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

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.

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

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.

The World Wide Lightning Location Network and Convective Activity in Tropical Cyclones

2011 ◽  
Vol 139 (1) ◽  
pp. 175-191 ◽  
Author(s):  
Sergio F. Abarca ◽  
Kristen L. Corbosiero ◽  
David Vollaro
Keyword(s):  
Tropical Cyclones ◽  
World Wide ◽  
Inner Core ◽  
The United States ◽  
Vertical Shear ◽  
Lightning Flash ◽  
Convective Activity ◽  
Atlantic Basin ◽  
Peak Current ◽  
The World

Abstract Lightning flash density in tropical cyclones (TCs) is investigated to identify whether lightning flashes provide information on TC intensity and/or intensity change, to provide further insight into TC asymmetric convective structure induced by vertical shear and storm motion, and to assess how well the World Wide Lightning Location Network (WWLLN) is suited for the observation of TCs. The 24 Atlantic basin TCs that came within 400 km of the United States from 2004 to 2007 are studied. The National Lightning Detection Network is used to analyze flash density as a function of peak current and to evaluate the WWLLN. Flash density is shown to be smaller for hurricanes than for tropical depressions and storms, with this reduction being gradually more pronounced as flash peak current increases. The results suggest that flash density in the inner core is a parameter with potential for distinguishing intensifying versus nonintensifying TCs, particularly in the weaker storm stages where flash densities are largest. Vertical wind shear produces a strong downshear left (right) asymmetry in the inner core (outer rainbands), whereas motion asymmetries are less clear. The unprecedented azimuthal resolution used in this study suggests that as shear strengthens, the azimuthal region of convection in the inner core is sharpened from a width of ∼130° to a width of ∼60°. The radial distribution of flash density is shown to exhibit a relatively narrow region of little activity (between 60 and 120 km from the eye), with increased activity in both regions closer to, and more distant from, the center (i.e., the eyewall and outer rainbands, respectively). Finally, it is shown that the WWLLN captures the convective activity in Atlantic basin TCs remarkably well, despite its low detection efficiency.

Lightning, the Science. Part 1: Modern View

2021 ◽  
Vol 5 (5) ◽  
pp. 4-16
Author(s):  
Vladimir A. Rakov ◽  
Keyword(s):  
Forest Fires ◽  
Human Life ◽  
The United States ◽  
Lightning Strike ◽  
Lightning Flash ◽  
Commercial Aircraft ◽  
Electric Power Line ◽  
Triggered Lightning ◽  
Lightning Discharges ◽  
Cloud To Ground Lightning

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.

Quantifying parametric uncertainty in the Rothermel model

2008 ◽  
Vol 17 (5) ◽  
pp. 638 ◽  
Author(s):  
Edwin Jimenez ◽  
M. Yousuff Hussaini ◽  
Scott Goodrick
Keyword(s):  
Variance Reduction ◽  
Input Parameter ◽  
Parametric Uncertainty ◽  
Fire Spread ◽  
The United States ◽  
Linear System Of Equations ◽  
Spread Model ◽  
Non Linear System ◽  
The Impact ◽  
Sensitivity Derivative

The purpose of the present work is to quantify parametric uncertainty in the Rothermel wildland fire spread model (implemented in software such as BehavePlus3 and FARSITE), which is undoubtedly among the most widely used fire spread models in the United States. This model consists of a non-linear system of equations that relates environmental variables (input parameter groups) such as fuel type, fuel moisture, terrain, and wind to describe the fire environment. This model predicts important fire quantities (output parameters) such as the head rate of spread, spread direction, effective wind speed, and fireline intensity. The proposed method, which we call sensitivity derivative enhanced sampling, exploits sensitivity derivative information to accelerate the convergence of the classical Monte Carlo method. Coupled with traditional variance reduction procedures, it offers up to two orders of magnitude acceleration in convergence, which implies that two orders of magnitude fewer samples are required for a given level of accuracy. Thus, it provides an efficient method to quantify the impact of input uncertainties on the output parameters.

scholarly journals Effect of indirect lightning strike to 66kV transmission line in Java-Bali system

2018 ◽  
Vol 197 ◽  
pp. 11001
Author(s):  
Aristo Adi Kusuma ◽  
Putu Agus Aditya Pramana ◽  
Brian Bramantyo S.D.A. Harsono ◽  
Buyung Sofiarto Munir
Keyword(s):  
Transmission Line ◽  
Transmission Lines ◽  
Lightning Strike ◽  
Actual Condition ◽  
Peak Current ◽  
Lightning Strikes ◽  
Detection Systems ◽  
Current Magnitude ◽  
Lightning Detection ◽  
Insulator Flashover

Based on Java-Bali grid disturbance data, the 66kV transmission lines that is close to or intersect with 150kV or 500kV transmission line is often experienced earth fault due to insulator flashover. The insulator flashover can be caused by indirect lightning strike since lightning strikes tend to strike higher structure. Therefore, this paper will determine the effect of indirect lightning strike on 150kV or 500kV transmission line to 66kV transmission line by modeling and simulation using application of transient analysis. Variation of lightning peak current magnitude and gap between 66kV transmission line and transmission line with higher voltage is performed during simulation. The range of peak current magnitude follows the data from lightning detection systems, while the value of gap follows the data from actual condition. It is found that higher current peak and closer gap will cause higher transient overvoltage on insulator of 66kV transmission line thus insulator flashover may occur more frequent. Addition of earth wire on 66kV transmission line and gap between each transmission by organizing the sag of conductor can be performed to minimize the insulator flashover.

scholarly journals PROFESSOR ZDZISŁAW ŻYGULSKI JR.: AN OUTSTANDING PERSON, A GREAT PERSONALITY, A MUSEUM PROFESSIONAL, A RESEARCHER ON ANTIQUE WEAPONS, ORIENTAL ART AND EUROPEAN PAINTING (1921–2015)

Muzealnictwo ◽  
2017 ◽  
Vol 58 (1) ◽  
pp. 2-13
Author(s):  
Teresa Grzybkowska
Keyword(s):  
Museum Studies ◽  
The United States ◽  
Leonardo Da Vinci ◽  
Large Set ◽  
New York University ◽  
History Of Art ◽  
The World ◽  
History Of ◽  
Polish Art ◽  
Set Up

Professor Zdzisław Żygulski Jr. (1921–2015) was one of the most prominent Polish art historians of the second half of the 20th century. He treated the history of art as a broadly understood science of mankind and his artistic achievements. His name was recognised in global research on antique weapons, and among experts on Rembrandt and Leonardo da Vinci. He studied museums and Oriental art. He wrote 35 books, about 200 articles, and numerous essays on art; he wrote for the daily press about his artistic journeys through Europe, Japan and the United States. He illustrated his publications with his own photographs, and had a large set of slides. Żygulski created many exhibitions both at home and abroad presenting Polish art in which armour and oriental elements played an important role. He spent his youth in Lvov, and was expatriated to Cracow in 1945 together with his wife, the pottery artist and painter Eva Voelpel. He studied English philology and history of art at the Jagiellonian University (UJ), and was a student under Adam Bochnak and Vojeslav Molè. He was linked to the Czartoryski Museum in Cracow for his whole life; he worked there from 1949 until 2010, for the great majority of time as curator of the Arms and Armour Section. He devoted his whole life to the world of this museum, and wrote about its history and collections. Together with Prof. Zbigniew Bocheński, he set up the Association of Lovers of Old Armour and Flags, over which he presided from 1972 to 1998. He set up the Polish school of the study of militaria. He was a renowned and charismatic member of the circle of international researchers and lovers of militaria. He wrote the key texts in this field: Broń w dawnej Polsce na tle uzbrojenia Europy i Bliskiego Wschodu [Weapons in old Poland compared to armaments in Europe and the Near East], Stara broń w polskich zbiorach [Old weapons in Polish armouries], Polski mundur wojskowy [Polish military uniforms] (together with H. Wielecki). He was an outstanding researcher on Oriental art to which he dedicated several books: Sztuka turecka [Turkish art], Sztuka perska [Persian art], Sztuka mauretańska i jej echa w Polsce [Moorish art and its echoes in Poland]. Prof. Zdzisław Żygulski Jr. was a prominent educator who enjoyed great respect. He taught costume design and the history of art and interiors at the Academy of Fine Arts in Cracow, as well as Mediterranean culture at the Mediterranean Studies Department and at the Postgraduate Museum Studies at the UJ. His lectures attracted crowds of students, for whose needs he wrote a book Muzea na świecie. Wstęp do muzealnictwa [Museums in the world. Introduction to museum studies]. He also lectured at the Florence Academy of Art and at the New York University. He was active in numerous Polish scientific organisations such as PAU, PAN and SHS, and in international associations such as ICOMAM and ICOM. He represented Polish art history at general ICOM congresses many times. He was also active on diverse museum councils all over Poland.

Automated Lightning Flash Detection in Nighttime Visible Satellite Data

2011 ◽  
Vol 26 (3) ◽  
pp. 399-408 ◽  
Author(s):  
Richard L. Bankert ◽  
Jeremy E. Solbrig ◽  
Thomas F. Lee ◽  
Steven D. Miller
Keyword(s):  
Satellite System ◽  
Lightning Strike ◽  
False Alarms ◽  
Lightning Flash ◽  
Infrared Imager ◽  
Defense Meteorological Satellite Program ◽  
Lightning Detection ◽  
Mapping Array ◽  
Automated Technique ◽  
Spectral Channels

Abstract The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) nighttime visible channel was designed to detect earth–atmosphere features under conditions of low illumination (e.g., near the solar terminator or via moonlight reflection). However, this sensor also detects visible light emissions from various terrestrial sources (both natural and anthropogenic), including lightning-illuminated thunderstorm tops. This research presents an automated technique for objectively identifying and enhancing the bright steaks associated with lightning flashes, even in the presence of lunar illumination, derived from OLS imagery. A line-directional filter is applied to the data in order to identify lightning strike features and an associated false color imagery product enhances this information while minimizing false alarms. Comparisons of this satellite product to U.S. National Lightning Detection Network (NLDN) data in one case as well as to a lightning mapping array (LMA) in another case demonstrate general consistency to within the expected limits of detection. This algorithm is potentially useful in either finding or confirming electrically active storms anywhere on the globe, particularly those occurring in remote areas where surface-based observations are not available. Additionally, the OLS nighttime visible sensor provides heritage data for examining the potential usefulness of the Visible-Infrared Imager-Radiometer Suite (VIIRS) Day/Night Band (DNB) on future satellites including the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP). The VIIRS DNB will offer several improvements to the legacy OLS nighttime visible channel, including full calibration and collocation with 21 narrowband spectral channels.

scholarly journals Event-based sampling for reducing communication load in realtime human motion analysis by wireless inertial sensor networks

2016 ◽  
Vol 2 (1) ◽  
pp. 711-714 ◽  
Author(s):  
Daniel Laidig ◽  
Sebastian Trimpe ◽  
Thomas Seel
Keyword(s):  
Joint Angle ◽  
Inertial Sensor ◽  
Ground Truth ◽  
Human Motion ◽  
Human Motion Analysis ◽  
Large Set ◽  
Fusion Algorithm ◽  
The Cost ◽  
Realtime Measurement ◽  
Event Based

AbstractWe examine the usefulness of event-based sampling approaches for reducing communication in inertial-sensor-based analysis of human motion. To this end we consider realtime measurement of the knee joint angle during walking, employing a recently developed sensor fusion algorithm. We simulate the effects of different event-based sampling methods on a large set of experimental data with ground truth obtained from an external motion capture system. This results in a reduced wireless communication load at the cost of a slightly increased error in the calculated angles. The proposed methods are compared in terms of best balance of these two aspects. We show that the transmitted data can be reduced by 66% while maintaining the same level of accuracy.

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