Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

Nichman, Leonid; Fuchs, Claudia; Järvinen, Emma; Ignatius, Karoliina; Höppel, N.; Dias, António; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea C.; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul; Dorsey, J. R.; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, C. R.; Kristensen, Thomas Bjerring; Steiner, Gerhard; Donahue, Neil M.; Flagan, Richard C.; Gallagher, Martin; Kirkby, J.; Möhler, Ottmar; Saathoff, H.; Schnaiter, M.; Stratmann, Frank; Tomé, António

doi:10.5194/acp-16-3651-2016

Cited by 17 publications

(24 citation statements)

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“…Järvinen et al (2016) also show that ice crystals can be near spherical. The low signal caused in the CAS polarisation detector by this type of crystal can lead to an underestimation of the glaciation degree of a mixed-phase cloud if it is derived from aspherical cloud particle fractions (see also Nichman et al, 2016). In addition, there are variations in the S-pol signals that are caused by the orientation of the crystal with respect to the laser beam (Baumgardner et al, 2014).…”

Section: Nixe-cas-dpol -Particle Asphericity Detectionmentioning

confidence: 99%

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

et al. 2017

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Abstract. The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and −38 • C (273 to 235 K), where cloud particles can either be frozen or liquid. The extensive data set covers four airborne field campaigns providing a total of 139 000 1 Hz data points (38.6 h within clouds) over Arctic, midlatitude and tropical regions. We develop algorithms, combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types: liquid clouds, clouds in which liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener-BergeronFindeisen process and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate our measurements during the Arctic spring, while clouds dominated by the WegenerBergeron-Findeisen process are most common in midlatitude spring. The coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at midlatitudes at −5 to −10 • C (268 to 263 K) and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperature is shown to be consistent with the theory of evolution of mixedphase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

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Section: Nixe-cas-dpol -Particle Asphericity Detectionmentioning

confidence: 99%

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

et al. 2017

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“…The side scatter detector is used for particle sizing by total scattering intensity, and the backscatter detectors are used to measure P (parallel to the incident laser light) and S (perpendicular to the incident laser light) polarization for phase discrimination: ice crystals depolarize more light than water droplets because of anisotropy of ice compared to liquid water (e.g., Wettlaufer et al, 1999;Thomson et al, 2009), and this change in depolarization signal is used to differentiate the two phases (Liou and Lahore, 1974;Nicolet et al, 2010;Clauss et al, 2013;Nichman et al, 2016). The OPC laser (Osela ILS-640-250-FTH-1.5MM-100uM) is a continuous-wave 500 mW 670 nm laser with a top-hat beam profile.…”

Section: Spin Chamber Designmentioning

confidence: 99%

The SPectrometer for Ice Nuclei (SPIN): an instrument to investigate ice nucleation

et al. 2016

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Abstract. The SPectrometer for Ice Nuclei (SPIN) is a commercially available ice nucleating particle (INP) counter manufactured by Droplet Measurement Technologies in Boulder, CO. The SPIN is a continuous flow diffusion chamber with parallel plate geometry based on the Zurich Ice Nucleation Chamber and the Portable Ice Nucleation Chamber. This study presents a standard description for using the SPIN instrument and also highlights methods to analyze measurements in more advanced ways. It characterizes and describes the behavior of the SPIN chamber, reports data from laboratory measurements, and quantifies uncertainties associated with the measurements. Experiments with ammonium sulfate are used to investigate homogeneous freezing of deliquesced haze droplets and droplet breakthrough. Experiments with kaolinite, NX illite, and silver iodide are used to investigate heterogeneous ice nucleation. SPIN nucleation results are compared to those from the literature. A machine learning approach for analyzing depolarization data from the SPIN optical particle counter is also presented (as an advanced use). Overall, we report that the SPIN is able to reproduce previous INP counter measurements.

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“…Takahashi, 1990Takahashi, , 2006Suzuki et al, 2014), the primary component is a video camera with flash lamp that takes video images of falling particles introduced into the instrument; the studies by Takahashi also use an induction ring to measure the electric charge of the particles. The videosonde has been primarily used for studies of precipitating clouds in the Asian monsoon region (Takahashi, 2006), while the HYVIS has been used for studies of midlatitude cirrus clouds (Orikasa et al, 2013;Orikasa and Murakami, 2015). The balloonborne particle-measuring instrument, called the backscattersonde (Rosen and Kjome, 1991), shines a flash-lamp beam periodically on the ambient air and measures the amount of backscattered light.…”

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“…Nichman et al, 2016), the Small Ice Detector mark 2 (SID-2; e.g. Cotton et al, 2010), and the Cloud Particle Spectrometer with Polarization Detection (CPSPD; Baumgardner et al, 2014).…”

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Development of a cloud particle sensor for radiosonde sounding

et al. 2016

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Abstract. A meteorological balloon-borne cloud sensor called the cloud particle sensor (CPS) has been developed. The CPS is equipped with a diode laser at ∼ 790 nm and two photodetectors, with a polarization plate in front of one of the detectors, to count the number of particles per second and to obtain the cloud-phase information (i.e. liquid, ice, or mixed). The lower detection limit for particle size was evaluated in laboratory experiments as ∼ 2 µm diameter for water droplets. For the current model the output voltage often saturates for water droplets with diameter equal to or greater than ∼ 80 µm. The upper limit of the directly measured particle number concentration is ∼ 2 cm −3 (2×10 3 L −1 ), which is determined by the volume of the detection area of the instrument. In a cloud layer with a number concentration higher than this value, particle signal overlap and multiple scattering of light occur within the detection area, resulting in a counting loss, though a partial correction may be possible using the particle signal width data. The CPS is currently interfaced with either a Meisei RS-06G radiosonde or a Meisei RS-11G radiosonde that measures vertical profiles of temperature, relative humidity, height, pressure, and horizontal winds. Twenty-five test flights have been made between 2012 and 2015 at midlatitude and tropical sites. In this paper, results from four flights are discussed in detail. A simultaneous flight of two CPSs with different instrumental configurations confirmed the robustness of the technique. At a midlatitude site, a profile containing, from low to high altitude, water clouds, mixed-phase clouds, and ice clouds was successfully obtained. In the tropics, vertically thick cloud layers in the middle to upper troposphere and vertically thin cirrus layers in the upper troposphere were successfully detected in two separate flights. The data quality is much better at night, dusk, and dawn than during the daytime because strong sunlight affects the measurements of scattered light.

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Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

Cited by 17 publications

References 50 publications

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

The SPectrometer for Ice Nuclei (SPIN): an instrument to investigate ice nucleation

Development of a cloud particle sensor for radiosonde sounding

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