Further laboratory studies of the charging of graupel during ice crystal interactions

Keith, W. D.; Saunders, C. P. R.

doi:10.1016/0169-8095(90)90028-b

Cited by 82 publications

(64 citation statements)

References 26 publications

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“…The charge transfer measurements were carried out in a cold room cloud chamber system described by Keith and Saunders [ 1990]. A water boiler provided vapor throughout the experiment to create a supercooled water droplet cloud whose initial spectrum, determined in the present work with a continuous Formvat replicatot [Hallett, 1976] and uncorrected for sampler/droplet collision efficiency, is shown in Figure 4 was opened, and the resultant target charging was recorded on a chart recorder.…”

Section: Methodsmentioning

confidence: 99%

“…Jayaratne et al [1983] determined the dependence of charge transfer on temperature, liquid water content, graupel/crystal velocity, and ice crystal size; they suggested that the usual thunderstorm dipole, positive above negative, could be accounted for by the negative charging of graupel above a "charge-sign reversal temperature level" with the positive crystals being carried aloft in the updraft; below the "reversal level", graupel pellets charge positively and fall to form a lower positive charge region. The dependencies of the magnitude of the charge transfer on ice crystal size for crystals up to 800 ttm and on graupel/crystal velocity for velocities up to 25 m s '• at constant rime accretion rate, achieved by reducing the liquid water content (LWC) appropriately as the speed was increased, were determined in laboratory experiments by Keith and Saunders [1990]. They found that charge transfer increases with crystal size but is limited by the reverse transfer of charge in the local high field region between the near surfaces of the pellet and ice crystal when they separate.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory studies of the influence of the rime accretion rate on charge transfer during crystal/graupel collisions

Saunders¹,

Peck²

1998

J. Geophys. Res.

247

244

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Abstract. The process of thunderstorm electrification by charge transfers between ice crystals and riming graupel pellets (the noninductive process) has been the subject of extensive study in the laboratory in Manchester. Quantitative dependencies of the sign and magnitude of charge transfer have previously been determined as functions of ice crystal size, graupel/crystal relative velocity, temperature, and the effective liquid water content (EW) in the cloud experienced by the riming graupel pellets. We now present results of laboratory studies of thunderstorm charging in terms of the rime accretion rate (RAR = EW x V), which combines into one variable the velocity and EW dependence of the sign of graupel charging on temperature. The magnitude of the charge transfer can be determined from its dependence on the crystal size and graupel velocity, while the sign of the timer charging can now be determined from a new figure showing the dependence of the charge sign on RAR and temperature. This figure may be used to compare charge transfer results from other laboratories obtained over a range of graupel/crystal velocities. These new experiments extend the temperature range of the previous studies and indicate that negative charging of graupel can occur at temperatures as high as -2øC in conditions of low RAR, while at temperatures below-30øC, more positive graupel charging is noted than in the earlier work.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laboratory studies of the influence of the rime accretion rate on charge transfer during crystal/graupel collisions

Saunders¹,

Peck²

1998

J. Geophys. Res.

247

244

View full text Add to dashboard Cite

show abstract

“…1997; Saunders and Peck, 1998;Jayaratne, 1996Jayaratne, , 1998], and functional equations have been fitted to the data over limited regimes. Keith and Saunders [1990] showed that the charge transfer to the target depended on crystal size and speed as power laws, with exponents varying over particular ranges of size and temperature in the positive and negative charging regimes. The data were extended and further analyzed by Saunders et al [1991].…”

Section: Application Of the Theory To Charging Inmentioning

confidence: 99%

Theory of charge and mass transfer in ice‐ice collisions

Dash¹,

Mason²,

Wettlaufer³

2001

J. Geophys. Res.

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Abstract. A new model describes charge and mass transfer in ice-ice collisions in terms of fundamental molecular physics. Drawing on clues from results of recent and earlier experiments, the theory treats the collisions as interlinked events acting in three stages: before collision, during contact, and withdrawal. The theory provides quantitative descriptions of charge and mass transfer and their dependence on growth rate, temperature, and impact energy. Application of the theory to experimental simulations of thunderstorm charging explains general trends in terms of basic microscopic processes.

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“…As in Mansell et al (2005), the charge exchanged per rebounding collision δq is limited to prevent unreasonable charging rate. Based on Keith and Saunders (1990), it is assumed that the charging rate of the pristine ice crystal with D max ∼ 100 µm is the most limiting one, that is 30(10) fC per collision with graupel (aggregate) particles. We take a larger value (100 fC) for the graupel-snow collisions because it corresponds roughly to an average of the saturation levels when the particle sizes reach ∼1 mm (see Saunders, 1990 or Fig.…”

Section: Charge Separation Mechanismsmentioning

confidence: 99%

CELLS v1.0: updated and parallelized version of an electrical scheme to simulate multiple electrified clouds and flashes over large domains

et al. 2012

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Abstract. The paper describes the fully parallelized electrical scheme CELLS which is suitable to simulate explicitly electrified storm systems on parallel computers. Our motivation here is to show that a cloud electricity scheme can be developed for use on large grids with complex terrain. Large computational domains are needed to perform real case meteorological simulations with many independent convective cells.The scheme computes the bulk electric charge attached to each cloud particle and hydrometeor. Positive and negative ions are also taken into account. Several parametrizations of the dominant non-inductive charging process are included and an inductive charging process as well. The electric field is obtained by inverting the Gauss equation with an extension to terrain-following coordinates. The new feature concerns the lightning flash scheme which is a simplified version of an older detailed sequential scheme. Flashes are composed of a bidirectional leader phase (vertical extension from the triggering point) and a phase obeying a fractal law (with horizontal extension on electrically charged zones). The originality of the scheme lies in the way the branching phase is treated to get a parallel code.The complete electrification scheme is tested for the 10 July 1996 STERAO case and for the 21 July 1998 EU-LINOX case. Flash characteristics are analysed in detail and additional sensitivity experiments are performed for the STERAO case. Although the simulations were run for flat terrain conditions, they show that the model behaves well on multiprocessor computers. This opens a wide area of application for this electrical scheme with the next objective of running real meterological case on large domains.

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Further laboratory studies of the charging of graupel during ice crystal interactions

Cited by 82 publications

References 26 publications

Laboratory studies of the influence of the rime accretion rate on charge transfer during crystal/graupel collisions

Laboratory studies of the influence of the rime accretion rate on charge transfer during crystal/graupel collisions

Theory of charge and mass transfer in ice‐ice collisions

CELLS v1.0: updated and parallelized version of an electrical scheme to simulate multiple electrified clouds and flashes over large domains

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