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Lightning also is one of the most beautiful and mysterious events in nature, something to admire, from a safe distance - and to study in detail. Right: Look but don't touch (meaning stay inside; don't stand in the open or near trees or power lines). Lightning is as deadly as it is beautiful. Credit: Chuck Clark, NOAA. The Global Hydrology and Climate Center (GHCC) will host the 11th quadrennial International Conference on Atmospheric Electricity, June 7-11 at Guntersville State Park in north Alabama. Scientists attending this conference study thunderstorms, lightning and other electrical properties of the atmosphere. This will be the first time that the conference has been held in the Southeast. |
May 24, 1999:
By the time you finish reading this sentence, lightning will
have struck more than 100 times across the Earth. Each delivers
about 1 trillion watts of electricity in manner of microseconds.
The highly conductive lightning channel heats the air to over
15,000 deg. C (27,000 deg. F), which is almost three times the
surface temperature of the sun.|
Beginning in 1980, scientists from this group have studied lightning and thunderstorm from NASA's ER-2 high altitude aircraft and later from the Space Shuttle. In the Mesoscale Lightning Experiment, the Shuttle 's payload bay cameras observed lightning on the nightside of the Earth during crew sleep periods. |
Left:
A frame from TV images taken aboard the Space Shuttle (STS-35;
April 28, 1990) shows lightning outshining city lights - and
a sprite reaching for the top of the atmosphere. (NASA)
NASA and the Air Force continue to have a deep interest because of the potential for lightning to destroy rockets: their metal bodies and long conducting trail of hot gas can readily trigger lightning flashes.
Lightning distribution as seen by the Optical Transient Detector aboard MicroLab 1 during September 1995-August 1997. (NASA/GHCC) "The U.S. is one of the most active countries in the field of Atmospheric Electricity," Christian said. "Japanese scientists also are active. However, it tends to concentrate on the physics of the lightning event, perhaps because its power industry plays such an active role. In the United States, there is also much interest in the meteorological aspects of the science." In addition, groups from around the world including scientists from Japan, Russia, Germany, France, Sweden, China and India are actively involved in the field. The conference will be large, with scientists from 28 countries in attendance. Christian expects more than 200 scientists will turn out to present papers. |
Despite
its fascinating nature and the damage and death it causes, only
a relatively small number of groups around the world study lightning.
"We think that lightning responds very rapidly to what is happening in the center of clouds with electrical energy being generated within minutes of changes in convective intensity," Christian said. The ability to monitor closely what is happening inside the clouds could be a valuable tool for predicting what might happen next - including the potential for a tornado. Recent advances in radar, including NEXRAD, have improved the weather forecaster's ability to tell if a tornado is spinning out of a storm cell, but they still lag in their ability to measure the vertical velocity of these storms, which are important clues to the overall puzzle. Establishing multiple operational Doppler radar networks around the nation or placing fleets of weather radars in orbit is impractical.
But watching for lightning from space might be a viable alternative, Christian said. His team has been studying designs for a lightning mapping sensor that would be added to weather satellites in geostationary orbit. The sensor would watch the entire continent and focus in on areas where lightning activity seems to be sharply increasing and decreasing. A sudden jump in activity may be the clue that scientists have been seeking for detecting an intensifying storm that might be a precursor to tornadoes. This dramatic increase in lightning, signifying intensification of the storm's vertical motion is generally followed by a sharp decrease, suggesting collapse. |
Right: Many scientists view lightning as the most
visible (and dangerous) part of a much larger global electrical
circuit in which the ground itself is, well, the ground plane.
(NASA)|
Left: A tornado aims for Dimmet, Texas. (NOAA) The linkage is that strong upward convection leads to high lightning rates and increased vorticity. Then the convection collapses and generates downdrafts, leading to a sharp decrease in the lightning and setting the conditions for the onset of a tornado. Validation of this effect could enhance warning capabilities with space-based lightning sensors providing up to 10 extra minutes more warning time for severe weather intensification and tornadoes. In addition to this tantalizing discovery, the GHCC's lightning team has found that lightning loves land. Maps of global lightning frequency shows that lightning occurs most often in storms over land. Further, they have hypothesized that lightning loves land because the heating of the continents creates stronger convection.
Space-based observations of lightning will be only one of dozens of topics covered at at the Atmospheric Electricity Conference. Several papers will be presented on sprites, the tantalizing flashes of light that dance high over the tops of storm, seemingly into space. While the physics of this phenomenon is not understood, it is possible that sprites play important roles in the global electrical circuit and upper atmospheric chemistry. Other papers will cover the 3-dimensional structure of lightning, the physics of charge generation and lightning initiation, and studies of lightning variations with weather phenomena such as El Nino. Sessions will be dedicated to lightning characteristics, lightning detection and protection, thunderstorm characteristics, fair weather electricity, global lightning and lightning chemistry. |
On April 17, 1995,
the OTD observed a steady rise in lighting activity in a supercell
storm over Oklahoma. Just before the spacecraft passed out of
view of the storm, the lightning rates dropped sharply. A few
minutes later, a tornado was observed descending out of the storm.
| Lightning Stories from this conference |
|
Human
Voltage (June 18, 1999) Scientists discuss biology, safety,
and statistics of lightning strikes. Lightning research at NASA/Marshall and the Global Hydrology and Climate Center. More Space Science Headlines - NASA research on the web NASA's Earth Science Enterprise Information on Earth Science missions, etc. |
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