TELEX The Thunderstorm
Electrification and Lightning Experiment
BY DONALD R. MACGORMAN, W. DAVID RUST, TERRY J. SCHUUR,
MICHAEL I. BIGGERSTAFF, JERRY M. STRAKA, CONRAD L. ZIEGLER,
EDWARD R. MANSELL, ERIC C. BRUNING, KRISTIN M. KUHLMAN,
NICOLE R. LUND, NICHOLAS S. BIERMANN, CLARK PAYNE,
LARRY D. CAREY, PAUL R. KREHBIEL, WILLIAM RISON,
KENNETH B. EACK, AND WILLIAM H. BEASLEY
Measurements during TELEX by a light-
ning mapping array, polarimetric and
mobile Doppler radars, and balloon-borne
electric-field meters and radiosondes
show how lightning and other electrical
properties depend on storm structure,
updrafts, and precipitation formation.
I
n May–June 2003 and 2004, the Thunderstorm Electrification and Lightning
Experiment (TELEX) brought together researchers and students from one federal
and five university organizations to study how lightning and other electrical storm
properties depend on storm structure, updrafts, and precipitation formation. By com-
bining their resources, scientists employed an extensive array of sensors, including
an 11-cm-wavelength polarimetric Doppler radar, two 5-cm-wavelength mobile
Doppler radars, a mobile atmospheric sounding system, balloon-borne electric-field
meters, an instrumented storm-penetrating T-28 aircraft, and a three-dimensional
lightning mapping network. Anytime, day or night, storms occurred X
A TELEX balloon crew releases a
balloon from its high-wind launch
tube to fl y into a supercell storm
on 24 May 2004 for an in situ
sounding of electric fi eld, winds, and
thermodynamic properties. Photo
by Ken Eack.
997
JULY 2008AMERICAN METEOROLOGICAL SOCIETY |

in central Oklahoma, teams scrambled into position
to observe them. The ground-based mobile facilities
acquired data for a broad spectrum of storm types on
7 days from 10 May through 5 June in 2003 and on
15 days from 15 May through 30 June in 2004.
GOALS OF TELEX. The field program had
three primary emphases: 1) storms having electrical
structure inverted from the usual vertical polarity,
2) lightning and other electrical properties of the
stratiform region of mesoscale convective systems,
and 3) developing operational applications of tech-
nologies that map all types of lightning.
Inverted-polarity electrical structure. The existence
of storms having inverted-polarity electrical struc-
ture has been established only recently. In most
thunderstorms, positive charge dominates in the
upper region (a relatively thin region colder than
roughly –25°C), and negative charge dominates
the middle region (somewhere between roughly
–10° and –25°C), though storms also have other
charge regions, particularly at lower altitudes (e.g.,
Williams 1989; MacGorman and Rust 1998, 49–53;
Stolzenburg et al. 1998b). Observations by the Severe
Thunderstorm Electrification and Precipitation Study
(STEPS) during the summer of 2000 found unexpect-
edly, however, that many thunderstorms on the High
Plains reverse these polarities, with the upper region
dominated by negative charge and the middle region
dominated by positive charge (Rust and MacGorman
2002; Lang et al. 2004a; Rust et al. 2005; MacGorman
et al. 2005; Wiens et al. 2005; Weiss et al. 2008). A
primary goal of the STEPS field program had been
to determine why the cloud-to-ground lightning
activity in a large fraction of High Plains storms is
dominated by flashes that lower positive charge to
ground (positive ground f lashes) instead of the usual
negative charge (negative ground flashes). The answer
appears to be that the vertical polarity of the charge
structure in many High Plains storms is inverted.
Now the issue is to determine why the electrical
structure is inverted.
A primary goal of TELEX, therefore, was to collect
additional comprehensive datasets to test and revise
hypotheses that have been offered to explain how a
storm’s electrical structure can become inverted. All
such hypotheses thus far depend on a noninductive
electrification mechanism involving rebounding
collisions between actively riming graupel and smaller
ice particles. Over the last 10–15 yr, most of the scien-
tific community has come to accept this mechanism
as the primary one for electrifying thunderstorms,
at least during initial stages (e.g., Takahashi and
Miyawaki 2002; Saunders et al. 2006; discussion on
pages 65–70 and 226–228 of MacGorman and Rust
1998), though other mechanisms also contribute.
This mechanism tends to put charge of one
polarity on graupel and charge of the opposite
polarity on smaller ice particles during rebounding
collisions, followed by differential sedimentation
that separates the charge by polarity into different
regions as the graupel and smaller particles are trans-
ported by the wind. At moderate riming rates over
most of the mixed-phase region, the noninductive
mechanism tends to place negative charge on graupel
and positive charge on the smaller rebounding ice
particle. However, at warmer temperatures ( –10°C)
and at larger riming rates regardless of temperature
in the mixed phase region, it tends to place positive
charge on graupel and negative charge on the smaller
ice particle. At very low riming rates, laboratory
experiments have disagreed concerning the polarity
and magnitude of charge that is transferred.
The usual result of these tendencies for charge
distributions (though a simplified view of a typical
thunderstorm) is that the negative charge that domi-
nates at middle levels has two contributions: small ice
AFFILIATIONS: MACGORMAN, RUST, ZIEGLER, AND MANSELL—NOAA/
OAR/National Severe Storms Laboratory, and Cooperative
Institute for Mesoscale Meteorological Studies, University of
Oklahoma, Norman, Oklahoma; SCHUUR—Cooperative Institute
for Mesoscale Meteorological Studies, University of Oklahoma,
and National Severe Storms Laboratory, Norman, Oklahoma;
BIGGERSTAFF, STRAKA, BRUNING, KUHLMAN, LUND, AND PAYNE—
Cooperative Institute for Mesoscale Meteorological Studies,
University of Oklahoma, and National Severe Storms Laboratory,
and School of Meteorology, University of Oklahoma, Norman,
Oklahoma; BIERMANN AND BEASLEY—School of Meteorology,
University of Oklahoma, Norman, Oklahoma; CAREY—Department
of Atmospheric Sciences, Texas A&M University, College Station,
Texas ; KREHBIEL, RISON, AND EACK—New Mexico Institute of Mining
and Technology, Socorro, New Mexico
CORRESPONDING AUTHOR: Donald R. MacGorman, National
Severe Storms Laboratory/WRDD, NWC, 120 David L. Boren
Blvd., Norman, OK 73072-7323
E-mail: don.macgorman@noaa.gov
The abstract for this article can be found in this issue, following the table
of contents.
DOI:10.1175/2007BAMS2352.1
In final form 6 December 2007
©2008 American Meteorological Society
998
JULY 2008|