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Abstract X-rays have been observed in natural downward cloud-to-ground lightning for over 20 years and in rocket-triggered lightning for slightly less. In both cases, this energetic radiation has been detected during the stepped and dart leader phases of downward negative flashes. More recently, X-rays have also been reported during the dart leader phase of upward negative flashes. In this study, we present the observations of four upward positive lightning flashes from the Säntis Tower (2.5 km ASL) in Switzerland. These consist of the simultaneous records of electric current passing through the tower, and electric field strength and X-ray flux 20 m from the tower base. One of the flashes was captured by a high-speed camera operating at 24,000 frames per second, stills from which are also presented. We detected X-rays during the initial phase of upward negative leader propagation, which can be associated with the leader-stepping process from electric field and current waveforms. To the best of our knowledge, this is the first time that such measurements are reported in the literature. The obtained time-synchronised data confirm that the X-ray emissions detected are associated with the initial steps of the upward negative leader. The frequency and energy of X-ray pulses appear to decrease as functions of time, with pulses disappearing altogether within the first millisecond of the leader initiation. X-ray emission also appears to be correlated with the maximum current-derivative and the electric field change of leader steps, consistent with cold electron runaway. These observations contribute to improving our understanding of upward lightning, which is a primary source of damage to tall structures such as wind turbines and telecommunications towers, as well as aircraft during takeoff and landing.

Abstract Introduction The current research investigates into the application of various thunderstorm indices to predict severe thunderstorm occurrences during the monsoon season across four distinct regions in India. Methods: The study assesses the prediction model’s efficacy using various skill scores and the Weather Research and Forecasting (WRF) model has been integrated for 30 h with double moment microphysics scheme NSSL-17 which accurately reproduces vertical and meteorological measures. Objective Furthermore, it investigates fifteen thunderstorm indices derived from the ERA5 dataset to identify the most effective index for forecasting severe thunderstorms. Results The results indicate that combining thunderstorm indices with skill scores, such as the Heidke Skill Score and True Skill Statistic, enhances the accuracy of severe thunderstorm predictions in the Indian monsoon season. The accurate predictions rely on determining optimal thresholds for each index. The study emphasizes the importance of using multiple indices rather relying solely on single measure for predicting severe thunderstorms. Advanced indices like the Energy Helicity Index (EHI) and Supercell Composite Parameter (SCP) perform well in forecasting extreme severe thunderstorms due to their strong reliance on wind shears. The EHI (> 1), and SCP (≥ 3.5), STP (≥ 1.2) along with low SRH at 3 km (100 m2/s2), indicated no evidence of helicity or tornado activity during the event. On the other hand, the CAPE, K Index, and VT Index demonstrate robust predictive capabilities for non-severe category thunderstorms. Conclusions Integrating numerous thunderstorm indices improves meteorologists’ forecasts, ensuring public safety. Based on this work, future research can improve severe weather forecasting models’ accuracy and reliability.

We have newly designed an electrostatic sensor, called an electric field mill (EFM), to simplify the estimation of the charge position and charge amount transferred by lightning discharges. It is necessary for this remote estimation of the transferred charge to measure electric field changes caused by charge loss at the time of a lightning strike at multiple locations. For multiple-station measurement of electric field changes, not only speed but also phase for exposure and shielding of the sensing plates inside each EFM of the array should be synchronized to maintain the sensitivities of the deployed instruments. Currently, there is no such EFM with specified speed and phase control performance of the rotary part. Thus, we developed a new EFM in which the rotary mechanism was controlled consistently to within 3% error by a GPS module. Five EFMs had been distributed in the Hokuriku area of Japan during the winter season of 2022–2023 for a test observation. Here we describe the design and a simple calibration method for our new EFM array. Data analysis method based on the assumption of a simple monopole charge structure is also summarized. For validation, locations of assumed point charges were compared with three-dimensional lightning mapping data estimated by radio observations in the MF-HF bands. Initial results indicated the validity to estimate transferred charge amounts and positions of winter cloud-to-ground lightning discharges with our new EFM array.

There are few reports on the near-field acoustic signals corresponding to lightning return strokes. One rocket-triggered lightning flash, which contains 13 return strokes, initial continuous current (ICC) processes, and abundant M-components, was observed in the summer of 2018 and reported in this study. The complete near-field acoustic pressure signals initiated by the flash were recorded and analyzed. It is found that the near-field acoustic pressure signals from each return stroke are composed of the first arrived N-shape shock waveform and the subsequent low-frequency oscillating waveforms. The characteristic of the acoustic waveforms has been parametrically defined and quantitatively analyzed, with a comprehensively acoustic-electrical correlation investigation. The acoustic pressure signals from intensive ICC processes and M-component pulses with different discharge intensities are also discussed. It is found that the too-close time interval between M-component and previous current pulses would affect the generation and measurement of the acoustic pressure waveforms from the M-component, even though the discharge amplitude is competitive and the wavefront is fast. The same phenomenon has also been observed in the acoustic signals from a return stroke with a too close interval from the previous pulse. The acoustic source localization with great accuracy for lightning channel reconstruction was realized based on the measured acoustic signals. The reconstructed channel structure agrees with that of the synchronously captured optical image. The study of the characteristics of acoustic signals from lightning discharge contributes to the recognition of thunder signals, source localization for channel reconstruction, and understanding of the lightning discharge process. [ABSTRACT FROM AUTHOR]

The determination of whether a cloud will evolve into a thunderstorm is beneficial for understanding thunderstorm formation and important for ensuring the safety of society. However, a clear understanding of the microphysics in clouds for the occurrence of lightning activity has not been attained. Vast field observations and laboratory experiments indicate that graupel, which is rimed ice, is a vital hydrometeor for lightning generation, and is the foundation of riming electrification. In this study, polarimetric radar and lightning observations are used to compare the ice microphysics associated with graupel between 57 isolated thunderstorms and 39 isolated non-thunderstorms, and the differences in radar parameters are quantified. Our results for the occurrence of lightning activity in clouds showed the following results: 1) the maximum difference in graupel volume on the −10 °C isotherm height between thunderstorms and non-thunderstorms reached approximately 7.6 km³; 2) the graupel particles approached spherical shapes with a mean ZDR value of 0.3 dB, which likely indicated heavily rimed graupel was present; and 3) 98.2 % of thunderstorms were equipped with the ZDR column, and the mean depth was ~2.5 km³. Our study deepens our understanding of lighting physics and thunderstorm formation. [ABSTRACT FROM AUTHOR]

Identical Lightning Imaging Sensors (LIS) aboard the Tropical Rainfall Measuring Mission satellite (TRMM LIS, 1998–2015) and International Space Station (ISS LIS, 2017–23) have provided over two decades of lightning observations over the global tropics, with ISS LIS extending coverage into the midlatitudes. Quantifying the detection performance of both LIS sensors is a necessary step toward generating a combined LIS climatological record and accurately combining LIS data with lightning detections from other sensors and networks. We compare lightning observations from both LIS sensors with reference sources including the Geostationary Lightning Mapper (GLM) and ground-based Earth Networks Total Lightning Network (ENTLN), Earth Networks Global Lightning Network (ENGLN), National Lightning Detection Network (NLDN), and Global Lightning Dataset (GLD360). Instead of a relative detection efficiency (DE) approach that assumes the perfect performance of the reference sensor, we employ a Bayesian approach to estimate the upper limit of the absolute DE (ADE) of each system being analyzed. The results of this analysis illustrate the geographical pattern of ADE as well as its diurnal cycle and yearly evolution. Reference network ADE increased by ∼15%–30% during the TRMM era, leading to a decline in TRMM LIS ADE. ISS LIS flash ADE has been relatively consistent at 61%–65%, about 4%–5% lower than TRMM LIS at the end of its lifetime. [ABSTRACT FROM AUTHOR]

Climate change's impact on lightning and thunderstorms is uncertain. This study evaluates the sensitivity of multiple Planetary Boundary Layer (PBL) parameterisation schemes within the WRF-ELEC model for simulating a severe lightning and thunderstorm event in Bihar on 25 June 2020. The aim is to understand how these schemes affect lightning and thunderstorm intensity. The model was integrated for 54 h at 0000 UTC on 24 June 2020 using 6-hourly NCEP FNL Operational Global Analysis data at 1° × 1° resolution over Bihar with double nested domains of 9 km (D1) and 3 km (D2). It effectively captures the peak lightning and thunderstorm activity from 0000 to 0900 UTC on 25 June 2020, significantly impacting certain regions. The study utilised ERA5 and IMDAA reanalysis datasets and NASA GPM IMERG daily data to analyse the event and assess the model's performance. Among the PBL schemes tested, ACM2, BouLac, SHsa, and MRF exhibit robust performance. Flash Origin Density (FOD) patterns broadly match observations, although occasional discrepancies occur in southern Bihar. Convective Available Potential Energy (CAPE) and precipitation (mm) analysis reveals anticipated trends. Statistical scores highlight strong performance by ACM2, UW, and GBM schemes in POFD/FAR. The MRF scheme excels in POD/Hit Rate, and the UW scheme achieves the highest score for 24-h accumulated total precipitation. HSS and GSS/ETS underscore the superior performance of the UW and GBM schemes. This study offers insights into lightning and thunderstorm simulations over Bihar with diverse PBL parameterisation schemes in the WRF-ELEC model. [ABSTRACT FROM AUTHOR]

Goal. Decision of problem scientific and technical task on the reliable generating and measuring in the conditions of high-voltage electrophysics laboratory basic component of complete pulse current of artificial lightning with the rationed amplitude-temporal parameters (ATPs) with the use of the modernized generator of current of lightning of type of UITOM-1. Methodology. Bases of the applied electrical engineering, electrodynamics and electrophysics, electrophysics bases of technique of high-voltage and high pulse currents, bases of high-voltage pulse technique and measuring technique. Results. Information, which specify on a decision at Research and Design Institute «Molniya» of National Technical University «Kharkiv Polytechnic Institute» problem scientific and technical task, related to the reliable generating and measuring in the conditions of high-voltage electrophysics laboratory of complete pulse current of artificial lightning, which contains pulse A- (repeated pulse D-), intermediate B- and long-term C- (shortened long C*-) components of this current, is resulted, ATPs which answer the hard technical requirements of normative documents of the USA of SAE ARP 5412: 2013, SAE ARP 5414: 2013 and SAE ARP 5416: 2013. Short information is indicated about the applied electrical circuits of separate high-voltage generators of pulse currents of condenser type of GIC-A (GIC-D), GICB and GIC-C (GIC-C*), which it is worked as synchronous appearance on the general electrical loading in composition the modernized powerful high voltage generator of complete pulse e current of artificial lightning of type of UITOM-1, and in-use highvoltage measuring facilities which contain the heavy-current low-resistance shunts of type of SHK-300 for simultaneous registration with their help on examinee on stability to lightning devices objects of aviation and space-rocket technique of ATPs proper component of complete i pulse current of artificial lightning. Technical examples are resulted and the row of results of practical application of the indicated domestic powerful high-voltage proof-of-concept electrophysics equipment is described at the tests of elements of some aircrafts (ACs) on resistibility to the direct action on them of complete pulse current of artificial lightning with rationed ATPs. Originality. A problem is formulated and having the important applied value in area of aviation and space-rocket technique for the leading countries of the world scientific and technical task on the reliable generating and measuring in the conditions of high-voltage electrophysics laboratory indicated component of complete pulse current of artificial lightning with rationed ATPs and concrete electro-technological ways and hardware are indicated for its successful decision. Practical value. The use of the modernized powerful high-voltage generator of complete pulse current of artificial lightning of type of UITOM-1 developed in practice and created in Ukraine will allow to conduct the real verification on resistibility to the action of lightning of different side systems, devices and construction elements, containing metallic and composition materials, both again developed and modernized ACs, that will be instrumental in the increase of vitality of such ACs in the extreme terms of their flight and stay in an electrical active earthly atmosphere with flowing in it storm electrical discharges. [ABSTRACT FROM AUTHOR]

We observed five clusters of upper‐level compact intracloud discharges (CIDs) moving positive charge up over land and over water in Florida. The clusters each contained 3 to 6 CIDs, and the overall cluster duration ranged from 27 to 58 s. On average, the CIDs in a given cluster occurred 11 s apart and were separated by a 3D distance of about 1.5 km. All the clustered CIDs were located above the tropopause and were likely associated with convective surges that penetrated the stratosphere. The average periodicity of CID occurrence within a cluster (every 11 s) was comparable to the periodicity at which the average cluster area is expected to be bombarded by ≥1016 eV cosmic‐ray particles (every 5 s). Each of such energetic particles gives rise to a cosmic ray shower (CRS) and, in the presence of sufficiently strong electric field over a sufficiently large distance, to a relativistic runaway electron avalanche (RREA). We infer that each of our upper‐level CIDs is likely to be caused by a CRS‐RREA traversing, at nearly the speed of light, the electrified overshooting convective surge and triggering, within a few microseconds, a multitude of streamer flashes along its path, over a distance of the order of hundreds of meters (as per the mechanism recently proposed for lightning initiation by Kostinskiy et al., 2020, https://doi.org/10.1029/2020JD033191). The upper‐level CID clustering was likely made possible by the recurring action of energetic cosmic rays and the rapid recovery of the negative screening charge layer at stratospheric altitudes. Plain Language Summary: Compact intracloud discharges (CIDs) are non‐conventional lightning discharges inside the cloud that are characterized by a relatively small spatial extent (less than 1 km), very strong HF‐VHF (3–300 MHz) electromagnetic emissions, and characteristic wideband radiofrequency field pulses. It has been recently discovered, using space‐based detectors, that CIDs also produce optical signals, the so‐called blue flashes at cloud tops. Our understanding of the physics of CIDs is still poor. CIDs are usually solitary events, but we observed five clusters of CIDs, mostly at altitudes in the 18–20 km range, which were likely associated with kilometer‐scale convective surges that penetrated the stratosphere. Each cluster contained 3 to 6 CIDs, and the cluster duration ranged from 27 to 58 s. On average, the CIDs in a given cluster occurred 11 s apart and were separated by a 3D distance of about 1.5 km. Some CIDs within a cluster were essentially collocated, while being separated in time by up to several tens of seconds. We inferred that the CID clustering observed in our study was made possible by (a) the recurring action of omnipresent energetic cosmic rays and (b) the rapid recovery of the negative screening charge layer at stratospheric altitudes. Key Points: 5 clusters of 3–6 compact intracloud discharges (CIDs) moving positive charge up in convective surges overshooting the tropopause in Florida were examinedCID clustering was tight in both time and space: average time interval was 11 s and average 3D distance within a cluster was 1.5 kmCID clustering was made possible by recurring action of ≥1016 eV cosmic‐ray particles and rapid recovery of negative screening charge layer [ABSTRACT FROM AUTHOR]

During the 2022 New Mexico monsoon season, we deployed two X‐ray scintillation detectors, coupled with a 180 MHz data acquisition system to detect X‐rays from natural lightning at the Langmuir Lab mountain‐top facility, located at 3.3 km above mean sea level. Data acquisition was triggered by an electric field antenna calibrated to pick up lightning within a few km of the X‐ray detectors. We report the energies of over 240 individual photons, ranging between 13 keV and 3.8 MeV, as registered by the LaBr3(Ce) scintillation detector. These detections were associated with four lightning flashes. Particularly, four‐stepped leaders and seven dart leaders produced energetic radiation. The reported photon energies allowed us to confirm that the X‐ray energy distribution of natural stepped and dart leaders follows a power‐law distribution with an exponent ranging between 1.09 and 1.96, with stepped leaders having a harder spectrum. Characterization of the associated leaders and return strokes was done with four different electric field sensing antennas, which can measure a wide range of time scales, from the static storm field to the fast change associated with dart leaders. Plain Language Summary: During the 2022 monsoon season in New Mexico, Langmuir Lab scientists used special X‐ray detectors to study natural lightning over a mountain‐top facility. The team detected X‐ray emissions from 4 natural lightning flashes. The X‐rays are produced by the lightning precursor stage, called leader. Leaders travel long distances in the atmosphere and carve the way for lightning to transfer charge from the cloud to ground. After careful inspection of the energy content of the X‐ray photons, the team concluded that leaders traveling in virgin air, known as stepped leaders, emit more energetic X‐rays than leaders retracing previously established lightning channels, called dart leaders. Key Points: 5‐ns resolution allowed for the measurement of individual X‐ray photon energies from natural lightning and to confirm its power‐law spectrumStepped leader X‐rays come in a train of bursts lasting milliseconds, while dart leader X‐rays come effectively in a single burstStepped leaders have a harder energy spectrum than dart leaders, with a larger population of >1 MeV photons [ABSTRACT FROM AUTHOR]

The ability of numerical weather prediction models to accurately predict extreme weather events, such as thunderstorms marked by heavy rainfall and lightning activities, has consistently been of great importance for human life. The objective of this study is to assess the long‐term reliability of the European Centre for Medium‐Range Weather Forecasts Reanalysis version 5 (ERA5) rainfall in comparison to the Indian gauge‐adjusted Global Satellite Mapping of Precipitation (GSMaP_ISRO) rainfall at the time of lightning flashes measured by the Lightning Imaging Sensor (LIS) onboard the Tropical Rainfall Measuring Mission satellite over the Indian region during the years 2001–2014. This analysis will provide valuable insights into the intricate relationship between lightning flashes and precipitation under various terrain conditions (low, mid, or high), across oceanic regions (Bay of Bengal, Arabian Sea), and during different monsoon phases (normal, active, or deficit). According to a prolonged examination of LIS data, April–June accounts for ~50% of the total flashes, with the largest number of flashes occurring over the Himalayan and the northeastern part of India. According to hourly GSMaP_ISRO rainfall, the most substantial lightning‐associated rainfall happens an hour prior to lightning flash (T − 1) and within three hours after (T + 3), indicating a robust correlation between heavy rainfall and lightning activity during this time frame. The rainfall in the ERA5 reanalysis misses the intensity as well as duration of the peak rainfall at the time of lightning flashes. Furthermore, the ERA5 reanalysis rainfall depicts under (over)‐estimation of rainfall in plain (orographic) regions. The underestimation of ERA5 rainfall is very pronounced over the Indian Ocean and Bay of Bengal regions, mainly between flash time (T) to two hours after the flash time (T + 2). The results indicate that there is a requirement for additional enhancements in the ERA5 reanalysis rainfall for lightning occurrences. [ABSTRACT FROM AUTHOR]

The cloud electrification process has great significance in understanding the microphysical properties, electrical characteristics, and evolution of thunderstorms. This study employs an X‐band dual‐polarized multiparameter phased array weather radar (MP‐PAWR) to observe the electrical alignment signatures of ice particles before the first intracloud (IC) lightning flash, and to explore the evolution of the upper charge region in the early electrification stage of an isolated thunderstorm. Negative KDP signatures associated with vertically oriented ice particles by strong electric fields in the upper parts of the thunderstorm are analyzed by introducing composite KDP, which is defined as a minimum KDP value observed in a vertical column across all elevation scans at each specific horizontal grid point at and above a designated layer. About 7 min before the first IC lightning flash, the mean canting angle of ice particles in the upper parts of the cloud changed from horizontal to vertical by strong electric fields, and the concentration of vertically aligned ice particles on the top of the cloud reached the maximum 30 s before the first IC lightning flash. These signatures exhibit an early electrification process in the upper parts of the thunderstorm. These results indicate that with the high spatial and temporal resolution, MP‐PAWRs have the ability not only to detect the rapid evolution of microphysical structures but also to observe the early electrification of thunderstorms, which will facilitate forecasting IC lightning flash initiation combined with graupel presence signatures in the mixed‐phase region in normal operation. Plain Language Summary: The electrical alignment signatures of ice particles in the upper parts of the thunderstorms refer to the changes in the orientation of ice particles due to the variation of in‐cloud electric fields, which offer useful information in understanding the cloud electrification process. Based on the lightning data and observations from an X‐band dual‐polarized multiparameter phased array weather radar (MP‐PAWR) with high temporal and spatial resolution, the signatures related to the electrically aligned ice particles before the first intracloud (IC) lightning flash are analyzed, and the results show that the electrical alignment signatures of ice crystals could be a good indicator of initial electrification related to the upper charge region. These findings hold potential significance in enhancing lightning forecasting capabilities. Key Points: The electrical alignment signatures strengthen before the first intracloud lightning flash and weaken following with itThe composite KDP is introduced to analyze the electrical alignment signatures of ice crystals in thunderstormsElectrical alignment signatures of ice crystals could be a good indicator of initial electrification [ABSTRACT FROM AUTHOR]

This article, published in Frontiers in Energy Research, discusses the calculation and analysis of lightning-induced voltage in 10-kV overhead distribution lines. The study uses the Agrawal coupling model and second-order finite difference-time domain (FDTD) method to determine the voltage and examines the influence of lightning position. The research suggests that surge arresters should be installed at a density of at least one group per 200-300 meters to effectively limit lightning-induced voltage. The document provides theoretical support for understanding lightning-induced voltage in overhead lines and the allocation of lightning protection resources. Additionally, the article includes a list of references and citations for further research on lightning-induced voltages on overhead power lines. [Extracted from the article]

Lightning is responsible for the most area annually burned by wildfires in the extratropical region of the Northern Hemisphere. Hence, predicting the occurrence of wildfires requires reliable forecasting of the chance of cloud-to-ground lightning strikes during storms. Here, we describe the development and verification of a probabilistic lightning-strike algorithm running on a uniform 20 km grid over the continental USA and Alaska. This is the first and only high-resolution lightning forecasting model for North America derived from 29-year-long data records. The algorithm consists of a large set of regional logistic equations parameterized on the long-term data records of observed lightning strikes and meteorological reanalysis fields from NOAA. Principal Component Analysis was employed to extract 13 principal components from a list of 611 potential predictors. Our analysis revealed that the occurrence of cloud-to-ground lightning strikes primarily depends on three factors: the temperature and geopotential heights across vertical pressure levels, the amount of low-level atmospheric moisture, and wind vectors. These physical variables isolate the conditions that are favorable for the development of thunderstorms and impact the vertical separation of electric charges in the lower troposphere during storms, which causes the voltage potential between the ground and the cloud deck to increase to a level that triggers electrical discharges. The results from a forecast verification using independent data showed excellent model performance, thus making this algorithm suitable for incorporation into models designed to forecast the chance of wildfire ignitions. [ABSTRACT FROM AUTHOR]

Measurement of lightning current plays a critical role in the field of atmospheric electricity. Traditionally, Rogowski coils or low-resistance shunts were employed for measuring lightning currents in the range from several amperes up to several hundreds of kilo-amperes, and high-value resistors were utilized for measuring corona discharge currents at sub-ampere levels. However, these approaches were not suitable for continuously recording the vast range of lightning currents. For this sake, we have developed a lightning current measurement system equipped with a shock-tolerant low-noise amplifier module. With the system installed on a tall tower, sub-ampere level currents just before the lightning initiation were observed for the first time. To confirm the authenticity of the recorded currents, the background noise of the measurement system and surrounding environment were identified, and a digital multi-frequency notch filter was proposed for de-noising. Results show that the system can achieve a current identification level of 50 mA even in complex electromagnetic environments, while having a measurement capability of 220 kA. [ABSTRACT FROM AUTHOR]

To achieve automatic recognition of lightning images, which cannot easily be handled using the existing methods and still requires significant human resources, we propose a lightning image dataset and a preprocessing method. The lightning image data over five months were collected using a camera based on two optical observation stations, and then a series of batch labeling methods were applied, which greatly reduced the workload of subsequent manual labeling, and a dataset containing more than 30,000 labeled samples was established. Considering that lightning varies rapidly over time, we propose a time sequence composite (TSC) preprocessing method that inputs lightning's time-varying characteristics into a model for better recognition of lightning images. The TSC method was evaluated through an experiment on four backbones, and it was found that this preprocessing method enhances the classification performance by 40%. The final trained model could successfully distinguish between the "lightning" and "non-lightning" samples, and a recall rate of 86.5% and a false detection rate of 0.2% were achieved. [ABSTRACT FROM AUTHOR]

Lightning flash rate data measured by the Tropical Rainfall Measuring Mission (TRMM) for the period 1996–2013 over India are analysed to study the spatial and temporal variation of lightning over India during different seasons. The convective available potential energy (CAPE) and other thermodynamic parameters data for the same period are taken for analysis. This study confirms a systematic increase in lightning flash rate density in India during the last two decades. The annual lightning flash rate density is high along the windward side of the Himalayan foothills with two peaks, one over northwestern parts of India (>50 flashes·km−2·year−1) and the other over northeastern parts of India (>40 flashes·km−2·year−1). The pre‐monsoon (March–May) (0.176 flasheskm−2·year−1) and monsoon (June–September) (0.159 flashes·km−2·year−1) lightning trends are the largest contributors in explaining the annual trend of 0.099 flashes·km−2·year−1. All seasons have shown more or less positive trends while post‐monsoon (October–December) has shown a negative trend (−0.013 flashes·km−2·year−1). The seasonal variations show that the lightning is increasing more over northwest India during the monsoon and northeast India during the pre‐monsoon. To further understand the connection between lightning and climate change, a few thermodynamic or microphysical properties are also analysed. This analysis suggests that the high CAPE values together with thermodynamics and cloud microphysical processes are necessary for organized convection and lightning over this region. Additionally, correlation analysis is adopted to identify the main influencing factors and regions contributing to lightning variability. The increase in lightning activity is found to be due to an increase in CAPE, low‐level moisture content and temperature. The increase in temperature and moisture is attributed to the land use land cover (LULC) changes in India. The impact of the above proxies on lightning varies from region to region and season to season. As several regions are undergoing rapid transformation due to human activity, this study provides insights into the need to understand land use related changes to local and regional lightning activity. [ABSTRACT FROM AUTHOR]

Electrical injuries can be devastating, and data is lacking in low-resource settings. We aimed to identify predictors of mortality following electrical and lightning injuries (ELI) in Malawi. We performed a retrospective observational study of patients presenting with ELI and burn injuries at a tertiary hospital in Malawi from 2011 to 2020. Outcomes were compared and predictors of mortality were modeled. A total of 382 ELI and 6371 burn patients were included. The mean ages for ELI and burn groups were 24 ± 14 and 11 ± 14 years, respectively (p < 0.01). Most patients were injured at home (91% in the burn group versus 51% in the ELI group, p < 0.01). The crude mortality rate in the ELI group was 28%, compared to 12% in the burn group (p < 0.01). On multivariate logistic regression, predictors of mortality included ELI (odds ratio [OR] 13.3, 95% confidence interval [CI] 7.2–24.5) and total body surface area burned (OR 1.1, 95% CI 1.1–1.1). Predicted mortality for ELI has increased over time (p = 0.05). ELI confers more than 13 times higher odds of mortality than burn injuries in Malawi, with mortality risk increasing over time. More efforts are needed to prevent electrical hazards and implement timely interventions for patients with ELI. • Electrical and lightning injuries (ELI) comprise 5% of burn-related presentations. • Mortality rate resulting from ELI is 28% and has been increasing in the last decade. • ELI has more than 13 times the odds of mortality than other burn injury mechanisms. [ABSTRACT FROM AUTHOR]

Thunderstorms endanger life and infrastructure. The accurate and precise prediction of thunderstorms is therefore helpful to enable protection measures and to reduce the risks. This manuscript presents the latest developments to improve thunderstorm forecasting in the first few hours. This includes the description and discussion of a new Julia-based method (JuliaTSnow) for the temporal extrapolation of thunderstorms and the blending of this method with the numerical weather prediction model (NWP) ICON. The combination of ICON and JuliaTSnow attempts to overcome the limitations associated with the pure extrapolation of observations with atmospheric motion vectors (AMVs) and thus increase the prediction horizon. For the blending, the operational ICON-D2 is used, but also the experimental ICON-RUC, which is implemented with a faster data assimilation update cycle. The blended products are evaluated against lightning data. The critical success index (CSI) for the blended RUC product is higher for all forecast time steps. This is mainly due to the higher resolution of the AMVs (prediction hours 0–2) and the rapid update cycle of ICON-RUC (prediction hours 2–6). The results demonstrate the potential of the rapid update cycle to improve the short-term forecasts of thunderstorms. Moreover, the transition between AMV-driven nowcasting to NWP is much smoother in the blended RUC product, which points to the advantages of fast data assimilation for seamless predictions. The CSI is well above the critical value of 0.5 for the 0–2 h forecasts. Values below 0.5 mean that the number of hits (correct informations) is lower than the number of failures, which results from the missed cells plus false alarms. The product is then no longer useful in forecasting thunderstorms with a spatial accuracy of 0.3 degrees. Unfortunately, with RUC, the CSI also drops below 0.5 when the last forecast is more than 3 h away from the last data assimilation, indicating the lack of model physics to accurately predict thunderstorms. This lack is simply a result of chaos theory. Within this context, the role of NWP in comparison with artificial intelligence (AI) is discussed, and it is concluded that AI could replace physical short-term forecasts in the near future. [ABSTRACT FROM AUTHOR]

The present study aimed to develop an accurate lightning risk classification and warning model for target points by using 1404 sets of data from four types of historical thunderstorm processes in Guangdong. Four machine learning algorithms were employed, and seven forecast factors, such as the physical characteristics of lightning occurrence around the target point, the breeding environment of lightning hazard, and the characteristics of the disaster-bearing body, were adopted to conduct multi-index evaluation and analysis of each risk early warning model. The results showed that the random forest algorithm exhibited the highest early warning accuracy in both the no-level model (95%) and the four-level model (73%). In contrast, the traditional convolutional neural network model proved to be ineffective for this purpose. Canton Tower was selected as the target point for model feasibility verification, and a lightning safety risk warning grading model tailored to the characteristics of thunderstorms in Guangdong was obtained. Finally, based on the identified deficiencies in the research process, ideas and methods for future optimization were proposed. [ABSTRACT FROM AUTHOR]

A comparative analysis of the attachment efficacy of sharpened vs blunted air terminals under a strong background DC electric field, similar to conditions found in naturally occurring lightning events, is presented. Testing was conducted using an oil-free, 17-stage, 1.4 MV bipolar Marx generator with a biased discharge plane that emulated the conditions found prior to the lightning return stroke. The biased discharge plane allowed the introduction of a strong DC electric field and subsequent corona formation on a time scale much longer than the brief duration over which the downward leader propagates. Initial observations indicate that despite a higher background electric field at the sharpened terminals, leading to pre-discharge corona formation where none is seen on the blunt terminal, both the sharpened and blunted terminals exhibit similar attachment probabilities during discharge events, with some discharge events attaching to both terminals. [ABSTRACT FROM AUTHOR]

Existing underground lightning electromagnetic field predictive methods are only relevant to conductivity distributions that are homogeneous or layered. In order to expand the scope of application of lightning electromagnetic field computation, the effect of heterogeneous soil conductivity on the electromagnetic field of lightning return is examined in depth. The current distribution in the lightning return channel is characterized by the dual Heidler discharge channel base current and MTLE return model. Using the full-wave finite element approach, a two-dimensional axisymmetric model is created. The time distribution characteristics of the lightning electromagnetic field in a soil with heterogeneous conductivity are evaluated. According to the research, the lightning electromagnetic field's, horizontal electric field, vertical electric field, and azimuthal magnetic field components are negatively, bipolarly, and positively distributed in the subsurface, respectively. The horizontal electric field dominates the subterranean electromagnetic field. The high conductivity of the soil has a significant attenuation effect on the high-frequency components of the lightning electromagnetic field's three electromagnetic components. The initial response of the horizontal electric field of a nonhomogeneous soil is dependent on the conductivity at the surface of soil, followed by a gradual dependence on the conductivity in deeper soil sections. The subsurface distribution of vertical electric and azimuthal magnetic fields tend to stratify in response to a nonhomogeneous drop in soil conductivity. [ABSTRACT FROM AUTHOR]

The present paper deals with new modeling to reproduce the electric discharge in the rod-plane air gap system with rubber insulating barrier under AC and impulse voltage. This model considers the randomness character of discharge evolution which is governed by the electric field. The discharges shape obtained by this model are compared with ones given by experimental tests. The established model reproduces correctly the forms of discharges obtained by experimental tests under AC voltage. It is found that the behavior of the electrical discharge depends not only on the dimension (thickness and width) of the insulating barriers but on its positions in the air gap as well. It is to highlight that the mode of applied voltage is of key importance barrier. Experimental investigation shows that the developed arc can evolve on 1 to 4 channels. The generated discharges in AC voltage distinguish by the formation of a multiple-channel arc. Whereas, the discharge under lightning impulse voltage found to progress in a single channel whatever the barrier position and dimensions. The model confirms that electric field is the most important factor in the behavior of the rodinsulating barrier-plane system submitted to high voltage. [ABSTRACT FROM AUTHOR]

Visible Light Communication (VLC) is a ubiquitous communication method that enables Lighting-Emitting Diodes (LEDs) to be used as illumination and for data transfer in wireless connections. Previous researchers have focused to infrared channel modelling. This research explores the use of VLC indoors and demonstrates its advantages over Radio Frequency (RF) communications, especially in restricted areas like laboratories, hospitals, aircraft, and houses. Since RF can be hazardous to human health, VLC offers a safer alternative with a higher data rate for multimedia applications. This work, uses an uncovered room as a case study for indoor VLC broadband communication. Eight symmetrically positioned Light-Emitting Diodes (LEDs) on the ceiling as transmitters and a photodiode on the floor acts as a receiver to assess the level of lighting, optical power, and Signal-to-Noise Ratio (SNR) distribution. The computation was performed using the MATLAB software. Results showed that when the LED's half-power semi-angle (φ1/2) ranges from 25° to 65°, the average lighting ranges from 600 (lx) to 800 (lx), respectively. However, a signal power of 23 dBm and an SNR of 60 dB at (φ1/2) = 65° are sufficient for communication and illumination, while average power of 10 dBm and SNR of 20 dB at (φ1/2) = 15° are insufficient for the transmission of data in the room. [ABSTRACT FROM AUTHOR]

This article discusses the results of physical simulation of the influence of electromagnetic radiation from lightning discharges and thunderclouds on completely dielectric and armored fiber-optic cables. Lightning discharges were simulated using an experimental facility that allows the creation of artificial electrically active clouds. It has been shown that discharges from an artificial thundercloud near a fiber-optic cable cause rapid changes in the angle of rotation of the plane of polarization of radiation transmitted along the cable. This effect is observed for both armored and completely dielectric fiber-optic cables of moderate length. Completely dielectric cables of longer lengths are less sensitive to rapid changes in the electromagnetic field, but are sensitive to slow changes in the electric field. [ABSTRACT FROM AUTHOR]

Forest fires ignited by lightning accounted for 68.28% of all forest fires in the Greater Khingan Mountains (GKM) region of northeast China. Forecasting the incidence of lightning-triggered forest fires in the region is imperative for mitigating deforestation, preserving biodiversity, and safeguarding distinctive natural habitats and resources. Lightning monitoring data and vegetation moisture content have emerged as pivotal factors among the various influences on lightning-induced fires. This study employed innovative satellite remote sensing technology to swiftly acquire vegetation moisture content data across extensive forested regions. Firstly, the most suitable method to identify the lightning strikes that resulted in fires and two crucial lightning parameters correlated with fire occurrence are confirmed. Secondly, a logistic regression method is proposed for predicting the likelihood of fires triggered by lightning strikes. Finally, the method underwent verification using five years of fire data from the GKM area, resulting in an AUC value of 0.849 and identifying the primary factors contributing to lightning-induced fires in the region. [ABSTRACT FROM AUTHOR]

Lightning discharge from thunderstorms is a major weather hazard that leads to substantial loss of lives and properties in Bangladesh, particularly in the pre-monsoon season (March–May) due to frequent lightning activity. In this study, numerical simulations in predicting the lightning flashes using diagnostic and explicit lightning parameterization options in WRF (Weather Research and Forecasting) model are performed for three selected pre-monsoon lightning events (01 April 2019, 26 May 2020 and 20 May 2021) over Bangladesh. Additionally, this study investigates the WRF model sensitivity to five microphysics and three planetary boundary layer schemes. The combination of Morrison and YSU (Yonsei University scheme) is found to be the best configuration by comparing the RMSE (root mean square error) of hourly area averaged rainfall. The lightning flash counts are estimated by using four diagnostic methods based on (1) maximum updraft intensity ( w max ), (2) 20 dBZ cloud top, (3) level of neutral buoyancy, (4) Lightning Potential Index (LPI) conditioned to cloud hydrometeors and updraft, and (5) an explicit physics-based method from cloud electrification referred to as WRF-Elec. The WWLLN (World Wide Lightning Location Network) and NASA LIS (Lightning Imaging Sensor) observations are used to compare the simulated lightning flashes for the selected events. The study also analyzes 24-h (hour) accumulated rainfall that shows a good consistency with the observations from NASA GPM datasets. An assessment based on Fraction Skill Score (FSS) and performance diagrams is carried out to achieve deeper insights into the performance of model simulation in predicting rainfall. In a qualitative assessment framework, the spatial patterns of lightning flashes derived from WRF-Elec simulations, used for predicting the primary regions of lightning events, exhibit good agreement with observations. [ABSTRACT FROM AUTHOR]

Introduction: The reliability of power equipment is the foundation for maintaining the reliability of the power grid. As a core device for limiting overvoltage in the power grid, lightning arresters have received widespread attention, and ensuring their reliability is crucial. Methods: To improve the reliability of zinc oxide surge arresters in the power system, the fault characteristics and health assessment methods of zinc oxide surge arresters were studied using reliability centered condition-based maintenance(RCCM). Firstly, the fault characteristic of zinc oxide lightning arresters in operation over years were collected and analyzed from different aspects. Then the effective state quantities corresponding to different types of defects and their detection methods were proposed. The health status evaluation model for zinc oxide lightning arrester was established, and the effectiveness of the evaluation model was verified through fault cases. Results and Discussion: It shows that the proposed state quantities and RCCM method are suitable for the actual operation and maintenance of zinc oxide lightning arresters. It can reduce the workload and improve the efficiency of existing operation and maintenance of lightning arresters. [ABSTRACT FROM AUTHOR]

Electric power distribution networks are exposed to both internal and external disturbances. Lightning strikes are among the latter and are responsible for a significant percentage of damage in distribution transformers, especially in rural areas. Electric utilities must pay special attention to prevent damage and service interruption due to these unforeseeable events. In this context, Surge Protection Devices (SPDs) combined with a series of external air gaps are designed to safeguard electric equipment and systems from transient over-voltages. There are several well-known models of SPDs in the specialized literature; nonetheless, few studies have been carried out with external gaps and multi-gaps. The main contribution of this paper is a methodology to model the disruptive effect in an external air gap by determining the parameters of Kind's and Chowdhuri's models using the integration method. The adjustment of the model parameters is carried out by a genetic algorithm (GA). The proposed model was tested and validated using experimental measurements, and its capability to predict the time-to-breakdown under different impulse voltages was verified. [ABSTRACT FROM AUTHOR]

The study of lightning radiation spectra is of great importance for the scientific study of lightning physics and lightning protection systems of the electromagnetic threat of lightning. The frequency spectra characteristics of very high frequency (VHF) electric field radiation with the corresponding low frequency (LF) electric field changes during various events of the physical process of the seven positive ground flash events have been analyzed using the short-time Fourier transform (STFT) method. It was found that the frequency range of initial breakdown (IB), leader (L), and continuing current (CC) was 24-52 MHz, 30-50 MHz, and 30- 50 MHz, respectively, with the arithmetic mean (AM) initial breakdown (IB), leader (L), and continuing current (CC) of 39 MHz, 39 MHz, and 38 MHz, respectively. The differences in the frequency spectral pattern range of 24-52 MHz between different positive ground flash events may indicate that these events have different discharge mechanisms and that frequency domain information is required to identify these various discharge events. We also found that time delay between wideband and narrowband return stroke (RS) radiation is about 2-17 µs. [ABSTRACT FROM AUTHOR]

Indonesia is frequently plagued by intense lightning activity, leading to a multitude of incidents causing harm and devastation. As a proactive measure to mitigate future damages, an extensive research endeavor focusing on lightning peak currents was under taken in the maritime tropical continent region, particularly in Cilacap. This research aimed to curtail potential risks and enhance safety measures in the region. The impetus for this investigation stemmed from a series of incidents involving tank explosions in Cilacap, located in Central Java, Indonesia. These occurrences served as pivotal triggers, prompting a comprehensive analysis of lightning peak current statistics. According to the data collected, there exists a 85% probability of a lightning event in Cilacap producing a peak current of 18 kA. The implications of this research extend beyond the local scope, as the statistical insights gleaned from this study can serve as a foundational basis for the development of both national and international lightning protection standards. By integrating local statistics into the broader framework, a more comprehensive and effective approach to lightning protection can be devised, fostering greater resilience and safety measures not only in Cilacap but also in regions facing similar challenges globally. [ABSTRACT FROM AUTHOR]

Low Reynolds number fluid flows are governed by the Stokes equations. In two dimensions, Stokes flows can be described by two analytic functions, known as Goursat functions. Brubeck and Trefethen [SIAM J. Sci. Comput., 44 (2022), pp. A1205-A1226] recently introduced a lightning Stokes solver that uses rational functions to approximate the Goursat functions in polyg- onal domains. In this paper, we present the LARS algorithm (lightning-AAA rational Stokes) for computing two-dimensional (2D) Stokes flows in domains with smooth boundaries and multiply con- nected domains using lightning and AAA rational approximation [Y. Nakatsukasa, O. Sète, and L. N. Trefethen, SIAM J. Sci. Comput., 40 (2018), pp. A1494-A1522]. After validating our solver against known analytical solutions, we solve a variety of 2D Stokes flow problems with physical and engineering applications. Using these examples, we show rational approximation can now be used to compute 2D Stokes flows in general domains. The computations take less than a second and give solutions with at least 6-digit accuracy. [ABSTRACT FROM AUTHOR]

This article describes a concept whereby future operational polarimetric phased array radars (PPAR) routinely monitor ice crystal alignment regions caused by thundercloud electric fields with volume scan updates (∼12 min−1) sufficient to resolve the temporal variation due to lightning and subsequent rapid electric field regeneration in nonsevere thunderstorms. Routine observations of crystal alignment regions may enhance thunderstorm nowcasting through comparison of their temporal and spatial structure with other polarimetric signatures, integration with lightning detection data, and assimilation into convection resolving numerical weather prediction models. If crystal alignment observations indicate strong electrification well in advance of the first lightning strike and likewise reliably indicate the decay of strong electric fields at the end of a storm, this capability may improve warning for lightning-sensitive activities such as airport ramp operations and space launch. Experimental observations of crystal alignment volumes in central Oklahoma severe storms and their relation to those storms' structures are presented and used to motivate discussion of possible PPAR architectures. In one case—a tornadic supercell—these observations illustrate an important limitation. Even the hypothesized 12 min−1 volume scan update rate would not resolve the temporal variation of the crystal alignment regions in such storms, suggesting that special, adaptive scanning methods may be appropriate for such storms. We describe how future operational phased array radars could support a crystal alignment measurement mode via parallel, time-multiplexed processing and discuss potential impacts on the radar's primary weather observation mission. We conclude by discussing research needed to better understand technical challenges and operational benefits. [ABSTRACT FROM AUTHOR]

Knowledge about regions where lightning occurs is important both for understanding storm development and direction. This can assist in very short-term weather forecasts and in developing lightning warning systems, aiming to minimize exposure of people and equipment in the open sky. A survey on the occurrence of lightning in different types of land use and coverage and different elevation strata in the region of the Itacaiúnas River watershed (IRW), located in the Carajás Mineral Province, in the Eastern Amazon, from 2012 to 2021 was conducted. The results showed significant differences in the occurrence of lightning in mining areas and deforested areas. When comparing the large proportion of deforested areas with the mining area, the results suggested that in IRW mining areas, the lightning incidence is expressively higher. The assessment of electrical activity at different elevations in the region suggested that the slope of the terrain and its thermodynamic effects on the formation of storms have more influence than altitude on lightning activity. The results showed the importance of adopting initiatives aimed at protecting both the local population and mining workers, as well as equipment exposed to the open sky in this region. [ABSTRACT FROM AUTHOR]

In the context of global climate change, lightning disasters have emerged as a serious environmental factor that restricts the sustainable development of megacities. This paper provides a review of the research on the impact of urbanization on thunderstorm processes and lightning activity, exploring various aspects, such as aerosols, urban thermal effects, urban dynamic effects, and building morphology. Despite numerous significant achievements in the study of the impact of air pollutants on lightning activity, there is no consensus on whether aerosols serve to enhance or inhibit lightning activity. The temperature difference between the urban underlying surface and the natural underlying surface could sustain and promote the occurrence and development of convective systems, thus enhancing lightning activity. In terms of urban dynamics, the barrier effect has led to the maximum center of lightning appearing at the edge of a built-up area, which might be associated with factors, such as urban heat island (UHI) intensity, wind speed, synoptic background, and city size. Additionally, the size of a city and the height of the buildings was also an influencing factor on lightning activity. In summary, scholars have made progress in understanding the characteristics and drivers of urban lightning activity in recent years, but there are still some urgent problems that need to be solved: (1) How to analyze, comprehensively, the spatiotemporal patterns of urban lightning activity under different thunderstorm intensity backgrounds? (2) How to conduct analysis to investigate the influence of alterations in the boundary layer structure, water–heat energy balance, and water vapor circulation processes on urban lightning activity in the context of urbanization? (3) How to couple numerical models of different scales to enhance the understanding of the impact of complex underlying surfaces on urban lightning activity? Future studies could investigate the relationship between urbanization and thunderstorm/lightning activity using a combination of observational data, numerical modeling, and laboratory experiments, which holds promise for providing valuable theoretical insights and technical support to enhance the prediction, nowcasting, early warning, and risk assessment of thunderstorms and lightning in urban areas. [ABSTRACT FROM AUTHOR]

In recent years, there has been a notable surge in lightning events within the Arctic region. This is possibly due to the ongoing trend of global warming that is particularly pronounced in the Arctic. This study focuses on instances of rare lightning activity in the proximity to the North Pole in the last decade. We hypothesize that these occurrences are linked to augmented land heating in Eurasia rather than solely due to the increasing temperatures in the Arctic region. This assertion is substantiated by model simulations using the Weather Research and Forecasting model. [ABSTRACT FROM AUTHOR]

Data from four lightning networks collected during three quasi-linear convective systems (QLCS) are used to understand the differences in detection for optimizing their combined use. Additionally, using unique aspects from each network provides a more complete picture of lightning in a thunderstorm. The four lightning networks examined include a Lightning Mapping Array (LMA), the Earth Networks Total Lightning Network (ENTLN), the Geostationary Lightning Mapper (GLM), and the National Lightning Detection Network (NLDN). The data from each network are inter-matched and locations where each network uniquely detected a flash versus all are analyzed in reference to three QLCSs, including two QLCSs that occurred in the Southeast (22 March 2022 and 30 March 2022) during the Propagation, Evolution, and Rotation in Linear Systems (PERiLS) field campaign, and one case from Oklahoma (26 February 2023). Unique aspects of the lightning provided by each network are examined, including flash initiation altitude, size, type, and energy. Lightning flash trends and characteristics for each QLCS are similar between networks in general, but deviate in certain conditions and locations. Times of decreased matching between networks were associated with localized increases in lightning rates, smaller flash sizes, and lower-energy flashes. The differences in each network's performance across the QLCSs demonstrates the importance of understanding the limitations in each and the advantage of using multiple networks. [ABSTRACT FROM AUTHOR]

Based on the lightning observation data from the Fengyun-4A (FY-4A) Lightning Mapping Imager (FY-4A/LMI) and the Lightning Imaging Sensor (LIS) on the International Space Station (ISS), we extract the "event" type data as the lightning detection results. These observations are then compared with the cloud-to-ground (CG) lightning observation data from the China Meteorological Administration. This study focuses on the characteristics of lightning activity in Southeast China, primarily in Jiangxi Province and its adjacent areas, from April to September, 2017-2022. In addition, with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis data, we further delved into the potential factors influencing the distribution and variations in lightning activity and their primary related factors. Our findings indicate that the lightning frequency and density of the FY-4A/LMI, ISS-LIS and CG data are higher in southern and central Jiangxi, central Fujian Province, and western and central Guangdong Province, while they tend to be lower in eastern Hunan Province. In general, the high-value areas of lightning density for the FY-4A/LMI are located in inland mountainous areas. The lower the latitude is, the higher the CG lightning density is. High-value areas of the CG lightning density are more likely to be located in eastern Fujian and southeastern Zhejiang Province. However, the high-value areas of lightning density for the ISS-LIS are more dispersed, with a scattered distribution in inland mountainous areas and along the coast of eastern Fujian. Thus, the mountainous terrain is closely related to the high-value areas of the lightning density. The locations of the high-value areas of the lightning density for the FY-4A/LMI correspond well with those for the CG observations, and the seasonal variations are also consistent. In contrast, the distribution of the high-value areas of the lightning density for the ISS-LIS is more dispersed. The positions of the peak frequency of the FY-4A/LMI lightning and CG lightning contrast with local altitudes, primarily located at lower altitudes or near mountainsides. K-index and convective available potential energy (CAPE) can better reflect the local boundary layer conditions, where the lightning density is higher and lightning seasonal variations are apparent. There are strong correlations in the annual variations between the dew-point temperature (Td) and CG lightning frequency, and the monthly variations of the dew-point temperature and CAPE are also strongly correlated with monthly variations of CG lightning, while they are weakly correlated with the lightning frequency for the FY-4A/LMI and ISS-LIS. This result reflects that the CAPE shows a remarkable effect on the CG lightning frequency during seasonal transitions. [ABSTRACT FROM AUTHOR]

Lightning is one of the most spectacular and dangerous atmospheric phenomena that can cause serious risks to human life and property. The microphysical and radiative effects of atmospheric aerosols help to form and suppress convective clouds, respectively, which cause lightning activities. The present study has been undertaken to analyse the climatology and trends of lightning flash rate density (FRD) and aerosol optical depth (AOD) and assess the association of FRD with AOD and other meteorological parameters over eastern India, one of the lightning-prone zones in India. For this purpose, gridded FRD data (0.5°×0.5°) developed by WGLC and MODIS-Terra AOD data (1°×1°) have been used over the study area during 2010–2020. Major lightning activities have been observed during the pre-monsoon and monsoon seasons. The eastern part of the region, including parts of West Bengal, Bihar, Jharkhand, and Himalayan foothills has been found to be the annual lightning hotspot. Overall, an increasing trend of annual lightning has been noticed over the study area. Annual AOD over Gangetic Plain has been found to be much higher than in other regions. Seasonal variation of AOD, i.e., an increase of AOD from pre-monsoon to monsoon and declination afterwards, has been observed over Chhota Nagpur plateau. Increasing AOD trends have been found during pre-monsoon, monsoon as well as annually over the majority of the study area. Correlation analysis has indicated that convective available potential energy (CAPE) has played a major role in lightning activities over this region. In general, AOD has been found to affect lightning through microphysical effects. However, contrasting relation has been noticed over the Gangetic plains during winter because of the absence of lightning due to low convective activities and the presence of high AOD due to shallow boundary layer, anthropogenic activities, and prevailing wind patterns. [ABSTRACT FROM AUTHOR]

Lightning‐generated nitrogen oxides (LNOx) have an impact on the concentration of ground‐level ozone which acts as a toxic air pollutant, thereby negatively influencing human health and the environment. To understand the impact of LNOx on ground‐level ozone, we simulated four thunderstorm events in Tehran using the WRF‐Chem model. As observations of LNOx are not available, we evaluated the temporal distribution of the simulated ground‐level ozone concentration against an air quality monitoring station. We also compared the simulation results against the spatial distribution of the total column ozone from the Ozone Monitoring Instrument. WRF‐Chem performs well in the simulation of ground‐level ozone concentration, with the best performance for an event with the highest lightning activity (correlation coefficient of 0.91). The analysis of the spatial distribution of the observed and simulated total column ozone also indicates the good performance of WRF‐Chem. Hourly variation in the simulated LNOx during lightning activity is compared against both hourly variation in the observed ground‐level ozone and the number of lightning for four thunderstorm events. There is an agreement between the simulated LNOx and the observed ground‐level ozone during lightning for two events, with correlation coefficients of 0.55 and 0.57. LNOx emissions enhance ozone production in the middle to upper troposphere, which can subsequently contribute to an increase in ground‐level ozone by transport, vertical mixing, and chemistry. In addition, the initiation of chemical processes in response to cloud‐to‐ground lightning strikes may contribute to an increase in both LNOx and the concentration of ground‐level ozone. Plain Language Summary: Lightning‐generated nitrogen oxides (LNOx) contribute to higher ground‐level ozone, which acts as a harmful air pollutant for humans and the environment. We applied the WRF‐Chem model to simulate four thunderstorm events in Tehran, aiming to understand the impact of LNOx on ground‐level ozone concentration. Overall, WRF‐Chem performs well in the simulation of ground‐level ozone, particularly for an event with the highest lightning activity. The comparison of the spatial distribution of the observed and simulated total column ozone also indicates the good performance of WRF‐Chem. By comparing the simulated LNOx against the observed ground‐level ozone, we found that WRF‐Chem performs well for two thunderstorm events. The produced ozone in the middle to upper troposphere due to LNOx emissions can be transported downward and increase ground‐level ozone. Cloud‐to‐ground lightning strikes also contribute to an increase in both LNOx and ground‐level ozone pollution, which can negatively influence human health and the environment. Key Points: The simulated ground‐level ozone concentration is consistent with the observationThe initiation of chemical processes in response to cloud‐to‐ground lightning contributes to an increase in both LNOx and surface ozoneLNOx influence tropospheric ozone production, which can contribute to an increase in ground‐level ozone [ABSTRACT FROM AUTHOR]

The research involves conducting high voltage tests to determine lightning attachment locations on an aircraft model and constructing a streamer discharge simulation model in a 20 cm combined gap. The investigation focuses on the air streamer discharge of a non-uniform electric field in the combined gap through experiments and numerical simulation. The results reveal that the discharge process in the electrode-aircraft model gap closely aligns with the final jump stage of natural lightning. Notably, the surface charge density on the aircraft model exhibits a negative correlation with the radius of curvature. Due to the enhanced electric field strength, the aircraft model tips with bigger curvatures have a greater likelihood of initiating streamer discharge. Once the streamer bridges the electrode-aircraft model gap, the accumulation of space charge results in the aircraft's surface charge reaching an order of magnitude higher than the initial induced charge. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polymer composites (CFRPC) are being used as primary structures in many applications. However, unlike metallic materials, they are susceptible to damage by lightning strikes. When lightning strikes, due to its poor electrical conductivity, the composite material generates localized resistive heating near the strike area. This resistive heat causes elevated temperatures near the strike area, which leads to material property changes and the structural material's stiffness and strength reduction. As part of this study, a finite element (FE)-based coupled electro-thermo-mechanical modeling approach was adopted to simulate the effect of lightning strikes on a unidirectional (UD) carbon fiber reinforced polymer composite model to predict the residual compressive strength of the material. In the current study, a two-dimensional (2D), micromechanical finite element model of CFRPC was used to quantify its residual compressive response when subjected to simulated lightning strikes with different peak currents using the software ABAQUS. The normalized residual compressive strengths for various peak currents obtained from the proposed electro-thermo-mechanical model were compared with the available experimental data from the literature. The effectiveness of an electrically conductive protective coating in minimizing the compressive strength reduction was also evaluated. Further, the optimum electrical conductivity of the coating in terms of the matrix conductivity, for maintaining the desired compressive strength was also estimated. Furthermore, the effect of change in thickness of the conductive coating in compressive strength change was evaluated by considering two different coating thicknesses. The results show that for a given peak current, the thinner coating will not compromise the compressive strength as long as the conductance of the thin and thick coating is the same. [ABSTRACT FROM AUTHOR]

A separable connector is used for the power cables and apparatuses in renewable energy systems. The shield of the collector cable is sometimes an open circuit at one end to reduce power loss due to the shield current. However, this has a disadvantage from the viewpoint of lightning protection. The semiconductive part of the separable connector is grounded for safety. The ground potential rise due to a direct lightning strike to a wind tower sometimes damages the collector cables and power apparatuses in the wind tower. Combustion in a cable is one of the most serious types of lightning‐caused damage. This paper describes an experimental study on fire ignition in a collector cable caused by a ground potential rise due to a direct lightning strike to a receptor. The mechanism leading to fire ignition is discussed based on the experimental results. This paper also proposes a countermeasure against such fire ignition. [ABSTRACT FROM AUTHOR]

• Most geophysical processes, including electric discharges, influence Schumann Resonance. • Statistical fitting process applied to five years of Schumann Resonance data. • Patterns on the classification of the Schumann Resonance compared with thunderstorm hotspots. • Links established between lightning activity and statistical classification. The Schumann resonance is an electromagnetic phenomenon, a product of lightning activity inside the earth-ionosphere cavity. Five years of Schumann resonance records are analyzed by a novel methodology that segments the records into time intervals and finds the probability distribution that best describes each segment. Then patterns are extracted from the resulting time series and compared against known patterns of global lightning activity to further test the power of the methodology under study. The Quality of Fit indices show how over 95% of the segments analyzed are properly described by the distribution that fit them best. The relationship between global lightning activity and the number of segments identified as Gaussian emerges clearly. A link between Laplacian segments and local lightning activity is explored as well. This presents transient statistical fitting as an alternative for characterizing complex phenomena by identifying different segments with a probability distribution, then identifying circumstances that segments with the same distributions have in common. This study further validates the chosen analysis tool, showing its capacity to offer information on the activity of thunderstorms in the time segments analyzed from the Schumann resonance data. It presents an additional source of information that complements the usual techniques used to study the signal in the frequency domain. [ABSTRACT FROM AUTHOR]