Light-scattering properties of plate and column ice crystals generated in a laboratory cold chamber

Barkey, Brian; Bailey, Martin J.; Liou, Kuo‐Nan; Hallett, John

doi:10.1364/ao.41.005792

Cited by 32 publications

(18 citation statements)

References 12 publications

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“…Case A data (non-halo case) represented by red symbols are distributed over a smaller MVD range (< 130 µm) and with sizes larger than 20 µm. This size appears to delineate the lower limit of ice crystal size responsible (at visible wavelengths) for halo formation according to earlier laboratory studies (Sassen and Liou, 1979;Barkey et al, 2002) and theoretical results (Mishchenko and Macke, 1999). In situ observations at the South Pole station (Shcherbakov et al, 2006a;Lawson et al, 2006) also reported very well-marked 22 • halo peaks with pristine ice crystals no larger than 100 µm.…”

Section: Discussionsupporting

confidence: 81%

“…Observations of cloud ice particles tend to show much smoother scattering behaviour compared with modelling results obtained in laboratory studies (Sassen and Liou, 1979;Crépel et al, 1997;Barkey et al, 2002). The first in situ observations of azimuthal scattering patterns also confirmed that smooth scattering phase functions prevail in cirrus clouds Auriol et al, 2001;Field et al, 2003a;Gayet et al, 2004;Baumgardner et al, 2005). Defaults in crystal geometry, roughness of the ice surface or imperfect internal structure are known to hamper the formation of halos (see among others Baran and Labonnote, 2007).…”

Section: Introductionmentioning

confidence: 57%

“…Modelling studies of scattering phase functions show that these features are an indication of highly regular pristine ice crystals (see among others Takano and Liou, 1989;Iaquinta et al, 1995;Macke et al, 1996a;Yang et al, 2001;Um and McFarquhar, 2010). Observations of cloud ice particles tend to show much smoother scattering behaviour compared with modelling results obtained in laboratory studies (Sassen and Liou, 1979;Crépel et al, 1997;Barkey et al, 2002). The first in situ observations of azimuthal scattering patterns also confirmed that smooth scattering phase functions prevail in cirrus clouds Auriol et al, 2001;Field et al, 2003a;Gayet et al, 2004;Baumgardner et al, 2005).…”

Section: Introductionmentioning

confidence: 65%

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Optical properties of pristine ice crystals in mid-latitude cirrus clouds: a case study during CIRCLE-2 experiment

et al. 2011

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Abstract. In this paper, we describe in situ observations of mid-latitude cirrus cloud band carried out on 16 May 2007 during the CIRCLE-2 experiment. The Polar Nephelometer and the Cloud Particle Imager (CPI) instruments with PMS FSSP-300 and 2D-C probes were used for the description of the optical and microphysical cloud properties. Two selected cloud regions are compared and discussed in detail. Significant differences in optical properties are evidenced in terms of 22 • halo occurrences even though prevalent planarplate ice crystals are observed in both cloud regions. Featureless scattering phase functions are measured in the first cloud region located near the trailing edge of the cirrus-band at about 11 800 m/−57 • C. In contrast, well pronounced 22 • halo peaks are observed with predominant similar-shaped ice crystals near the cirrus-band leading edge at 7100 m/−27 • C. CPI ice crystal images with Polar Nephelometer observations are carefully analysed and interpreted from a theoretical light scattering model in order to explain occurrence and non-occurrence of the 22 • halo feature. The results highlight that the halo peaks are inherent only in perfect plate ice crystals (or pristine crystals). On the basis of previous datasets in mid-latitude cirrus, it is found that simple pristine crystals are uncommon whereas particles with imperfect or complex shapes are prevalent. As a result, phase functions that are smooth and featureless best represent cirrus scattering properties.

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 65%

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Optical properties of pristine ice crystals in mid-latitude cirrus clouds: a case study during CIRCLE-2 experiment

et al. 2011

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“…The HG phase function is very smooth, while that of spheres features icebow and glory peaks not seen for real snow along with very low sideward scattering. Based on a comparison of a few shape models with phase function measurements for laboratory-generated ice crystals (Barkey et al, 2002), Kokhanovsky and Zege (2004) recommended, instead of spheres, the use of Gaussian random spheres (Muinonen et al, 1996;Nousiainen and Muinonen, 1999) or Koch fractals (Macke et al, 1996), which both exhibit a relatively featureless phase function. Since Gaussian random spheres have several free parameters while Koch fractals have none (except for the degree of distortion for randomized Koch fractals), Koch fractals were selected by Kokhanovsky and Zege (2004).…”

Section: P Räisänen Et Al: Parameterization Of Single-scattering Prmentioning

confidence: 99%

Parameterization of single-scattering properties of snow

et al. 2015

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Abstract. Snow consists of non-spherical grains of various shapes and sizes. Still, in many radiative transfer applications, single-scattering properties of snow have been based on the assumption of spherical grains. More recently, second-generation Koch fractals have been employed. While they produce a relatively flat phase function typical of deformed non-spherical particles, this is still a rather ad hoc choice. Here, angular scattering measurements for blowing snow conducted during the CLimate IMpacts of Short-Lived pollutants In the Polar region (CLIMSLIP) campaign at Ny Ålesund, Svalbard, are used to construct a reference phase function for snow. Based on this phase function, an optimized habit combination (OHC) consisting of severely rough (SR) droxtals, aggregates of SR plates and strongly distorted Koch fractals is selected. The single-scattering properties of snow are then computed for the OHC as a function of wavelength λ and snow grain volume-to-projected area equivalent radius r vp . Parameterization equations are developed for λ = 0.199-2.7 µm and r vp = 10-2000 µm, which express the single-scattering co-albedo β, the asymmetry parameter g and the phase function P 11 as functions of the size parameter and the real and imaginary parts of the refractive index. The parameterizations are analytic and simple to use in radiative transfer models. Compared to the reference values computed for the OHC, the accuracy of the parameterization is very high for β and g. This is also true for the phase function parameterization, except for strongly absorbing cases (β > 0.3). Finally, we consider snow albedo and reflected radiances for the suggested snow optics parameterization, making comparisons to spheres and distorted Koch fractals.

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“…On one hand, snow strongly reflects UV light, and plants, which absorb it, are therefore expected to show up in high contrast against the light (UV-reflecting) background. Where plants are closely surrounded by or even partially covered with snow, however, heterogeneous angular scattering of UV off randomly orientated snow crystals (Barkey et al, 2002;Kokhanovsky and Zege, 2004;Shcherbakov et al, 2006) potentially reduces this contrast. This possibility raises the question of how diminutive Arctic plants lying in the snow where Rangifer feed (Pruitt, 1959;LaPerriere and Lent, 1977;Skogland, 1978) appear under natural UV illumination.…”

Section: Introductionmentioning

confidence: 99%

Ultraviolet Vision May Enhance the Ability of Reindeer to Discriminate Plants in Snow

Tyler¹,

Jeffery²,

Hogg³

et al. 2014

ARCTIC

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ABSTRACT. In reindeer/caribou (Rangifer tarandus), the lens and cornea of the eye transmit ultraviolet (UV) light, and the retinae respond to it electrophysiologically. Here we tie this finding to the unusual visual environment experienced by these animals and propose that their sensitivity to UV light enhances vision at the low luminance characteristic of the polar winter. For such visual enhancement to occur, it is essential that functional components of the environment, such as forage plants, be visually salient under natural UV luminance. It is not self-evident, however, that this is the case. Although organic material generally absorbs UV radiation, powerful scattering of UV light by snow crystals potentially reduces contrast with the background. We therefore recorded UV images of vegetation in situ on snow-covered pasture under natural winter (March) luminance in northern Norway. For each vegetation scene, we made three monochrome digital images at 350 -390 nm (UV-Only), 400 -750 nm (No-UV), and 350 -750 nm (control), respectively. Plants at the snow surface appeared in high achromatic contrast against snow in UV-Only images. The contrast was substantially greater in the UV-Only images than in corresponding images in which UV was blocked. We conclude that plants are visually salient under natural UV luminance at wavelengths to which Rangifer are sensitive. This sensitivity is likely to improve the animals' ability to discriminate forage in snow, particularly at low but relatively UV-enriched twilight luminance.Key words: albedo, caribou, Rangifer, reindeer, foraging, snow, ultraviolet, vascular plants, vision RÉSUMÉ. Le cristallin et la cornée de l'oeil du caribou (aussi connu sous le nom de renne) (Rangifer tarandus) transmettent une lumière ultraviolette (UV), à laquelle la rétine envoie une réponse électrophysiologique. Ici, nous faisons le lien entre cette observation et l'environnement visuel inhabituel de ces animaux, puis nous proposons que leur sensibilité à la lumière UV enrichit leur vision dans la faible luminance de l'hiver polaire. Pour que cet enrichissement ait lieu, il est essentiel que les composantes fonctionnelles de l'environnement, comme les plantes fourragères, soient visuellement saillantes sous la luminance UV naturelle. Il ne va cependant pas de soi que c'est le cas. Bien que la matière organique absorbe généralement le rayonnement ultraviolet, la diffusion puissante de la lumière UV découlant de la présence des cristaux de neige peut avoir pour effet de réduire le contraste avec l'arrière-plan. Par conséquent, nous avons enregistré des images ultraviolettes de la végétation in situ dans des pâturages couverts de neige sous la luminance naturelle de l'hiver (en mars), dans le nord de la Norvège. Pour chacune des scènes de végétation, nous avons fait trois images monochromes numériques, soit 350 à 390 nm (UV seulement), 400 à 750 nm (sans UV) et 350 à 750 nm (contrôlé), respectivement. Les plantes à la surface de la neige apparaissaient en fort contraste achromatique contre la neige...

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Light-scattering properties of plate and column ice crystals generated in a laboratory cold chamber

Cited by 32 publications

References 12 publications

Optical properties of pristine ice crystals in mid-latitude cirrus clouds: a case study during CIRCLE-2 experiment

Optical properties of pristine ice crystals in mid-latitude cirrus clouds: a case study during CIRCLE-2 experiment

Parameterization of single-scattering properties of snow

Ultraviolet Vision May Enhance the Ability of Reindeer to Discriminate Plants in Snow

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