A theoretical study of the effect of electric charges on the efficiency with which aerosol particles are collected by ice crystal plates

Martin, J. J.; Wang, P.K; Pruppacher, H. R.

doi:10.1016/0021-9797(80)90494-4

Cited by 49 publications

(9 citation statements)

References 17 publications

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“…The calculations presented here apply to scavenging by liquid cloud droplets, but the method of including diffusion could be extended to scavenging by ice crystals. Previous work (without diffusion) has been reviewed by Pruppacher and Klett [1997, section 18.6.6], and theoretical results due to Martin et al [1980] have been compared with experimental data by Murakami et al [1985], for large ice crystals. A comprehensive treatment of scavenging by ice crystals is given by Wang [2002], with examples of effects of opposite sign charges on the aerosol particles and ice crystals.…”

Section: Discussionmentioning

confidence: 99%

Electric charge modulation of aerosol scavenging in clouds: Rate coefficients with Monte Carlo simulation of diffusion

Tinsley

2010

J. Geophys. Res.

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[1] The effects of electric charge on the scavenging by droplets of aerosol particles, particularly cloud condensation nuclei, appear to have a significant effect on cloud properties and climate. The effects on scavenging are calculated here in a trajectory model relative to the falling droplets, with a Monte Carlo simulation of particle diffusion along the trajectory. The charges are in the range 5-100 elementary charges, consistent with the measured and modeled deposition of small amounts of charge by the flow everywhere of atmospheric electric current density (part of the global circuit) through clouds. Particles move through a corrected Stokes flow field, under the influence of gravitational, phoretic, electric, and drag forces while diffusing. For the general situation of like charges on droplets and aerosol particles, the model simulates the long-range electrical repulsive force that has a net effect of reducing the collision rates for small particles (radii less than about 0.1 mm) below the values for combined Brownian diffusion and phoretic forces. It also simulates the net effect for larger particles of the short-range attractive electric forces in increasing the rate coefficients above the Brownian and phoretic values. Initial validation is provided by treating the case of ventilation in pure Brownian diffusion, for which new and more accurate ventilation coefficients are obtained as a function of the Péclet number. These are applicable to combined diffusion and phoretic scavenging with pure inverse square scavenging forces. The rate constants obtained for the electrical effects, comparable to those for Brownian and phoretic scavenging process, lead to time scales for scavenging in clouds of a few hours, consistent with observations of significant electrical effects on clouds associated with modulation of the global circuit.

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Section: Discussionmentioning

confidence: 99%

Electric charge modulation of aerosol scavenging in clouds: Rate coefficients with Monte Carlo simulation of diffusion

Tinsley

2010

J. Geophys. Res.

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“…For nonoverlapping cases of 0.001 < small radius < 10 μm and 42 < large radius < 310 μm, the coagulation kernel is overridden further as follows. Wang et al [1978] and Martin et al [1980] derived overall collision kernels that accounted for gravitation, thermophoresis, diffusiophoresis, particle charge, Brownian motion, and Brownian diffusion enhancement, but not turbulent shear or turbulent inertial motion. Their kernel was in the form of the first expression below, which equals the second expression In this equation, r j is the big‐particle radius (cm), B P , Ii is the mobility (s g −1 ) of small particles of radius r i (cm), C Ii , Jj is a complex parameter (g cm 3 s −2 ) that depends on charge, thermophoresis, and diffusiophoresis, D p , Ii is the diffusion coefficient (cm 2 s −1 ) of the small particle, F p , Ii , Jj is the ventilation coefficient for the small particle impacting the large particle, K B , Ii , Jj is the Brownian diffusion collision kernel (cubic centimeter per particle per second), K DE, Ii , Jj is the Brownian diffusion enhancement collision kernel, and for the case of a small particle interacting with a large particle, [ K B + K DE ] Ii , Jj = 4π D p , i r i F p , i , j .…”

Section: Aerosol‐cloud Processesmentioning

confidence: 99%

“…[38] For nonoverlapping cases of 0.001 < small radius < 10 mm and 42 < large radius < 310 mm, the coagulation kernel is overridden further as follows. Wang et al [1978] and Martin et al [1980] derived overall collision kernels that accounted for gravitation, thermophoresis, diffusiopho-resis, particle charge, Brownian motion, and Brownian diffusion enhancement, but not turbulent shear or turbulent inertial motion. Their kernel was in the form of the first expression below, which equals the second expression K tot;Ii;Jj ¼ 4pB P;Ii C Ii;Jj exp B P;Ii C Ii;Jj =D p;Ii r j F p;Ii;Jj À Á À 1…”

Section: Hydrometeor-hydrometeor Coagulationmentioning

confidence: 99%

Development of mixed‐phase clouds from multiple aerosol size distributions and the effect of the clouds on aerosol removal

Jacobson¹

2003

J. Geophys. Res.

105

115

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This paper provides numerics for cloud and precipitation development from multiple aerosol size distributions and examines the effect of clouds and precipitation on aerosol removal. Numerical techniques are given for (1) simultaneous liquid and ice growth onto multiple aerosol size distributions, (2) diffusiophoretic, thermophoretic, gravitational, etc., coagulation among liquid, ice, and graupel, and their aerosol components, (3) contact freezing (CF) of drops by size‐resolved interstitial aerosols, (4) heterogeneous plus homogeneous freezing, (5) liquid drop breakup, (6) coagulation of cloud hydrometeors and incorporated aerosols with interstitial aerosols, (7) coagulation of precipitation hydrometeors with interstitial and below‐cloud aerosols (washout), (8) removal of precipitation and incorporated aerosols (rainout), (9) below‐cloud evaporation/sublimation to smaller hydrometeors and aerosol cores, (10) gas washout, and (11) aqueous chemistry. Major conclusions are (1) hydrometeor‐hydrometeor coagulation appears to play a substantial role in controlling aerosol‐particle number globally, (2) washout (aerosol‐hydrometeor coagulation) may be a more important in‐plus below‐cloud removal mechanism of aerosol number than rainout (the opposite is true for aerosol mass), (3) close‐in diameter dual peaks in observed cloud distributions may be in part due to different activation characteristics of different aerosol distributions, (4) evaporative cooling at liquid drop surfaces in subsaturated air may be a mechanism of drop freezing (termed “evaporative freezing” here), and (5) heterogeneous‐homogeneous freezing may freeze more upper‐tropospheric drops than CF, but neither appears to affect warm‐cloud hydrometeor distributions or aerosol scavenging substantially.

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“…Such charging can cause ice crystals to orient (Vonnegut, 1965) and possibly levitate (Gibbard et al, 1995) in the electrical atmosphere of thunderclouds. Surface charging can modify many atmospheric processes such as collection of ions, aerosols, and droplets by ice (Martin et al 1980;Pruppacher and Klett, 1980 p. 619), and aggregation of snow crystals in clouds (Odencrantz and Buecher, 1967;Finnegan and Pitter, 1988) and in wind-blown snow (Schmidt, 1982). The transfers of charge when an ice particle strikes another ice surface or another material are examples of contact charging involving electronic insulators, one of the oldest problems of an electrical nature (Castle, 1997).…”

Section: Introductionmentioning

confidence: 99%

Charging of ice-vapor interfaces: applications to thunderstorms

Nelson¹,

Baker

2003

Atmos. Chem. Phys.

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Abstract. The build-up of intrinsic Bjerrum and ionic defects at ice-vapor interfaces electrically charges ice surfaces and thus gives rise to many phenomena including thermoelectricity, ferroelectric ice films, sparks from objects in blizzards, electromagnetic emissions accompanying cracking in avalanches, glaciers, and sea ice, and charge transfer during ice-ice collisions in thunderstorms. Fletcher's theory of the ice surface in equilibrium proposed that the Bjerrum defects have a higher rate of creation at the surface than in the bulk, which produces a high concentration of surface D defects that then attract a high concentration of OH − ions at the surface. Here, we add to this theory the effect of a moving interface caused by growth or sublimation. This effect can increase the amount of ionic surface charges more than 10-fold for growth rates near 1 µm s −1 and can extend the spatial separation of interior charges in qualitative agreement with many observations. In addition, ice-ice collisions should generate sufficient pressure to melt ice at the contact region and we argue that the ice particle with the initially sharper point at contact loses more mass of melt than the other particle. A simple analytic model of this process with parameters that are consistent with observations leads to predicted collisional charge exchange that semiquantitatively explains the negative charging region of thunderstorms. The model also has implications for snowflake formation, ferroelectric ice, polarization of ice in snowpacks, and chemical reactions in ice surfaces.

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A theoretical study of the effect of electric charges on the efficiency with which aerosol particles are collected by ice crystal plates

Cited by 49 publications

References 17 publications

Electric charge modulation of aerosol scavenging in clouds: Rate coefficients with Monte Carlo simulation of diffusion

Electric charge modulation of aerosol scavenging in clouds: Rate coefficients with Monte Carlo simulation of diffusion

Development of mixed‐phase clouds from multiple aerosol size distributions and the effect of the clouds on aerosol removal

Charging of ice-vapor interfaces: applications to thunderstorms

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