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On August 19, 2012, the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite captured a sequence of seven blue discharges within one minute that emanated from a parent thunderstorm over Lake Taihu in East China. The analysis of lightning activity produced in the thunderstorm indicates that at least six of these events occurred in association with negative NBEs that were concurrent with the blue discharge by less than 1 ms, and negative CGs occurred within 6 s before each blue discharge, which is in agreement with the modeling presented by Krehbiel et al. [2008]. Therefore, the frequent occurrence of negative CGs could provide the favorable condition for the production of blue discharges, and negative NBEs are probably the initial event of blue discharges. The detection of negative NBEs might provide a convenient approach to detect the occurrence of blue discharges as lightning bolt shooting upward from the top of energetic thunderstorms.

An 8-year analysis of hailstorms is presented. A comprehensive set of six hundred hailstorms that occurred in 172 different days in various parts of Germany is used to characterise these events. The analysed observations include measurements from a lightning location system, precipitation radar, as well as information from automated cell detection algorithms based on radar reflectivity and radial winds which are combined with severe weather reports. Additionally to the storms' parameters during the time of the observed hail, the temporal evolution of the storms' characteristics is analysed in order to study the convective life-cycle and identify parameters with predictive skill. A special focus is on the lightning characteristics of the convective cells. A feature that is shown to occur in many of the analysed severe hail cases is the lightning jump, i.e., a rapid increase in the total lightning density. It occurs well before the observed hail and has thus a great potential to increase the lead time of warnings of severe hail events. Instead of fixed thresholds for the definition of a lightning jump, a lightning jump intensity parameter is introduced and tested. The analysis also reveals that half to the storms show a pulsating lightning activity. Nearly three quarters of the hail events are associated with a mesocyclone that was automatically detected in radar data. As expected, high reflectivity values were measured during the time of the observed hail.

It has been argued in the technical literature, and widely reported in the popular press, that cosmic ray air showers (CRASs) can initiate lightning via a mechanism known as relativistic runaway electron avalanche (RREA), where large numbers of high energy and low energy electrons can, somehow, cause the local atmosphere in a thundercloud to transition to a conducting state. In response to this claim, other researchers have published simulations showing that the electron density produced by RREA is far too small to be able to affect the conductivity in the cloud sufficiently to initiate lightning. In this paper, we compare 74 days of cosmic ray air shower data collected in north central Florida during 2013, 2014, and 2015, the recorded CRASs having primary energies on the order of 1016 eV to 1018 eV and zenith angles less than 38 degrees, with Lightning Mapping Array (LMA) data, and we show that there is no evidence that the detected cosmic ray air showers initiated lightning. Furthermore, we show that the average probability of any of our detected cosmic ray air showers to initiate a lightning flash can be no more than 5 percent. If all lightning flashes were initiated by cosmic ray air showers, then about 1.6 percent of detected CRASs would initiate lightning, therefore we do not have enough data to exclude the possibility that lightning flashes could be initiated by cosmic ray air showers.

A World Meteorological Organization weather and climate extremes committee has judged that the world’s longest reported distance for a single lightning flash occurred with a horizontal distance of 321 km (199.5 mi) over Oklahoma in 2007, while the world’s longest reported duration for a single lightning flash is an event that lasted continuously for 7.74 seconds over southern France in 2012. In addition, the committee has unanimously recommended amendment of the AMS Glossary of Meteorology definition of lightning discharge as a “series of electrical processes taking place within 1 second” by removing the phrase “within one second” and replacing with “continuously.” Validation of these new world extremes (a) demonstrates the recent and on-going dramatic augmentations and improvements to regional lightning detection and measurement networks, (b) provides reinforcement regarding the dangers of lightning, and (c) provides new information for lightning engineering concerns. Fil: Lang, Timothy J.. NASA Marshall Space Flight Center; Estados Unidos Fil: Pédeboy, Stéphane. Météorage; Francia Fil: Rison, Willlliam. Institute of Mining and Technology, Department of Electrical Engineering; México Fil: Cerveny, Randallll S.. Arizona State Universit, School of Geographical Sciences and Urban Planning; Estados Unidos Fil: Montanyà, Joan. Universidad Politécnica de Catalunya; España Fil: Chauzy, Serge. University of Toulouse/CNRS, Laboratoire d’Aérologie; Francia Fil: MacGorman, Donald R.. NOAA/National Severe Storms Laboratory; Estados Unidos Fil: Holle, Ronald L.. Vaisala, Inc.; Estados Unidos Fil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina Fil: Zhang, Yijun. Chinese Academy of Meteorological Sciences, Laboratory of Lightning Physics and Protection Engineering; China Fil: Carbin, Gregory. NOAA/Storm Prediction Center; Estados Unidos Fil: Mansell, Edward R.. NOAA/National Severe Storms Laboratory; Estados Unidos Fil: Kuleshov, Yuriy. Royal Melbourne Institute of Technology University, Bureau of Meteorology and School of Mathematical and Geospatial Sciences; Australia Fil: Petersrson, Thomas C.. World Meteorological Organization, Commission for Climatology; Estados Unidos Fil: Brunet, Manola. University of East Anglia, School of Environmental Sciences,Climatic Research Unit; Reino Unido. Universitat Rovira I Virgili; España Fil: Driouech, Fatima. Direction de la Météorologie Nationale, Climate Studies Service; Marruecos Fil: Krahenbuhl, Daniel S.. Arizona State University, School of Geographical Sciences and Urban Planning; Estados Unidos

The physical mechanism of lightning attachment to grounded structures is one of the most important issues in lightning physics research, and it is the basis for the design of the lightning protection systems. Most of what is known about the attachment process comes from leader propagation models that are mostly based on laboratory observations of long electrical discharges or from observations of lightning attachment to tall structures. In this paper we use high-speed videos to analyze the attachment process of downward lightning flashes to an ordinary residential building. For the first time, we present characteristics of the attachment process to common structures that are present in almost every city (in this case, two buildings under 60 m in Sao Paulo City, Brazil). Parameters like striking distance and connecting leaders speed, largely used in lightning attachment models and in lightning protection standards, are revealed in this work.

The averaged data of observations oflightning strikes in North Asia in 2009-2014 are presented. The pattern is retrieved from the data of World Wide Lightning Location Network (WWLLN); one station of this network is located in Yakutsk. The dependence of thunderstorm activity on latitude, longitude, and altitude is demonstrated.

Continuing current is a process in lightning in which the current in a conducting channel can flow for much longer than in a typical lightning discharge. The phenomenon can be characterized by the continuous optical emission that accompanies the current flow. Using the Lightning Imaging Sensor (LIS), lightning with continuing current is identified on a global scale. Lightning that contains optical emission over at least five consecutive LIS frames, roughly 7-9ms, are classified as continuing current flashes. This differs from typical lightning discharges that produce optical emission for one or two consecutive frames. Of the flashes detected by LIS, 11.2% contain continuing current. These flashes optically radiate over a larger footprint and have a longer duration than ones that do not. The spatial distribution of these flashes indicate that regions of high lightning activity may not be correlated with a high likelihood of continuing current flashes. Further, oceanic and winter lightning are shown to have a higher proportion of continuing current flashes. Finally, 25-40% of flashes identified by LIS to have continuing current have only an intracloud pulse detected by the National Lightning Detection Network (NLDN), with no cloud to ground strokes detected.

Optical lightning sensors like the Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) measure total lightning across large swaths of the globe with high detection efficiency. With two upcoming missions that employ these sensors – LIS on the International Space Station (ISS-LIS) and the Geostationary Lightning Mapper (GLM) on the GOES-R satellite – there has been increased interest in what these measurements can reveal about lightning and thunderstorms in addition to total flash activity. Optical lightning imagers are capable of observing the characteristics of individual flashes that include their sizes, durations, and radiative energies. However, it is important to exercise caution when interpreting trends in optical flash measurements because they can be affected by the scene. This study uses coincident measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite to examine the properties of LIS flashes and the surrounding cloud regions they illuminate. These combined measurements are used to assess to what extent optical flash characteristics can be used to make inferences about flash structure and energetics. Clouds illuminated by lightning over land and ocean regions that are otherwise similar based on TRMM measurements are identified. Even when LIS flashes occur in similar clouds and background radiances, oceanic flashes are still shown to be larger, brighter, longer lasting, more prone to horizontal propagation and to contain more groups than their land-based counterparts. This suggests that the optical trends noted in literature are not entirely the result of radiative transfer effects, but rather stem from physical differences in the flashes.

For the study of characteristics of the lightning around the capsized “Oriental Star” incident, this paper analyzes the lightning space distribution in the surrounding, preliminary judging from characteristics of the lightning figure out the form of disastrous weather patterns. It is concluded that: the wreck accident happened in lightning highest frequency period, also most lightning frequency region, as well as the biggest negative rather than positive lightning current time bucket and region. The latest lightning is less than 300 m from the accident, leads to a higher possibility of damage to the ship communications equipment by lightning electromagnetic induction, which needs to further strengthen the safety precautions against ships during a thunderstorm.

We have described a new probabilistic method for calculating and assessing lightning striking terrestrial explosive objects using a combined criterion for the emergence of upward streamer and leader discharges from the elements of the object being protected and lightning rods taking into account the probabilistic nature of the avalanche–streamer and streamer–leader transitions, the trajectories of a downward stepped lightning leader and lightning current. It has been shown that the disregard of possible formation of uncompleted streamer discharges from the elements of the object in the electric field of a downward lightning leader, which can ignite explosive emission, decreases the rated probability of the object being damaged by a lightning stroke by several times.

For lightning research, we monitor particle fluxes from thunderclouds, the so-called thunderstorm ground enhancements (TGEs) initiated by runaway electrons, and extensive air showers (EASs) originating from high-energy protons or fully stripped nuclei that enter the Earth's atmosphere. We also monitor the near-surface electric field and atmospheric discharges using a network of electric field mills. The Aragats “electron accelerator” produced several TGEs and lightning events in the spring of 2015. Using 1-s time series, we investigated the relationship between lightning and particle fluxes. Lightning flashes often terminated the particle flux; in particular, during some TGEs, lightning events would terminate the particle flux thrice after successive recovery. It was postulated that a lightning terminates a particle flux mostly in the beginning of a TGE or in its decay phase; however, we observed two events (19 October 2013 and 20 April 2015) when the huge particle flux was terminated just at the peak of its development. We discuss the possibility of a huge EAS facilitating lightning leader to find its path to the ground.

This study evaluates a method for estimating the cloud-to-ground (CG) lightning flash rate from microwave remote sensing data. Defense Meteorological Satellite Program satellites have been in operation since 1987 and include global-viewing microwave sensors that capture thunderstorms as brightness temperature depressions. The National Lightning Detection Network (NLDN) has monitored CG lightning in the United States since 1997. This study investigates the relationship between CG lightning and microwave brightness temperature fields for the contiguous United States from April to September for the years 2005–12. The findings suggest that an exponential function, empirically fit to the NLDN and SSM/I data, provides lightning count measurements that agree to within 60%–70% with NLDN lightning, but with substantial misses and false alarms in the predictions. The discrepancies seem to be attributable to regional differences in thunderstorm characteristics that require a detailed study at smaller spatial scales to truly resolve, but snow at higher elevations also produces some anomalous microwave temperature depressions similar to those of thunderstorms. The results for the contiguous United States in this study are a step toward potentially using SSM/I data to estimate CG lightning around the world, although the sensitivity of the results to regional differences related to meteorological regimes would need further study.

The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) was the first specifically dedicated instrument to observe lightning-induced transient luminous events (TLE) sprites, elves, halos, and gigantic jets from space. The Imager is an intensified CCD system operating in the visible wavelength region with a filter wheel to select from 6 positions with filters. The Imager has a 5°x20° (vertical x horizontal) field of view (FOV). The Spectrophotometer (SP) is populated with 6 photometers with individual filters for emissions from the far ultra-violet to the near-infrared. An Array Photometer with two channels operating in the blue and red provides altitude profiles of the emission over 16 altitude bins each. The Associated Electronics Package (AEP) controls instrument functions and interfaces with the spacecraft. ISUAL was launched May 21, 2004 into a sun-synchronous 890 km orbit on the Formosat-2 satellite and has successfully been collecting data ever since. ISUAL is running on the night side of the orbit and is pointed to the east of the orbit down towards the limb. The instrument runs continuously and writes data to a circular buffer. Whenever the SP detects a sudden signal increase above a preset threshold, a trigger signal is generated that commands the system to keep the data for about 400 msec starting from ~50 msec before the trigger. Over its lifetime of ~11 years the system recorded thousands of TLE and also successfully observed aurora and airglow.

This paper reviews recent advances in understanding the physical processes of artificially triggered lightning and natural lightning as well as the progress in testing lightning protection technologies, based on a series of lightning field campaigns jointly conducted by the Chinese Academy of Meteorological Sciences and Guangdong Meteorological Bureau since 2006. During the decade-long series of lightning field experiments, the technology of rocket-wire artificially triggered lightning has been improved, and has successfully triggered 94 lightning flashes. Through direct lightning current waveform measurements, an average return stroke peak current of 16 kA was obtained. The phenomenon that the downward leader connects to the lateral surface of the upward leader in the attachment process was discovered, and the speed of the upward leader during the connection process being significantly greater than that of the downward leader was revealed. The characteristics of several return strokes in cloud-to-ground lighting have also been unveiled, and the mechanism causing damage to lightning protection devices (i.e., ground potential rise within the rated current) was established. The performance of three lightning monitoring systems in Guangdong Province has also been quantitatively assessed.

Thunderstorms have been observed to introduce infrasonic oscillations in the ionosphere, but it is not clear what processes or which parts of the thunderstorm generate the oscillations. In this paper, we present a new technique that uses an array of ground-based GPS total electron content (TEC) measurements to locate the source of the infrasonic oscillations and compare the source locations with thunderstorm features to understand the possible source mechanisms. The location technique utilizes instantaneous phase differences between pairs of GPS-TEC measurements and an algorithm to best fit the measured and the expected phase differences for assumed source positions and other related parameters. In this preliminary study, the infrasound waves are assumed to propagate along simple geometric raypaths from the source to the measurement locations to avoid extensive computations. The located sources are compared in time and space with thunderstorm development and lightning activity. Sources are often found near the main storm cells, but they are more likely related to the downdraft process than to the updraft process. As a result, the sources are also commonly found in the convectively quiet stratiform regions behind active cells and are in good coincidence with extensive lightning discharges and inferred high-altitude sprites discharges.

The lightning generated by explosive volcanic eruptions is of interest not only as a promising technique for monitoring volcanic activity, but also for its broader implications and possible role in the origin of life on Earth, and its impact on the atmosphere and biosphere of the planet. However, at present the genetic mechanisms and physical properties of volcanic lightning remain poorly understood, as compared to our understanding of thundercloud lightning. Here, we present joint magnetotelluric (MT) data and video imagery that were used to investigate the physical properties of electrical discharges generated during explosive activity at Sakurajima volcano, Japan, and we compare these data with the characteristics of thundercloud lightning. Using two weeks of high-sensitivity, high-sample-rate MT data recorded in 2013, we detected weak electromagnetic signals radiated by volcanic lightning close to the crater. By carefully inspecting all MT waveforms that synchronized with visible flashes, and comparing with high-speed (3000 frame/s) and normal-speed (30 frame/s) videos, we identified two types of discharges. The first type consists of impulses (Type A) and is interpreted as cloud-to-ground (CG) lightning. The second type is characterized by weak electromagnetic variations with multiple peaks (Type B), and is interpreted as intra-cloud (IC) lightning. In addition, we observed a hybrid MT event wherein a continuous weak current accompanied Type A discharge. The observed features of volcanic lightning are similar to thunderstorm lightning, and the physical characteristics show that volcanic lightning can be treated as a miniature version of thunderstorm lightning in many respects. The overall duration, length, inter-stroke interval, peak current, and charge transfer all exhibit values 1–2 orders of magnitude smaller than those of thunderstorm lightning, thus suggesting a scaling relation between volcanic and thunderstorm lightning parameters that is independent of the type of charged particles. On the other hand, the polarities, which are estimated by long-time (3.4 yrs) MT (32 samples/s) and video (30 frame/s) observations, are different than those of normal thunderstorm lightning. These observations are consistent with the notion that charge structures in volcanic ash plumes are highly disordered and are characterized by numerous small charged regions with high charge density.

The recent discovery of long recovery, early VLF scattering events (LOREs) indicates that the electric field changes from lightning discharges are capable of producing long-lasting disturbances (up to tens of minutes) in the upper mesosphere and lower ionosphere. Comparison of lightning mapping array, broadband (up to 10 MHz) electric field, and VLF (∼300 Hz to 42 kHz) magnetic field measurements shows that the field changes produced by initial breakdown (IB) processes and the following leaders in natural, cloud-to-ground lightning discharges are detectable in VLF magnetic field measurements at long distances. IB radiation has been detected in VLF for lightning discharges occurring up to 2630 km away from the VLF observing station. Radio atmospherics associated with 52 LOREs, 51 regular recovery events, and 3098 flashes detected by National Lightning Detection Network and/or GLD360 were examined for IB radiation occurring up to 15 ms before the return stroke. Our analysis reveals that in contrast to regular recovery early VLF events, LOREs are strongly associated with lightning discharges which exhibit an intense IB process and a fast first leader (typical duration

The Lightning and Sprites Observation (LSO) experiment was designed to test a new concept of nadir-viewing sprite measurement on board the International Space Station using spectral differentiation methods for lightning and sprite identification. It was composed of two calibrated cameras: one equipped with a narrowband filter at 763 nm to maximize the contrast between sprites and lightning, and the other to monitor lightning. The LSO was operated at night during 15 days from 2001 to 2004 during which 197 lightning flashes, several sprites, hundreds of gas flares, and tens of cities were analyzed. The main strength of this experiment was its high spatial resolution of about 400 m. The structural details of some lightning are thus observed highlighting complex systems. Some features such as the nonlinear increase of the lightning-illuminated cloud top area with the peak radiance and the radial decrease of the lightning flash radiance were quantified. The median area is 129 km2 with median minor and major axes of 12 and 16 km. Two methods of sprite identification are presented and applied to the most intense sprite events observed by LSO. The sprite diameter is 5 km and it is shifted of about 22 km from the center of the parent lightning. A ratio of 1.7% is deduced for lightning flashes between the radiances measured by both cameras. These observations should be useful for the preparation or the analysis of future space missions dedicated to nadir-viewing observations of sprites.

Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM-GLIMS) started the nadir observations of lightning discharges and transient luminous events (TLEs) from the International Space Station (ISS) since November 2012. In the nadir observations, JEM-GLIMS optical instruments have to simultaneously detect incomparably intense lightning emissions and weak TLE emissions. To distinguish TLEs, especially sprite events, from lightning events, combined data analytical methods are adopted: (1) a subtraction of the wideband camera image from the narrowband camera image, (2) a calculation of the intensity ratio between different photometer channels, and (3) an estimation of the polarization and charge moment changes for the TLE-producing lightning discharges. We succeeded in identifying numbers of sprite events using the combined analytical methods, and here we report three sprite events detected by JEM-GLIMS as a case study. In the subtracted images, sprite emissions are located over the area of the sprite-producing lightning emissions. However, these sprites and sprite-producing lightning discharges did not occur at the nadir point of the ISS. For this reason, the geometry conversion of the sprite and sprite-producing lightning emissions as observed from the point just over the sprite-producing lightning discharges is performed. In the geometry-converted images, the locations of the sprite emissions are clearly displaced by 8–20 km from the peak positions of the sprite-producing lightning emissions. Thus, the first quantitative spatial distributions of sprites and sprite-producing lightning discharges from the JEM-GLIMS nadir observations are revealed.

Thunderstorm cell-lightning activity is discussed in terms of analysing a thunderstorm's lightning frequency–equipotential temperature relationship. Thunderstorms were tracked using Doppler radars in five-minute time steps. Lightning is assigned to the nearest thunderstorm cell, it is characterised by lightning frequency data using LINET. Equipotential temperature is not directly estimated, instead the notion of air mass catchment is introduced to represent it. It is shown in this paper that the thunderstorm cell with maximum lightning frequency in the current time step is almost always the so-called leading storm cell. The lightning frequency activity of the non-leading storm cells is not significant.

The purpose of this paper is to introduce electrical discharge phenomena known as transient luminous events above thunderstorms to the lightning protection community. Transient luminous events include the upward electrical discharges from thunderstorms known as starters, jets, and gigantic jets, and electrical discharges initiated in the lower ionosphere such as sprites, halos, and elves. We give an overview of these phenomena with a focus on starters, jets, gigantic jets, and sprites, because similar to ordinary lightning, streamers and leaders are basic components of these four types of transient luminous events. We present a few recent observations to illustrate their main properties and briefly review the theories. The research in transient luminous events has not only advanced our understanding of the effects of thunderstorms and lightning in the middle and upper atmosphere, but also improved our knowledge of basic electrical discharge processes critical for sparks and lightning.

Synoptic and mesoscale cyclonic systems over the ocean and seas are often accompanied by thunderstorm activity, the intensity and spatial distribution of which is modulated by the dynamic structure of these systems. Lightning discharges are sources of electromagnetic radiation in the range of very low frequencies (VLF) and are detected by VLF location finders. Using the World Wide Lightning Location Network (WWLLN), relations between characteristics of fields of detected lightning discharges in the north-western part of the Pacific Ocean and those of fields of meteorological elements of weather formations estimated by data of remote sensing of the Earth by satellites are studied by an example of tropical cyclones. We illustrate a technique permitting one to connect thunderstorm activity parameters (frequency and intensity, as well as spatial distribution of lightning discharges) with the structure of weather systems over oceans and seas and with the intensity and forms of mesoscale formations distinguished in these systems by fields of the near-water wind vortex (the fields are obtained using a scatterometer) and by satellite images in the visible and infrared ranges. The relations between the frequency and density of lightning discharges in the range of influence of a tropical cyclone (TC) and spatial distribution of the near-water wind vortex are demonstrated by an example of individual TCs of 2005–2013.

Recent development in lightning discharges including transient luminous events (TLEs) and global electric circuit are discussed. Role of solar activity, convective available potential energy, surface temperature and difference of land–ocean surfaces on convection process are discussed. Different processes of discharge initiation are discussed. Events like sprites and halos are caused by the upward quasi-electrostatic fields associated with intense cloud-to-ground discharges while jets (blue starter, blue jet, gigantic jet) are caused by charge imbalance in thunderstorm during lightning discharges but they are not associated with a particular discharge flash. Elves are generated by the electromagnetic pulse radiated during lightning discharges. The present understanding of global electric circuit is also reviewed. Relation between lightning activity/global electric circuit and climate is discussed.

This research focuses on the climatology of cloud-to-ground (CG) lightning flashes based on PERUN lightning detection network data from 2002 to 2013. To present various CG lightning flash characteristics, 10 km × 10 km grid cells are used, while for estimating thunderstorm days, circles with radii of 17.5 km in the 1 km × 1 km grid cells are used. A total of 4 328 892 CG lightning flashes are used to analyze counts, density, polarity, peak current, and thunderstorm days. An average of 151 days with thunderstorm (appearing anywhere in Poland) occurs each year. The annual number of days with thunderstorms increases southeasterly from the coast of the Baltic Sea (15–20 days) to the Carpathian Mountains (30–35 days). The mean CG lightning flash density varies from 0.2 to 3.1 flashes km−2 yr−1 with the highest values in the southwest–northeast belt from Kraków-Częstochowa Upland to the Masurian Lake District. The maximum daily CG lightning flash density in this region amounted to 9.1 km−2 day−1 (3 July 2012). The monthly variation shows a well-defined thunderstorm season extending from May to August with July as the peak month. The vast majority of CG lightning flashes were detected during the daytime (85%) with a peak at 1400 UTC and a minimum at 0700 UTC. Almost 97% of all CG lightning flashes in the present study had a negative current, reaching the highest average monthly values in February (55 kA) and the lowest in July (24 kA). The percentage of positive CG lightning flashes was the lowest during the summer (2%–3%) and the highest during the winter (10%–20%).

The Imager of Sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT-2 satellite was launched in 2004 and records transient luminous events (TLEs). ISUAL is an instrument composed of an imager and a multichannel spectrophotometer which is able to measure the brightness from far ultraviolet to near infrared for TLEs and lightning flashes. Several types of TLEs have been identified, classified, and documented between 2004 and 2014. However, no statistical analyses on lightning have already been realized. In this paper, we focus on lightning flashes which did not induce TLEs. Statistics about brightness or temporal dynamic are presented from fitted waveforms from far ultraviolet to near infrared, after having corrected for atmospheric effects for each spectrophotometer channels. We demonstrate that the lightning/satellite distance and the altitude of the lightning need to be taken into account. The lightning waveforms from each spectrophotometer channel could be modeled as an exponential pulsed function which the shape could be explained by the photon propagation in the cloud. The median values at 777.4 nm are 1.63 × 10−6 W m−2 for the maximum brightness, 5.85 × 104 J for the total energy at the source, 414 µs for the full width half maximum, 620 µs for the full width at quarter of maximum, and 170 µs for the risetime. Results are compared with previous experiments performed from visible to near-infrared domains. The median temporal variables for near-infrared waveforms are shorter than the values of the UV waveforms.

The Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite has previously been used to build climatologies of mean lightning flash rate across the global tropics and subtropics. This new work explores climatologies of thunderstorm occurrence as seen by LIS and the conditional mean flash rates when thunderstorms do occur. The region where thunderstorms are seen most often by LIS extends slightly farther east in central Africa than the corresponding region with the highest total mean annual flash rates. Presumably this reflects a difference between more frequent thunderstorm initiation in the east and upscale growth as storms move westward. There are some differences between locations with the greatest total lightning flash counts and those where thunderstorms occur most often. The greatest conditional mean flash rates—considering only those TRMM orbits that do have lightning in a given grid box—are found in subtropical regions. The highest values are in Argentina, with the central United States, Pakistan, eastern China, and the east coast of Australia also having particularly high values.

The Imager of Sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT-2 satellite, launched in 2004, records Transient Luminous Events (TLEs). ISUAL has an imager and a spectrophotometer that observe TLEs all over the globe. Among these phenomena, elves are particularly difficult to detect. ISUAL often records events that correspond to significant far ultraviolet (FUV) emissions in the spectrophotometer but have no discernible TLEs in the imager. These FUV events are called “dim” elves. Therefore, it is important to develop mathematical tools to analyze the data to obtain a better evaluation of the number of elves and their occurrence. Multivariate approaches are applied to characterize the unlabeled events. The first approach is the principal component analysis which distinguishes two different groups, one including elves and dim elves. The second approach is the PARallel FACtor analysis which provides a waveform model for each group. These methodologies confirm that FUV signal is the evidence of TLE presence. A crude classification method was then suggested taking into account these results. The proportion of elves, relatively to the considered ISUAL data set, is found to be about 40%. It is similar to previous results and confirms that relatively weak lightning peak current is sufficient to produce elves. This new strategy demonstrates the potential for discriminating between lightning and TLEs without prior knowledge within the selectivity of the FUV spectral band.

This paper aims at analyzing the broadband part of electromagnetic emission from thunderclouds in a frequency range of tens of kilohertz to hundreds of megahertz. A model of the intracloud lightning discharge formation is presented. The lightning formation is described as a stochastic growth of the branching discharge channels, which is determined by the electrostatic field. The dynamics of the electric field and of the charge distribution over the lightning structure is calculated deterministically. The effect of the initial charge density in the cloud and the parameters of the conducting channels on spatio-temporal characteristics of the currents and structure of the lightning discharge is studied. The discharge radio emission is calculated by summing up the radiation fields of each channel at the observation point. The standard model for a separate discharge current is adopted, and the electromagnetic radiation in the far zone is estimated. It is found that the obtained frequency spectra exhibit a universal power-law behavior. The results of the modeling agree with known experimental data.

This paper presents a recent characterization review of three cloud-to-ground lightning parameters [lightning peak current, ground flash density, and keraunic level (KL)] used in engineering applications based on available data from studies conducted in some tropical countries of Central and South America (Brazil, Colombia, Costa Rica, and Venezuela), considering seasonal and spatial variation aspects. There are some differences between the behaviors of the analyzed parameters in tropical areas in comparison with those published in the literature for temperate ones. The most significant conclusion is that historical data suggest that the highest ground flash density are located between latitude of 8° and 10° north. This value is much higher than the highest values reported for countries located in temperate regions. It is seen from the KL analysis that this parameter varies depending on the latitude with values up to 200 thunderstorm days (TDs).

This study examines coordinated storm and triggered lightning observations made in July–August 2013 at the International Center for Lightning Research and Testing to determine why triggered flashes in Florida typically transition from an upward vertical channel entering the cloud to horizontal structure near the storm's melting level. Data from a balloon-borne electric field meter, a mobile 5 cm wavelength radar, and a small-baseline VHF Lightning Mapping Array acquired during a period in which three flashes were triggered on 1 August confirmed the hypothesis that the transition to horizontal lightning structure just above the melting level occurred in a layer of negative charge. This experiment was the first to provide vertical profiles of the electric field in Florida storms, from which their vertical charge distribution could be inferred. Three dissipating storms observed on different days all had negative charge near the melting level, but a growing mature storm had positive charge there.

The purpose of this paper is to summarize the enormous contributions of FS2 (FORMOSAT-2 or Formosa satellite #2) in both Earth and transient luminous events (TLEs) observations in 10 years. As a small satellite operated for 10 years (20 May 2004 to 20 May 2014) in orbit, FS2 keeps its two unique characteristics: (1) to orbit 14 revolutions around the Earth per day with daily revisit capability, and (2) to provide the capabilities of Earth observation in sunlight time and TLEs observation in eclipsed time every day. It carries two payloads: the remote sensing instrument (RSI) for Earth imaging in satellite׳s day time and the imager of sprites and upper atmospheric lightning instrument (ISUAL) for scientific observations in satellite׳s night time, respectively. Daily revisit capability provides changes of events on Earth in either short time (several days) or long term (several years). Examples include: Indian Ocean earthquake and tsunami (December 2004), disintegration of Wilkins Ice Shelf in Antarctica region (2006–2014, long term), Sichuan earthquake (May 2008), Tohoku earthquake and tsunami (March 2011), polar regions (2006–2014, long term), etc. In the TLEs observation, ISUAL had recorded more than 35,000 events in 10 years with 73.93% elves, 6.54% red sprites, 5.81% halos, 13.42% blue jets and 0.30% gigantic jets. Major contributions of FS2 in this specific scientific area are presented. In particular, current and future research topics on TLEs are discussed. Also, major contributions of FS2׳s RSI to the United Nations Institute for Training and Research (UNITAR) Operational Satellite Applications Programme (UNOSAT) and Group of Earth Observation System of Systems (GEOSS) are summarized. This paper also addresses briefly the health status of FS2 after working 10 years in orbit.

Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM-GLIMS) is a space mission to conduct the nadir observations of lightning discharges and transient luminous events (TLEs). The main objectives of this mission are to identify the horizontal distribution of TLEs and to solve the occurrence conditions determining the spatial distribution. JEM-GLIMS was successfully launched and started continuous nadir observations in 2012. The global distribution of the detected lightning events shows that most of the events occurred over continental regions in the local summer hemisphere. In some events, strong far-ultraviolet emissions have been simultaneously detected with N2 1P and 2P emissions by the spectrophotometers, which strongly suggest the occurrence of TLEs. Especially, in some of these events, no significant optical emission was measured by the narrowband filter camera, which suggests the occurrence of elves, not sprites. The VLF receiver also succeeded in detecting lightning whistlers, which show clear falling-tone frequency dispersion. Based on the optical data, the time delay from the detected lightning emission to the whistlers was identified as ∼10 ms, which can be reasonably explained by the wave propagation with the group velocity of whistlers. The VHF interferometer conducted the spaceborne interferometric observations and succeeded in detecting VHF pulses. We observed that the VHF pulses are likely to be excited by the lightning discharge possibly related with in-cloud discharges and measured with the JEM-GLIMS optical instruments. Thus, JEM-GLIMS provides the first full set of optical and electromagnetic data of lightning and TLEs obtained by nadir observations from space.

Polarimetric radar data are used to develop lightning cessation guidance for the Cape Canaveral area of central Florida. For this purpose, 80 nonsevere thunderstorm cells in 2012, mostly during the warm season, are analyzed. In-cloud and cloud-to-ground lightning data for the storms are obtained by combining information from the second-generation Lightning Detection and Ranging (LDAR-II) network and the National Lightning Detection Network (NLDN). Storms are tracked using the Warning Decision Support System–Integrated Information (WDSS-II) software, producing time series of radar- and lightning-derived parameters. The 80 storms are split into two categories: 1) 50 isolated storms whose lightning initiation sources are confined to the core or anvil region of the storm and 2) 30 nonisolated cells whose lightning channels are initiated in a nearby active storm and extended to the dissipating study cell. Trends in polarimetric radar parameters at different temperature levels are studied for 40 of the 50 isolated storms to develop cessation guidance. Results based on a completely independent sample of 10 storms reveal that the best-performing cessation algorithm utilizes the presence of graupel and horizontal reflectivity ≥35 dBZ at the −10°C temperature altitude. Lightning is not expected 10 min after both thresholds are no longer met. However, this relationship does not apply to nonisolated cells because a neighboring storm could still be electrically active. Results show that a stratiform cloud region connecting the decaying storm to an active storm might facilitate further channel propagation that might not have occurred otherwise. Thus, the proposed cessation guidelines are not recommended for nonisolated cells.

This paper presents the analysis of five events where simultaneous lightning currents were registered in different wind turbines of a wind farm with lightning monitoring equipment installed. Measurements from current monitoring devices installed at the wind turbines and observations from auto-triggering video cameras were correlated with data from the U.S. National Lighting Detection Network. In all five events, the correlation showed that a cloud-to-ground (CG) lightning stroke with high peak current struck the ground within 10 km of the affected turbines at the time of the currents in the wind turbines. The polarity of the CG discharges was negative in two events and positive in the three remaining events, which were also accompanied by small intracloud pulses. According to the analysis of the data for each event, the simultaneous discharges at the wind turbines are most likely caused by the nearby CG strokes, involving mechanisms that vary depending on the polarity of the associated CG stroke. The analysis also suggests that the event of upward lightning from wind turbines triggered by nearby lightning activity occurs very often and therefore it should be considered carefully in the processes of assessing the lightning exposure of the wind turbines, designing the lightning protection, and defining validation tests.

In recent years, lightning and thunderstorm detection techniques have been rapidly developed in many regions of Asia. As the most populous continent, hazards caused by lightning and related phenomena are being paid more and more attentions and lightning observations and detections are booming in many countries. In this paper, we will give a brief review on recent progress of lightning and thunderstorm detection techniques in Asia. First, we will introduce several widely used lightning location systems including VHF interferometers, VHF time-of-arrival systems and LF time-of-arrival systems. As an example, a newly-developed system called BOLT is described and recent observation results are introduced. Second, we will review studies of a special type of intracloud discharge called “narrow bipolar event” (NBE). NBE studies in Asia are flourishing in recent years and are making great contributions to the understanding of various properties of NBE. Finally, we will introduce a fast-scanning phased array radar (PAR) system installed in Osaka University. This radar system has a temporal resolution of 10–30 s, which is much faster than the traditional weather radar and is ideal for observations of fast-evolving storm structures and the analysis of their relationship with lightning activities. Preliminary observation results with PAR are described.

Ion Chemistry and Composition of the Atmosphere, A.A. Viggiano and F. Arnold Meteorologic Aspects of Thunderstorms, E.R. Williams Thunderstorm Electrification, C.P.R. Saunders Lightning Currents, T. Ogawa Lightning Detection from Ground and Space, R.E. Orville Artificially Triggered Lightning, K. Horii and M. Nakano Ball Lightning, H. Kikuchi Lightning and Atmospheric Chemistry: The Rate of Atmospheric NO Production, M.G. Lawrence, W.L. Chameides, P.S. Kasibhatla, H.Levy II, and W. Moxim Lightning Within Planetary Atmospheres, K. Rinnert Quasistatic Electromagnetic Phenomena in the Atmosphere and Ionosphere, R.H. Holzworth Schumann Resonances, D.D. Sentman Low-Frequency Radio Noise, A.C. Frazer-Smith Radio Noise Above 300 kHz due to Natural Causes, D.E. Proctor Atmospheric Noise and Its Effects of Telecommunication System Performance, A.D. Spaulding

A long-standing question in lightning studies has concerned how lightning is initiated in thunderstorms, given the absence of physical conductors. Remote sensing observations of discharges are starting to provide the answer to this question, obtained in large part with radio frequency instruments and techniques. A recent important and unexpected step in this process has come from observations of the phenomenon called narrow bipolar events (NBEs) at NM Tech's mountain-top Langmuir Laboratory observatory in central New Mexico [1]. NBEs are fast, high current, short duration discharges that are the strongest natural sources of VHF radiation on earth [2]. They occur either in isolation from other discharges in a storm, or sometimes at the beginning of intracloud (IC) discharges [3, 4], but otherwise have eluded explanation for nearly four decades.

The study of electric field is an important tool for lightning research. Electric Field Mills (EFMs) are electromechanical devices used to observe static atmospheric electric fields during fair weather and during storm conditions. EFM readings show significant changes in electric field due to an approaching thunderstorm and particularly, during lightning periods. Attempts to comprehend the variations prior to and after a strike has been done by observatories all over the world. This paper focuses on identifying characteristic changes in atmospheric electric field prior to a lightning strike. Both static and dynamic field changes are studied by means of literature survey and static field variations are also studied through analysis of EFM data from Sonnblick Observatory, Austria and National Centre for Earth Science Studies (NCESS), Trivandrum, Kerala. During thunderstorms and the few seconds prior to lightning, significant changes are observed in both static and dynamic electric fields. Static field changes include a magnitude rise and reversal of direction of electric field from the fair weather situation, and dynamic field changes are characterized by the occurrence of Preliminary Breakdown Pulses(PBP) which is the dynamic electrical activity inside the cloud before a strike. This study, by identifying the characteristic changes in atmospheric electric field prior to lightning strike by comparing multiple observations from different parts of the world, points to great possibilities in the field of lightning prediction.

The turbulent pockets of air inside storms can help to build up static electricity in the atmosphere, according to a new study.

The importance of atmospheric electricity research has been increasingly recognized in recent decades. Research on atmospheric electricity has been actively conducted since the 1980s in China. Lightning physics and its effects, as important branches of atmospheric electricity, have received more attention because of their significance both in scientific research and lightning protection applications. This paper reviews atmospheric electricity research based primarily on ground-based field experiments at different regions in China in the last decade. The results described in this review include physics and effects of lightning, rocket-triggered lightning and its physical processes of discharge, thunderstorm electricity on the Tibetan Plateau and its surrounding areas, lightning activity associated with severe convective storms, the effect and response of lightning to climate change, numerical simulation of thunderstorm electrification and lightning discharge, lightning detection and location techniques, and transient luminous events above thunderstorms.

Article history: Comprehensive observations of lightning flashes striking at a 325-m-tall meteorology tower were conducted in Beijing, China, during the summer of 2012. The images from high speed camera and normal video camera and the measurements of electric field changes were examined to investigate the characteristics of upward negative lightning initiated from the tower. Among eight upward lightning flashes documented during two thunderstorms, four were self-initiated eventswithoutlightning activitynearbyprior totheirinitiation,twoweretriggeredbythenearby positive cloud-to-ground lightning (+CG) with the initiation of the upward leaders from the tower lagged 0.4 ms and 5 ms behind, respectively, and the remaining two were triggered by nearby intra-cloud lightning activities. The average 2-D speed of the upward positive leader was 1.0 × 10 5

Observing from southern Taiwan on 2 August 2010, a thunderstorm near Luzon Island, Philippines, about 500 km away was found to produce 72 transient luminous events (TLEs). Besides optical images, ULF and VLF sferics of lightning from this thunderstorm were also recorded. This work examines the characteristics of TLE-producing lightning through studying their ULF and VLF sferics. The attenuation of ULF and VLF sferics in the Earth cavity is obtained through analyzing the sferics associated with Imager of Sprite and Upper Atmospheric Lightning elves that occurred within ~1500 km of Taiwan. Amplitudes of the ULF and the VLF sferics are found to vary as D−0.871 and D−1.207, respectively, where D is the source distance from the sferic stations. After normalizing the sferics from the 2 August 2010 storm to 500 km distance, the ratio of the peak ULF and the VLF magnetic fields is found to be distinct for different TLE-producing lightning. The ratio for the halo-producing lightning is nearly 3 times that of the elve-producing lightning, but it is comparable to that of the halo-sprite-producing lightning, although the ULF strength for the halo-sprite lightning is significantly larger than that for the halo lightning. Therefore, it is possible to distinguish between the TLE-types using the ULF to VLF peak ratio or the strength of ULF/VLF band emissions of the parent lightning. Comparison of numerically simulated and the observed lightning radiation fields indicates that the best fit discharge time of the elve lightning is about 100 µs, while that for the halo-producing lightning is between 200 and 500 µs.

Data gathered from the US National Lightning Detection Network (TM) (NLDN) show that the peak currents of lightning flashes striking the sea are significantly higher than those of lightning flashes striking the land. We suggest that the unfavorable conditions for the formation of positive charge pockets in maritime clouds lead to lightning initiation at higher cloud potentials compared to their land counterparts, resulting in larger peak currents in negative lightning flashes striking the sea. As the positive charge pocket does not promote positive ground strokes, no such discontinuity should be expected in positive first return strokes to ground between land and sea.

An investigation on lightning characteristics and damage to wind turbines was performed on Jeju and Gangwon regions. The lightning data from January 2010 to September 2013 detected by IMPACT ESP were collected and analyzed in detail. Hangyeong and Seongsan wind farms of Jeju province and Taebaek, Changjuk, Taegisan and Gangwon wind farms of Gangwon province were selected for this study. Lightning rates and lightning damage events at the six wind farms were compared with each other. Lightning maps for the two regions were drawn using lightning frequency data. As a result, lightning frequency of Gangwon region was higher than that of Jeju region, while lightning strength of Gangwon was weaker than that of Jeju. Lightning rates were assessed to be good for all of the six wind farms. No lightning damage to wind turbines occurred at the two wind farms of Jeju, while some lightning damage to wind turbines took place at the four wind farms of Gangwon. Key Words ：Wind Energy, Lightning Frequency, Lightning Map, Lightning Rate

Since its launch on 20 May 2004, FORMOSAT-2 (FS2, Formosa satellite ♯2) has been operated on orbit for more than 9 years. It carries two payloads: the remote sensing instrument (RSI) for Earth observations and the imager of sprites and upper atmospheric lightning instrument (ISUAL) for the purpose of scientific observations. The RSI is operating at daytime while ISUAL is active at night-time. To meet both mission objectives simultaneously, the satellite operations planning has been more complicated. In order to maximize the usage of the on-board resources, the satellite attitude maneuver activities and power charge/discharge cycles have been scheduled cautiously in every detail. Under such fully engaged operations scenario and with a design life of 5 years, it is inevitable that the satellite encountered many anomalies, either permanent or temporary. In particular, one attitude gyro (totally four) and one reaction wheel (totally four) have been failed. This paper presents the major anomalies and resolutions in the past years. Many iterations and trade-offs have been made to minimize the effect on mission operations of the handicapped FORMOSAT-2. It still can provide about 80% of the designed functions and capabilities.