Lightning

WHAT IS LIGHTNING?

Lightning is the electrical discharge between positively and negatively charged regions within clouds. The electrical discharge serves as an equalization process between the charged regions, and can travel from cloud-to-cloud, cloud-to-ground, or cloud-to-air. Visually, lightning is comprised of bright flashes of light called strokes. The loud sound of thunder that accompanies lightning is a sonic shock wave produced by the rapid expansion of the air surrounding the lightning channel during the stroke, similar to a sonic boom. Lightning and thunder occur at the same time, however, because light travels faster than the speed of sound, lightning may be observed sooner than thunder is heard.

Image Source: Wikimedia Commons

Image Source: NOAA NSSL

Why does lightning occur?

Growing ice particles within a cloud interact with each other through collision, causing the particles to fracture and break apart. It is currently believed that smaller ice particles tend to acquire a positive charge, while the larger particles acquire a more negative charge. Under the influences of thunderstorm updrafts and gravity, these particles separate until the upper portion of the cloud acquires a net positive charge, and the lower portion of the cloud becomes negatively charged. This separation of charge produces electrical potential both within the cloud and between the cloud and ground. Eventually, the electrical resistance in the air between the charged regions breaks down and a flash begins. The resulting lightning strokes are an electrical discharge between the positive and negative regions of a thunderstorm.

Where does lightning occur?

Lightning occurs in many places around the world. Over the land, much more lightning is observed than over ocean regions. In addition, not all land regions experience the same amount of lightning. Spatial differences in lightning distribution may result from the variable topography and weather patterns of different regions. The place on Earth with the most lightning strikes per square kilometer is Lake Maracaibo, a large tidal bay in northern Venezuela. Here lightning occurs 300 nights a year.

Data Source: LIS 0.1 Degree Very High Resolution Gridded Lightning Full Climatology

HOW IS LIGHTNING OBSERVED?

Lightning can be detected by a variety of ground-based, mobile and space-based instrument systems such as those flown aboard research aircraft, lightning arrays, and optical sensors on satellites. By measuring and monitoring changes in Earth’s electric field, lightning can be detected using instruments such as electric field mills, interferometers and radio frequency antennas. Arranging these instruments in lightning arrays allows scientists to locate, map and study the spatial and temporal structure of lightning through triangulation. In addition, lightning can be detected optically using instruments such as the lightning imaging sensor (LIS) and high speed cameras that monitor changes in light, or the electromagnetic spectrum, to detect lightning flashes from space and Earth’s surface. The table below provides an overview of the instruments used to obtain GHRC lightning data.

GHRC Lightning Instruments

INSTRUMENT	PLATFORM	PLATFORM TYPE	APPLICATION
Lightning Imaging Sensor (LIS)	ISS TRMM	Spaceborne	Lightning climatology Mesoscale phenomena Convective precipitation
Optical Transient Detector (OTD)	OrbView-1 (formerly MicroLab-1)	Spaceborne	Optical lightning detection Lightning discharge detection Radiant energy measurements
Radio Frequency (RF) Antenna	NLDN LDAR WWLLN LMA NAMMA	Ground based	Lightning flash detection Lightning polarity Signal strength Lightning mapping
Lightning Instrument Package (LIP)	DC-8 ER-2 Global Hawk UAV	Airborne	Tropical cyclone development Electric field measurements Electrical structure of storms Total lightning Electric charge Air conductivity
Electric Field Mill	Ground station	Ground based	Lightning development/ dissipation Lightning warnings Electric field strength Electric charge
Operational Line Scanner (OLS)	DMSP-5B-F3 DMSP-F1 DMSP-F7 DMSP-F8 DMSP-F10 DMSP-F12	Spaceborne	Nighttime lightning detection Lightning discharge

RESEARCH AND APPLICATION AREAS

Relevant Publications

Climatology

Cecil, D. J., Buechler, D. E., & Blakeslee, R. J. (2014). Gridded lightning climatology from TRMM-LIS and OTD: Dataset description. Atmospheric Research, 135, 404-414, doi:10.1016/j.atmosres.2012.06.028.

Williams, E. R. (2005). Lightning and climate: A review. Atmospheric Research, 76(1), 272-287, doi:10.1016/j.atmosres.2004.11.014.

Science Application Areas

Schultz, C. J., Petersen, W. A., & Carey, L. D. (2011). Lightning and severe weather: A comparison between total and cloud-to-ground lightning trends. Weather and forecasting, 26(5), 744-755, doi:10.1175/WAF-D-10-05026.1.

Curran, E. B., Holle, R. L., & López, R. E. (2000). Lightning casualties and damages in the United States from 1959 to 1994. Journal of Climate, 13(19), 3448-3464, doi:10.1175/1520-0442(2000)013<3448:LCADIT>2.0.CO;2 .

McCaul Jr, E. W., Goodman, S. J., LaCasse, K. M., & Cecil, D. J. (2009). Forecasting lightning threat using cloud-resolving model simulations. Weather and Forecasting, 24(3), 709-729, doi:10.1175/2008WAF2222152.1.

Physical Processes

Fierro, A. O., Mansell, E. R., MacGorman, D. R., & Ziegler, C. L. (2013). The implementation of an explicit charging and discharge lightning scheme within the WRF-ARW model: Benchmark simulations of a continental squall line, a tropical cyclone, and a winter storm. Monthly Weather Review, 141(7), 2390-2415, doi:10.1175/MWR-D-12-00278.1.

MacGorman, D.R. and Rust, W. D. (1998). The electrical nature of storms. Oxford University Press. 432 pp.

Williams, E. R. (2009). The global electrical circuit: A review. Atmospheric Research, 91(2), 140-152, doi:10.1016/j.atmosres.2008.05.018.

Rakov, V. A., & Uman, M. A. (2003). Lightning: physics and effects. Cambridge University Press. 700 pp.

Rakov, V. A., & Uman, M. A. (1998). Review and evaluation of lightning return stroke models including some aspects of their application.Electromagnetic Compatibility, IEEE Transactions on, 40(4), 403-426, doi:10.1109/15.736202.

DATE UPDATED
Oct 19th, 2018

AUTHOR(S)
Kaylin Bugbee
Patrick Gatlin
Leigh Sinclair
Deborah Smith
Amanda Weigel