Lightning, the Science. Part 1: Modern View

Lightning can be defined as a transient, high-current (typically tens of kA) electric discharge in air whose length is measured in km. As for any discharge in air, lightning channel is composed of ionized gas, that is, of plasma, whose peak temperature is typically 30,000 K, about five times higher than the temperature of the surface of the Sun. Lightning was present on Earth long before human life evolved and it may even have played a crucial role in the evolution of life on our planet. The global lightning flash rate is some tens to a hundred km per second. Each year, some 25 million cloud-to-ground lightning discharges occur in the United States, and this number is expected to increase by about 50% due to global warming over the 21st century. Lightning initiates many forest fires, and over 30% of all electric power line failures are lightning related. Each commercial aircraft is struck by lightning on average once a year. A lightning strike to an unprotected object or system can be catastrophic. In the first part of the article, an overview of thunderclouds and their charge structure is given, basic lightning terminology is introduced, and different types of lightning (including the so-called rocket-triggered lightning) are described. For the most common negative cloud-to-ground lightning, main lightning processes are identified and the existing hypotheses of lightning initiation in thunderclouds are reviewed.

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on the prevention of lighting

Bulletin of the American Meteorological Society ◽

10.1175/1520-0477-50.7.514 ◽

1969 ◽

Vol 50 (7) ◽

pp. 514-521 ◽

Cited By ~ 2

Author(s):

C. D. Stow

Keyword(s):

United States ◽

Forest Fires ◽

Western United States ◽

Agricultural Crops ◽

Loss Of Life ◽

The World ◽

Lightning Discharges ◽

Cloud To Ground Lightning ◽

Recreational Resources

The destructive nature of cloud-to-ground lightning strokes is well known. Loss of life and damage to buildings and other man-made structures may to a large extent be prevented by the judicial use of lightning conductors and screens but no comparable protection may be offered to expanses of agricultural crops or forests. According to Fuquay (1967) lightning is the greatest single cause of forest fires in the western United States: during the period 1946–1962, 140,000 such fires occurred causing severe losses of timber, wildlife, watershed, and recreational resources. Comparable losses occur regularly in other parts of the world. The only solution is the suppression or modification of cloud-to-ground lightning discharges. Methods of suppression are described, some of which may turn out to be practical ways of achieving this aim.

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A Review of Positive and Bipolar Lightning Discharges

Bulletin of the American Meteorological Society ◽

10.1175/bams-84-6-767 ◽

2003 ◽

Vol 84 (6) ◽

pp. 767-776 ◽

Cited By ~ 75

Author(s):

V. A. Rakov

Keyword(s):

Forest Fires ◽

Return Stroke ◽

Winter Storms ◽

Convective Systems ◽

Lightning Channel ◽

Different Types ◽

Mesoscale Convective ◽

Lightning Discharges ◽

Cloud To Ground Lightning ◽

Positive Return

Characteristics of lightning discharges that transport either positive charge or both positive and negative charges to the ground are reviewed. These are termed positive and bipolar lightning discharges, respectively. Different types of positive and bipolar lightning are discussed. Although positive lightning discharges account for 10% or less of global cloud-to-ground lightning activity, there are five situations that appear to be conducive to the more frequent occurrence of positive lightning. These situations include 1) the dissipating stage of an individual thunderstorm, 2) winter thunderstorms, 3) trailing stratiform regions of mesoscale convective systems, 4) some severe storms, and 5) thunderclouds formed over forest fires or contaminated by smoke. The highest directly measured lightning currents (near 300 kA) and the largest charge transfers (hundreds of coulombs or more) are thought to be associated with positive lightning. Two types of impulsive positive current waveforms have been observed. One type is characterized by rise times of the order of 10 μs, comparable to those for first strokes in negative lightning, and the other type is characterized by considerably longer rise times, up to hundreds of microseconds. The latter waveforms are apparently associated with very long, 1–2 km, upward negative connecting leaders. The positive return-stroke speed is of the order of 108 m s−1. Positive flashes are usually composed of a single stroke. Positive return strokes often appear to be preceded by significant in-cloud discharge activity, then followed by continuing currents, and involve long horizontal channels. In contrast to negative leaders, which are always optically stepped when they propagate in virgin air, positive leaders seem to be able to move either continuously or in a stepped fashion. The reported percentage of bipolar flashes in summer storms ranges from 6% to 14% and from 5% to 33% in winter storms. Bipolar lightning discharges are usually initiated by upward leaders from tall objects. It appears that positive and negative charge sources in the cloud are tapped by different upward branches of the bipolar-lightning channel.

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Diurnal Variations of NLDN-Reported Cloud-to-Ground Lightning in the United States

Monthly Weather Review ◽

10.1175/mwr-d-13-00121.1 ◽

2014 ◽

Vol 142 (3) ◽

pp. 1037-1052 ◽

Cited By ~ 27

Author(s):

Ronald L. Holle

Keyword(s):

United States ◽

The United States ◽

Maximum Activity ◽

Lightning Flash ◽

Diurnal Changes ◽

Lightning Detection ◽

Cloud To Ground Lightning ◽

Local Mean ◽

Composite Maps ◽

Mean Time

Abstract National maps of cloud-to-ground lightning flash density (in flashes per square kilometer per year) for one or more years have been produced since the National Lightning Detection Network (NLDN) was first deployed across the contiguous United States in 1989. However, no single publication includes maps of cloud-to-ground flash density across the domain and adjacent areas during the entire diurnal cycle. Cloud-to-ground lightning has strong and variable diurnal changes across the United States that should be taken into account for outdoor lightning-vulnerable activities, particularly those involving human safety. For this study, NLDN cloud-to-ground flash data were compiled in 20 km by 20 km grid squares from 2005 to 2012 for the lower 48 states. A unique feature of this study is that maps were prepared to coincide with local time, not time zones. NLDN flashes were assigned to 2-h time periods in 5° longitude bands. Composite maps of the 2-h periods with the most lightning in each grid square were also prepared. The afternoon from 1200 to 1800 local mean time provides two-thirds of the day’s lightning. However, lightning activity starts before noon over western mountains and onshore along the Atlantic and Gulf of Mexico coasts. These areas are where recurring lightning-vulnerable recreation and workplace activities should expect the threat at these times, rather than view them as an anomaly. An additional result of the study is the midday beginning of lightning over the higher terrain of the western states, then the maximum activity moves steadily eastward. These storms pose a threat to late-afternoon and evening recreation. In some Midwest and plains locations, lightning is most frequent after midnight.

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THE MANIFESTATION OF A GENERAL PLANETARY CRISIS AT THE BEGINNING OF THE THIRD MILLENNIUM

Intellect XXІ ◽

10.32782/2415-8801/2021-1.6 ◽

2021 ◽

Author(s):

Valeriy Kovalyov ◽

Olena Ataeva

Keyword(s):

Forest Fires ◽

Social Order ◽

Transition Period ◽

Human Life ◽

Industrial Relations ◽

Economic Restructuring ◽

The United States ◽

The Third ◽

Third Millennium ◽

The Future

The article reveals the essence and preconditions of the global crisis in nature and society at the beginning of the third millennium. The purpose of human life as a manifestation of its society is defined in accordance with the requirements of the objectively existing laws of human evolution on the way to extracurricular society. In particular, attention is paid to such cataclysms of the planet that interfere with human life in the present and future, such as earthquakes, devastating typhoons, temperature fluctuations, downpours, tsunamis, or, conversely, droughts that lead to vegetation, crop failures, forest fires and more , to eliminate which humanity has limited opportunities. A significant impact on the state of natural conditions of our planet is caused by changes in solar activity. Changes in the survival of mankind, such as the emergence of viral diseases, including plague, Ebola, coronavirus and others, which endanger human life and lead to changes in production and living conditions, which in turn forces people to join forces in the struggle for survival. Possible ways to eliminate or mitigate the devastating effects of the planetary crisis in the context of human existence through socio-economic restructuring within the modern era, the trends of which are currently manifested in the socio-economic confrontation of such countries, on the one hand as the United States, on the other – Russia and China, which are heading to the social and economic space. The main provisions of the methodology for quantifying social changes on the path of socio-economic restructuring of mankind in the future by indicators: the level of labor potential, human and physical capital, wages, as representatives of existing industrial relations in the world. In particular, methods have been invented to analyze and calculate the level of wages as an economic category of the transition period to the direct social order in the future of mankind on such elements as the minimum, additional and stimulating wages. The scientific approaches to determining the degree of social maturity of society in the present and future, which distort the progress of mankind to its ultimate goal – the restructuring of extracurricular, direct community structure, its existence on the planet.

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Cloud-to-Ground Lightning Flash Density and Thunderstorm Day Distributions over the Contiguous United States Derived from NLDN Measurements: 1993–2018

Monthly Weather Review ◽

10.1175/mwr-d-19-0211.1 ◽

2019 ◽

Vol 148 (1) ◽

pp. 313-332 ◽

Cited By ~ 4

Author(s):

Thomas L. Koehler

Keyword(s):

United States ◽

The United States ◽

Horizontal Resolution ◽

Precipitation Anomaly ◽

Lightning Flash ◽

Southern Rocky Mountains ◽

Weather Observations ◽

Cloud To Ground Lightning ◽

The Mean ◽

Southern Florida

Abstract This study employs cloud-to-ground (CG) lightning flash data from the U.S. National Lightning Detection Network (NLDN) to examine temporal and spatial distributions of lightning flash and thunderstorm day (TD) occurrences over the contiguous United States from 1993 to 2018. TD distributions are estimated from NLDN CG flashes using 4 thunder audibility approximations: 5 and 10 nautical mile (n mi; 1 n mi = 1.852 km) audibility ranges, and minima of 1 and 2 flashes within the audibility range. The 26-yr period examined is longer than previous studies using NLDN data, and the TD results can be compared directly to climatologies derived from surface weather observations dating back to the late 1890s. Results based on the abundant NLDN data avoid limitations introduced by the coarse horizontal resolution of surface observations inherent in pre-NLDN TD climatologies. Annual mean flash density and annual and monthly mean TD distributions are derived from almost 568 million NLDN CG flashes. A mean annual maximum of more than 16 flashes km−2 is found near Tampa, Florida. The mean annual TD maximum of 113 days (from at least 2 flashes within 10 n mi) occurs in southern Florida. Regions exceeding 70 TDs are found from eastern Texas eastward into Florida, and over the southern Rocky Mountains. Large positive deviations from the mean number of TDs extend from Texas northwestward into Colorado during 2003–07, followed by large negative deviations over the same region during 2008–12. Both deviation patterns are similar to expected summertime precipitation anomaly patterns over the United States during El Niño and La Niña years, respectively.

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The Daily Cloud-to-Ground Lightning Flash Density in the Contiguous United States and Finland

Monthly Weather Review ◽

10.1175/2010mwr3517.1 ◽

2011 ◽

Vol 139 (5) ◽

pp. 1323-1337 ◽

Cited By ~ 24

Author(s):

Antti Mäkelä ◽

Pekka Rossi ◽

David M. Schultz

Keyword(s):

United States ◽

Detection Efficiency ◽

Quantitative Measure ◽

The United States ◽

Lightning Flash ◽

Upper Midwest ◽

Lightning Detection ◽

Operational Forecasting ◽

Central United States ◽

Cloud To Ground Lightning

A method is developed to quantify thunderstorm intensity according to cloud-to-ground lightning flashes (hereafter ground flashes) determined by a lightning-location sensor network. The method is based on the ground flash density ND per thunderstorm day (ground flashes per square kilometer per thunderstorm day) calculated on 20 km × 20 km fixed squares. Because the square size roughly corresponds to the area covered by a typical thunderstorm, the flash density for one square defines a unit thunderstorm for the purposes of this study. This method is tested with ground flash data obtained from two nationwide lightning-location systems: the National Lightning Detection Network (NLDN) in the contiguous United States and the portion of the Nordic Lightning Information System (NORDLIS) in Finland. The distribution of daily ground flash density ND is computed for all of Finland and four 800 000 km2 regions in the United States (identified as western, central, eastern, and Florida). Although Finland and all four U.S. regions have median values of ND of 0.01–0.03 flashes per square kilometer per thunderstorm day—indicating that most thunderstorms produce relatively few ground flashes regardless of geographical region—the most intense 1% of the storms (as measured by the 99th percentiles of the ND distributions within each region) show much larger differences among regions. For example, the most intense 1% of the ND distributions is 1.3 flashes per square kilometer per thunderstorm day in the central U.S. region, but only 0.2 flashes per square kilometer per thunderstorm day in Finland. The spatial distribution of the most intense 1% of the ND distributions illustrates that the most intense thunderstorm days occur in the central United States and upper Midwest, which differs from the maxima of the average annual flash density NA and the number of thunderstorm days TD, both of which occur in Florida and along the coast of the Gulf of Mexico. This method for using ND to quantify thunderstorm intensity is applicable to any region as long as the detection efficiency of the lightning-location network is high enough or known. This method can also be employed in operational forecasting to provide a quantitative measure of the lightning intensity of thunderstorms relative to climatology.

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Global ground strike point characteristics in negative downward lightning flashes – part 2: Algorithm validation

10.5194/nhess-2021-13 ◽

2021 ◽

Author(s):

Dieter R. Poelman ◽

Wolfgang Schulz ◽

Stephane Pedeboy ◽

Leandro Z. S. Campos ◽

Michihiro Matsui ◽

...

Keyword(s):

Input Parameter ◽

Lightning Discharge ◽

Ground Truth ◽

The United States ◽

Lightning Strike ◽

Lightning Flash ◽

Large Set ◽

Success Rates ◽

Peak Current ◽

Termination Point

Abstract. At present the lightning flash density is a key input parameter to assess the risk of occurrence of a lightning strike in a particular region of interest. Since it is known that flashes tend to have more than one ground termination point on average, the use of ground strike point densities as opposed to flash densities is more appropriate. Lightning location systems (LLSs) do not directly provide ground strike point densities. However, ingesting their observations into an algorithm that groups strokes in respective ground strike points results in the sought after density value. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points. The output of the algorithms is tested against a large set of ground-truth observations taken from different regions around the world, including Austria, Brazil, France, Spain, South Africa and the United States of America. These observations are linked to the observations made by local LLSs in order to retrieve the necessary parameters of each lightning discharge and serves as inputs for the algorithms. It follows that all three of the algorithms perform well, with success rates up to about 90 % to retrieve the correct type of the strokes in the flash, i.e., whether the stroke creates a new termination point or follows a pre-existing channel. The most important factor that influences the algorithms' performance is the accuracy by which the strokes are located by the LLS. Additionally, it is shown that the strokes' peak current plays an important role, whereby strokes with a larger absolute peak current have a higher probability of being correctly classified compared to the weaker strokes.

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Global ground strike point characteristics in negative downward lightning flashes – Part 2: Algorithm validation

Natural Hazards and Earth System Science ◽

10.5194/nhess-21-1921-2021 ◽

2021 ◽

Vol 21 (6) ◽

pp. 1921-1933

Author(s):

Dieter R. Poelman ◽

Wolfgang Schulz ◽

Stephane Pedeboy ◽

Leandro Z. S. Campos ◽

Michihiro Matsui ◽

...

Keyword(s):

Input Parameter ◽

Lightning Discharge ◽

Ground Truth ◽

The United States ◽

Separation Distance ◽

Lightning Strike ◽

Lightning Flash ◽

Large Set ◽

Peak Current ◽

Termination Point

Abstract. At present the lightning flash density is a key input parameter for assessing the risk of occurrence of a lightning strike in a particular region of interest. Since it is known that flashes tend to have more than one ground termination point on average, the use of ground strike point densities as opposed to flash densities is more appropriate. Lightning location systems (LLSs) do not directly provide ground strike point densities. However, ingesting their observations into an algorithm that groups strokes into respective ground strike points results in the sought-after density value. The aim of this study is to assess the ability of three distinct ground strike point algorithms to correctly determine the observed ground-truth strike points. The output of the algorithms is tested against a large set of ground-truth observations taken from different regions around the world, including Austria, Brazil, France, Spain, South Africa and the United States of America. These observations are linked to the observations made by a local LLS in order to retrieve the necessary parameters of each lightning discharge, which serve as input for the algorithms. Median values of the separation distance between the first stroke in the flash and subsequent ground strike points are found to vary between 1.3 and 2.75 km. It follows that all three of the algorithms perform well, with success rates of up to about 90 % to retrieve the correct type of the strokes in the flash, i.e., whether the stroke creates a new termination point or follows a pre-existing channel. The most important factor that influences the algorithms' performance is the accuracy by which the strokes are located by the LLS. Additionally, it is shown that the strokes' peak current plays an important role, whereby strokes with a larger absolute peak current have a higher probability of being correctly classified compared to the weaker strokes.

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Seasonal, Monthly, and Weekly Distributions of NLDN and GLD360 Cloud-to-Ground Lightning

Monthly Weather Review ◽

10.1175/mwr-d-16-0051.1 ◽

2016 ◽

Vol 144 (8) ◽

pp. 2855-2870 ◽

Cited By ~ 17

Author(s):

Ronald L. Holle ◽

Kenneth L. Cummins ◽

William A. Brooks

Keyword(s):

United States ◽

New England ◽

The United States ◽

Lightning Flash ◽

Time Space ◽

Lightning Detection ◽

Cloud To Ground Lightning ◽

Annual Total ◽

The Caribbean ◽

Using Data

Abstract Annual maps of cloud-to-ground lightning flash density have been produced since the deployment of the National Lightning Detection Network (NLDN). However, a comprehensive national summary of seasonal, monthly, and weekly lightning across the contiguous United States has not been developed. Cloud-to-ground lightning is not uniformly distributed in time, space, or frequency. Knowledge of these variations is useful for understanding meteorological processes responsible for lightning occurrence, planning outdoor events, anticipating impacts of lightning on power reliability, and relating to severe weather. To address this gap in documentation of lightning occurrence, the variability on seasonal, monthly, and weekly scales is first addressed with NLDN flash data from 2005 to 2014 for the 48 states and adjacent regions. Flash density and the percentage of each season’s portion of the annual total are compiled. In spring, thunderstorms occur most often over southeastern states. Lightning spreads north and west until by June, most areas have lightning. New England, the northern Rockies, most of Canada, and the Florida Peninsula have a small percentage of lightning outside of summer. Arizona and portions of adjacent states have the highest incidence in July and August. Flash densities reduce in September in most regions. This seasonal, monthly, and weekly overview complements a recent study of diurnal variations of flashes to document when and where lightning occurs over the United States. NLDN seasonal maps indicate a summer lightning dominance in the northern and western United States that extends into Canada using data compiled from GLD360 network observations. GLD360 also extends NLDN seasonal maps and percentages into Mexico, the Caribbean, and offshore regions.

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