Tutorial
Lightning Detection
Thunderstorms
present significant hazards to aviation. These include severe turbulence, wind
shear, heavy precipitation and lightning. Fortunately, the electromagnetic pulses
given off by lightning provide NASA researchers with means to study and track
thunderstorms. Future space-based lightning detection and reporting of lightning
flashes in real-time will provide valuable additional information to existing
weather sensing systems. This capability will give weather forecasters the ability
to more readily evaluate threats due to lightning, thunderstorm intensity and
growth, as well as storm dissipation throughout the United States.
NASA is demonstrating that real-time lightning detection from space during day
and night with the resolution to resolve individual thunderstorm cells is now
possible.
The
Lightning Imaging Sensor (LIS), is a space based instrument used to detect the
distribution and variability of total lightning (cloud-to-cloud, intracloud,
and cloud-to-ground lightning) that occurs in the tropical regions of the globe.
The LIS is a science instrument aboard the TRMM Observatory, which was launched
on 28 November 1997 from the Tanegashima Space Center in Japan.
The Optical Transient Detector (OTD) featured a highly compact combination of
optical and electronic elements. It was developed as an in-house project at
NASA's Marshall Space Flight Center in Huntsville, Alabama. The name, Optical
Transient Detector, refers to its capability to detect the momentary changes
in an optical scene which indicate the occurrence of lightning. The OTD instrument
was a major advance over previous technology in that it can gather lightning
data under daytime conditions as well as at night. In addition, it provided
much higher detection efficiency and spatial resolution than has been attained
by earlier lightning sensors. Launched in 1995, it continued to collect data
for five years, will beyond its two-year expected life span.
 Map of lightning distribution. Click image for closer view. |
U-2 and ER-2 high altitude
airplanes have been used to study the electrical and optical characteristics of lightning activity in thunderstorms.
Flying at an altitude of 20 km and at speeds of 200 meters per second, they are capable of flying over very large
thunderstorms. Much has been learned from these aircraft observations. To complement the optical measurements from
aircraft, video lightning images have been taken during a number of space shuttle flights while conducting the
Mesoscale Lightning Observation Experiment (MLE). These observations have revealed many interesting lightning events.
Here on the ground, a NASA developed Lightning Detection and Ranging (LDAR) system has provided a safe, productive
work environment at the Kennedy Space Center (KSC) and the Eastern Range since 1992. Now private industry and the
public at large stand to benefit from the space age technology.
NASA has joined with the private sector to develop LDAR systems that meet both NASA and commercial needs. The technology
has commercial applications in aviation as well as the electric utility, atmospheric research, commercial rocket
launch, recreation, construction and meteorological industries.
Current two-dimensional commercial systems only locate cloud-to-ground lightning. NASA's three-dimensional LDAR
system also pinpoints the location and altitude of in-cloud and cloud-to-cloud lightning by measuring the exact
arrival times of electromagnetic pulses.
Forecasters have found LDAR measurements to be extremely valuable for identifying the existence, intensity, growth,
and dissipation of thunderstorms. This capability is very useful during the "heat of battle", when numerous,
potentially hazardous storms are simultaneously growing and decaying in the forecast warning area of responsibility.
To learn more about NASA's lightning research, visit Marshall Space Flight Center's NASA Lightning Primer and Lightning and Atmospheric Electricity pages.