ICAE International Commission on Atmospheric Electricity

ICAE 2003 Versailles

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and Poster Format


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Tuesday 10 th June



Session A4 Storm Electrification IV (poster)

  T. C. Marshall, M. Stolzenburg, L. M. Coleman, P. R. Krehbiel, W. Rison, and R. J. Thomas
Using Balloon Measurements to Verify and Quantify Radar and LMA Inferences About Thunderstorms
  Y. Michalowski
"Warm thunderstorm"- myth or reality
Y. Michalowski
Errors during aircraft measurements of the electric field and ways to reduce them
  K. Michimoto, T. Shimura, T. Suzuki and T. Hanada
A Study of Winter Thunderstorms in the Hokuriku Coastal Area, Japan
  R. P. Mitzeva, B. D. Tsenova, and C. P. R. Saunders
A modelling study of the effect of cloud supersaturation on non-inductive charge transfer
  Y. Muhong, S. Anping, and Z. Yijun
Numerical Study on Impact of Electrical Structure on Dynamic Development in Thunderstorm
  P. Jungwirth, D. Rosenfeld and V. Buch
A possible new molecular mechanism of thundercloud electrification
  A. A. Sinkevich, J. A. Dovgaluk, and V. D. Stepanenko
Corona discharge in clouds (overview)
  Y. Sonoi, Y. Maekawa, Z-I. Kawasaki, and S. Fukao
Correlation Coefficients between Disturbance Indexes and Updraft associated with Lightning Discharges Observed by Two kinds of Radars and SAFIR
  A. E. Sorokin
Charge Spectra of Colliding Ice Crystals and Graupels
  A. E. Sorokin
Selective ion charging of droplets in thunderstorms under arbitrary oriented electric field
  J. M. Straka, E. R. Mansell, C. L. Ziegler, D. R. MacGorman, and M. S. Gilmore
Electrification, lightning and microphysics in a simulated, 'bow echo' severe storm
T. Ushio, S. Heckman, H. Christian, Z-I. Kawasaki, and K. Okamoto
Vertical Development of Lightning Activity observed by the LDAR system -Lightning Bubbles
J. S. Wettlaufer and J. G.Dash
Positive and Negative Cloud-to-Ground Lightning
K. C. Wiens, S. A. Tessendorf, and S. A. Rutledge
STEPS June 29, 2000 Supercell: Observations of Kinematic, Microphysical, and Electrical Structure
J. C. Willett and J. E. Dye
A Simple Model to Estimate Electrical Decay Times in Anvil Clouds
C. Ziegler, E. Mansell, D. MacGorman, and J. Straka
Electrification and lightning in a simulated tornadic, supercell storm


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"Warm thunderstorm" - myth or reality"

Yuri Michalowski
tel. (812)7075238, (812)7075142
tel/fax (812)7075135,(812)2478681


The answer to the question about possibility of the existence of "the warm storms" is very actual for understanding the mechanism of the cloud electrification and in forecasting lightning. Analysis of the works that corroborate the existence of the warm storms shows that there are no enough reliable instrument observations of the warm storms. And what is more, even instrument measurements carried by the great researchers in this field (D.R. Fitzgeradl, H.R. Byers, B. Vonnegut, C.B. Moore, I.M. Imyanitov, I.M. Shwarts) that showed high values of the electric fields in warm clouds give rise to doubts, because the question of accuracy of measurements of electric field, particularly inside clouds, has not been solved till now.

In order to analyze the beginning of the convective cloud electrification we have carried a great number of aircraft experiments (in various climatic zones -from northwest of Russia till subtropical zone of the Caucus and in Cuba, and in different seasons and over different surfaces - and, sea, and mountains).

We have established that electrification was not recorded till the on-board radar could record large particles inside supercooled part of the cloud.

Thus, the results our experiments (in the first place!) and analysis of the articles about the "warm storms" bring us to conclude that the thunderstorm processes in the clouds without ice particles - is a myth.


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Errors during aircraft measurements of the electric field and ways to reduce them

Yuri Michalowski
tel. (812)7075238, (812)7075142
tel/fax (812)7075135,(812)2478681


Main Geophysical Observatory, St. Petersburg, Russia Analysis is suggested of basic errors appearing during aircraft measurements of the vector electric field in the atmosphere (E) and of the aircraft charge (self-charge) (Q). A technique is described to reduce errors in measuring the value of Q during flights outside clouds and other aerosol formations. Such errors are produced by inaccurate retrieval of form factors for E and Q. The form factors account for the fact that an aircraft is an electrically charged body of complex shape. Various approaches are pursued to compensate for the aircraft self-charge. Measurements are specifically taken in prescribed flight regimes when a priori information becomes available on E, on its separate components, or on the relation between these components and the value and sign of Q. Electric field measurements in clouds and aerosol formations are aggravated with additional difficulties since current generators acting upon the aircraft are highly powerful. Hence the principal assumptions on the homogeneity of the external field and the equipotentiality of the aircraft surface are violated. Certain approaches are suggested to reduce such errors in these conditions.  


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A Study of Winter Thunderstorms in the Hokuriku Coastal Area, Japan
Koichiro MICHIMOTO, Takatsugu SHIMURA, Tomoyuki SUZUKI and Takashi HANADA

For about a century, studies concerning summer thunderstorms in the middle latitude zone have elucidated data on both their meteorological and electrical features. By contrast, winter thunderstorms have been studied only for the last few decades.

For both reasons of scientific interest and the practical purpose of preventing serious damage by winter thunderbolts to aircrafts and electric power systems, studies of winter thunderstorms have currently become one of the focuses of lightning research.

The authors carried out thunderstorm observations in winter in the vicinity of Komatsu airport, which is situated on the Hokuriku coastline, for about 20 years. They used radar with CAPPI (Constant Altitude Plane Position Indicator) performance for thundercloud observations, a VHF sferics direction-finder system for lightning detection, and a network of field mills installed on 27 sites mutually separated by about 10 km for the investigation of thundercloud electrical structure.

The present work elucidates the meteorological and electrical nature of winter thunderstorms and clarifies how the aerological conditions determine the grade of the lightning activity.

Also, the authors will introduce a new direction-finding system (SAFIR), which will be installed in the vicinity of Komatsu airport by the next early spring. We can present newest results, which will be obtained by these new SAFIR system.

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A modelling study of the effect of cloud supersaturation on non-inductive charge transfer

R P Mitzeva and B D Tsenova,
Department of Meteorology, Faculty of Physics, University of Sofia, Sofia-1164, Bulgaria

C P R Saunders,
Physics Department, UMIST, Manchester, M60 1QD, England


Numerical studies are under way into the impact of cloud supersaturation on the sign of non-inductive charge transfer during graupel/ice crystal interactions in thunderstorms. Results from laboratory studies have led to the idea that the diffusional growth rates of the interacting ice surfaces may influence the sign of the charge transferred during brief collisional contact. The ice crystals grow by vapour diffusion in a supersaturated environment while the graupel surface may grow by diffusion under low accretion rate conditions, but will sublimate when heated sufficiently by riming. The graupel surface is also influenced, even under net sublimation conditions, by the vapour released to it from droplets freezing on its surface. In a cloud the diffusional growth rates are also affected by ventilation as the supercooled droplets and their local environment flow past the riming surface.

The model is used to investigate the influence of supersaturation on the detailed properties of riming graupel particles - the changes of surface temperature, growth rate and sublimation/growth state as a function of supersaturation will be estimated. The sign of electric charge transferred during ice crystal collisions is determined according to the concept of relative vapour diffusional growth rates of the colliding particle surfaces, according to Baker et al 1987 and Dash et al 2001.

The variable parameters available in the model may be adjusted to represent the environmental supersaturation conditions in the laboratory experiments of Takahashi 1978/2002, Saunders et al 1998, and Pereyra et al 2000 and will be used to determine charge sign sensitivity to supersaturation, temperature and the rate of rime accretion.


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Numerical Study on Impact of Electrical Structure on Dynamic Development in Thunderstorm

Yan Muhong, Sun Anping and Zhang Yijun


In this paper, a new three-dimensional dynamics and electrification coupled model has been developed for investigating the characteristics of microphysics, dynamics and electrification inside thunderstorms and for numerical study on the impact of electric structure on dynamic development in cloud. The model include not only the coupling of electrification with dynamical and microphysical processes, but also the lightning discharge process and screening layer effect at the cloud top as well. Beside diffusion and capture processes of small ions to six classes of hydrometeors, the inductive and non-inductive charging mechanisms are more specifically considered in this model. The results indicate that the direct impact of electric field force on dynamic field is very small. The vorticity produced by electric force is 10-4/s and the vorticity produced by dynamic is 10-6/s. But the electric force can influence the fall velocity of solid and liquid rainfall particle, microphysical processes between three phase hydrometeors. These processes increase water vapor amount about 41% and potential heat about 19.4%. Therefore the dynamic field structure occurs to change and corresponding vorticity produced by electric action is 10-4/s, the same as dynamic vorticity.


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A possible new molecular mechanism of thunder cloud electrification

Pavel Jungwith
J. Heyrovrký Institute of Physical Chemistry, Academy of Science of the Czech Republic and Center for Complex Molecular System and Biomolecules, Dolejškova
3, 18223 Prague 8, Czech Republic

Daniel Rosenfeld
Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

Victoria Buch
Department of Physical Chemistry and Frit Haber Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

It is well established that electrification occurs when charge is transfered between small and large ice particles colliding in a thundercloud that contains strong updrafts. The small ice particles rise with one type of charge and the large ice particles (graupels) fall and cary with them downward the other type of charge, which is most often negative, so that normally lightning lowers negative charge from cloud to the ground. Currently, the nature of the charge transfer between the colliding ice particles is not very well understood on the atomic level, and no present microscopic theory can explain fully the charge transfer, or even the sign of the charging. Here we propose a new charge separation mechanism that is based on molecula simulations of the collisions, keeping track of the individual charges as they move in the form of salt ions from one ice particle to another. This mechanism invokes charge separation at the surface of a thin layer of salt solution covering the graupel (the salt originates from the cloud condensation nuclei and is ejected to the surface during freezing of the droplets). Under normal conditions, when sulfates dominate as cloud condensation nuclei, this ionic mechanism is consistent with the prevailing negative lightning in thunderclouds. Moreove , with dearth of sulfate anions, the present mechanism predicts a shift towards positive charging. This fits well to a large range of observations of enhanced positive lightning, connected with smoke rich in chlorides and nitrates, that could not be explained satisfactorily previously.
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Corona discharge in clouds (overview)

Sinkevich A.A., Dovgaluk J.A. , Stepanenko V.D.
A.I.Voeikov Main Geophysical Observatory
E-mail sinkev@main.mgo.rssi.ru

Dr. Sinkevich A.A.
Chief of Cloud Physics, Cloud Seeding and Solar Radiation Studies Department, A.I.Voeikov Main Geophysical Observatory, Karbyshev str.7, St.Petersburg, Russia, 194021
E-mail sinkev@main.mgo.rssi.ru


Investigations within the field of corona discharges have been directed to study the following problems of cloud physics and atmospheric electricity:

1. Studies of the conditions when corona discharges take place in clouds;

2. Assessment of corona discharges intensity (volume frequency);

3. Studies of droplets and crystals charging due to corona;

4. Measurements of electric current due to corona;

5. Assessments of corona discharges role in ion concentration changers in clouds;

6. Studies of corona role in formation of streamers and lightning;

7. Influence of corona discharges on microphysical transformations in clouds;

8. Role of corona dischargers in electromagnetic emission by clouds.

Role of corona discharges in cloud characteristics formation is not yet clear now, though attempts were carried out to study different aspects of their influence on this or that process. Overview of the results of investigations in the field of corona discharges in clouds is presented in the report. It includes analyze of the resent and earlier publications. We pay most attention to the above formulated items. Item 1 was most seriously investigated. It includes results of studies of corona origination in dependence of cloud particle dimensions, their phase, electrical field strength, pressure, particle interactions and particles charges. Nearly 50 publications are analyzed to prepare proposed report.


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Correlation Coefficients between Disturbance Indexes and Updraft associated with Lightning Discharges Observed by Two kinds of Radars and SAFIR

Technical Research Center. The Kansai Electric Power Co., INC.

Development of Communication Engineering, Osaka Electro-Communication University

Department of Communication Engineering, Graduate School of Engineering, Osaka University

Radio Science for Space and Atmosphere, Kyoto University


The authors have been investigating many characteristics of thunderclouds which produce lightning discharges in winter along the coast of the Sea of Japan, using C or X-band radars or a Ka-band Doppler radar, SAFIR, LLS and so on. In these observations, especially, we have carried out the simultaneous observations by C-band radar and Ka-band Doppler radar from 1999 to 2002. As the results of those observations, we have discovered and analyzed a number of interesting results in winter thunderclouds. The key results are as follows:

  1. We examined two cores of the high intensity radar echoes of more than 40 dBZ observed by C-band radar and found that there is a significant difference of the size of precipitation particles (mainly graupel) for these two type of radar echoes.
  2. Based on this difference, we made it clear that the size of precipitation particles that produced lightning discharges are much larger than those with no lightning discharges.
  3. Also, we analyzed both data for the disturbance index levels observed by C-band radar and the differential radial velocities observed by the Ka-band Doppler radar. From this analysis, we recognized that there are close relationships between the regions with high disturbance indexes and the region with large differential velocities that possibly show high convective activities.

We presented preliminary observational results in the 5th IWPL in 2001. And we have succeeded further statistical analyses of thoes observed data.

In this paper, especially, we will present these statistical results where the correlation coefficients between the disturbance index and the updraft convection indicates a rather high value of, say, 0.86. Moreover, we will provide other interesting observational and analyzed results at the Conference next year.


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TopFull program for A4 Session





TopFull program for A4 Session

Electrification, lightning and microphysics in a simulated, 'bow echo' severe storm

Jerry M. Straka, Associate Professor
Atmos. Sci. and Atmos. Physics, School of Meteorology, University of Oklahoma, 100 E. Boyd St. rm. 1310 Norman, OK 73019
PH WK: (405)-325-5503/6561
PH HM: (405)-447-5595 (try first)
FAX (405)-325-7689
E-mail jstraka@ou.edu

Edward R. Mansell
CIMMS/Univ. of Oklahoma

Conrad L. Ziegler,
National Severe Storms Laboratory

Donald R. MacGorman

Matt S. Gilmore
CIMMS/Univ. of Oklahoma


This study uses a numerical cloud model to examine how the microphysics and the dynamics of 'bow echo' storms affect electrification and lightning production. 'Bow echo' storms produce some of the fiercest and most widespread wind damage of storms in the severe storm spectrum. However, because they have not been studied much with polarimetric radar or lightning mapping systems, we don't know much about lightning production in them or about what can be inferred about the from trends in lightning. Moreover, we don't know if lightning observations might help play a role in operational forecasting the severe weather with these storms as might be possible with supercell storms. In this work we will present an idealized 'bow echo' simulation of lightning, electrification, and microphysics by a three-dimensional numerical model with advanced numerics, microphysics parameterizations, electrification parameterizations, and lightning schemes.

The primary focus will be on electrification and lightning development at the relatively early, large, 'tall echo' stage (after about one hour in the simulation), the development of the start of the 'bow echo' stage (after about three hours), and the severe storm 'bow echo' stage (after about four hours). The three stages represent the times when an operational forecaster might first recognize the possible development of a 'bow>> echo', the onset of a 'bow echo', and the full blown severe weather stages of the 'bow echo'. Where and how lightning fits into these times is not yet known. Use of an advanced numerical model is one way to help establish hypotheses to help direct future observations to test the hypotheses.


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Vertical Development of Lightning Activity observed by the LDAR system
-Lightning Bubbles

Tomoo Ushio, Ken-ichi Okamoto,
Osaka Prefecture University

Stan Heckman, Hugh Christian,
NASA/National Space Science and Technology Center

Zen-Ichiro Kawasaki,
Osaka University

Tomoo Ushio, Ph. D.
Aero-space Eng. Dept., Osaka Prefecture University, Gakuencho Sakai, Osaka, 599-8531, Japan
Tel. +81 72 254 9245
Fax. +81 72 254 9906
e-mail. ushio@tomooushio.com


In this study, we have examined a vertical correlation between lightning activity and storm development by using the data from the LDAR and the Melbourne Radar in Florida. In some Florida thunderstorms cells, impulsive VHF radiation from lightning channels begin abruptly in a layer that is typically 3-6 km in diameter, 1-3 km tall, and initially located just above the freezing level. At least 10% of the 1060 hour period analyzed here showed a feature of the ascending concentrations of lightning activity which we call 'Lightning Bubbles'. One example of the bubble is shown in the figure below. In 208 cases described here, 58% of the lightning bubbles ascended with a velocity 11-17 m/s. Often in summer, as one region ascended, a new lightning bubble would abruptly begin near the freezing level. This subsequent region would be horizontally displaced a kilometer or two from the starting point of the previous region. In winter, no more than one ascending region was seen in any one storm. A detailed examination of the structure of lightning associated with the rising layers of lightning activity indicates that these layers were comprised to negative leaders, which tend to propagate through positive charge. This suggests that the rising layer of lightning activity is due to the ascent of an upper positive charge in storms.


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Positive and Negative Cloud-to Ground Lightning*

Depts. of Physics and Geology and Geophysics, Yale University,

Dept. of Physics, University of Washington


Positive cloud-to ground lightning (+ CGL) occurs in a minor fraction of all thunderstorms [1]. We propose that the microscopic mechanism is the same as in the more common negative CGL, whereas the different polarity is due to the macroscopic cloud dynamics [2]. The origin of collisional charging involves three stages in the basic process [3]. In the first stage kinetic roughening of the surface is induced by rapid growth from the vapor, causing an increased density of grain boundaries, steps and dislocations which pin OH- ions at surface sites. During a subsequent encounter between two ice particles, a thin interfacial layer is momentarily melted by the collisional energy, into which the negative ions are liberated. When the particles separate they take approximately equal shares of the interfacial layer, hence the particle that had been growing more rapidly suffers a net loss of negative charge. Ice growth in clouds can occur via two direct mechanisms: (a) deposition from vapor on ice particles, and (b) riming of graupel, as supercooled droplets impacting the graupel freeze and their vapor condenses on the surrounding areas of the same particle or other particles [4]. In storms typical of the - CGL, process (a) is dominant, in which small particles are growing while rising in updrafts, so that the positively charged small particles are carried to upper regions of the cloud, and the negatively charged graupel is the dominant charge carrier in the lower regions. However, as the growth rate of rising particles increases, the charge transfer saturates, and reverses [3]. Hence, we speculate that in storms producing + CGL, either (i) the process outlined above is weaker, so that the graupel becomes positively charged, or (ii) the saturation effect is dominant. The reversal of the polarity in case (i) is consistent with some observations that + CGL is more common in the late stages of violent storms, where updrafts are weaker [1].

*Research supported by the Bosack-Kruger Foundation.


[1] D.R. MacGorman and W.D. Rust, The Electrical Nature of Storms (Oxford University Press, New York, 1998).

[2] We focus here on + CGL that originates from the lower regions of a thundercloud, distinguished from lightning originating from strongly sheared cloud tops.

[3] J.G. Dash, B.L. Mason and J.S. Wettlaufer, Theory of charge and mass transfer in ice-ice collisions, J. Geophys. Res. 106, 20395-20402 (2001).

[4] B. Baker, M.B Baker, E.R. Jayaratne, J. Latham and C.P.R. Saunders, The influence of diffusional growth rates on the charge transfer accompanying rebounding collisions between ice crystals and soft hailstones, Quart. J. Roy. Met. Soc. 113, 1193-215 (1987).


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STEPS June 29, 2000 Supercell: Observations of Kinematic, Microphysical, and Electrical Structure

Kyle C. Wiens, Sarah A. Tessendorf, and Steven A. Rutledge
Department of Atmospheric Science
Colorado State University - Fort Collins, Colorado, USA


We investigate the kinematic, microphysical and electrical evolution of a tornadic supercell storm which occurred on June 29, 2000 during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). This storm was well-sampled by at least two Doppler radars and one multi-parameter radar from 21:30 through 01:20 UTC. In addition, the location and intensity of the lightning activity in this storm was measured by the National Lightning Detection Network (NLDN) and the New Mexico Tech Lightning Mapping Array (LMA).

Flash rates in this storm exceeded 300 flashes per minute. The storm produced only intracloud flashes for the first two hours. When the storm did produce cloud-to-ground (CG) flashes, they were almost all positive (+CGs). Interestingly, +CGs occured only when hail was present. The NLDN and LMA data indicate that these +CG flashes usually clustered near the precipitation core of the storm and that the +CGs originated from a positive charge region at mid-levels (6-8 km MSL), not the anvil.


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A Simple Model to Estimate Electrical Decay Times in Anvil Clouds

J.C. Willett,
P.O. Box 41, Garrett Park, MD 20896, USA; J.E. Dye, NCAR/MMM, P.O. Box 3000, Boulder, CO 87307, USA


Anvil clouds are a cause for concern to the space-launch community because they are known occasionally to be strongly electrified and because they are suspected to be capable of storing charge for long periods of time. Therefore, during 2000 and 2001 an experiment was conducted in the vicinity of the NASA Kennedy Space Center, Florida, to measure both the ambient electrostatic fields and the size/shape distributions of the cloud and precipitation particles in cirrus anvils [Dye, et al., presented at the AGU Fall Annual Meeting, San Fransisco, CA, Dec., 2001].

Based on a suggestion by Paul Krehbiel [personal communication, 1998], a simple model has been developed to calculate the temporal decay of electric field, E(t), within a previously charged anvil cloud, given a measured particle-size distribution, N(d). This model envisions a microphysically uniform, horizontally homogeneous, quiescent cloud containing a thin layer of positive charge between two thin, negative screening layers. Thus,

dE/dt = -2ekn(t)E(t)/e 0 (1)

in the bulk of the cloud, where e is the electronic charge, k is the small-ion mobility, n(t) is the polar small-ion density (positive and negative assumed equal), and e 0 is the dielectric permittivity of free space. Krehbiel [Conductivity of clouds in the presence of electric fields, unpublished manuscript, NMIMT, September 14, 1967] had shown that the conduction-current density becomes constant -- independent of both k and E(t) -- when the electric field is strong enough. In this limit the field decay is linear and can become quite slow.

The present analysis begins with the steady-state, small-ion budget equation in a population of stationary, mono-disperse, spherical cloud particles, from Pruppacher and Klett [Microphysics of Clouds and Precipitation, 1978, Eq. 17-40]. After neglect of small-ion recombination, simplification to uncharged particles, generalization to allow non-spherical shapes, and use of the "Einstein relation," this becomes,

q Ae(d)kN(d)n(t)E(t) + [C(d)/e 0][kKT/e]N(d)n(t) (2)

where q is the ionization rate, Ae(d) is the effective electrical cross section of a particle of diameter, d, C(d) is the electrical capacitance of that particle, K is Boltzmann's constant, and T is absolute temperature. When N(d) is a particle-size spectrum, the right-hand side of (2) must be regarded as an integral over the size distribution. The first term on the right represents the small-ion loss rate due to field-driven attachment of ions to cloud particles, which dominates at high enough field intensity, leading to Krehbiel's [1967] result. The second term is the diffusive loss rate, which dominates at low fields, producing an exponential decay of electric field.

Equation 2 can be solved for n(t) and inserted into (1) to give a first-order, non-linear differential equation for dE/dt. This differential equation has been solved numerically to obtain E(t) for various observed particle-size spectra. In a companion paper at this conference [Dye, et al., The Decay of Electric Field in Anvils: Observations and Comparison with Model Calculations], the resulting electrical-decay times are discussed in relation to the observed radar, microphysical, and electrical structure of anvil clouds . Below we present one example of this calculation for a particularly dense anvil that was penetrated at 210730 UT on 13 June 2000 at a flight altitude of 10 Kft. The left figure gives the measured size distribution. The red curve in the right figure shows a magnified section of the computed E(t). The calculation was begun with an assumed electric-field intensity of 50 KV/m at t = 0 (not shown). The green line is an extrapolation of the initial linear field decay to zero, yielding an estimated electrical-decay time of 5569 s (more than 1-1/2). Notice that the transition from field-driven attachment to diffusion as the dominant small-ion loss mechanism causes the field decay to change from linear to exponential at low fields.


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Electrification and lightning in a simulated tornadic, supercell storm

Conrad L. Ziegler, Senior Research Meteorologist
Models and Assimilation Team
Forecast Research and Development Division
National Severe Storms Laboratory, 1313 Halley Circle Norman, Oklahoma 73069
ph: (405) 366-0489
FAX: (405) 579-0808
email: ziegler@nssl.noaa.gov

Edward R. Mansell
CIMMS/Univ. of Oklahoma

Donald R. MacGorman

Jerry M. Straka
Univ. of Oklahoma


This study reports results of electrification and lightning evolution in a supercell storm simulated with the recently upgraded OU/NSSL three-dimensional cloud model. The model includes airflow dynamics, as well as comprehensive parameterizations of cloud microphysics, ion and hydrometeor charging, and lightning. The environment of the simulated storm is based on a sounding obtained near the tornadic supercell Binger, Oklahoma, USA storm of 22 May 1981. A series of 3-hour storm simulations have been performed, changing the type of non-inductive charging and strength of inductive charging from run to run to examine their impact on simulated electrification and lightning.

Preliminary simulations produced a supercell storm similar in several key respects to the Binger storm: including persistent intense updrafts; high reflectivities with mid-level BWER and low-level hook echoes; hail; and a deep mesocyclone extending from near ground to 10 km (AGL). The early electrification, exponential in character and driven mainly by non-inductive mechanisms, produced the first IC flash after about 30 minutes of simulated storm development. Charge regions were elevated in the main updraft relative to surroundings, in agreement with earlier studies. Subsequent simulated electrification was very intense, with total lightning rates exceeding 100 flashes/min after 1.5 hour. Frequent ground flashes of both polarities were simulated, with peak CG rates reaching 10 flashes/min. Trends were suggested between updraft intensity, precipitating ice mass, and total lightning rates.


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