High-Speed Photography of Airborne Atmospheric Particles

Cannon, Theodore W.

doi:10.1175/1520-0450(1970)009<0104:hspoaa>2.0.co;2

Cited by 9 publications

(5 citation statements)

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“…This distance is close to the theoretical and experimental prediction of the distance required for large drops (greater than 2 mm) to reach the V t from rest under atmospheric conditions of 1000 mb and 20 • C (Wang and Pruppacher, 1977). However, the laboratory simulations from a recent study of Chowdhury et al (2016) have also shown that the required fall distances to reach the V t are slightly smaller than the theoretical values, with ∼ 7 (10) m for a drop size of 2.6 (3.7) mm. These results suggest that the fall distance in our experimental setup should be adequate for studying the V t .…”

Section: Instruments and Indoor Experimental Settingssupporting

confidence: 80%

Measuring Droplet Fall Speed with a High-Speed Camera: Indoor Accuracy and Potential Outdoor Applications

Yu¹,

Hsieh²,

Yuter³

et al. 2016

Preprint

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Abstract. The acquisition of accurate rain drop fall speed measurements outdoors in natural rain represents a long-standing and challenging issue in the meteorological community. Feasibility experiments were conducted to evaluate the indoor accuracy of fall speed measurements made with a high-speed camera and to evaluate its capability for outdoor applications. An indoor experiment operating in calm conditions showed that the high-speed imaging technique can provide fall speed measurements with a mean error of 4.1~9.7% compared to Gunn and Kinzer’s empirical fall speed-size relationship for typical sizes of rain and drizzle drops. Results obtained using the same apparatus outside in summer afternoon showers indicated larger, positive and negative velocity deviations compared to the indoor measurements. These observed deviations suggest that ambient flow and turbulence play a role in modifying drop fall speeds which can be quantified with future outdoor high-speed camera measurements. Because the fall speed measurements, as presented in this article, are analyzed on the basis of tracking individual, specific rain drops, sampling uncertainties commonly found in the widely adopted optical disdrometers can be significantly mitigated.

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Section: Instruments and Indoor Experimental Settingssupporting

confidence: 80%

Measuring Droplet Fall Speed with a High-Speed Camera: Indoor Accuracy and Potential Outdoor Applications

Yu¹,

Hsieh²,

Yuter³

et al. 2016

Preprint

View full text Add to dashboard Cite

show abstract

“…These results suggest that the fall distance in our experimental setup should be adequate for studying the V t . The bright-field illumination technique (Cannon, 1970;Jones et al, 2003;Testik et al, 2006), provided by a light source standing in front of the lens (Fig. 1), was used to produce a bright background and a dark drop silhouette.…”

Section: Instruments and Indoor Experimental Settingsmentioning

confidence: 99%

Measuring droplet fall speed with a high-speed camera: indoor accuracy and potential outdoor applications

Hsieh

Yuter

et al. 2016

Atmos. Meas. Tech.

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Abstract. Acquisition of accurate raindrop fall speed measurements outdoors in natural rain by means of moderatecost and easy-to-use devices represents a long-standing and challenging issue in the meteorological community. Feasibility experiments were conducted to evaluate the indoor accuracy of fall speed measurements made with a high-speed camera and to evaluate its capability for outdoor applications. An indoor experiment operating in calm conditions showed that the high-speed imaging technique can provide fall speed measurements with a mean error of 4.1-9.7 % compared to Gunn and Kinzer's empirical fall-speed-size relationship for typical sizes of rain and drizzle drops. Results obtained using the same apparatus outside in summer afternoon showers indicated larger positive and negative velocity deviations compared to the indoor measurements. These observed deviations suggest that ambient flow and turbulence play a role in modifying drop fall speeds which can be quantified with future outdoor high-speed camera measurements. Because the fall speed measurements, as presented in this article, are analyzed on the basis of tracking individual, specific raindrops, sampling uncertainties commonly found in the widely adopted optical disdrometers can be significantly mitigated.

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“…The configuration of the particle imager, which is based on optical microscopy, is in part similar to some imaging systems used for precipitation or cloud particle measurements (Cannon 1970;Lawson et al 2001;Schö n et al 2011). As shown schematically in Fig.…”

Section: Particle Imager a Optical Configurationmentioning

confidence: 99%

Improved Imaging and Image Analysis System for Application to Measurement of Small Ice Crystals

Kühn

Grishin

Sloan

2012

Journal of Atmospheric and Oceanic Technology

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Accurate knowledge of ice particle size and shape distribution is required for understanding of atmospheric microphysical processes. While larger ice particles are easily measured with a variety of sensors, the measurement of small ice particles with sizes down to a few micrometers remains challenging. Here the authors report the development of a system that measures the size and shape of small ice particles using a novel combination of high-resolution imaging and high-speed automated image classification. The optical system has a pixel resolution of 0.2 mm and a resolving power of approximately 1 mm. This imaging instrument is integrated into a cryogenic flow tube that allows precise control of experimental conditions. This study also describes an automated method for the high-speed analysis of high-resolution particle images. Each particle is located in the image using a Sobel edge detector, the border is vectorized, and a polygon representing the border is found. The vertices of this polygon are expressed in complex coordinates, and an analytic implementation of Fourier shape descriptors is used for piecewise integration along the edges of the polygon.The authors demonstrate the capabilities of this system in a study of the early-stage growth of ice particles, which are grown for approximately 1 min at fixed temperature and saturated water vapor concentrations in the cryogenic flowtube. Ice particle shapes and size distributions are reported and compared with habit diagrams found in the literature. The capability of the shape recognition system is verified by comparison with manual classification.

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High-Speed Photography of Airborne Atmospheric Particles

Cited by 9 publications

References 0 publications

Measuring Droplet Fall Speed with a High-Speed Camera: Indoor Accuracy and Potential Outdoor Applications

Measuring Droplet Fall Speed with a High-Speed Camera: Indoor Accuracy and Potential Outdoor Applications

Measuring droplet fall speed with a high-speed camera: indoor accuracy and potential outdoor applications

Improved Imaging and Image Analysis System for Application to Measurement of Small Ice Crystals

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