A High Speed Particle Phase Discriminator (PPD-HS) for the classification of airborne particles, as tested in a continuous flow diffusion chamber
dc.contributor.author
Mahrt, Fabian
dc.contributor.author
Wieder, Jörg
dc.contributor.author
Dietlicher, Remo
dc.contributor.author
Smith, Helen R.
dc.contributor.author
Stopford, Chris
dc.contributor.author
Kanji, Zamin A
dc.date.accessioned
2022-06-22T09:18:54Z
dc.date.available
2019-01-04T16:33:03Z
dc.date.available
2019-05-07T06:07:36Z
dc.date.available
2022-06-22T09:18:54Z
dc.date.issued
2019-02-22
dc.identifier.issn
1867-8610
dc.identifier.other
10.5194/amt-2019-36
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/313787
dc.identifier.doi
10.3929/ethz-b-000313787
dc.description.abstract
A new instrument, the High Speed Particle Phase Discriminator (PPD-HS) developed at the University of Hertfordshire, for sizing individual cloud hydrometeors and determining their phase is described herein. PPD-HS performs an in-situ analysis of the spatial intensity distribution of near forward scattered light for individual hydrometeors yielding shape properties. Discrimination of spherical and aspherical particles is based on an analysis of the symmetry of the recorded scattering patterns. Scattering patterns are collected onto two linear detector arrays, reducing the complete 2D scattering pattern to scattered light intensities captured onto two linear, one dimensional strips of light sensitive pixels. Using this reduced scattering information, we calculate symmetry indicators that are used for particle shape and ultimately phase analysis. This reduction of information allows for detection rates of a few hundred particles per second.
Here, we present a comprehensive analysis of instrument performance using both spherical and aspherical particles, generated in a well-controlled laboratory setting using a Vibrating Orifice Aerosol Generator (VOAG) and covering a size range of approximately 3–32 micron. We use supervised machine learning to train a random forest model on the VOAG data sets that can be used to classify any particles detected by PPD-HS. Classification results show that the PPD-HS can successfully discriminate between spherical and aspherical particles, with misclassification below 5 % for diameters > 3 micro meter. This phase discrimination method is subsequently applied to classify simulated cloud particles produced in a continuous flow diffusion chamber setup. We report observations of small, near-spherical ice crystals at early stages of the ice nucleation experiments, where shape analysis fails to correctly determine the particle phase. Nevertheless, in case of simultaneous presence of cloud droplets and ice crystals, the introduced particle shape indicators allow for a clear distinction between these two classes independent of optical particle size. We conclude that PPD-HS constitutes a powerful new instrument to size and discriminate phase of cloud hydrometeors and thus study microphysical properties of mixed-phase clouds, that represent a major source of uncertainty in aerosol indirect effect for future climate projections.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
Copernicus
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/4.0/
dc.title
A High Speed Particle Phase Discriminator (PPD-HS) for the classification of airborne particles, as tested in a continuous flow diffusion chamber
en_US
dc.type
Working Paper
dc.rights.license
Creative Commons Attribution 4.0 International
ethz.journal.title
Atmospheric Measurement Techniques Discussions
ethz.journal.abbreviated
Atmos. meas. tech., Pap. open discuss.
ethz.size
37 p.
en_US
ethz.publication.place
Göttingen
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02717 - Institut für Atmosphäre und Klima / Inst. Atmospheric and Climate Science::03690 - Lohmann, Ulrike / Lohmann, Ulrike
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02717 - Institut für Atmosphäre und Klima / Inst. Atmospheric and Climate Science::03690 - Lohmann, Ulrike / Lohmann, Ulrike
en_US
ethz.relation.isPreviousVersionOf
10.3929/ethz-b-000348877
ethz.date.deposited
2019-01-04T16:33:04Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2019-05-07T06:08:44Z
ethz.rosetta.lastUpdated
2023-02-07T03:41:58Z
ethz.rosetta.versionExported
true
ethz.COinS
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Working Paper [6077]