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Author: Wiedensohler, A. × End date: 2019 × Start date: 2010 × DDC: 550 × Publisher: Milton Park : Taylor & Francis × Subject: measurement method ×

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    State of mixing, shape factor, number size distribution, and hygroscopic growth of the Saharan anthropogenic and mineral dust aerosol at Tinfou, Morocco
    (Milton Park : Taylor & Francis, 2017) Kaaden, N.; Massling, A.; Schladitz, A.; Müller, T.; Kandler, K.; Schütz, L.; Weinzierl, B.; Petzold, A.; Tesche, M.; Leinert, S.; Deutscher, C.; Ebert, M.; Weinbruch, S.; Wiedensohler, A.
    The Saharan Mineral Dust Experiment (SAMUM) was conducted in May and June 2006 in Tinfou, Morocco. A H-TDMA system and a H-DMA-APS system were used to obtain hygroscopic properties of mineral dust particles at 85% RH. Dynamic shape factors of 1.11, 1.19 and 1.25 were determined for the volume equivalent diameters 720, 840 and 960 nm, respectively. During a dust event, the hydrophobic number fraction of 250 and 350 nm particles increased significantly from 30 and 65% to 53 and 75%, respectively, indicating that mineral dust particles can be as small as 200 nm in diameter. Lognormal functions for mineral dust number size distributions were obtained from total particle number size distributions and fractions of hydrophobic particles. The geometric mean diameter for Saharan dust particles was 715 nm during the dust event and 570 nm for the Saharan background aerosol. Measurements of hygroscopic growth showed that the Saharan aerosol consists of an anthropogenic fraction (predominantly non natural sulphate and carbonaceous particles) and of mineral dust particles. Hygroscopic growth and hysteresis curve measurements of the ‘more’ hygroscopic particle fraction indicated ammonium sulphate as a main component of the anthropogenic aerosol. Particles larger than 720 nm in diameter were completely hydrophobic meaning that mineral dust particles are not hygroscopic.
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    Submicrometer aerosol particle distributions in the upper troposphere over the mid-latitude North Atlantic - Results from the third route of 'CARIBIC'
    (Milton Park : Taylor & Francis, 2017) Hermann, M.; Brenninkmeijer, C.A.M.; Slemr, F.; Heintzenberg, J.; Martinsson, B.G.; Schlager, H.; Van Velthoven, P.F.J.; Wiedensohler, A.; Zahn, A.; Ziereis, H.
    Particle number and mass concentrations of submicrometer aerosol particles were determined for the upper troposphere over the mid-latitude North Atlantic within the Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container project (CARIBIC, http://www.caribic-atmospheric.com). Between May 2001 and April 2002, 22 flights from Germany to the Caribbean were conducted using an automated measurement container on a B767 passenger aircraft. Spatial and seasonal probability distributions for ultrafine and Aitken mode particles as well as mass concentrations of particulate sulphur in 8–12 km altitude are presented. High particle number concentrations (mostly 2500–15 000 particles cm-3 STP) are particularly found in summer over the western North Atlantic Ocean close to the North American continent. The distributions together with an analysis of particle source processes show that deep vertical transport is the dominant process leading to most of the events with high particle number concentrations (8000 particles cm-3 STP) for ultrafine particles as well as for Aitken mode particles. This study emphasizes the importance of deep vertical transport and cloud processing for the concentration of aerosol particles in the upper troposphere.