ICAE International Commission on Atmospheric Electricity


ICAE 2003 Versailles

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Benjamin Franklin
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Tuesday 10 th June

 


11:00

SESSION A2 Storm Electrification II (poster)


   
11:00 D. W. Rust, D. R. MacGorman, P. R. Krehbiel, R. Thomas, E. Bruning, and S. Stroman
The Status of our Search for Inverted-Polarity Electrical Structures in Thunderstorms
   
11:15

M. Stolzenburg, T. C. Marshall, L. M. Coleman, P. R. Krehbiel, R. J. Thomas, W. Rison, and T. Hamlin
Evolution of Electric Charge and Lightning Type in Developing Thunderstorms

   
11:30 R. J. Blakeslee, C. L. Croskey, M. D. Desch, W. M. Farrell, R. A. Goldberg, J. G. Houser, H. S. Kim, D. M. Mach, J. D. Mitchell, and J. C. Stoneburner
The Altus Cumulus Electrification Study (ACES): A UAV-Based Science Demonstration
   
11:45 P. Krehbiel, W. Rison, R. Thomas, T. Hamlin, J. Harlin, and Y. Zhang
Thunderstorm Observations with the Lightning Mapping Array
   
12:00 M. Ishii, M. Saito, J-I. Hojo, and K. Kami
Location of charges associated with cloud-to-ground flashes in winter
   
12:15 T. Morimoto, T. Shimura, and Z. Kawasaki
Three-dimensional lightning observations and consideration to charge distribution inside thunderclouds using the broadband interferometer

 


The Status of our Search for Inverted-Polarity Electrical Structures in Thunderstorms
 

W. David Rust, Donald R. MacGorman, Paul R. Krehbiel, Ron Thomas, Eric Bruning, and Stephanie Stroman

Dave Rust,
NOAA/National Severe Storms Laboratory, 1313 Halley Cir, Norman, OK 73069 USA
dave.rust@noaa.gov

 

We have a few examples of storms that appear to have inverted-polarity electrical structure. By this, we mean that the normal polarities of charge in two or more vertically separated regions of a storm are reversed. The evidence that such might exist originally came from both the order of the polarities in the peak in the profile of the vertical component of the electric field with altitude and from inferred charge structures using one-dimensional Gauss's law. The possibly-inverted structures are compared with typical (i.e., noninverted) conceptual models of storm structure. The balloon sounding data do not conclusively prove that inverted-polarity thunderstorms exist, but they support it. Realizing the uncertainties from use of 1-d Gauss, we have implemented additional ways to help determine the gross electrical structure of thunderstorms. One is the lightning mapping array data, from which charge polarity can often be determined for those charge regions involved in the lightning. The second is three-dimensional vector analysis of the electric field profiles along the balloon flight track to help find charge regions. Each region of lightning activity tends to occur in and near a charge region inferred from the electric field sounding, as has been hypothesized. We continue to test the hypothesis that inverted-polarity electrical structures can exist in thunderstorms. The current status is that we are trying to confirm the existence of inverted-polarity electrical structures in a few cases in which we have soundings in and near the convective region of the storm. The analyses are still under way. The soundings and conclusions for these cases will be presented.

 

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The Altus Cumulus Electrification Study (ACES):
a UAV-based Science Demonstration
 

R. J. Blakeslee, H. S. Kim,
NASA Marshall Space Flight Center, Huntsville, AL 35812, U.S.A.

C. L. Croskey, J. D. Mitchell
The Pennsylvania State University, University Park, PA, 16802, U.S.A.

M. D. Desch, W. M. Farrell, R. A. Goldberg, J. G. Houser,
NASA Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.

D. M. Mach
University of Alabama in Huntsville, Huntsville, AL 35899, U.S.A.

J. C. Stoneburner
General Atomics - Aeronautical Systems, Inc., San Diego, CA, 92127, U.S.A.

 

The Altus Cumulus Electrification Study (ACES) is an uninhabited aerial vehicle (UAV)-based project that investigated thunderstorms in the vicinity of the Florida Everglades in August 2002. ACES was conducted to investigate storm electrical activity and its relationship to storm morphology, and to validate satellite-based lightning measurements. In addition, as part of the NASA sponsored UAV-based science demonstration program, this project provided a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. ACES employed the Altus II aircraft, built by General Atomics - Aeronautical Systems, Inc. Key science objectives simultaneously addressed by ACES are to:

(1) investigate lightning-storm relationships,
(2) study storm electrical budgets, and
(3) provide Lightning Imaging Sensor validation.

The ACES payload included electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. ACES contributed important electrical and optical measurements not available from other sources. Also, the high altitude vantage point of the UAV observing platform (up to 55,000 feet) provided "cloud-top" perspective. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high altitude flight, the Altus was flown near, and when possible, over (but never into) thunderstorms for long periods of time that allowed investigations to be conducted over entire storm life cycles. An innovative real time weather system was used to identify and vector the aircraft to selected thunderstorms and safely fly around these storms, while, at the same time monitor the weather near our base of operations. In addition, concurrent ground-based observations that included radar (Miami and Key West WSR88D, NASA NPOL), satellite imagery, and lightning (NALDN and Los Alamos EDOT) enable the UAV measurements to be more completely interpreted and evaluated in the context of the thunderstorm structure, evolution, and environment.

 

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Thunderstorm Observations with the Lightning Mapping Array
 

Paul Krehbiel, William Rison, Ronald Thomas, Timothy Hamlin, Jeremiah Harlin,
New Mexico Institute of Mining and Technology, Socorro, New Mexico USA

Yijun Zhang
Cold and Arid Regions Environmental Research Institute, Lanzhou, China

 

At the previous International Conference we reported results obtained from initial operation of the Lightning Mapping Array (LMA) during the 1998 MEaPRS program in Central Oklahoma. Since then the LMA has been operated in two additional field programs, first at Langmuir Laboratory in central New Mexico during 1999 and then during STEPS 2000 in northwestern Kansas and eastern Colorado. The Oklahoma observations provided the first good glimpse of the spectacular lightning activity in large Great Plains storms and revealed several previously unknown features of this lightning activity, including the occurrence of numerous small discharges in the upper part of strong convective surges, the existence of lightning `holes' in association with the convective surges and with tornados, and the occurrence of inverted polarity intracloud lightning discharges. These basic results were confirmed and substantially expanded upon in the STEPS studies of High Plains storms. The most astounding result of the STEPS observations has been the finding that hail and supercell storms of the study a) have an overall electrical structure that is inverted in polarity from that of normal storms, b) can go for long periods of time (up to several hours and sometimes encompassing the entire lifetime of a storm) without producing any cloud-to-ground (CG) lightning discharges, and c) that it is relatively common for the storms to become anomalously electrified. The anomalous storms produce the predominantly positive CG lightning activity that was the original impetus for STEPS; what the mapping data have shown is that the onset of the +CG activity in the convective stages of a storm is for some reason associated with strong convective surges in storms. Observations of the complete lightning sequence in several STEPS storms has indicated the basic features of how the anomalous electrification develops. At the same time, the New Mexico observations are providing a valuable and contrasting view of the electrification in `normal' storms. In addition, the New Mexico observations provide a clear explanation of ground-based electric field measurements below storms and, in conjunction with balloon soundings of electric field profiles inside storms by Marshall et al., are showing how the lightning activity is related to the storm electrical structure and how it modifies the electrical structure.

 

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Location of charges associated with cloud-to-ground flashes in winter
 

Masaru Ishii, Mikihisa Saito (University of Tokyo), Jun-Ichi Hojo (Lightning Research Office), and Kouichirou Kami (Hokuriku Electric Power Co.)

Masaru Ishii
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-Ku, Tokyo 153-8505, Japan
fax: +81-3-54526241
ishii@iis.u-tokyo.ac.jp

 

Cloud-to-ground lightning flashes in winter have been observed by a network of 8 VHF receivers, 8 slow antennas and 5 fast antennas on the coast of the Sea of Japan. VHF radiation sources are located by the TOA method. C-G negative flashes in summer were also observed and analyzed to confirm the performance of the observation system. 12 positive C-G flashes observed in winter of 2000 and 2001 have been analyzed so far, and charges associated with 13 positive C-G strokes were located by using data from slow antennas.

The calculated heights of the charges related to 12 strokes out of 13 were below 2.5 km. In these data, field changes associated with downward leaders were not eliminated due to the complex field waveforms, and the leader charge contributed to the calculated low altitudes of positive charges. Positive charge layers in the clouds are also identified from VHF sources associated with negative leaders. By this method, heights of positive charge layers of 8 flashes out of the 12 analyzed flashes were estimated, and 5 flashes showed agreement in the charge heights estimated by different methods.

It is concluded that majority of positive charges neutralized by C-G strokes in winter exist below 3 km or in a temperature region warmer than -15 degrees C. This result contradicts the only other report on the charge heights of winter lightning, where 6 positive C-G strokes were analyzed. It was reported that 4 positive charges were located in colder regions than -20 degrees C, and "tilted dipole" model was proposed. The authors would suggest revision of the statistics on the charge structure of winter thunderstorms.

 

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