TY  - JOUR
A1  - Nichman, Leonid
A1  - Fuchs, Claudia
A1  - Järvinen, Emma
A1  - Ignatius, Karoliina
A1  - Höppel, Niko Florian
A1  - Dias, Antonio
A1  - Heinritzi, Martin
A1  - Simon, Mario
A1  - Tröstl, Jasmin
A1  - Wagner, Andrea Christine
A1  - Wagner, Robert
A1  - Williamson, Christina
A1  - Yan, Chao
A1  - Connolly, Paul J.
A1  - Dorsey, James Robert
A1  - Duplissy, Jonathan
A1  - Ehrhart, Sebastian
A1  - Frege, Carla
A1  - Gordon, Hamish
A1  - Hoyle, Christopher Robert
A1  - Kristensen, Thomas Bjerring
A1  - Steiner, Gerhard
A1  - Donahue, Neil McPherson
A1  - Flagan, Richard C.
A1  - Gallagher, Martin William
A1  - Kirkby, Jasper
A1  - Möhler, Ottmar
A1  - Saathoff, Harald
A1  - Schnaiter, Martin
A1  - Stratmann, Frank
A1  - Tomé, Antonio
T1  - Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments
T2  - Atmospheric chemistry and physics
N2  - Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid–viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to tropical troposphere layer analysis.
Y1  - 2016
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/41889
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-418897
UR  - http://www.atmos-chem-phys.net/16/3651/2016
SN  - 1680-7324
SN  - 1680-7316
N1  - © Author(s) 2016. CC Attribution 3.0 License.
VL  - 16
IS  - 5
SP  - 3651
EP  - 3664
PB  - European Geosciences Union
CY  - Katlenburg-Lindau
ER  -