Intense Lightning Research Articles

Damaging thunderstorms in Finland in June 2021

AbstractThunderstorms are common in Finland, however, high‐impact damaging cases do not occur every summer. On 21–23 June 2021, three damaging thunderstorms, named Ahti, Paula and Aatu, occurred in Finland. We provide an overview of the thunderstorms and their environment and impacts. The thunderstorms led to heavy rain, hail, intense lightning and, most notably, extensive forest damage due to strong surface wind gusts.

Role of Lightning Activity in Deciphering Atmospheric Gravity Waves (AGWs) Induced D‐Region Ionospheric Perturbations During Extremely Severe Cyclonic Storm (ESCS) Fani

AbstractThe study presents detailed meteorological characteristics of extremely severe cyclonic storm (ESCS) Fani, and subsequent Atmospheric Gravity Waves (AGWs) induced D‐region ionospheric perturbations and the role of lightning activity in it. The cyclone shaped as a weak disturbance over the north Indian Ocean (2.7°N, 89.7°E) on 25 April 2019. The disturbance intensified and evolved into ESCS Fani over Bay of Bengal (BoB) on 30 April, had landfall on 03 May, and dissipated after 04 May 2019. What makes Fani unique is its long life span of ∼10 days, and only ESCS to occur after ∼30 years over the BoB. Fani attained a minimum cloud top temperature of about −80°C, and a corresponding maximum cloud top altitude of about ∼17 km. Such meteorological conditions presented a strong convection process in the towering cumulonimbus in inner and outer rain bands, resulting in intense lightning activity. The peak lightning flash rate observed was ∼375 min−1. SABER observations confirmed the coupling of atmosphere with ionosphere with strong AGWs in middle atmosphere during Fani. NWC (19.8 kHz) Very Low Frequency signal intersecting the track of Fani is used to decipher D‐region ionospheric perturbations induced by AGWs from Fani. The results show the presence of increased AGW activity in D‐region during the cyclone period when compared to that of the pre‐ and post‐cyclone periods. The periods of the observed gravity waves are between ∼13 and 20 min, highlighting the important role of lightning activity and AGWs in atmosphere‐ionosphere coupling.

Genesis of column sprites: formation mechanisms and optical structures

Sprite discharges are electrical discharges that initiate from the lower ionosphere during intense lightning storms, manifesting themselves optically as flashes of light that last a few milliseconds. This study unravels sprite initiation mechanisms and evolution into distinctive morphologies like glows and beads, using direct 3D numerical simulations that capture the intricate electrical discharge processes. We clarify various morphological aspects of sprites such as the halo dynamics, column glows, branching, streamer reconnection, and bead formation. The results advance our understanding of sprites and their connection to thunderstorm dynamics, and puts quantitative analysis of their effect on Earth’s climate within reach.

Influence of Aerosols on Lightning Activities in Java Island, Indonesia

Lightning is one of the natural disasters that cause significant financial losses and even fatalities. Therefore, it is necessary to understand the characteristics of lightning and related factors take appropriate preventive and mitigation measures. This work investigated the influence of aerosols and atmospheric thermodynamic factors on lightning in Java Island using 16 years of data (1998 - 2013) from the Tropical Rainfall Measuring Mission (TRMM) satellite. Aerosol data were obtained from the Modern Era Retrospective Analysis for Research and Applications version 2 (MERRA-2). Furthermore, convective available potential energy (CAPE) and potential temperature data were taken from the fifth-generation ECMWF atmospheric reanalysis (ERA-5) data. The intensity of lightning strikes in the western part of Java, such as Jakarta and Banten, is higher than in the eastern part, corresponding to the distribution pattern of aerosols, especially sulfate aerosols, sea salt aerosols, and black carbon aerosols. Sea salt aerosols have an inverse relationship with lightning, as these coarse-sized aerosols tend to inhibit convection. An increase in CAPE and potential temperature generally leads to higher lightning intensity. However, in cases where CAPE values are extremely high, such as in Jakarta, the intensity of lightning decreases. A similar pattern can be observed with potential temperature. An inverse relationship between lightning and potential temperature is observed in regions at higher elevations. The peak time for CAPE and potential temperature coincide with the peak intensity of lightning, which typically occurs during the rainy season, while the peak of AOD occurs earlier, during the pre-monsoon (September-October-November). The highest values of sea salt AOD are observed during the dry season (June-July-August) when lightning is minimal. These variations in peak times are particularly evident in the western regions of Java, where AOD values are high. The findings of this study can aid in lightning disaster mitigation efforts on Java Island. HIGHLIGHTS The intensity of lightning strikes in the western part of Java is higher than in the eastern part Sea salt aerosols have an inverse relationship with lightning, as these coarse-sized aerosols tend to inhibit convection An increase in CAPE and potential temperature generally leads to higher lightning intensity The peak time for CAPE and potential temperature coincide with the peak intensity of lightning The highest values of sea salt AOD are observed during the dry season when lightning is minimal GRAPHICAL ABSTRACT

Lightning and Gravity Wave Signatures Produced by the Hunga‐Tonga Volcanic Eruption on Global Geomagnetic Data

AbstractAcoustic gravity waves (AGWs) have a significant impact on the thermosphere‐ionosphere (T‐I) system by increasing ionisation variability, transporting energy, velocity, momentum, and creating additional horizontal gradients in the T‐I, all of which influence electromagnetic wave propagation and cause changes in the geomagnetic field. Ground magnetic disturbance measurements can thus map the global and local spatial distribution of T‐I current systems. The Hunga‐Tonga volcano eruption released a tremendous amount of mass and energy into the atmosphere on 15 January 2022, causing AGWs. Furthermore, the related lightning strikes disrupt the Global electric circuit. In this study, we look at (a) global geomagnetic disturbances caused by AGW constrained by VTEC amplitudes at two different sectors, (b) Schuman resonances (SR) parameters derived from modulations of ELF observations caused by the intense lightning phenomena that accompanied the volcanic eruption. Our analysis shows that (a) registration timing of geomagnetic disturbance at each observatory indicates the different modes of propagation between 180 and 350 m/s, indicating low‐frequency AGW components, (b) noticeable changes in SR frequency modes (7–21 Hz) occurred in the total power between 04:15 and 05:45 UT hr at Patiyasar, India, linked to heightened lightning activity, (c) velocities are found to be similar at similar distances in the northern and southern hemispheres from Hunga‐Tonga, (d) time difference between the SR and geomagnetic disturbance signature at observatories is found to have no relation with distance from the eruption, (e) fluctuations in VTEC at the Indian and Russian sectors show that the geomagnetic disturbances are linked to ionospheric perturbations.

Characteristics of the Blitzortung.org Lightning Location Catalog in Japan

We evaluated the detection efficiency and location accuracy of lightning discharges in Japan using Blitzortung.org, a volunteer-based network for locating lightning discharges from sferics measured by very low frequency (VLF) electromagnetic receivers that have been deployed worldwide in recent years. A comparison of the flash rate (the detected lightning rate per area and period) from Blitzortung.org with that from the satellite-based OTD/LIS and the ground-based World Wide Lightning Location Network (WWLLN) observations showed that Blitzortung.org clearly observed intense lightning activity in and around the Kanto area, including Tokyo, in summer, which is typical of Japanese lightning activity. However, it did not clearly observe lightning activity in and around the Nansei Islands, including Okinawa. Conversely, Blitzortung.org observed winter lightning activity in the Hokuriku area and off the Kanto. In addition, event studies have compared the detection efficiency and location accuracy of Blitzortung.org with those of the Japanese Lightning Location Network (JLDN) to infer their absolute values. The latest detection efficiency of Blitzortung.org in the Kanto area was estimated at roughly 90%. The mean location accuracy was estimated at up to 5.6 km.

Lightning Rings and Gravity Waves: Insights Into the Giant Eruption Plume From Tonga's Hunga Volcano on 15 January 2022

AbstractOn 15 January 2022, Hunga Volcano in Tonga produced the most violent eruption in the modern satellite era, sending a water‐rich plume at least 58 km high. Using a combination of satellite‐ and ground‐based sensors, we investigate the astonishing rate of volcanic lightning (>2,600 flashes min−1) and what it reveals about the dynamics of the submarine eruption. In map view, lightning locations form radially expanding rings. We show that the initial lightning ring is co‐located with an internal gravity wave traveling >80 m s−1 in the stratospheric umbrella cloud. Buoyant oscillations of the plume's overshooting top generated the gravity waves, which enhanced turbulent particle interactions and triggered high‐current electrical discharges at unusually high altitudes. Our analysis attributes the intense lightning activity to an exceptional mass eruption rate (>5 × 109 kg s−1), rapidly expanding umbrella cloud, and entrainment of abundant seawater vaporized from magma‐water interaction at the submarine vent.

Observations of Elves and Radio Wave Perturbations by Intense Lightning

AbstractElectromagnetic pulses (EMPs) and quasi‐static electric fields (QE) from powerful lightning heat and ionize the lower ionosphere. The EMP disturbance may appear as an elve at ∼80–95 km altitude, and the QE field as a halo or a sprite at ∼60–80 km altitude. Both are thought to perturb crossing radio signals because of changes to the electrical conductivity of the regions. Here we present an analysis of 63 elves and corresponding radio signal perturbations from an almost stationary thunderstorm system that allows us to untangle some of the dependencies of perturbations on the lightning characteristics. The amplitude perturbations of a VLF‐transmitter signal are characterized as either long‐recovery, early events (LOREs) or as early events. We find that LOREs are related to lightning with high peak currents and bright elves, and that their sign (amplitude increase or decrease) depends on the relative locations of the transmitter, disturbance and receiver. Based on a subset of strokes, lightning with elves has on average ∼3 times the impulse charge‐moment‐change and power in broadband as lightning of similar peak currents without elves. The early events occur without observed elves, sprites or halos. They recover in ∼10–100 s and are observed for both polarities of cloud‐to‐ground lightning and for intracloud flashes. It is proposed that these observations may relate to regions of reduced conductivity caused by an electron attachment/detachment process at lower heights, or by electron enhancements associated with TLEs that are too dim to be detected by the camera.

Электромагнитные УНЧ/КНЧ-колебания, вызванные извержением вулкана Тонга

The eruption of the Tonga volcano on January 13 and 15, 2022 and related intense lightning activity led to the excitation of a number of specific electromagnetic oscillations in different frequency ranges. We examine properties of these oscillations, using data from magnetometers of various types located in Kamchatka and in the Pacific region. We confirmed that there might have been a geomagnetic response to the formation of an acoustic resonance between the Earth surface and the ionosphere: localized harmonic oscillations with a frequency 3.5–4.0 mHz, which lasted for ~1.5 hr, were detected ~15 min after the beginning of the eruption at distance of ~800 km. An increase was observed in the intensity of the Schumann resonance at stations in the Far East. Broadband emission stimulated by intense volcanic lightning was detected to occur in the Pc1 range (2–5 Hz). The emission presumably results from the excitation of the magnetosonic waveguide in the upper ionosphere by lightning activity.

Электромагнитные УНЧ/КНЧ-колебания, вызванные извержением вулкана

The eruption of the Tonga volcano on January 13 and 15, 2022 and related intense lightning activity led to the excitation of a number of specific electromagnetic oscillations in different frequency ranges. We examine properties of these oscillations, using data from magnetometers of various types located in Kamchatka and in the Pacific region. We confirmed that there might have been a geomagnetic response to the formation of an acoustic resonance between the Earth surface and the ionosphere: localized harmonic oscillations with a frequency 3.5–4.0 mHz, which lasted for ~1.5 hr, were detected ~15 min after the beginning of the eruption at distance of ~800 km. An increase was observed in the intensity of the Schumann resonance at stations in the Far East. Broadband emission stimulated by intense volcanic lightning was detected to occur in the Pc1 range (2–5 Hz). The emission presumably results from the excitation of the magnetosonic waveguide in the upper ionosphere by lightning activity.

Risk Assessment of Buildings due to Lightning Impulses: A Case Study at College of Science and Technology

Lightning Impulse protection has become important aspect of any electrical installation due to its destructive impacts. Due to changing weather patterns the intensity of lightning has been increasing over the years. The impacts due to lightning impulses usually in domestic installations are destructive and often the electrical supply lines are damaged with service interruptions. College of Science and Technology (CST), is located at foothills of the Himalayas with sub-tropical climate and it experiences minimum of 12-16 lightning events per square kilometers per year. Therefore, the region experiences severe lightning events especially in the late spring, summer and early autumn seasons. In this research a risk assessment of building electrical installations is being analyzed to manage and mitigate the impacts due to lightning impulses by using IEEE 62305 standard to evaluate the risks. The risk assessment for case study location at College of Science and Technology, shows that the earth resistance is beyond the permissible limit as per national and international standards and lightning protection systems are being proposed at various locations in the campus. The current study does not include all the buildings of the CST campus but only selected buildings are assessed for impacts due to lightning impulses.

Diurnal and Seasonal Variability of ERA5 Convective Parameters in Relation to Lightning Flash Rates in Poland

Abstract The relationship between convective parameters derived from ERA5 and cloud-to-ground (CG) lightning flashes from the PERUN network in Poland was evaluated. All flashes detected between 2002 and 2019 were divided into intensity categories based on a peak 1-min CG lightning flash rate and were collocated with proximal profiles from ERA5 to assess their climatological variability. Thunderstorms in Poland are the most frequent in July, between 1400 and 1600 UTC and over the southeastern parts of the country. The highest median of most unstable convective available potential energy (MUCAPE) for CG lightning flash events is from June to August, between 1400 and 1600 UTC (around 900 J kg−1), whereas patterns in 0–6-km wind shear [deep-layer shear (DLS)] are reversed, with the highest median values during winter and night (around 25 m s−1). The best overlap of MUCAPE and DLS (MUWMAXSHEAR parameter) is in July–August, typically between 1400 and 2000 UTC with median values of around 850 m2 s−2. Thunderstorms in Poland are the most frequent in MUCAPE below 1000 J kg−1, and DLS between 8 and 15 m s−1. Along with increasing MUCAPE and DLS, peak CG lightning flash rates increase as well. Compared to DLS, MUCAPE is a more important parameter in forecasting any lightning activity, but when these two are combined together (MUWMAXSHEAR) they are more reliable in distinguishing between thunderstorms producing small and high CG lightning flash rates. Our results also indicate that higher CG lightning flash rates result in thunderstorms more frequently associated with severe weather reports (hail, tornado, wind). Significance Statement Each year severe thunderstorms produce considerable material losses and lead to deaths across central Europe; thus, a better understanding of local storm climatologies and their accompanying environments is important for operational forecasters, emergency managers, and risk estimation. In this research we address this issue by analyzing 18 years of lightning intensity data and collocated atmospheric environments. Thunderstorms in Poland are the most frequent in July between 1400 and 1600 UTC and form typically in environments with low atmospheric instability and moderate vertical shear of the horizontal wind. The probability for storms producing intense lightning increases when both of these environmental parameters reach higher values.

Global Distribution and Spectral Features of Intense Lightning by the ISUAL Experiment

AbstractDuring the 12 years of the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) experiment onboard the Taiwanese FORMOSAT‐2 satellite (2004/07/01–2016/6/20), 297,349 transient events were recorded, but only 48,414 events (16.3%) were manually classified as transient luminous events (TLEs). Since the main target of ISUAL is to observe TLEs, only the top ∼0.82% of intense lightning can meet the trigger threshold, which means the ISUAL experiment can also serve as a space‐borne intense lightning survey. An autonomous lightning identification algorithm was developed in this work to screen and locate lightning flashes in images, and 292,248 intense lightning discharges were identified successfully. Combining the statistical analysis of lightning events and unique spectral observations of ISUAL, the global distribution of intense lightning with spectral characteristics was constructed. The intense lightning occurrence rate of ISUAL was 1.29 fl s−1, and the land‐to‐ocean ratio 1.27. Intense lightning is most active near the equator, and the bimodal pattern peaks in April and September, different from the typical lightning behavior that occurs in the northern hemisphere during the summertime from July to August. In addition, the spectral statistics show that more than 95% of intense lightning is accompanied by nitrogen band emissions (1PN2, 2PN2, 1NN2+). Far‐ultraviolet photons mainly come from the radiation processes in the mesosphere to the ionosphere, and its radiation flux may correlate with lightning energies. Further, a significant 777.4 nm background enhancement is recognized in South America, which may affect the trigger of space‐borne 777.4 nm lightning surveys.

Under the surface: Pressure-induced planetary-scale waves, volcanic lightning, and gaseous clouds caused by the submarine eruption of Hunga Tonga-Hunga Ha'apai volcano

We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ​km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (∼1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ∼12 ​h, the eruptive volume and mass are estimated at 1.9 ​km3 and ∼2 900 ​Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters.

Structure of Energy Precipitation Induced by Superbolt‐Lightning Generated Whistler Waves

AbstractLightning superbolts are unusually intense lightning strokes. It has been well known that lightning can induce electron precipitation through the whistler waves it generates, but the characteristic of such precipitation in the extreme case of a superbolt has not yet been investigated. In this work, we use the numerical method developed by Bortnik et al. (2006a, https://doi.org/10.1029/2005ja011182, 2006b, https://doi.org/10.1029/2005ja011398) to model the precipitation induced by a superbolt event reported by Ripoll et al. (2021, https://doi.org/10.1038/s41467021237406). The modeled frequency spectrum agrees well with in situ measurements, adding confidence to the model performance. The precipitation flux is decomposed into contributions from different frequency components and different resonance types, thus revealing the underlying structure of the precipitation. The temporal signature of global precipitation on the ground surface is produced for potential comparison with observations by upcoming satellite missions.

Physical mechanisms associated with the intense lightning over Indian region

AbstractIndian subcontinent receives ~80% of its annual total rainfall during Indian summer monsoon (ISM) and since last 100 years the prediction of interannual variability of ISM is limited due to incomplete understanding of various processes and their localized influence on the development of varying scales of convective systems. The present study reports that the intense lightning contributed from the deepest convections occurring over Indian subcontinent are concentrated in four specific regions: (a) southwest coast, (b) Gangetic‐Brahmaputra plain, (c) Himalayan foothills and (d) southeast coast. The spatial and temporal variations of deep convections, size of “convection fractions” and associated physical mechanisms are described. It shows an annual cycle of systematic onset and withdrawal of deep convections and associated lightning depending on region and season. The southwest coast region is developing very deep convections during premonsoon and postmonsoon seasons but less lightning during monsoon. While Arabian Sea sources high moisture to this region in monsoon season, the orographic lift of low‐level westerlies by Western Ghats may effectively assist the warm rain processes and produce highest rainfall, low lightning and low area of deep convections. Highest flash rates, high number of days with lightning and higher area of convection are observed in Gangetic‐Brahmaputra plain but relatively lower rainfall compared to southwest coast region during monsoon. The sustained strong updrafts over the Gangetic‐Brahmaputra plain region are supported by the moisture source from warmer Bay of Bengal, incidence of monsoon trough and the continental heating. Significant lightning activity observed in northwest part of Himalayan foothills during winter is associated with Western Disturbances (WD) phenomena. The diurnal variation of lightning flash rate and size of “convective fraction” in these regions show two modes at 1200 and 1800 UTC and it indicates active day time surface heating and nocturnal cooling processes together contribute to total rainfall.

Formation factors of the most electrically active thunderstorm days over Poland (2002–2020)

This research documents atmospheric conditions and development of high electrically active thunderstorm days that occurred over Poland in period 2002–2020. The 8 days with the highest number of detected cloud-to-ground flashes during one storm cell life cycle were analyzed. The study used data from the PERUN lightning detection and location system, ERA5-reanalysis, vertical atmospheric soundings, and synoptic maps as well. As a result of the analysis, it can be concluded that the development of thunderstorms is positively influenced by the low-pressure area above the North Sea and the atmospheric fronts with zone of wind convergence in the lower troposphere. The analyzed storm systems on the analyzed days were created in the atmosphere of a high vertical wind shear (from 10 to 18 m s−1), lifted index (from +0.04 to –8.22), thermodynamic instability (CAPE 1000–3700 J kg−1), rich boundary layer moisture (mixing ratio: 12–14 g kg−1), and high tropospheric moisture (total column water vapour >50 kg m−2). Very moist air masses ahead of the storm systems provided consistent access to large amounts of latent heat released into the clouds and intensified upward mass fluxes and development of intense lightning activity from Cumulonimbus cloud.

Study of daytime high-altitude discharges using plasma-chemistry model

The paper considers the formation of electric fields in the atmosphere at altitudes of 50–70 km after especially powerful tropospheric cloud-to-ground discharges, leading to the initiation of high-altitude discharges. It is known that a necessary condition for initiation of a nighttime sprite is the electric field of uncompensated charge in a cloud of more than 128 Td at an altitude of about 75–80 km, while the field 80–100 Td leads to the development of a halo. High conductivity in daytime conditions does not allow the electric field to penetrate to altitudes of 75–80 km, and the region of a possible initiation of high-altitude discharges shifts lower. The normalized field required for the discharge initiation is the same as for nighttime conditions. Thus, for the initiation of the atmospheric discharge at daytime several times more intense lightning discharge in the troposphere is needed. Perturbations of the concentrations of ions, neutral compounds, excited atoms and molecules along with disturbances of the atmospheric conductivity and electric field are studied. The uncompensated charge of a parent flash is typically characterized by the impulse charge moment (ICM) of several hundred C⋅km for nighttime discharges. Modeling of daytime conditions was carried out in the range of 2000–4000 C⋅km, which leads to the formation at an altitude of 50–70 km of a normalized electric field of a near-breakdown value. It is shown that there are two scenarios of development of the discharge, with and without a rapid increase in electron concentration, which are studied in detail by assuming ICM values of 3750 C⋅km and 2750 C⋅km respectively. During a discharge with an ICM of 2750 C⋅km, the decrease in the concentration of electrons in the electric field is caused by their attachment to molecular oxygen, and no sharp increase in electron concentration occurs; the concentrations of the most significant ions and electrons reach unperturbed values in less than a second. The normalized electric field reaches a maximum value of 100 Td, and this scenario corresponds to the development of a halo. For an ICM of 3750 C⋅km, an initial decrease in the electron concentration is followed by the formation of an avalanche of electrons characterized by an increase in their concentration by more than an order of magnitude relative to the initial value. The maximum normalized electric field reaches 128 Td, this scenario corresponds to the development of a sprite. Thus, the possibility of the initiation of high-altitude discharges (presumably sprites and halos) in daytime conditions at altitudes of 50–70 km after especially powerful lightning discharges in the troposphere is shown, the dynamics of the disturbance of the chemical balance and atmospheric conductivity is studied.

Spatiotemporal Lightning Activity Detected by WWLLN over the Tibetan Plateau and Its Comparison with LIS Lightning

AbstractHerein, we compared data on the spatiotemporal distribution of lightning activity obtained from the World Wide Lightning Location Network (WWLLN) with that from the Lightning Imaging Sensor (LIS). The WWLLN and LIS both suggest intense lightning activity over the central and southeastern Tibetan Plateau (TP) during May–September. Meanwhile, the WWLLN indicates relatively weak lightning activity over the northeastern TP, where the LIS suggests very intense lightning activity, and it also indicates a high-density lightning center over the southwestern TP that is not suggested by the LIS. Furthermore, the WWLLN lightning peaks in August in terms of monthly variation and in late August in terms of 10-day variation, unlike the corresponding LIS lightning peaks of July and late June, respectively. Other observation data were also introduced into the comparison. The blackbody temperature (TBB) data from the Fengyun-2E geostationary satellite (as a proxy of deep convection) and thunderstorm-day data support the spatial distribution of the WWLLN lightning more. Meanwhile, for seasonal variation, the TBB data are more analogous to the LIS data, whereas the cloud-to-ground (CG) lightning data from a local CG lightning location system are closer to the WWLLN data. It is speculated that the different WWLLN and LIS observation modes may cause their data to represent different dominant types of lightning, thereby leading to differences in the spatiotemporal distributions of their data. The results may further imply that there exist regional differences and seasonal variations in the electrical properties of thunderstorms over the TP.

Study of Daytime High-Altitude Discharges Using Plasma-Chemistry Model

The paper considers the formation of electric fields in the atmosphere at altitudes of 50-70 kmafter powerful tropospheric cloud-to-ground discharges, leading to the initiation ofhigh-altitude discharges. A necessary condition for initiation of a nighttimesprite is the electric field of uncompensated charge in a cloud of more than 128 Td at an altitudeof 75–80 km, while the field 80–100 Td leads to the development of a halo. High conductivity in daytime conditions does not allow the electric field to penetrate to altitudes of 75–80 km,and the region of a possible initiation of high-altitude discharges shifts lower. The normalizedfield required for the discharge initiation is the same as for nighttime conditions. Thus, for theinitiation of the atmospheric discharge at daytime several times more intense lightning dischargein the troposphere is needed. The uncompensated charge of a parent flash is typically characterized by the impulse charge moment (ICM) of several hundred C⋅km for nighttime discharges. Modeling of daytime conditions was carried out in the range of 2000–4000 C⋅km, which leads to the formation at an altitude of 50–70 km of a normalized electric field of a near-breakdown value.It is shown that there are two scenarios of development of the discharge, with and without arapid increase in electron concentration, which are studied in detail for ICM values of3750 C⋅km and 2750 C⋅km respectively. During a discharge with an ICM of 2750 C⋅km no sharp increase in electron concentration occurs. The concentrationsof the most significant ions and electrons reach unperturbed values in less than a second. Thenormalized electric field reaches a maximum value of 100 Td leading tothe development of a halo. For an ICM of 3750 C⋅km, an initial decrease in the electron concentration is followed by the formation of an avalanche of electrons with concentration by an order of magnitude exceeding the initial value. The maximum normalized electric field reaches 128 Td, this scenario corresponds to the development ofa sprite. Thus, the possibility of the initiation of high-altitude discharges (presumably spritesand halos) in daytime conditions at altitudes of 50-70 km after powerful lightningdischarges in the troposphere is shown, the dynamics of the disturbance of the chemical balanceand atmospheric conductivity is studied.