Charge transfer associated with temperature gradients in ice crystals grown in a diffusion chamber

1964 ◽  
Vol 90 (385) ◽  
pp. 266-274 ◽  
Author(s):  
J. Latham
Keyword(s):  
Charge Transfer ◽  
Diffusion Chamber ◽  
Temperature Gradients ◽  
Ice Crystals

scholarly journals Estimating Surface Attachment Kinetic and Growth Transition Influences on Vapor-Grown Ice Crystals

2020 ◽  
Vol 77 (7) ◽  
pp. 2393-2410
Author(s):  
Gwenore F. Pokrifka ◽  
Alfred M. Moyle ◽  
Lavender Elle Hanson ◽  
Jerry Y. Harrington
Keyword(s):  
Diffusion Chamber ◽  
Ice Crystals ◽  
Growth Theory ◽  
Growth Data ◽  
Surface Attachment ◽  
Mass Growth ◽  
Vapor Growth ◽  
Deposition Coefficient ◽  
Direct Use ◽  
Large Decline

AbstractThere are few measurements of the vapor growth of small ice crystals at temperatures below −30°C. Presented here are mass-growth measurements of heterogeneously and homogeneously frozen ice particles grown within an electrodynamic levitation diffusion chamber at temperatures between −44° and −30°C and supersaturations si between 3% and 29%. These growth data are analyzed with two methods devised to estimate the deposition coefficient α without the direct use of si. Measurements of si are typically uncertain, which has called past estimates of α into question. We find that the deposition coefficient ranges from 0.002 to unity and is scattered with temperature, as shown in prior measurements. The data collectively also show a relationship between α and si, with α rising (falling) with increasing si for homogeneously (heterogeneously) frozen ice. Analysis of the normalized mass growth rates reveals that heterogeneously frozen crystals grow near the maximum rate at low si, but show increasingly inhibited (low α) growth at high si. Additionally, 7 of the 17 homogeneously frozen crystals cannot be modeled with faceted growth theory or constant α. These cases require the growth mode to transition from efficient to inefficient in time, leading to a large decline in α. Such transitions may be, in part, responsible for the inconsistency in prior measurements of α.

Electric charge transfer associated with temperature gradients in ice

1961 ◽  
Vol 260 (1303) ◽  
pp. 523-536 ◽  
Keyword(s):  
Charge Transfer ◽  
Electric Charge ◽  
Contact Time ◽  
Temperature Gradients ◽  
Potential Difference ◽  
Contact Period ◽  
Maximum Charge ◽  
Different Temperatures ◽  
Electric Potentials ◽  
Set Up

The development of electric potentials in ice crystals under the influence of temperature gradients is investigated both theoretically and experimentally. The maintenance of a steady temperature gradient across a piece of ice is accompanied by concentration gradients of H + and OH - ions; because of the much greater mobility of H + ions, these diffuse more rapidly into the colder part of the ice and, in the steady state, a potential difference is set up across the ice crystal, the colder end being positive. A theory of this effect predicts a surface density of charge on the ends of the ice of σ = 5 x 10 -5 (d T /d x ) e. s. u. cm -2 and a potential difference across a uniform specimen of about 2Δ T mV, where Δ T is the temperature difference across the ends. These values are quite well confirmed by a series of experiments on specimens of highly purified ice. When two pieces of ice of initially different temperatures are brought into temporary contact and separated, the warmer acquires a negative charge and the colder an equal positive charge. The theory indicates that a maximum charge transfer of 3 x 10 -3 Δ T , e. s. u. cm -2 should occur with a contact time of about 0.01 s and that it should thereafter decline as the two pieces of ice become more nearly equal in temperature. The theoretical value for the charge developed for a contact time of ~ 0.01 s is well confirmed by experiments which also show that very little charge separation occurs if the contact period exceeds ½ s. Experiments in which the ice was contaminated with carbon dioxide, hydrofluoric acid, and sodium chloride in concentrations of up to 50 times that normally present in rain water, showed that the electrification was not greatly influenced by these impurities. These phenomena are thought to be of basic importance in the generation of electric charge in thunderstorms, this aspect being developed in the following paper.

scholarly journals Using depolarization to quantify ice nucleating particle concentrations: a new method

2017 ◽  
Vol 10 (12) ◽  
pp. 4639-4657 ◽  
Author(s):  
Jake Zenker ◽  
Kristen N. Collier ◽  
Guanglang Xu ◽  
Ping Yang ◽  
Ezra J. T. Levin ◽  
...  
Keyword(s):  
Standard Procedure ◽  
Diffusion Chamber ◽  
Operating Conditions ◽  
Ice Crystals ◽  
New Method ◽  
State University ◽  
Analysis Method ◽  
Colorado State University ◽  
Nominal Size ◽  
Wide Range

Abstract. We have developed a new method to determine ice nucleating particle (INP) concentrations observed by the Texas A&M University continuous flow diffusion chamber (CFDC) under a wide range of operating conditions. In this study, we evaluate differences in particle optical properties detected by the Cloud and Aerosol Spectrometer with POLarization (CASPOL) to differentiate between ice crystals, droplets, and aerosols. The depolarization signal from the CASPOL instrument is used to determine the occurrence of water droplet breakthrough (WDBT) conditions in the CFDC. The standard procedure for determining INP concentration is to count all particles that have grown beyond a nominal size cutoff as ice crystals. During WDBT this procedure overestimates INP concentration, because large droplets are miscounted as ice crystals. Here we design a new analysis method based on depolarization ratio that can extend the range of operating conditions of the CFDC. The method agrees reasonably well with the traditional method under non-WDBT conditions with a mean percent error of ±32.1 %. Additionally, a comparison with the Colorado State University CFDC shows that the new analysis method can be used reliably during WDBT conditions.

scholarly journals Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

2014 ◽  
Vol 14 (22) ◽  
pp. 12357-12371 ◽  
Author(s):  
N. B. Magee ◽  
A. Miller ◽  
M. Amaral ◽  
A. Cumiskey
Keyword(s):  
Surface Roughness ◽  
Environmental Scanning Electron Microscopy ◽  
Diffusion Chamber ◽  
Ice Crystals ◽  
Environmental Scanning ◽  
Ice Crystal ◽  
Hexagonal Ice ◽  
Wide Range ◽  
Ice Surfaces ◽  
Cloud Modeling

Abstract. Here we show high-magnification images of hexagonal ice crystals acquired by environmental scanning electron microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions in which rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from −10 °C to −40 °C, in supersaturated and subsaturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomenon interpreted as evidence of 2-D nucleation. New knowledge about the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to supplemental videos of ice growth and sublimation are provided.

scholarly journals Using depolarization to quantify ice nucleating particle concentrations: a new method

2017 ◽  
Author(s):  
Jake Zenker ◽  
Kristen N. Collier ◽  
Guanglang Xu ◽  
Ping Yang ◽  
Ezra J. T. Levin ◽  
...  
Keyword(s):  
Diffusion Chamber ◽  
Operating Conditions ◽  
Ice Crystals ◽  
New Method ◽  
State University ◽  
Analysis Method ◽  
Size Discrimination ◽  
Colorado State University ◽  
Wide Range

Abstract. We have developed a new method to determine ice nucleating particle (INP) concentrations observed by a Continuous Flow Diffusion Chamber (CFDC) under a wide range of operating conditions. In this study, we evaluate differences in particle optical properties detected by the Cloud and Aerosol Spectrometer with POLarization (CASPOL) to differentiate between ice crystals, droplets, and aerosols. The depolarization signal from the CASPOL instrument is used to determine the occurrence of water droplet breakthrough (WDBT) conditions in the CFDC, under which traditional determination of ice nucleating particle concentrations by size discrimination fails. To overcome the challenge of WDBT, we design a new analysis method using depolarization ratio that can extend the range of operating conditions of the CFDC. The method agrees reasonably well with the traditional method under non-WDBT conditions with a mean percent error of ±32.1 %. Additionally, a comparison with the Colorado State University (CSU) CFDC shows that the new analysis method can be used reliably during WDBT conditions.

scholarly journals A High Speed Particle Phase Discriminator (PPD-HS) for the classification of airborne particles, as tested in a continuous flow diffusion chamber

2019 ◽  
Author(s):  
Fabian Mahrt ◽  
Jörg Wieder ◽  
Remo Dietlicher ◽  
Helen R. Smith ◽  
Chris Stopford ◽  
...  
Keyword(s):  
Particle Shape ◽  
Continuous Flow ◽  
High Speed ◽  
Scattered Light ◽  
Diffusion Chamber ◽  
Ice Crystals ◽  
Supervised Machine Learning ◽  
Particle Phase ◽  
New Instrument ◽  
Phase Discriminator

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.

scholarly journals A high-speed particle phase discriminator (PPD-HS) for the classification of airborne particles, as tested in a continuous flow diffusion chamber

2019 ◽  
Vol 12 (6) ◽  
pp. 3183-3208 ◽  
Author(s):  
Fabian Mahrt ◽  
Jörg Wieder ◽  
Remo Dietlicher ◽  
Helen R. Smith ◽  
Chris Stopford ◽  
...  
Keyword(s):  
Particle Shape ◽  
Continuous Flow ◽  
High Speed ◽  
Scattered Light ◽  
Diffusion Chamber ◽  
Ice Crystals ◽  
Supervised Machine Learning ◽  
Particle Phase ◽  
New Instrument ◽  
Phase Discriminator

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 2-D 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 µm. 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 µm. 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 the 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. From our laboratory experiments we conclude that PPD-HS constitutes a powerful new instrument to size and discriminate the phase of cloud hydrometeors. The working principle of PPD-HS forms a basis for future instruments to study microphysical properties of atmospheric mixed-phase clouds that represent a major source of uncertainty in aerosol-indirect effect for future climate projections.

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