NOAA National Severe Storms Laboratory
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LIGHTNING FAQs

NSSL does not archive lightning data, but there are several other companies that do. We actually purchase lightning data ourselves (we do not have the funds to maintain our own network) and have strict rules about how we can use it.

It's not clear how far lightning can strike from a storm. We do know lightning has struck more than 10 miles from the storm in an area of clear sky.

Never say always! Lightning USUALLY strikes the tallest object. It makes sense that the tallest object is most attractive, because it is the easiest path for the lightning to take.

Lightning is an electrostatic discharge accompanied by the emission of visible light and other forms of electromagnetic radiation.

Since the 1980s, cloud-to-ground lightning flashes have been detected and mapped in real time across the entire US by several networks. In 1994, the networks were combined into one national network consisting of antennas that detect the angle from ground strike points to an antenna (direction-finder antenna), that detect the time it took for them to arrive at an antenna (time-of-arrival method), or a combination of both detection methods. The network is operated by Vaisala.

Flashes have also been detected from space during the past few years by an optical sensor . This experimental satellite covers the earth twice a day in tropical regions. The satellite also detects flashes that do not strike the ground, but cannot tell the difference between ground strikes and cloud flashes.

Lightning Detection and Prediction

How is lightning detected?

Real-time mapping

Cloud-to-ground lightning network data have been collected in real-time since the late 1970's. The first uses were for forest fire detection and utilities. Other groups have found the network data useful in aerospace and military operations, explosives handling, aviation operations, communications, and meteorological research and applications.

Currently, cloud-to-ground and intra-cloud lightning flashes are detected by antennas and mapped in real-time across the entire U.S. by the National Lightning Detection Network, a system developed by the New Mexico Institute of Mining and Technology (NMIMT). THE NLDN consists of antennas that (a) detect the angle from ground strike points to an antenna (direction-finder antenna), (b) that detect the time it took for them to arrive at an antenna (time-of-arrival method), or (c) a combination of both detection methods.

In the image below, lightning strike data from the National Lightning Detection Network shows positive (+) and negative (-) cloud-to-ground lightning strikes from a 1995 Chicago storm. The most recent strikes are gold; the oldest are white. Lightning strike data such as this is usually purchased from companies who manage the data.

Flashes have also been detected from space during the past few years by an optical sensor. This experimental satellite covers the earth twice a day in tropical regions. The satellite also detects flashes that do not strike the ground, but cannot tell the difference between ground strikes and cloud flashes.

Newer lightning mapping techniques show that some supercell thunderstorms have "lightning holes" where updrafts are located and precipitation is scarce. If these holes form, as suspected, just before a storm becomes severe, this information could alert forecasters to developing severe conditions.

Can lightning be predicted?

We can predict IF lightning will occur because we know that lightning always occurs in convection (thunderstorm). But, it is impossible to forecast individual strikes since lightning is so widespread, frequent and random. Our understanding of cloud electrification processes is still incomplete. While forecasters can't predict every strike, they can forecast the likelihood of intense lightning activity and show past lightning strike data. As scientists learn more about the electrical nature of thunderstorms, their findings may provide clues to the formation of other types of hazardous weather associated with thunderstorm environments.

HOW DOES NSSL CONTRIBUTE?

Lightning Mapping
NSSL purchases and uses these detailed 3-D maps from the NLDN to learn how storms produce these flashes and how each flash type is related to other storm hazards. Scientists also learned how to use trends in the flash rate and location of each type of lighting to help identify the development of thunderstorms, the growth of updrafts, and the formation of precipitation and downdrafts.

Oklahoma Lightning Mapping Array (OK-LMA)
The OK-LMA, also developed at the NMIMT, is a 3-D mapping system installed across central Oklahoma to detect and measure all lighting, including flashes that stay in the clouds. The OK-LMA allows NSSL to investigate how lightning characteristics relate to updrafts, precipitation, and severe storm processes. Scientists also used the OK-LMA to investigate using lighting data in weather forecast models.

The OK-LMA consists of a central station in Norman, OK, and ten stations distributed across central Oklahoma. The system maps 3-D lightning structure to a range of 75km and the 2-D lightning structure to a range of 200km.

Lightning Research
Scientists recently found evidence for inverted-polarity electrical structures within thunderstorms. This means that the normal polarities of charge in two or more vertically-separated regions of a storm are reversed. The evidence for this came from electric field data obtained with free-flying instrumented balloons. There are still too few observations to know if such "upside down" thunderstorms commonly exist and if so, where and why they occur.

Researchers are using information from radars about types of precipitation (rain, hail, graupel), what happens when they bump into each other, and location information to help understand the electrical nature of storms.

NSSL and other scientists are finding ways to use trends in the flash rate and location of cloud-to-ground lightning relative to the storm to help identify the development of thunderstorms, the growth of updrafts, and the formation of precipitation and downdrafts.

Scientists are also investigating techniques for including lightning mapping data into mesoscale forecast models.

NSSL researchers are using a 3-D cloud model to investigate the full life-cycle of a multi-cell storm. The model has shown how graupel or other droplets could help form regions of lower charge within the storm.

Mobile Laboratories
NSSL developed the first truly mobile facility for obtaining upper-air soundings of the atmosphere. Researchers used 15-passenger vans modified to be mobile laboratories. They mounted a Cross-Chain Loran Atmospheric Sounding System inside, and invented a high-wind launch device for releasing helium-filled balloons in very high winds. This pioneering capability allowed NSSL to take upper-air soundings in the vicinity of tornadoes and drylines, gathering critically needed observations in the near-storm environment of thunderstorms. In addition, these mobile labs and ballooning systems provided the first vertical profiles of electric fields inside a thunderstorm leading to a new conceptual model of electrical structures within convective storms.

Field Projects
One way researchers test their theories is by observing severe thunderstorms and taking measurements in the field and later analyzing the results. Large-scale field experiments with a primary focus on atmospheric electricity include MEaPRS, the MCS Electrification and Polarimetric Radar Study designed to investigate polarization radar signatures and electrification processes in MCS's; STEPS, the Severe Thunderstorm Electrification and Precipitaiton Study to make meteorological and electrical observations of supercell thunderstorms; and TELEX, the Thunderstorm Electrification and Lightning EXperiment to learn how lighting and other electrical storm properties are dependent on storm structure, updrafts, and precipitation. TELEX used balloon soundings to measure the electric field profile of storms.

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