Detlef; Wendisch, Manfred; Eckhardt, Sabine; Stohl, Andreas
    An extraordinary aerosol situation over Leipzig, Germany in April 2002 was investigated with a comprehensive set of ground-based volumetric and columnar aerosol data, combined with aerosol profiles from lidar, meteorological data from radiosondes and air mass trajectory calculations. Air masses were identified to stem from the Arctic, partly influenced by the greater Moscow region. An evaluation of ground-based measurements of aerosol size distributions during these periods showed that the number concentrations below about 70 nm in diameter were below respective long-term average data, while number, surface and volume concentrations of the particles larger than about 70 nm in diameter were higher than the long-term averages. The lidar aerosol profiles showed that the imported aerosol particles were present up to about 3 km altitude. The particle optical depth was up to 0.45 at 550 nm wavelength. With a one-dimensional spectral radiative transfer model top of the atmosphere (TOA) radiative forcing of the aerosol layer was estimated for a period with detailed vertical information. Solar aerosol radiative forcing values between −23 and −38 W m−2 were calculated, which are comparable to values that have been reported in heavily polluted continental plumes outside the respective source regions. The present report adds weight to previous findings of aerosol import to Europe, pointing to the need for attributing the three-dimensional aerosol burden to natural and anthropogenic sources as well as to aerosol imports from adjacent or distant source regions. In the present case, the transport situation is further complicated by forward trajectories, indicating that some of the observed Arctic haze may have originated in Central Europe. This aerosolwas transported to the European Arctic before being re-imported in the modified and augmented form to its initial source region.
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    Structure, variability and persistence of the submicrometre marine aerosol
    (Milton Park : Taylor & Francis, 2017) Heintzenberg, Jost; Birmili, Wolfram; Wiedensohler, Alfred; Nowak, Andreas; Tuch, Thomas
    Submicrometre dry number size distributions from four marine and one continental aerosol experiment were evaluatedjointly in the present study. In the marine experiments only data with back trajectories of at least 120 h without landcontact were used to minimize continental contamination. Log-normal functions were fitted to the size distributions.Basic statistics of the marine aerosol indicate a closed character of the size distribution at the lower size limit as opposedto an open character for corresponding continental data. Together with the infrequent occurrences of marine particlesbelow20 nmthis finding supports hypotheses and model results suggesting lowprobabilities of homogeneous nucleationin the marine boundary layer. The variability of submicrometre marine number concentrations was parametrized witha bimodal log-normal function that quantifies the probability of finding different number concentrations about a givenmedian value. Together with a four-modal log-normal approximation of the submicrometre marine size distributionitself, this model allows a statistical representation of the marine aerosol that facilitates comparison of experiments andvalidation of aerosol models. Autocorrelation at the one fixed marine site with a minimum of interruptions in timesseriesrevealed a strong size dependency of persistence in particle number concentration with the shortest persistenceat the smallest sizes. Interestingly, in the marine aerosol (at Cape Grim) persistence exhibits a size dependency thatlargely matches the modes in dg0, i.e. near the most frequent geometric mean diameters number concentrations aremost persistent. Over the continent, persistence of particle numbers is strongly constrained by diurnal meteorologicalprocesses and aerosol dynamics. Thus, no strong modal structure appears in the size-dependent persistence at Melpitz.As with the aerosol variability, marine aerosol processes in models of aerosol dynamics can be tested with these findings.
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    Horizontal homogeneity and vertical extent of new particle formation events
    (Milton Park : Taylor & Francis, 2017) Wehner, Birgit; Siebert, Holger; Stratmann, Frank; Tuch, Thomas; Wiedensohler, Alfred; PetäJä, Tuukka; Dal Maso, Miikka; Kulmala, Markku
    During the SATURN campaign 2002, new particle formation, i.e. the occurrence of ultrafine particles was investigated simultaneously at four ground-based measurement sites. The maximum distance between the sites was 50 km. Additionally, vertical profiles of aerosol particles from 5–10 nm have been measured by a tethered-balloonborne system at one of the sites. In general, two different scenarios have been found: (i) new particle formation was measured at all sites nearly in parallel with subsequent particle growth (homogeneous case) and (ii) new particle formation was observed at one to three sites irregularly (inhomogeneous case) where subsequent particle growth was often interrupted. The homogeneous case was connected with stable synoptical conditions, i.e. the region was influenced by a high pressure system. Here, the horizontal extent of the phenomenon has been estimated to be 400 km at maximum. In the vertical dimension, the ultrafine particles are well mixed within the entire boundary layer. In the inhomogeneous case the new particle formation depends mainly on the incoming solar radiation and was often interrupted due the occurrence of clouds. Thus, single point measurements are not representative for a larger region in that case.