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| Titel |
The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds |
| VerfasserIn |
P. Kupiszewski, E. Weingärtner, P. Vochezer, M. Schnaiter, A. Bigi, M. Gysel, B. Rosati, E. Toprak, S. Mertes, U. Baltensperger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-03), S.3087-3106 |
| Datensatznummer |
250116517
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| Publikation (Nr.) |
 copernicus.org/amt-8-3087-2015.pdf |
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| Zusammenfassung |
| Climate predictions are affected by high uncertainties partially due
to an insufficient knowledge of aerosol–cloud interactions. One of the
poorly understood processes is formation of mixed-phase clouds (MPCs)
via heterogeneous ice nucleation. Field measurements of the
atmospheric ice phase in MPCs are challenging due to the presence of
much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented
in this paper, is a novel inlet designed to selectively sample
pristine ice crystals in mixed-phase clouds and extract the ice
residual particles contained within the crystals for physical and
chemical characterization. Using a modular setup composed of a cyclone
impactor, droplet evaporation unit and pumped counterflow virtual
impactor (PCVI), the ISI segregates particles based on their inertia
and phase, exclusively extracting small ice particles between 5 and
20 μm in diameter. The setup also includes optical
particle spectrometers for analysis of the number size distribution
and shape of the sampled hydrometeors.
The novelty of the ISI is a droplet evaporation unit, which separates
liquid droplets and ice crystals in the airborne state, thus avoiding
physical impaction of the hydrometeors and limiting potential
artefacts. The design and validation of the droplet evaporation unit
is based on modelling studies of droplet evaporation rates and
computational fluid dynamics simulations of gas and particle flows
through the unit. Prior to deployment in the field, an
inter-comparison of the optical particle size spectrometers and
a characterization of the transmission efficiency of the PCVI was
conducted in the laboratory. The ISI was subsequently deployed during
the Cloud and Aerosol Characterization Experiment (CLACE) 2013 and 2014 – two
extensive international field campaigns encompassing comprehensive
measurements of cloud microphysics, as well as bulk aerosol, ice
residual and ice nuclei properties. The campaigns provided an important
opportunity for a proof of concept of the inlet design. In this work
we present the setup of the ISI, including the modelling and
laboratory characterization of its components, as well as field measurements
demonstrating the ISI performance and validating the working principle of the inlet.
Finally, measurements of biological aerosol during a Saharan dust event (SDE)
are presented, showing a first indication of enrichment of bio-material in sub-2 μm ice residuals. |
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