No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Russian Studies on Atmospheric Electricity in 2019–2022
Abstract
This review contains the most significant results of Russian studies in the field of atmospheric electricity in 2019–2022. It is part of the Russian National Report on Meteorology and Atmospheric Sciences to the International Association of Meteorology and Atmospheric Sciences (IAMAS). The report was presented and approved at the XXVIII General Assembly of the International Union of Geodesy and
Geophysics ((IUGG). The review is followed by a list of the main published works on the studies of atmospheric electricity of Russian scientists in 2019–2022.
ResearchGate has not been able to resolve any citations for this publication.
Given the various consequences associated with thunderstorms, accurate forecasts of the time and location of thunderstorms can potentially have a wide range of benefits for industries such as industry, energy, transportation, agriculture, etc. In recent decades, in some regions of Russia, visual and aural methods of thunderstorm observation have been supplemented with instrumental monitoring (ground-based lightning detection systems). Global lightning systems include the World Wide Lightning Location Network (WWLLN), which detects electrical discharges such as cloud-to-ground and cloud-to-cloud with a 24-hour recording of the time and coordinates of lightning discharges. The aim is a spatio-temporal analysis of lightning discharge density distribution over the territory of Western Siberia using the WWLLN data and comparison of high-density centers with the fields of K-index values. Based on WWLLN data, the number of lightning discharges was calculated for a grid with 0.1° x 0.1° cells by longitude and latitude for the areas of 50-64N and 60-95E for the period 2016-2020. The area of each cell was then calculated, and the density of lightning discharges p was calculated [discharge/(km2xyear)j. Analysis of temporal variability (multi-year and seasonal) of lightning activity was carried out both for the whole territory under study and for individual settlements. Calculation of lightning density was carried out for 5 km radius zones in the center of each settlement.K-Index ERA5 reanalysis product was used to estimate the degree of atmospheric instability; reanalysis data processing and visualization were performed in the MATLAB mathematical package using the author's script. Five regions with an average annual lightning density exceeding the values of the neighboring regions by a factor of three were singled out within the investigated area. These regions are located over Kondinsky lowland (pmax ~1,4 discharge/(km^2*year)), Sredneobskaya lowland, Ob-Irtysh interfluves (pmax ~1 discharge/(km^2*year)), the eastern periphery of the Southern Urals and the northwestern periphery of the Altai-Sayan mountain country (pmax ~0,8 discharge/(km^2*year)). The following lightning discharge densities were recorded for the largest settlements in Western Siberia's central and southern regions: Khanty-Mansiysk (0.76 discharge/(km^2*year)) had the highest value, while Kyzyl city (0.08 discharge/(km^2*year)) had the lowest. The average lightning discharge density across all sites was 0.25 discharge/(km^2*year).The basic intensity of lightning activity falls in June-August (about 88 %). Even during this period, the number of lightning strikes in neighboring territories can vary by four or more times. The spatial location of the band of increased thunderstorm activity is generally consistent with the location of the northern periphery of the zone with average KIND values > 30°.
Kostinskiy et al. (2015b), https://doi.org/10.1002/2015GL065620, using a high‐speed infrared (2.5–5.5 μm) camera, discovered the so‐called unusual plasma formations (UPFs) in artificial clouds of charged water droplets. UPFs had complex morphology including both streamer‐like regions and hot channel segments. They were observed both in the presence and in the absence of hot leader channels developing from the grounded plane toward the cloud. In this paper, which is aimed at revealing the genesis of UPFs, we present two UPFs that occurred inside the initial corona streamer burst of positive polarity emitted from the grounded plane, prior to the formation (or in the absence) of associated hot leader channel. These streamer bursts developed at speeds of 5–7 × 10⁵ m/s over 1–1.5 m before entering the optically visible negatively charged cloud and producing UPFs at its periphery. Hot channel segments within UPFs were formed in very short times of the order of 1 μs or less. It is not clear if the UPFs were caused solely by the enhanced electric field near the charged cloud boundary or other factors also played a role. Occurrence of UPFs may be a necessary component of the lightning initiation process.
A new mechanism of charge transport inside a thundercloud is suggested and numerically investigated. The considered mechanism can be called “relay” because it is provided by a dynamical network of a relatively small amount of continuously decaying and arising conducting plasma formations. It manifests itself in two consecutive modes corresponding to pre-streamer and streamer/leader stages of thundercloud development. The first one is provided by dynamics of conducting ionic spots recently described by Iudin et al.1 that prepare conditions for initiation of positive streamers. The second mode relies on dynamical network of streamer/leader discharges and finally results in the formation of a compact well-conducting structure that bridges an area of strong electric field inside a thundercloud and can be associated with a lightning “seed”. The effectiveness of relay charge transport strongly depends on the relative proportion of conductive elements (plasma formations) and drastically increases in the field-dependent case.
This research compares the spatial and temporal variability of lightning activity associated with wildfires in several natural geographical zones of Western Siberia from 2016–2021. The study was based on the World Wide Lightning Location Network (WWLLN) and The Fire Information for Resource Management System (FIRMS) for the warm (April–October) season. It was revealed that areas of hotspots and lightning activity most often coincide in the southwestern part of the territory (near Khanty-Mansiysk and Tyumen), in the mountain regions (Kuznetsk Alatau, Altai), and in the northern part of Kazakhstan. Maximum values of lightning occur in July for the whole territory of Western Siberia, and maximum values of hotspots occur in April in the central and southern regions of Western Siberia. Despite the largest number of fires in the south of the territory, the probability of ignition from lightning over the whole warm season is higher in the northern parts of Western Siberia; it reaches up to 30%. Thus, the revealed lightning–fire association allows us to better understand this process in the region that will be useful in the prediction of the potential fire danger in different natural zones.
Currently, many researchers have an interest in the investigation of the electric field in the fair-weather electric environment along with its diurnal and seasonal variations across all regions of the world. However, a similar study in the southern part of Western Siberia has not yet been carried out. In this regard, the paper aims to estimate the mean values of the electric field and their variations in this area using the example of Tomsk. The time series of one-minute average potential gradient values as well as other quantities obtained from the geophysical observatory of the Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences (IMCES SB RAS, Tomsk, Russia) from 2006 to 2020 is used in this study. The mean annual value of the potential gradient in Tomsk is 282 V/m and usually varies from 161 to 372 V/m. The diurnal variations in potential gradient per year on average are characterized by oscillations of the continental type with a double maximum and minimum. The main minimum of diurnal variations is 7 h and the main maximum is 21 h of local time (00 and 14 UTC, respectively). According to the annual mode, the maximum potential gradient is observed in February, and the minimum is recorded in June.
Worldwide maps of lightning activity have been obtained from the ground-based World Wide Lightning Location Network (WWLLN) for 2007–2009. We have compiled these maps separately for different seasons and UT periods, using WWLLN data on the time and coordinates of each of the recorded lightning. The total number of flashes of lightning in WWLLN data is by an order of magnitude smaller than in satellite data from Optical Transient Detector and the Lightning Imaging Sensor satellites. However, the key features of the spatial distribution and seasonal trends coincide well. The main difference observed is the absence of diurnal variation (similar to Carnegie curve) in WWLLN data against the satellite one. This concerns the global lightning number as well as its density in major thunderstorm regions. The solar local time dependence is also weak in WWLLN data. We show that in 2007–2009 the mean latitude of lightning observation is shifted to the summer hemisphere up to 10° from the annual mean value. From the beginning of 2007 to the end of 2009, the global monthly average number of flashes of lightning increased threefold. We attribute this fact primarily to improved processing techniques in WWLLN. The constructed maps are necessary for numerical simulation of the Global Electric Circuit.
Проведен анализ 11-летних временных рядов количества грозовых разрядов суммарно по территориям двух крупных областей повышенной плотности молний (более 10 раз по сравнению со значениями на окружающем пространстве): условно обозначенных как восточный регион — 40–55º с.ш., 110–140º в.д., и западный регион — 47–62º с.ш., 60–90º в.д. Дискретное разложение рядов (разрешение в 1 сутки) с помощью вейвлет-функции Мейера до 5 уровня (восточный) и 4 уровня (западный) показало смещение максимума сезонного хода грозовой активности в регионах в начало и ближе к августу из года в год с периодом около 3 лет. Периодичность в вариациях грозовой активности более выражена в Фурье-спектрах в западном регионе: 4, 7, 14 дней. Плотность молний в Северной Азии в пространстве можно описать как пояс вокруг 50º с.ш. со смещением южнее на востоке и значительном увеличении плотности в двух областях. Предложено аналитическое выражение в виде изменяющейся с долготой гауссовой функции широтного хода, суммированной с линейной функцией фонового спада общего уровня активности к северу. Параметры, входящие в гауссову функцию, представлены зависимостью плотности от долготы. Параметр широты достаточно аппроксимируется линейной функцией долготы, параметр уширения распределения по широте – суммой трех гауссовых функций. Их межгодовое изменение пренебрегалось в данном решении. Параметр, ответственный за описание пика плотности, описывается суммой двух гауссовых функций, и в их коэффициенты введена зависимость от года. Межгодовые вариации коэффициентов вторичных функций предложено представлять в виде суммы Фурье-рядов с двумя-тремя гармониками. Таким образом, получены оценки вариабельности параметров аналитического выражения широтно-долготного распределения плотности грозовых разрядов в десятилетнем масштабе
Computational model of high-current pulsed arcdischarge in air is proposed. This is, in general, two-dimensional model with taking into account gas dynamics of the discharge channel, real air thermodynamics in a wide range of pressure and temperature, electrodynamics of the discharge including pinch effect, and radiation. One-dimensional version of the model is tested and verified on several numerical and experimental works reported recently. It is concluded that low and moderate current discharges are satisfactorily described with the developed model. Then, developed model was applied to simulate the electric discharge in air for the currents of 1 - 250 kA and characteristic rise times in 13 - 25 µs, and results of calculations were compared with experimental ones. It was concluded that most of characteristics of the discharge are predicted well. Namely, arc column radius and shock wave position agree well with experimental data for all current amplitudes and rise times considered. Radial distributions of temperature and electron density also satisfactorily agree with experimental data. It was found that pinch effect should be considered for currents higher than 100 kA.
Plain Language Summary
The El Niño—Southern Oscillation (ENSO) is one of the most remarkable modes of climate variability on Earth. Being made up of irregularly alternating warm (El Niño) and cold (La Niña) phases, the ENSO affects atmospheric circulation, global temperature and rainfall patterns, agriculture, and economic output. Recent simulations have suggested that changes in global convection patterns due to ENSO should also affect surface atmospheric electric fields and currents in remote regions of the planet. Here, we present electric field measurements performed during 2006–2016 at Vostok station in the Antarctic that reveal clear patterns related to ENSO as earlier predicted by simulations. Measurements show that the shape of the diurnal variation of the surface electric field is significantly different for El Niño and La Niña years (with an especially pronounced effect during the super El Niño of 2015/16), which, according to simulations, is the result of changes in the global distribution of electrified clouds over the Pacific Ocean, Maritime Continent, and South America during ENSO events. This provides further evidence of the influence of climate fluctuations on the Earth's global electromagnetic environment.
It is traditionally accepted to define the dielectric strength of air as an electric field corresponding to the balance between the rates of impact ionization and electrons’ attachment to neutrals. Its reduced value is known to be about 110 Td regardless of the altitude above the mean sea level. In this study, the altitude profile of the critical electric field of atmospheric air in the 0–40 km altitude range is specified. Unlike the conventional approach, a wide range of additional plasma-chemical processes occurring in atmospheric air, such as electron detachment from negative ions and ion-ion conversion is taken into account. Atmospheric air is considered to be a mixture of N2:O2 = 4:1 containing a small amount of chemically active small gas components, such as water vapor, atomic oxygen, ozone, and several types of nitrogen oxides. It is shown that the dielectric strength of air falls noticeably compared to its conventional value. The results of the study can be important to solve the problems of initiation and propagation of lightning discharges, blue starters, and blue jets.
A comparison of thundercloud characteristics in different regions of the world was conducted. The clouds studied developed in India, China and in two regions of Russia. Several field projects were discussed. Cloud characteristics were measured by weather radars, the SEVERI instrument installed on board of the Meteosat satellite, and lightning detection systems. The statistical characteristics of the clouds were tabulated from radar scans and correlated with lightning observations. Thunderclouds in India differ significantly from those observed in other regions. The relationships among lightning strike frequency, supercooled cloud volume, and precipitation intensity were analyzed. In most cases, high correlation was observed between lightning strike frequency and supercooled volume.
Thunderstorm ground enhancements (TGEs) are fluxes of energetic particles multiplied in thunderclouds, which may be registered by ground‐based detectors. Using the Weather Research and Forecasting (WRF) Model, the state of the atmosphere with a 1‐km horizontal resolution is modeled for convective events accompanied by TGEs observed at the high altitude Aragats Research Station in Armenia (40.47 N, 44.18 E, 3,200 m above sea level). By comparing the data obtained in observations with the results of simulations using a microphysical parameterization for WRF, a technique is developed for estimating charge distribution parameters. A typical charge distribution in a TGE‐producing cloud is found to be well approximated by a two‐layered charge structure with a lower positive charge region formed by graupel particles and an upper negative charge region formed by snow particles. The characteristic charge density is 0.01 nC/m³ for the graupel cluster and −0.02 nC/m³ for the snow cluster. A vertical distance of about 1–2 km between the lower positive and upper negative layers is sufficient for the development of an energetic particle avalanche.
In this study, we used a tethered balloon equipped with an instrumented platform to examine the altitude distribution of principal quantities of the lowest atmospheric region of the global electric circuit (GEC), radon volumetric activity, and aerosol particles concentration. Altitude soundings covered approximately 0.5 km of the lowest atmosphere and were accompanied by simultaneous ground-based measurements. This method of spaced observations allowed us to analyze the spatial and temporal changes in electrical quantities of the atmospheric boundary layer (ABL) more deeply than was possible before. Using successive balloon ascents and descents as well as holding the platform at certain heights, long-lived space charge layers were discovered and the rate of change of charge in atmospheric columns of various thickness was estimated. A charge density of small ions was determined to be enclosed in a range from −20 pC m⁻³ to 30 pC m⁻³ reaching the highest values with rare exceptions directly at the earth's surface. It was found that the electric field vertical profiles tend a decrease during the day most pronounced in the lower 100 m. Similar behavior is also demonstrated by radon and aerosol particle concentration profiles. Based on the results of soundings, columnar electrical resistance, electric potential, and electromotive force acting in the ABL in fair-weather conditions are quantified. These estimates show the significant contribution of the ABL to the GEC, which must be taken into account when considering it.
The instrumental continuous monitoring of lightning activity in Yakutia has been carried by the lightning direction finder since the 2000s. Devices for detection of sferic (very low frequency radio pulses emitted by lightning discharges) in Yakutia were supplemented in 2009 with relatively short-range (effective detection radius up to 480 km) single-point Stormtracker and LD-250 direction finders from Boltek Corporation (Welland, ON, Canada). The Stormtracker gives a slightly overestimated ratio of CG strokes due to the amplitude threshold of a single-point direction finder, but the device has not changed over the years, which allows for the consideration of the annual dynamics of parameters. In 2009, a sensor in Yakutsk was included in the World Wide Lightning Location Network (WWLLN). The seasonal and diurnal variations of the total lightning stroke number in the central part and the entire area of Yakutia were obtained (up to 1200 km in radius and limited by latitude–longitude boundaries of 105–150° E, 55–75° N). The longest thunderstorm seasons are often observed in the southern part of Yakutia. There was a slight increase in the duration of the thunderstorm season until 2015 in the central part of Yakutia. The interannual variations in the total number of lightning strokes showed periodic fluctuations (with a period of about three years) over the whole area of Yakutia. The periods of high lightning activity shifted within a season from year to year, as revealed by the monthly stroke number variation. Thus, the maximum lightning rate occurred at the beginning of summer, in the middle or at the beginning of August, and had a period of about three years. Every summer, there were 2–3 periods of high lightning activity, resulting from the moving average with a two-week window (according to the longest duration of cyclones). If the periods of high lightning activity shifted toward the beginning of summer, a decrease in the number of days between seasonal peaks was observed. If the maximum shifted to the beginning of August, the number of days between peaks increased. The ratio of cloud-to-ground (CG) lightning strokes and the ratio of negative CG strokes was slightly decreasing by 2015 in the central part of Yakutia.
A fair-weather electric field has been observed near the Earth's surface for over two centuries. The field is sustained by charge generation in distant disturbed weather regions, through current flow in the global electric circuit. Conventionally, the fair-weather part of the global circuit has disregarded clouds, but extensive layer clouds, important to climate, are widespread globally. Such clouds are not electrically inert, becoming charged at their upper and lower horizontal boundaries from vertical current flow, in a new electrical regime-neither fair nor disturbed weather; hence it is described here as semi-fair weather. Calculations and measurements show the upper cloud boundary charge is usually positive, the cloud interior positive and the lower cloud boundary negative, with the upper charge density larger, but of the same magnitude (∼nC m-2) as cloud base. Globally, the total positive charge stored by layer clouds is approximately 105 C, which, combined with the positive charge in the atmospheric column above the cloud up to the ionosphere, balances the total negative surface charge of the fair-weather regions. Extensive layer clouds are, therefore, an intrinsic aspect of the global circuit, and the resulting natural charging of their cloud droplets is a fundamental atmospheric feature.
The development of a powerful supercell cloud is considered, from which large hail and a shower of catastrophic intensity have fallen for a long time. The analysis of radar and lightning-detection characteristics showed the presence of local extremes of intensity and currents of cloud-to-cloud and cloud-to-ground lightning discharges and allowed evaluating areas and intensities of hail, as well as cloud volumes with ice graupels of low and high density. The maximum values of thunderstorm characteristics occurred 1.5 hours after the mass and volume of the cloud with low-density graupels had reached their maxima. The maximum mass and volume of high-density graupels, the intensity and area of hail were reached approximately 2 hours later than the maximum thunderstorm characteristics.
The microwave diagnostics of discharges occurring in anartificial cloud of charged water droplets created in an open air simulatingthe environment of thunderclouds is implemented. An artificial cloud with adroplet size of about 1 microns is opaque in the visible range, sointra-cloud discharges are not available for investigation by traditionalmethods in the spark discharge physics based on the registration of visibledischarge radiation. Microwaves pass through such a cloud withoutnoticeable attenuation, they interact only with the plasma of dischargesoccurring in the cloud. The probing microwave radiation had a wavelength of8 mm. The attenuation of microwaves passed through the cloud was measuredwith temporary resolution of about 10 ns. The temporal characteristics ofintra-cloud discharges were investigated. Keywords: spark, leader, streamer, electromagnetic wave.\
Relativistic runaway electron avalanches (RREA) occurring in thunderstorm large-scale electric fields are one of the sources of atmospheric gamma radiation. Relativistic feedback is the generation of RREAs by positrons or backscattered gamma rays of the previously produced RREAs. In strong electric fields, relativistic feedback can make RREAs self-sustainable that hypothetically can cause a terrestrial gamma-ray flash (TGF). This paper introduces a kinetic approach to study the positron relativistic feedback, which is predominant for the directly observed conditions within thunderstorms. The criterion for self-sustaining production of RREAs by the positron feedback in thunderstorms is derived. The discovered criterion allows one to obtain the parameters of the thunderstorm electric field required for self-sustaining RREA development with positron feedback for any altitude. It is shown that the derived conditions of self-sustainable RREA development are not achieved for the parameters of electric field observed in real thunderclouds.
The study of the global distribution of sprites is based on the new parameterization and WWLLN (World Wide Lightning Location Network) data for 2016. The information on the position, time, and power (peak current) for cloud-to-ground discharges are taken from the archive of the WWLLN. Parameterizations of the sprite initiation probability are proposed for positive and negative discharges. In the calculations, only nighttime events are considered and the probabilistic nature of the sprite initiation, depending on the iCMC, is taken into account. It is shown that on average 870 nighttime sprites per twenty-four hours globally can be initiated, 41.4% over land and 58.6% over ocean. On the basis of the proposed parametrization, the regional distribution of sprites is analyzed, as well as seasonal and monthly distribution over land and ocean. The annual dynamics of the number of sprites over land and ocean has been investigated, revealing the maximum number of events in August and the minimum in January and February.
We present the data on the dynamics of the electric field strength and volume charge of two severe thunderstorms in different regions of the world, namely, in the North Caucasus (Russia) and in Beijing (China). The data were obtained as a result of modeling, using a numerical three-dimensional non-stationary model of convective clouds developed at the A. I. Voeikov Main GeophysicalObservatory. The modeling was based on rawinsonde data obtained during the modeled thunderstorm events. The spatial distribution of the electric field strength and space charge inside the cloud and in its vicinity was calculated. The multilayer charge structure of the cloud with thin layers of “shielding” charges is reproduced and the corresponding structure of the electric field strength is presented for each electrification stage. The dynamics features of the electrical structure of the studied cumulonimbus clouds are discussed. The case of modeling of a cloud with inverted polarity is considered. Verification of the numerical model based on empirical models of convective cloud electrification showed a satisfactory result.
Results of an investigation of the peculiarities of a spectrum of the electromagnetic signals induced nearby discharges between an artificial thunderstorm cell and a ground have presented. It was experimentally found that the impulse current parameters and an intensity, form, spectral characteristics of the induced electromagnetic signals depend on a variant of a discharge formation from an artificial thunderstorm cell (upward discharge, downward discharge, or counterpart discharge). Significant difference of the wavelet spectrum characteristics of the electromagnetic signals registered by the antennas in the vicinity of discharge formation has been found for these three variants. Significant difference of the spectral characteristics of the electromagnetic signals induced on nearby antennas during the time of the first and subsequent current impulses of a discharge between an artificial thundercloud and a ground: in average, subsequent discharges have more less characteristic frequencies. Possible reasons of that differences have discussed in paper. Role of the powerful streamer discharges during the main stage formation in the appearance of the ultrahigh frequency range of the induced electromagnetic signals has considered. Some dependencies between the spectral characteristics of signals registered by antennas and the parameters of the current impulses for the different variants of the main stage of the discharge between the artificial thunderstorm cell and the ground have been established. The possibility of applying the results obtained for improving the operation of lightning direction finding systems is being considered.
Simultaneous measurements of the brightness temperature and short-period electric field fluctuations were carried out to reveal possible connections between the electrification rate and turbulence intensity in clouds. The measurements were conducted in Nizhny Novgorod, Russia (56°19′37″N 44°00′27″E) in 2013 and 2018. The 8 mm radiometer was used to measure the brightness temperature of thermal radiation, and the vertical component of the atmospheric electric field were carried out using an electrostatic fluxmeter. With the use of meteorological data and electric field measurements the state of analyzed events has been classified into 4 types: cloudless atmosphere and high-level clouds (Cs), cumulus clouds (Cu), cumulonimbus clouds without lightning that cause strong electrical field disturbances near the ground surface (Cb), cumulonimbus thunderstorm clouds with lightning discharges (Cb⁺). Detailed statistical characteristics of brightness temperature fluctuations and short-period electric field fluctuations are obtained for the first time for the indicated types of events.
It is shown that measured spectral densities of the atmosphere brightness temperature and electric field fluctuations correspond well enough in the considered frequency range to the results of presented theoretical consideration. Precipitation particles in clouds can be considered herewith as passive scalar, and the movement of inhomogeneities in the particle density can be described by Kolmogorov theory. Since electric charges are located on the precipitation with small droplet and ice particles, an increase in the inhomogeneities of the water content means likely an increase in the inhomogeneities of the electric charge. For thunderclouds the estimates of the relative fluctuations of liquid water content give values of the order of tens of percent. There is a tendency towards a relative increase in brightness temperature fluctuations at high frequencies in the band around f ≈ 10⁻² Hz (and possibly higher than fmax ≈ 0.05 Hz) for the sequence of cloud types Cu, Cb, Cb⁺.
The development of an atmospheric electricity-monitoring network stimulates research into the relationship between the global electrical circuit and environmental conditions. Small air ions in the lower atmosphere are the main carriers of the conduction current and, at the same time, are themselves carried by atmospheric turbulence. However, it is not clear to what extent the statistics of fluctuations in the concentration of small ions in the electrode layer adjacent to the earth's surface bears the features of scalar turbulence. Based on field experiment data, the probability density functions of fluctuations of both the concentration of small ions and temperature are found to be non-Gaussian and approximated by a stable distribution model with the index of stability α in the range from 1.1 to 1.96. Observations have demonstrated that statistics of temperature fluctuations is more intermittent, compared to height-dependent statistics of fluctuations of the concentration of small ions. It is found that the autocorrelation function and second-order structure function have different behavior for the concentration of small ions and temperature in the time range 1–50 s.
The characteristics of hazardous meteorological phenomena in Nizhny Novgorod city based on the electric field observations are obtained in the present paper. As a result of the analysis of quasistationary electric field variation experimental data together with the meteorological data, statistics of thunderstorm events were obtained and their classification was carried out. The data of field observations are compared with the results of numerical calculations based on the WRF model.
It's a common knowledge for spark discharge researches that negative leaders in air always propagate in a step-wise manner. A new step forms when a space leader attaches to the primary negative one. Space leaders originate from small fusiform plasma formations which are called space stems. For now, there is no any established idea about how space stems form in conditions when the background electric field inside the negative corona volume is about three times less than the dielectric strength of air. In this study, we propose a new mechanism of space stem precursors formation which is based on the joint action of ionization and electron drifting processes occurring at the negative corona streamer burst boundary in the presence of strongly inhomogeneous stochastic electric field. It is supposed that electric field fluctuations are formed by chaotically positioned clusters of negative charge which can be considered as basic elements of spatio-temporal noise and are transported into the negative corona volume by negative streamer heads. The last are emanated from the newly-formed leader tip during the development of the negative corona streamer burst finishing the step-formation process. The model is applied to specify conditions, under which space stem precursor genesis is possible, and to analyze the peculiarities of proposed mechanism at different altitudes above sea level.
In this work, we study the space-time statistical features of variations in the atmospheric electric field (Ez) and space charge in the atmospheric boundary layer using a three-dimensional model and analysis of observational data. The model is a combination of large-eddy simulation supplemented with a subgrid kinematic model for scalar and the three-dimensional Poisson equation for the electric potential. Based on the calculated evolution of three-dimensional distributions of the space charge and electric potential, the variability of the spectral slopes of variations in the space charge, vertical potential difference, and the vertical component of the electric field Ez is investigated. The vertical profiles of Ez and the frequency power spectra of Ez variations at different heights computed are in reasonable agreement with the observed ones. It is shown that the cross-correlation of Ez at spatially separated points located on one straight line near the earth's surface decreases with increasing distance with a characteristic scale of a few tens meters and has a dependence on the angle between this line and the direction of the wind. Mean large-scale horizontal electric field defined through the position and amplitude of the potential extrema at the same height depends on height non-monotonically having a maximum value of about 5 V/m. Scaling exponents of structure functions for Ez variations are found to be significantly larger than those for space charge variations.
It is known that the global electric circuit (GEC) intensity can be characterised by a single global index, namely the ionospheric potential (IP), made up of contributions from electrified clouds all over the globe. Using the Weather Research and Forecasting model, we have reproduced the atmospheric dynamics for 2008–2018 and simulated the variation of the GEC by parameterising regional contributions to the IP in terms of convection and precipitation. Considering that the El Niño—Southern Oscillation (ENSO) can be quantitatively characterised by sea surface temperatures (SSTs) in the Niño 3.4 region, this allowed us to identify and study in detail the effect of ENSO on regional contributions to the GEC. Our simulations have shown that contributions to the GEC from the land and oceanic parts of the Earth's surface respond oppositely to the ENSO cycle. The oceanic contribution is positively correlated with the Niño 3.4 SST, largely owing to increases in convection over the Pacific Ocean. In contrast to the oceans, the land contribution shows a negative correlation with ENSO due to decreases in convection over the Maritime Continent and South America. The observed correlations are statistically significant and are clearly seen on the decadal timescale; at the same time contributions to the IP for individual years do not always clearly reflect the corresponding Niño 3.4 SST anomalies. During the two El Niños and two La Niñas that occurred between 2008 and 2018, the oceanic contribution always changed in phase with ENSO, increasing in El Niño years and decreasing in La Niña years; on the other hand, the contribution of land showed a clear variation in antiphase with ENSO only for the 2015/16 El Niño and 2010/11 La Niña, characterised by extremely large SST anomalies, with a small and indefinite effect for the two lesser events. When summing the contributions of land and ocean, two strong effects of opposite signs nearly counterbalance each other and we obtain a much less pronounced effect of ENSO on the total IP. This effect is generally positive since land and ocean provide nearly equal contributions to the GEC during Northern Hemisphere winters and, according to our analysis, the contribution of ocean is slightly more sensitive to ENSO than that of land.
The results of observations of radio emission from thunderclouds in a wide frequency range with a high temporal resolution carried out in the Upper Volga region near Nizhny Novgorod are compared with the data from worldwide and regional lightning location networks. Two parameters are chosen to characterize the radio emission: root mean square (corresponding to the emission intensity) and kurtosis (to testify to the presence of a pulsed component in the emission) of its distributions at short time intervals. It is shown that the intensity of radio emission as a whole reflects the level of thunderstorm activity at distances up to 50 km from the point of observation. A similar correlation also takes place for the kurtosis of the emission. Comparison with events detected by lightning location networks shows that they are often preceded by a well-defined behavior of the above parameters. The emission begins suddenly with a moderate level of intensity and a high value of kurtosis that lasts from few to more than one hundred of milliseconds. Then the kurtosis decreases permanently with approximately the same intensity of the emission that can correspond to a step leader stage of a lightning discharge. The radio frequency event is ended by a sharp increase in the emission intensity simultaneously with a decrease of the kurtosis to the background level, and exactly the same moment corresponds to a lightning location network event that can be associated with the return stroke of a lightning discharge. It should be mentioned that a number of events from lightning location networks have no such manifestations in the recorded radio emission and vice versa.
Рассматривается проблема формирования электрического состояния нижнего слояатмосферы вблизи поверхности земли. Исследуется электродинамическая модель неста-ционарного турбулентно-конвективного призменного слоя в приближении электродногоэффекта (ЭЭ). Исходная система состоит уравнений, описывающих ионизационные и ре-комбинационные процессы для аэроионов, и уравнения Пуассона для электрического поля.В зависимости от метеорологических условий в атмосфере отдельно рассмотрены моделиэлектродного слоя (ЭС) в приближениях классического и турбулентного ЭЭ, а также вприближении сильного турбулентного перемешивания. В качестве факторов, влияющих напространственно-временную структуру ЭС, выступают турбулентный и конвективныйперенос аэроионов, уровень ионизации воздуха и присутствие в нем субмикронного аэрозо-ля. Выявлены безразмерные параметры (критерии подобия) для электродинамическихуравнений, позволяющие осуществлять выбор соответствующего приближения для моде-лирования структуры электродного слоя в зависимости от атмосферных условий. В сво-бодной от аэрозоля атмосфере время установления стационарного состояния в электрод-ном слое составляет примерно 5 мин., для классического слоя (характерная высота около4-5 м), а в турбулентном - примерно 15 мин. (высота порядка 10 м). В случае сильного тур-булентного перемешивания масштаб распределения электрических величин возрастает досотен метров. Соотношение характерных скоростей турбулентного и конвективногопроцессов указывает на преобладающий физический механизм переноса ионов и формиро-вания структуры ЭС. Увеличение скорости конвективного переноса, направленного вниз,приводит к ослаблению механизма турбулентного перемешивания, а при переносе вверх,имеет место обратный эффект. Присутствие в атмосфере субмикронного аэрозоля при-водит к образованию тяжелых ионов, подвижность которых много меньше, чем у аэроио-нов. Однократно заряженные аэрозольные частицы с концентрацией, не превышающейчисло аэроионов, незначительно меняют пространственно-временные характеристик ЭС.Тогда как наличие в приземном воздухе многократно заряженных аэрозольных частиц,увеличивает время электрической релаксации и уменьшает высоту ЭС. При достаточнобольших концентрациях аэрозоля (больше числа аэроионов на порядок и более) необходимоучитывать его перенос турбулентно-конвективными потоками, а структура ЭС опреде-ляется только тяжелыми ионами.
A.A. Sin’kevich, Yu.P. Mikhailovskiy, M.L. Toropova, V.B. Popov, D.S. Starykh, Yu.A. Dovgalyuk,
N.E. Veremei. Thunderstorm with waterspout structure and lightning frequency dependence from its characteristics.
The aim of this work is to summarize the results of the study of the development of a high-depth thunderstorm over water area of the Gulf of Finland. A waterspout was observed under the base of the cloud. Remote
sensing methods were used in the study. The general conditions of atmospheric instability, microphysical and
electrical characteristics of the cloud are considered. Cloud microphysics and its relation with lightning frequency are discussed. High correlation was discovered between the frequency of lightning discharges and supercooled volume of the cloud, as well as precipitation flux.
A simplified and obvious electrotechnique model of the electric field enhancement in front of the propagating gas-discharge plasma channel is presented. A theory, developed some time ago by Yakovlenko, is criticized proving that a displacement of the electric field due to the plasma polarization behind the flat channel front is sufficient for the field enhancement ahead of the front. Arguing with this opinion, it is shown, in terms of the developed electrotechnique model, that for a significant field enhancement, as is known long ago, the cross-sectional area of the channel should be much less than that of the gas-discharge gap. The polarization self-acceleration of electrons is discussed.
We propose a small-scale transport model of the electric-discharge tree formation and analyze its implementation for a characteristic case of the thundercloud conditions. The following innovative features of the model can be emphasized: no connection to the spatial grid, high spatiotemporal resolution, and allowance for the asymmetry of the development of the positive and negative streamers and the time evolution of the discharge-channel parameters. The criterion of the streamer-to-leader transition, which is used in this work, is formulated in terms of the channel temperature and is based on the well-known mechanism of ionization-overheating instability, which is universal for the spark discharge. Within the framework of the described approach, a heated well-conducting leader channel is formed by combining the currents of tens of thousands of streamers, so that each of them initially has f negligible conductivity and a temperature that does not differ from the ambient temperature. The model bileader tree has electrodynamic characteristics that are intermediate between those known for the laboratory long spark and the developed lightning, which is expected for an “immature” lightning leader. The morphology and electrical parameters of the calculated discharge tree of the incipient model lightning leader agree with the modern data on the lightning-discharge development.
The problem of diffusion through the fluctuating medium, where processes of substance disintegration and reproduction are possible, was posed at the end of the last century. It was established that the action of multiplicative external noise on a system can result in qualitative reorganization of its dynamical behavior. When such reorganization leads to the appearance of a new stationary dynamic mode, it is customary to speak about a noise-induced phase or kinetic transition. In this paper the noise-induced kinetic transition in two-component environment where the interacting components have contrasting lifetimes and diffusion coefficients is considered. It is shown that the presence of an additional long-lived component can lead to a dramatic decrease in the system generation threshold. We called this effect the depository reproduction. Analytical consideration of the diffusion process in a fluctuating medium causes enormous difficulties even for a single component substance. Meanwhile, in some cases of practical interest, the problem consideration can be conducted using stochastic geometry and percolation theory in particular. In the present work the noise-induced kinetic transition in two-component distributed systems is studied by the tools of directed percolation. To present the depository reproduction effect more vividly we use a new numeral grossone that allows to express different infinitesimal and infinite numerals. It was shown that the reverse conversion of the long-lived component to the short-lived one ensures the survival of the system at significantly lower concentrations of production centers.
We report the observation results of the hard radiation flashes which accompanied the lightning discharges above the mountains of Northern Tien Shan. Time series of the counting rate intensity, numerical estimations of absolute flux, and energy distribution of accelerated electrons and of (20−2000) keV gamma rays were obtained at the height of 3700 m a. s. l., immediately within thunderclouds, and in closest vicinity (≲100 m) to discharge region. Two different kinds of radiation emission events are presented here: a relatively prolonged rise of gamma ray intensity with minute-scale duration (the thunderstorm ground enhancement, TGE) which has preceded a negative field variation, and a short sub-millisecond radiation burst, which accompanied a close lightning discharge in thundercloud. It was revealed also an indication to positron generation in thunderclouds at the time of gamma ray emission, as well as modulation of the neutron counting rate in Tien Shan neutron monitor which was operating at a (1.5–2) km order distance from the region of lightning development.
