Counterflow virtual impactor based collection of small ice particles in mixed-phase clouds for the physico-chemical characterization of tropospheric ice nuclei. sampler description and first case study

A ground-based sampling system named Ice-CVI is introduced that is able to extract small ice particles with sizes between 5 and 20 μ m out of mixed-phase clouds. The instrument is based on a counterflow virtual impactor (CVI) removing interstitial particles and is supplemented by additional modules that pre-segregate other constituents of mixed-phase clouds. Ice particles of 20 μ m and smaller are expected to grow only by water vapor diffusion and there is a negligible probability that they scavenge aerosol particles by impaction and riming. Thus, their residuals which are released by the Ice-CVI can be interpreted as the original ice nuclei (IN). In a first field test within the Cloud and Aerosol Characterization Experiment (CLACE-3) at the high alpine research station Jungfraujoch, the collection behavior of the single components and the complete system was evaluated under atmospheric sampling conditions. By comparing parameters measured by the Ice-CVI with corresponding results obtained from other inlets or with in-situ instrumentation it is verified that the small ice particles are representatively collected whereas all other mixed phase cloud constituents are effectively suppressed. In a case study it is observed that super-micrometer particles preferentially serve as IN although in absolute terms the IN concentration is dominated by sub-micrometer particles. Mineral dust (Si), non-volatile organic matter and black carbon could be identified as IN components by means of different chemical analyses. The latter suggests an anthropogenic influence on the heterogeneous ice nucleation in supercooled, tropospheric clouds.

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550 - Geowissenschaften

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0278-6826
1521-7388

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English

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No

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Published

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Peer review of the complete publication

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Closed

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MERTES, Stephan, Bart VERHEGGEN, Saskia WALTER, Paul CONNOLLY, Martin EBERT, Johannes SCHNEIDER, Keith N. BOWER, Julie COZIC, Stephan WEINBRUCH, Urs BALTENSPERGER und Ernest WEINGARTNER, 2007. Counterflow virtual impactor based collection of small ice particles in mixed-phase clouds for the physico-chemical characterization of tropospheric ice nuclei. sampler description and first case study. Aerosol Science and Technology. 7 September 2007. Bd. 41, Nr. 9, S. 848–864. DOI 10.1080/02786820701501881. Verfügbar unter: https://irf.fhnw.ch/handle/11654/46706

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