| Volume 4, | Number 1 | March/April 1996 |
A NASA lightning detector is intriguing scientists with the possibility of identifying the formation of tornadoes and severe storms from space. Research scientists at NASA's Marshall Space Flight Center in Huntsville, Alabama, are using data from the Optical Transient Detector (OTD) to build a global picture of the role of lightning in the atmosphere, including lightning produced by large storms. These data are significant because the "flash rate" of lightning may provide, in conjunction with other detection systems, an indication of the formation of tornadoes.
Launched April 3, 1995, aboard a Pegasus rocket, NASA's OTD has been observing lightning flashes as it passes over severe storms. Taking advantage of the perspective from orbit, the detector provides researchers a much more comprehensive view of lightning generated by severe storms than is generally available from ground observations.
On April 17, 1995, as the OTD passed over a severe storm in Oklahoma, the rate of lightning flashes peaked at more than 60 per minute, 40 seconds into the satellite's pass. The flash rate then decreased, and approximately 1 minute after the pass, observers saw a tornado touch the ground, said Dr. Hugh Christian, Principal Investigator of the OTD at Marshall's Global Hydrology and Climate Center.
Overall, the instrument detected almost 200 lightning flashes during its 3-minute pass. In contrast, the ground-based National Lightning Network (a privately-owned business), which detects only cloud-to-ground flashes, located nine flashes during the same period. This large difference suggests that the tornado was producing primarily intracloud lightning.
"We saw much more intense lightning activity produced by these clouds than was observed on the ground, both before and during tornado formation," explained Christian. "In the next months, we plan to perform detailed studies on the relationship between intracloud lightning and the formation of severe weather."
The increasing, then decreasing, lightning-flash rates produced by the Oklahoma storm may mirror the life cycle of air mass storms and might be an indication of the onset of downdrafts occurring before a tornado is formed, according to Christian. "While the Optical Transient Detector is a technological demonstration and is being used for ongoing lightning studies, it certainly provides a 'tantalizing carrot' of future lightning-detection possibilities," said Christian. "Further research and the experience gained with this lightning instrument could help develop sensors for real-time severe weather warnings and assist with identification of the formation of tornadoes."
The OTD program is part of NASA's Mission to Planet Earth, a coordinated research effort to study the Earth as a single global system. Scientists located at the Global Hydrology and Climate Center in Huntsville are now analyzing data from the OTD. Data are processed in the center's Optical Transient Detector Science Computer Facility and will be archived and distributed in the Earth Observing Systems Data Information System (EOSDIS).
Research from the Optical Transient Detector program may assist with the identification of the formation of tornadoes and lead to real-time severe weather warning systems.
For more information, contact Steve Roy at the Marshall Space Flight Center. Phone: 205/544-0034, E-Mail Steve.Roy@msfc.nasa.gov Please mention that you read about it in Innovation.
