Thunderstorm Activity Research Articles

Deterministic–Probabilistic Prediction of Forest Fires from Lightning Activity Taking into Account Aerosol Emissions

Forest fires arise from anthropogenic load and lightning activity. The formation of a thunderstorm front is due to the influence of a number of factors, including the emission of aerosol particles from forest fires. The purpose of this study is mathematical modeling of heat and mass transfer in vegetation firebrand carried out from a forest fire front, taking into account the formation of soot particles to predict forest fire danger from thunderstorm activity. Research objectives: (1) development of a deterministic mathematical model of heat and mass transfer in a pyrolyzed firebrand of vegetation, taking into account soot formation; (2) development of a probabilistic criterion for assessing forest fire danger from thunderstorms, taking into account aerosol emissions; (3) scenario modeling of heat and mass transfer and the formation of a thunderstorm front; (4) and the formulation of conclusions and proposals for the practical application of the developed deterministic–probabilistic approach to the prediction of forest fires from thunderstorms, taking into account aerosol emissions. The novelty of this study lies in the development of a new model of heat and mass transfer in a pyrolyzed vegetation firebrand and a new probabilistic criterion for forest fire danger due to thunderstorm activity, taking into account aerosol emission. The distributions of temperature and volume fractions of phases in a firebrand are obtained for various scenarios. Scenarios of surface fires, crown forest fires, and a fire storm are considered for typical types of coniferous vegetation. Cubic firebrands are considered in the approximation of a two-dimensional mathematical model. To describe the heat and mass transfer in the firebrand structure, a differential heat conduction equation is used with the corresponding initial and boundary conditions, taking into account the kinetic scheme of pyrolysis and soot formation. Variants of using the developed mathematical model and probabilistic criterion in the practice of protecting forests from fires are proposed. Key findings: (1) linear deterministic–probabilistic mathematical model to assess forest fire occurrence probability taking into account aerosol emission and lightning activity; (2) results of mathematical modeling of heat and mass transfer in firebrand taking into account soot formation; (3) and results of scenario modeling of forest fire occurrence probability for different conditions of lightning activity and aerosol emission.

Study of the Lightning Activity Over Poland for Different Solar Activity

Abstract The question of the connection between solar and thunderstorm activity is not new. The discussion among scientists began before the cosmic era. The correlations of the ground-based registration of the cosmic ray flux and meteorological observations have been performed since the 50s of the 20th century. The discussed problem is related to the influence of cosmic rays on the creation of clouds, particularly thunderstorm clouds. The intensity of the galactic cosmic ray flux is controlled by the density and velocity of the solar wind. The increase in the solar wind flux during high solar activity leads to decreasing galactic cosmic ray flux, but on the other hand, the solar activity creates solar cosmic rays. Using data from the PERUN system and the DEMETER satellite, we tried to estimate the connection between the thunderstorm activity in Poland and solar activity during the period of the DEMETER operational activity (2004–2010). The influence of thunderstorms on the ionosphere and its dependence on solar activity is also discussed. However, due to the short time interval of the available data covering an insignificant part of the solar cycle, close to the minimum activity, our findings are not fully conclusive. No correlation was found between the cosmic ray flux and lightning activity given by the number of the discharges. However, some of the most energetic lightning discharges in the analyzed period occurred close to the minimum of the solar activity and their appearance is discussed.

Trends toward Improving Passive Radio Engineering Facilities for Thunderstorm Activity Monitoring

Trends toward Improving Passive Radio Engineering Facilities for Thunderstorm Activity Monitoring

ХАРАКТЕРИСТИКИ И СТРУКТУРА МЕЗОМАСШТАБНЫХ КОНВЕКТИВНЫХ СИСТЕМ НАД ЗАПАДНОЙ СИБИРЬЮ ПО ДАННЫМ ДИСТАНЦИОННЫХ НАБЛЮДЕНИЙ

Many natural hazards are associated with deep convective clouds. Among them, mesoscale convective systems characterized by a large size and a long duration are the most dangerous. The estimates of their area, cloud top height, moisture content, duration, and intensity of related thunderstorm activity for Western Siberia were obtained using the data of radio and optical (passive and active) satellite sounding (for the summer months in 2010-2019) and World Wide Lightning Location Network (WWLLN, 2016-2020).

НАПРАВЛЕНИЯ СОВЕРШЕНСТВОВАНИЯ ПАССИВНЫХ РАДИОТЕХНИЧЕСКИХ СРЕДСТВ МОНИТОРИНГА ГРОЗОВОЙ АКТИВНОСТИ

The options for the development of passive radio engineering facilities for monitoring thunderstorm activity are presented. They allow reducing errors in determining the coordinates of lightning discharges by large-base systems by taking into account the transformation of atmospheric forms during the propagation in the Earth-ionosphere waveguide channel and improving the visual representation of lightning activity data using clustering algorithms for more detailed analysis aimed at improving reliability of determination of the current stage of the thunderstorm cloud development, with probabilistic assessment of a degree of its thunderstorm hazard and short-term forecast of subsequent propagation.

Lake Victoria Thunderstorms: Radar-Observed Initiation and Storm Evolution Modes

Abstract The enhanced observation period during the HIGHWAY field campaign in East Africa provided the opportunity to obtain continuous ground-based radar observations over the Lake Victoria basin. This provided insight into thunderstorm initiation processes and thunderstorm evolution. This insight is significant for it can lead to nowcasting thunderstorms over Lake Victoria, which is particularly important because of the >200 000 fishers using the lake daily and the extremely high number of drownings resulting from capsized boats caused by large waves and high winds from thunderstorms. Radar data from the south shoreline of Lake Victoria made it possible to observe thunderstorm activity over the entire lake. Unexpectedly the radar returns from high concentration of insects over the lake made it possible for the radar to observe boundary layer convergence lines. With this information a radar-trained forecaster could provide nowcasts of severe storm locations and by using extrapolation techniques provide nowcasts of their future location. In addition, rules for forecasting the timing and extent of nighttime thunderstorm activity over the lake based on radar monitoring of earlier activity along the northeast land/lake region are provided. While there are many obstacles to overcome, it is hoped that in the near future this possible life-saving information can be provided to Lake Victoria boaters. Significance Statement Radar data from the south shore of Lake Victoria has enabled new understanding of thunderstorm initiation and evolution over the lake. This understanding provides the potential to nowcast thunderstorms over Lake Victoria. This is particularly important because of the extremely high number of drownings that occur over the lake that result from capsized boats caused by large waves and high winds from thunderstorms. Radar-based rules are provided for forecasting and nowcasting the timing and severity of Lake Victoria thunderstorms.

Impact of aerosols and reactive trace gases concentrations in India

The current scenario united the elite professionals, researchers and scientists throughout the globe to accelerate the sharing of scientific findings making the future brighter on mother Earth. The concentration of reactive trace gases in the atmosphere modulates the human health appreciably. This study presents the changes of aerosol and reactive gases load in the atmosphere from the recent past with the help of CAMS data in Indian domain. Reactive trace gases and aerosols (NO2, O3, SO2, CO & AOD) are now being recognised as having both positive and negative radiative forcing effects. The effects of changes have been studied and found that the concentration of chemically reactive gases and aerosols load drop down from their 17 years long period average (LPA) appreciably (60-70 %) over IGP and 35-40 % in other parts of India except O3 (Increase 20-30 %) in India during the month of April-2020.
 It is observed that the results are agrees quite well with the actual recorded data of CPCB stations located at 12 different places of India. The difference observed between actual observations and CAMS reanalysis during April -2019 & 2020 show that aerosol load in terms of PM-2.5 & PM-10 is appreciably drop down (60-70 %) over IGP and 25-30 % in other parts of India. The concentration of other reactive gases (NO2, SO2 &CO) also drops down about 32 %, 7 %, 17 % over IGP and 16 %, 8 %, 9 % in other parts of India respectively. The concentration of Ozone shows slightly positive behaviour over IGP and negative at other parts of India. 
 Few pockets of Central and South of India show higher concentration may due to ongoing essential activities of cluster of industries or delayed slowdown. The other reason may be the influx of moisture due to the pre-monsoon thunder storm activity during this period. Vertical air flow Omega (positive) at 850 hPa NCEP/NCAR reanalysis also support the confinement of gases at lower levels. This study is further brought out a message for future that we should use the natural resources judiciously as their long term consumption can cause severe health problems and a psychological burden or stress globally during this COVID-19 spread period.

Thunderstorm Activity and Extremes in Vietnam for the Period 2015–2019

Within a meteorological capacity building project in Vietnam, lightning location data and manual (human-observed) thunderstorm day observations were analyzed for the period 2015–2019. The lightning location dataset, based on the global lightning detection system Vaisala GLD360, consists of a total of 315,522,761 lightning strokes. The results indicate that, on average, 6.9 million lightning flashes per year occur in the land areas of Vietnam; this equals a lightning flash density of 20 flashes km−2 yr−1. The largest average annual flash density values occur in three regions in North, Central and South Vietnam. The majority of lightning occurs in the monsoon season (April–September), peaking in May, while in October–March, the lightning activity is very modest. During individual intense thunderstorm days, the flash density may exceed 12 flashes km−2 day−1. Thunderstorms in Central Vietnam are generally more intense, i.e., more lightning is expected on average per one thunderstorm day in Central Vietnam than in other regions. This study is a continuation of several years of meteorological capacity building in Vietnam, and the results suggest that large socio-economic benefits can be received by understanding the local thunderstorm climatology in high detail, especially in a country such as Vietnam, where lightning causes substantial socio-economic losses annually.

SYNOPTIC CONDITIONS OF FORMATION AND FORECASTING OF THUNDERSTORMS IN THE TVER REGION

Цель исследования - на основе анализа многолетней динамики грозовой активности и метеорологических условий на территории Тверской области выявить основные синоптические условия образования гроз, и рассмотреть методы прогнозирования гроз и их оправдываемость на примере методов Вайтинга и индексов неустойчивости атмосферы. The purpose of the study is to identify the main synoptic conditions for the formation of thunderstorms on the basis of an analysis of the long-term dynamics of thunderstorm activity and meteorological conditions in the Tver region and to consider methods for forecasting thunderstorms and their justification on the example of Waiting's methods and atmospheric instability indices.

Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation

Abstract. El Niño–Southern Oscillation (ENSO) modulates severe thunderstorm activity in the US, with increased activity expected during La Niña conditions. There is also evidence that severe thunderstorm activity is influenced by the Arctic Oscillation (AO), with the positive phase being associated with enhanced activity. The combined ENSO–AO impact is relevant for situations such as in early 2021, when persistent, strong positive and negative AO events occurred during La Niña conditions. Here we examine the relation of a spatially resolved tornado environment index (TEI) with ENSO and the AO in climate model forecasts of February, March, and April conditions over North America. Bivariate composites on Niño 3.4 and AO indices show that TEI predictability is high (strong signals and probability shifts) when the ENSO and AO signals reinforce each other and low when they cancel each other. The largest increase in the expected value and variance of TEI occurs when Niño 3.4 is negative, and the AO is positive. Signal-to-noise ratios are higher during El Niño–negative AO than during La Niña–positive AO, but probability shifts are comparable.

Meteors observations by the orbital telescope TUS

The TUS (Tracking Ultraviolet Set-up) detector is the first fluorescence telescope aimed to measuring Extensive Air Showers (EAS) from space and operated till December 4th, 2017. Despite the main operation mode with a 0.8 μs temporal resolution of the TUS detector was devoted for EAS detection, also it was able to measure different slower luminescent phenomena in the near ultraviolet range. One of the TUS operation modes had 6.6 ​ms temporal resolution and was used to measure micro-meteors and thunderstorm activity. The high sensitivity of the device due to large area of an optical system, makes it a potentially powerful tool for studying dim and fast glow in the Earth's atmosphere. In this work we present the kinematics reconstruction of 13 events recorded by the TUS during 250 ​h of operation, which possess the expected characteristics produced by a meteor (characteristic linear track and light curve). We discuss the possible source of them and their luminosity. This experience of orbital meteor observations is useful for planning similar research in the future more sensitive space missions. • Reconstruction of meteoroid kinematics measured by orbital detector. • Meteor detection with temporal resolution of milliseconds. • Orbital highly sensitive UV telescope is a powerful detector of weak meteor glow.

Atmospheric Storm Anomalies Prior to Major Earthquakes in the Japan Region

Connections between atmospheric perturbations, e.g., thunderstorm activity, and major earthquakes are investigated along with the lithosphere–atmosphere coupling mechanism, concerning the earthquake prediction models. The present research attempts to recognize a possible link between atmospheric processes (rainfall, storms) and subsequent earthquakes (M > 6) across a wide area around Japan. Earthquake data and upper-atmosphere sounding data related to the Severe Weather Threat (SWEAT) index and Skew-T plots were obtained from two Japanese radiosonde stations, Hachijojima and Kagoshima. Using the cross-correlation function (CCF) method, it is shown that SWEAT conditions existed within 30 days before six major earthquakes in 2017 in the Japan region. The Seismo-Climatic Index (SCI) reached a mean of 2.00, 7–8, and 13–14 days before these earthquakes, indicating thunderstorms and extreme weather conditions, further supported by Skew-T plots. Low-pressure systems, deviating from the mean by as much as −50 to −250 m, and hot spots of increased precipitation ranging from ~80 to ~140 mm rainfall within 24 h were observed to be geographically associated with these earthquake events. The anomalous atmospheric conditions can be understood based on increased air ionization at the ground-to-air interface due to the influx of positive-hole charge carriers that are stress-activated deep in the lithosphere and spread through the rock column. When the positive electronic charge carriers are accumulated at the lithosphere, preferentially at topographic highs, some steep electric fields are observed capable of field-ionizing the air. The airborne ions then act as condensation nuclei for atmospheric moisture, thermal updrafts, cloud formation, and a statistically significant precipitation increase. This research was conducted based on some experimental indicators in a very important seismological region to examine the successfulness of the proposed mechanism and the given indicators as the possible proxies of pre-earthquake precursors. Hence, the main practical implication of the research can highlight a sustainable way for improving the managerial tools in the field of earthquake prediction.

Coarse sea spray inhibits lightning

The known effects of thermodynamics and aerosols can well explain the thunderstorm activity over land, but fail over oceans. Here, tracking the full lifecycle of tropical deep convective cloud clusters shows that adding fine aerosols significantly increases the lightning density for a given rainfall amount over both ocean and land. In contrast, adding coarse sea salt (dry radius > 1 μm), known as sea spray, weakens the cloud vigor and lightning by producing fewer but larger cloud drops, which accelerate warm rain at the expense of mixed-phase precipitation. Adding coarse sea spray can reduce the lightning by 90% regardless of fine aerosol loading. These findings reconcile long outstanding questions about the differences between continental and marine thunderstorms, and help to understand lightning and underlying aerosol-cloud-precipitation interaction mechanisms and their climatic effects.

Thunderstorm Activity Under Intermediate and Extreme Climate Change Scenarios

AbstractAssessing how increasing greenhouse gas concentrations may modify regional climates is an ongoing challenge. Relatively little work has examined how climate change may influence processes related to regional thunderstorm activity. This is important to consider in areas where thunderstorms are important for maintaining regional hydroclimates. This study focuses on three convection‐allowing climate simulations—namely, a retrospective simulation (1990–2005) and two possible climate change scenarios (2085–2100)—with domains encompassing the conterminous United States. Regional and seasonal variability is noted in the response of thunderstorm activity as measured by thresholds in simulated radar reflectivity factor in the two climate change scenarios. A decrease in thunderstorm activity is projected for the Southern Plains, whereas the Southeast and Midwest experience an increase in thunderstorm activity. An examination of environmental parameters related to thunderstorm activity reveals an overall increase in convective instability but spatially varying changes in convective inhibition.

Estimate of the source parameters of terrestrial gamma-ray flashes observed at low-Earth-orbit satellites

A special attention has been paid in the past decades to studies of terrestrial gamma-ray flashes (TGFs) observed above active thunderstorms. The physical mechanism of the TGF generation and its source location in the atmosphere have not been firmly established. A numerical modelling, such as Monte Carlo simulation, is commonly used to analyze the problem having regard to the complexity of basic electrodynamic and transport equations. Here, in contrast to previous numerical studies, we have constructed a suitably idealized analytical model of a point source of gamma-rays in a vertically inhomogeneous atmosphere. An energy-distribution of gamma photons is assumed to be determined by the energy spectrum of electron bremsstrahlung resulted from the relativistic runaway electron avalanche in a strong electric field. The absorption of photon energy due to photoelectric effect, Compton scattering and the electron-positron pair production have been accounted for approximately with an effective coefficient of energy absorption. A photon mean free path in the atmosphere is assumed to be dependent on its energy and altitude. A spatiotemporal distribution of gamma-ray flux density and photon fluence at a low-Earth orbit (LEO) are estimated as functions of the TGF source altitude, total number of photons emitted by the source, and other parameters. The model matches the LEO observations indicating that the TGF source is located at an altitude about 10−14 km. The same model can be applied for the description of the recently found downward-directed TGF detected by the large-area Telescope Array cosmic ray observatory.

Синхронные глобально наблюдаемые ультракороткопериодные импульсы

We have studied the properties of impulsive geomagnetic disturbances, which are observed synchronously at the network of induction magnetometers of the Institute of Solar-Terrestrial Physics (ISTP SB RAS) and Canadian stations of the CARISMA project [Mann, et al., 2008]. A feature of the pulses we detected is that their frequency range (f~5–30 Hz) lies at the junction of the ranges of two known classes of electromagnetic oscillations: ultra-low-frequency (ULF) oscillations (f<5–10 Hz), or geomagnetic pulsations, and extra-low frequency (ELF) oscillations (f~30–300 Hz); therefore, the 5–30 Hz range is poorly studied. The work is of undoubted interest for physics of processes in the magnetosphere–ionosphere–atmosphere system. Morphological analysis of the pulses detected has been carried out using data from ISTP stations. As a result, we obtained statistical characteristics of the pulses, plotted their dynamic spectra, and determined a number of unusual properties that distinguish them, on the one hand, from geomagnetic pulsations of the pulsed type (irregular pulsations of the Pi1B type), and, on the other hand, from higher frequency ELF and VLF signals (atmospherics, whistlers, etc.). On the basis of the results, we have made an assumption that a source of the pulses under study can be electrical sprites caused by powerful thunderstorms at middle and low latitudes. Using the results obtained by Wang, et al. in 2019 on spatial and temporal fixation of sprites in North China, we have confirmed that ultra-short-period pulses occur following the emergence of sprites. Thunderstorm activity, both local and global, is considered to be one of the main sources of excitation of the ionospheric Alfvén resonator (IAR), which plays an important role in coupling the ionosphere and the magnetosphere. The pulsed oscillations of interest may be one of the agents through which the energy of thunderstorms is transferred to IAR, thereby including the atmosphere in the system considered.

Synchronous globally observable ultrashort-period pulses

We have studied the properties of impulsive geomagnetic disturbances, which are observed synchronously at the network of induction magnetometers of the Institute of Solar-Terrestrial Physics (ISTP SB RAS) and Canadian stations of the CARISMA project [Mann, et al., 2008]. A feature of the pulses we detected is that their frequency range (f~5–30 Hz) lies at the junction of the ranges of two known classes of electromagnetic oscillations: ultra-low-frequency (ULF) oscillations (f<5–10 Hz), or geomagnetic pulsations, and extra-low frequency (ELF) oscillations (f~30–300 Hz); therefore, the 5–30 Hz range is poorly studied. The work is of undoubted interest for physics of processes in the magnetosphere–ionosphere–atmosphere system. Morphological analysis of the pulses detected has been carried out using data from ISTP stations. As a result, we obtained statistical characteristics of the pulses, plotted their dynamic spectra, and determined a number of unusual properties that distinguish them, on the one hand, from geomagnetic pulsations of the pulsed type (irregular pulsations of the Pi1B type), and, on the other hand, from higher frequency ELF and VLF signals (atmospherics, whistlers, etc.). On the basis of the results, we have made an assumption that a source of the pulses under study can be electrical sprites caused by powerful thunderstorms at middle and low latitudes. Using the results obtained by Wang, et al. in 2019 on spatial and temporal fixation of sprites in North China, we have confirmed that ultra-short-period pulses occur following the emergence of sprites. Thunderstorm activity, both local and global, is considered to be one of the main sources of excitation of the ionospheric Alfvén resonator (IAR), which plays an important role in coupling the ionosphere and the magnetosphere. The pulsed oscillations of interest may be one of the agents through which the energy of thunderstorms is transferred to IAR, thereby including the atmosphere in the system considered.

A Study on TGF Detectability at 2165 m Altitude: Estimates for the Mountain-Based Gamma-Flash Experiment

Gamma-Flash is an Italian program devoted to the realization of both a ground-based and an airborne gamma-ray and neutron detection system, for in situ measurements of high-energy phenomena correlated to thunderstorm activity, such as Terrestrial Gamma-ray Flashes (TGFs), gamma-ray glows, and associated neutron emissions. The ground-based Gamma-Flash experiment is currently under installation at the Osservatorio Climatico “Ottavio Vittori” (CNR-ISAC) on Mt. Cimone, in Northern-Central Italy (2165 m a.s.l.), and it will be operational starting in Summer 2022. We studied the detectability of TGFs in the surroundings of the ground-based Gamma-Flash experiment, to identify an investigable spatial region around the detectors from which typical TGFs can survive and be revealed onground. We carried out numerical simulations of gamma-ray propagation in the mid-latitude atmosphere, and we developed a qualitative analytical model to integrate the results. This analysis allows one to identify a spatial region extending up to 4 km distance on ground and up to 10 km altitude a.s.l., considering typical TGFs emitting ∼1018 gamma-ray photons at the source. Lightning sferics data acquired by the LINET network demonstrate that such a region is interested by frequent cloud-to-ground and intra-cloud lightning, pointing out the suitability of the location for the purposes of the Gamma-Flash program.

Thunderstorm Activity over the Qinghai–Tibet Plateau Indicated by the Combined Data of the FY-2E Geostationary Satellite and WWLLN

Thunderstorm activity over the Qinghai–Tibet Plateau (QTP) has important climatic effects and disaster impacts. Using the thunderstorm feature dataset (TFD) established based on the black body temperature (TBB) and cloud classification (CLC) products of the Fengyun-2E (FY-2E) geostationary satellite, as well as the lightning data of the World Wide Lightning Location Network (WWLLN), the temporal and spatial distributions and some cloud properties of the thunderstorms over the QTP were analyzed. Approximately 93.9% and 82.7% of thunderstorms over the QTP occur from May to September and from 12 to 21 o’clock local time, and the corresponding peaks are in August and at 14:00, respectively. There are three centers featuring frequent thunderstorms in the southeast, south-central, and southwest regions of the QTP. The average thunderstorm cloud area (the region with TBB ≤ −32 °C) is 1.8 × 104 km2. Approximately 32.9% of thunderstorms have strong convective cells (SCCs) composed of areas with TBB ≤ −52 °C. The average number and area ratio of SCCs are 3.6 and 25.4%, respectively, and their spatial distribution is given. The average cloud area and the number and area ratio of SCCs of extreme-lightning thunderstorms (thunderstorms with the top 10% of lightning numbers) are approximately 30.0, 3.9, and 1.5 times those of normal thunderstorms. The spatial distribution of the thunderstorm activity is quite different from that of lightning activity given by the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) over the northeastern and southwestern QTP, which may mean that the convection intensity, cloud structure, and charge structure of the thunderstorms over the QTP are different between different regions and seasons.

Thunderstorm activity at high latitudes observed at manned WMO weather stations

AbstractOngoing global warming particularly affects the coldest regions of our planet, where thunderstorm activity is considered to be the lowest. Scientific studies usually predict that lightning will become more frequent in polar areas in a warmer world. The aim of this study is to test this hypothesis and present the current knowledge on thunderstorm occurrence at high latitudes (>60°) based on SYNOP data from manned WMO stations operating from 2000 to 2019. According to this source, most thunderstorm events at high latitudes occur in summer (85%), when the air temperature ranges from 15 to 25°C (70%), during the days with positive temperature anomalies (75%) and negative sea‐level pressure anomalies (65%). The highest thunderstorm activity is observed over inland areas, especially in the European part of Russia. The changes in thunderstorm frequency are only visible at certain WMO manned stations and mostly during the summer months. The regional Kendall test revealed a statistically significant increase in the number of thunderstorm days north of 60°N in Interior Alaska, northwestern Canada, much of Siberia and European Russia. A decrease in thunderstorm frequency over a larger area was detected only on the shores of the southern Norwegian Sea, and seasonally in spring in the northern Urals. The observed trends were strongest in the Central Siberia and Interior Alaska regions, where the increase in the number of thunderstorm days exceeded 5 per decade. For the entire high‐latitude area, the change in the number of days with thunderstorms was statistically insignificant, but for stations located 250–1,000 km from the coastline, the averaged increase amounted 1 day per decade.