Distribution Of Thunderstorms Research Articles

Thunderstorm climatology of Slovakia between 1984–2023

Thunderstorms are among the most extreme meteorological phenomena that can cause widespread destruction and loss of life. Their occurrence varies significantly across different regions and times of the year. Despite various studies on thunderstorm activity across Central Europe, direct analyses based on data from the Slovak territory still need to be made available. Given Slovakia’s diverse natural conditions, there is a need for detailed knowledge about the frequency and spatial distribution of thunderstorms in this region. To address this knowledge gap, we analysed the frequency and spatiotemporal distribution of days with thunderstorm occurrences in Slovakia between 1984 and 2023, utilising climatological data from the Slovak Hydrometeorological Institute. We limited our analysis to data of days with close thunderstorms (thunderstorms occurring within 3 km of the monitoring station). Our findings reveal a significant variation in thunderstorm occurrences across Slovakia, with peak activity in the summer, especially in June and July. However, the spatial distribution of thunderstorms differed significantly across the country, with the highest frequency observed in mountainous regions and the east-central part of Slovakia. We found significant deceasing signals of the thunderstorm activity trends during the studied period, including analyses during the colder part of the year. Furthermore, our results underscore the critical role of synoptic situations in shaping these trends, where changes in certain atmospheric patterns were closely aligned with variations in thunderstorm frequency. The interaction between these synoptic conditions and regional topography was particularly evident, reinforcing the notion that topographical and environmental complexities substantially contribute to the observed thunderstorm distribution.

Developing an urban thunderstorm climatology for the Bangkok Metropolitan Region

This investigation builds upon and extends prior lightning research in the Bangkok Metropolitan Region (BMR) through the reconstruction of thunderstorm distribution, utilizing a novel lightning tracking algorithm. Five years (2016–2020) of lightning stroke data from the Global Lightning Dataset (GLD360) were used to identify 52 608 thunderstorms. Optimized hotspot analyses, track densities, and analyses of thunderstorms with respect to winds, landcover, and seasons were performed. Our findings suggest that significant modification of thunderstorm distribution within the region was due to urban landcover impacts on the local environment. Thunderstorm intensity, as measured by stroke counts and track length, also appeared to be sensitive to the urban environment. The thunderstorm distribution also highlighted areas prone to hazards such as flash flooding. By visualizing thunderstorms grouped by winds, thunderstorm initiation hotspots and track density corridors were identified. These corridors of augmented thunderstorm production tended to occur during specific months given the seasonal monsoon wind regime occurring across the BMR. As urbanization within the BMR continues, geospatial assessment of thunderstorms is important to inform forecast meteorologists, urban planners, government officials, and others who play a critical role in developing strategies, policies and insfrastructure that could mitigate thunderstorm impacts.

Seasonal dependence of the equatorial electrojets generated by thunderstorms

A model for the distribution of the ionospheric potential which drives the ionospheric currents closing the electric currents from/to the atmosphere is constructed. It is a part of the global electric circuit (GEC). Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric or ionospheric generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on high conductivity along the geomagnetic field. The model of the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network is used as a proxy for the electric currents to the ionosphere from the atmosphere above thunderstorm regions. The global distributions of the electric potential in the ionosphere are calculated for twelve months during a year with low solar activity. The designed models contain the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 200 A, and night-time ones (which are up to only half this value), while the total current of the GEC is taken equal between 1.5 and 2.5 kA in our model to satisfy the Carnegie data for the simulated dates and UT. The results are presented as diagrams of the currents in the electrojets depending on the geomagnetic longitude and month for 04 and 18 UT. These times are chosen to be the times of minimum and maximum fair weather electric field in accordance with the Carnegie results. The diagrams could help us to choose optimal conditions for measurements of the magnetic perturbations observed on the ground or by satellites to find the electrojets of the GEC which are obtained in our simulations.

METHODOLOGICAL FEATURES OF CALCULATING ERRORS IN THE MEASUREMENT OF ELECTROSTATIC FIELD STRENGTH

Measuring the intensity of the electric field of the atmosphere today has become a widespread task of modern meteorology. After all, the distribution of the intensity of the local electric field near the surface of the earth is closely related to the global distribution of thunderstorms and electrified clouds.
 The force characteristic of an electric field is its intensity. The change in the atmospheric electric field occurs relatively slowly, so electrostatic field mill (EFM) are most widely used to measure the electric field strength.
 Electrostatic field mills have been used to monitor the electric field in good weather, measure the vertical electric field inside clouds, and observe the movement and evolution of storms. Various designs of EFM have been developed and documented for more than a century, but since the subject is not popularized, their construction methods and calculation features are not documented. Therefore, there was a need to generalize the structure of the device and calculate its metrological characteristics.
 The work is aimed at increasing the accuracy of measurement and improving the hardware of electrostatic field mills. The task of increasing the accuracy of measuring the electrostatic field on a straight line depends on reducing the errors that occur in the device. The causes of these errors can be attributed to the imperfection of the measurement method or the inconsistency of the measurement object to its model, as well as the properties of the measurement tools. In previous studies, the authors used a mathematical model of the EF sensor, which does not correspond to the real shape of the signal, which created the need for its improvement.
 In this work, the authors proposed and substantiated a universal mathematical model of the EFM sensor. The paper also provides an analysis of the components of the proposed mathematical model, which will allow choosing the optimal structural parameters of the EFM sensor, which will increase its sensitivity. In addition, the paper proposed its own functional scheme of the EFM and developed a methodology for calculating its instrumental error, which allows to single out critical parameters during the selection of components for the construction of the device.
 The aspects considered in this article substantiate the relevance of increasing the accuracy of measuring the electrostatic field strength. The work carried out is the beginning of research aimed at improving the hardware of electrostatic field mills.

WWLLN Data Used to Model the Global Ionospheric Electric Field Generated by Thunderstorms

Electric currents flowing in the atmospheric global electric circuit (GEC) are closed by ionospheric currents. The physical and mathematical approach to simulate the ionospheric potential which drives these currents has been described in our previous papers. Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric current sources or generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on the high conductivity along the geomagnetic field; the Pedersen and Hall conductivities are calculated using empirical models. The potentials in the E- and F-layers of the ionosphere are considered to be constant along each magnetic field line. The main progress in comparison with previous versions of the model is obtained through applying the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network. Under typical conditions for July, under low solar activity in 2008, at 18:00 UTC, the calculated maximum potential difference in the ionosphere is 54 V. This newest version of our model contains the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 65 A, and night-time ones (of up to 40 A), while the total current flowing in the GEC is taken to be equal to 1.43 kA in our model to satisfy the Carnegie curve, i.e. the diurnal variation of the vertical electric field at ground level with UTC. The maximum of the electric potential is shifted from Africa to South-East Asia in the new model. The equatorial electrojets also change their position, direction and intensity.

Relative Importance of Large‐Scale Environmental Variables to the World‐Wide Variability of Thunderstorms

AbstractThis study uses a 16‐yr Tropical Rainfall Measuring Mission (TRMM) Convective Features (CFs) and ERA‐Interim reanalysis data to investigate the relative importance of four large‐scale environmental variables to thunderstorms with random forest models. These four variables include Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), low‐level wind shear, and warm cloud depth (WCD). First, these selected four environmental variables show a distinguished difference between CFs with and without lightning flashes. Specifically, CFs with at least one flash have higher CAPE, CIN, and lower WCD than those without lightning. Then, using these four variables, the geographical distribution of thunderstorms, especially the land‐ocean contrast in the occurrence of thunderstorms, is closely reproduced with a global random forest model. Such results suggest that a random forest model with key large‐scale environmental variables can be a useful tool to estimate the occurrence of global lightning thunderstorms. The study also investigates the relative importance of the selected variables to the occurrence of thunderstorms regionally. Relatively higher skill scores in the regional random forest model than the global one indicate the variation of roles of large scale environment variables over different regions. Though the data‐driven models can be utilized to estimate the occurrence of global thunderstorms, how to link the regional relative importance of these variable to the physical processes of thunderstorms needs further investigation.

A spatiotemporal analysis of lightning in the Bangkok Metropolitan Region

ABSTRACT This investigation analyzes the spatiotemporal lightning distribution from 2016 through 2020 for the Bangkok Metropolitan Region (BMR). Results suggest that significant urban augmentation of the lightning and subsequent thunderstorm distribution is occurring in the BMR. The distribution of lightning across the BMR is shaped by wind direction, wind speed and location of urban land cover. There exists a prominent two-peak (May and October) monthly distribution in the BMR lightning activity. October lightning counts are nearly double the amount occurring in May, with a lull in activity during July, August and the dry monsoonal months of December through March. However, both the number of lighting days and hours remain elevated from April through October, with thunderstorm lightning productivity highest in October, April, and September respectively. Lightning activity in the BMR is most frequent between 1100–1300 and 1900–2300 Local Standard Time. Significant enhancement of the lightning distribution occurs downwind of the Bangkok central business district and appears to be dependent on both the wind direction and speed. As wind speeds decrease, results suggest the spatial distribution of lightning strokes and lightning days become more focused over downtown Bangkok.

The Global Electric Circuit and Global Seismicity

Basing on the catalogue of earthquakes with a magnitude of M ≥ 4.5 for the period 1973–2017, a UT variation with an amplitude of ~10% in the number of earthquakes is revealed and compared with a UT variation in the ionospheric potential (IP) with an amplitude of ~18%. We demonstrate that the amplitude of the UT variation in the number of deep-focus earthquakes is greater compared with that of crustal earthquakes, reaching 19%. The UT of the primary maxima of both the IP (according to modern calculations) and of earthquake incidence coincides (near 17:00 UT) and is, by 2 h, ahead of the classical Carnegie curve representing the UT variation in the atmospheric electric field on the ground surface. The linear regression equation between these UT variations in the number of deep-focus earthquakes and the ionospheric potential is obtained, with a correlation coefficient of R = 0.97. The results support the idea that the processes of earthquake preparation are coupled to the functional processes of the global electric circuit and the generation of atmospheric electric fields. In particular, the observed increase in thunderstorm activity over earthquake preparation areas, provided by air ionization due to radon emanation, yields a clue as to why the global thunderstorm distribution is primarily continental. Another important conclusion is that, in observing the longitudinal distributions of earthquakes against the IP distribution, we automatically observe that all such events occur in local nighttime hours. Considering that the majority of earthquake precursors have their maximums at local night and demonstrating the positive deviation from the undisturbed value, we obtain a clue as to its positive correlation with variations in the ionospheric potential.

Time distribution of thunderstorms observed at Odesa AMSC at the beginning of the 21st century

The article presents the results of the research of thunderstorm activity at Odesa AMSC for the period of 2000-2019. Under conditions of intense warming, thunderstorm activity responds to the changes of temperature, humidity, radiation regime and atmospheric composition. Modern climate changes that are characterized by rising air temperatures have a decisive influence on the conditions under which dangerous weather phenomena are formed, thus monitoring of the thunderstorms formation in Ukraine is of great importance.
 The research includes the analysis of synoptic conditions of thunderstorm activity formation such as air-mass processes, frontal activity, and studies daily and daytime variability of the number of thunderstorm cases for the given period. The results of everyday meteorological observations of atmospheric phenomena conducted by Odesa AMSC within the period of 2000-2019 were used as input data to determine the characteristics of thunderstorm activity over city of Odesa. In order to identify the presence, time and duration of thunderstorm activity aviation weather diaries AV-6 were also reviewed. Certain synoptic materials were used to analyze the types of phenomena. Such materials include interactive database ARMsyn, surface synoptic charts for the periods of observation before and during the thunderstorms.
 It was established that during the period under study air-mass thunderstorms were formed in 370 cases of thunderstorm activity observed at the given observation post. Frontal thunderstorms occur less often: 241 cases over 20 years. The largest number of such thunderstorms is cold front thunderstorms amounting to 129 cases. 75 of them were identified as occlusion front thunderstorms. The least frequent were warm front thunderstorms – only 37 cases constituting 15% of the total number of frontal formations.
 During the studied period a total number of 620 thunderstorm cases was recorded, 195 of which are dry thunderstorms. Considerable attention is paid to the daily and daytime variability of thunderstorm cases number recorded by Odesa AMSC. With relation to the daily variation, more thunderstorms are observed during daytime amounting to 393 cases, 130 of which are dry thunderstorms. Night thunderstorms amount to 227 cases, 65 of which are dry thunderstorms. With relation to daytime distribution, more thunderstorms were detected in the afternoon.

A new link between El Niño—Southern Oscillation and atmospheric electricity

The global electric circuit (GEC) is a unique atmospheric system driven by the global distribution of thunderstorms and electrified shower clouds. The GEC unites electric fields and currents in the entire atmosphere and is characterized by the permanent production and dissipation of huge amounts of electrical energy. In this study, aimed at investigating the links between the GEC and El Niño—Southern Oscillation (ENSO), the GEC variability during 2008–2018 is simulated on the basis of reanalysis meteorological data using the Weather Research and Forecasting model and a parameterization of the ionospheric potential (IP), which is a natural measure of the GEC intensity. Modelling shows that strong El Niño and La Niña events influence the global distribution of electrified clouds over the Earth’s surface, thereby consistently affecting the shape of the diurnal variation of the GEC. Further analysis shows that anomalies in the Niño 3.4 sea surface temperature, which characterize the ENSO phase, and anomalies in the relative IP are positively correlated at 9:00–15:00 UTC and negatively correlated at 18:00–23:00 UTC. This correspondence between ENSO and the GEC is most prominent at 13:00 UTC and 21:00 UTC, and most pronounced anomalies in the relative IP around these hours are precisely associated with strong El Niño and La Niña events. In particular, during strong El Niños the relative IP is larger than usual around 13:00 UTC and smaller than usual around 21:00 UTC, whereas during strong La Niñas it behaves oppositely.

Analysis of lightning discharges activity within the territory of Buryatia in 2010-2016 based on WWLLN data

Thunderstorm activity is the main natural cause of forest fires. The development of new or modernization of existing systems for monitoring and forest fires forecasting requires the involvement of data on the spatial and temporal distribution of thunderstorms in monitorable forest areas. This article discusses the territory of the Republic of Buryatia (Russian Federation). The study of the spatial and temporal components of thunderstorm activity was carried out based on the World Wide Lightning Location Network (WWLLN) data. WWLLN data on thunderstorms locations for 2010-2016 were used. The network registers lightning discharges during the year. The thunderstorm season lasts from May to September. Archival WWLLN data for this period were selected. The resulting dataset allowed us to distinguish areas with different lightning activity. A high degree of spatial nonuniformity of thunderstorm activity in Buryatia was established. The number of lightning discharges begins to increase in May, the maximum is observed in July, and a recession occurs in August. Two daily maximum were revealed: the first maximum of number of lightning discharges is in the interval from 12 to o’clock and the second is about 19 o’clock of local time.

Analysis and forecast spatiotemporal distribution of thunderstorms and hail the territory of Belarus

The article is devoted to the study of the problem of ensuring the safety of aircraft during take-off and landing. Thunderstorm and hail is one of the most dangerous meteorological phenomena in aviation. To prevent accidents associated with these phenomena, it is necessary to clearly understand the patterns of their occurrence and spatial distribution. In connection with the rapid growth of passenger and cargo traffic, it is necessary to be able to receive and provide actual meteorological information in real mode, as well as to be able to receive high-quality and timely weather forecast. To study the spatial-temporal patterns of the distribution of thunderstorms and hail, Belgidromet’s meteorological instrumental data for 1989–2016 was processed, synoptic maps were analyzed in comparison with calculated forecasts, including WRF, and maps were made using ArcGIS.

MODIFICATIONS OF MESOSPHERIC CONDUCTIVITY IN SUDDEN IONOSPHERE DISTURBANCES AND CHANGES OF THE SCHUMANN RESONANCE FREQUENCIES

We present a technique for detecting modifications of the peak frequencies of Schumann resonance during the sudden ionospheric disturbances (SID) caused by the solar X-ray flares. A SID is associated with a sharp lowering of ionosphere at the sunlit hemisphere during the solar flares, which decreases the average ionosphere height increases Schumann resonance frequencies. The resonance frequencies and the characteristic heights of ionosphere are computed using the full wave solution for SID of different intensity. Power spectra of EZ field are computed using the 2D telegraph equations for the uniform distribution of thunderstorms in the cavity for several observer positions relative to the solar terminator. The weighted average frequency was found and linear dependence was found of this frequency on the SID intensity and/or on alteration of magnetic characteristic height. Results might be used in interpretations of Schumann resonance observations and estimation of ionosphere modification.

Vertical profile of atmospheric conductivity that matches Schumann resonance observations.

We introduce the vertical profile of atmospheric conductivity in the range from 2 to 98 km. The propagation constant of extremely low frequency (ELF) radio waves was computed for this profile by using the full wave solution. A high correspondence is demonstrated of the data thus obtained to the conventional standard heuristic model of ELF propagation constant derived from the Schumann resonance records performed all over the world. We also suggest the conductivity profiles for the ambient day and ambient night conditions. The full wave solution technique was applied for obtaining the corresponding frequency dependence of propagation constant relevant to these profiles. By using these propagation constants, we computed the power spectra of Schumann resonance in the vertical electric field component for the uniform global distribution of thunderstorms and demonstrate their close similarity in all the models. We also demonstrate a strong correspondence between the wave attenuation rate obtained for these conductivity profiles and the measured ones by using the ELF radio transmissions.

Sensitivity of the distribution of thunderstorms to sea surface temperatures in four Australian east coast lows

The relationship between the sea surface temperature (SST) distribution and the locations of thunderstorms during four Australian east coast lows is investigated using both lightning observations and numerical simulation results. The focus is placed on investigating changes in convective instability caused by the introduction of complex, high-resolution ocean eddy, and frontal structures present in Bluelink SST datasets. Global Position and Tracking System lightning data are overlaid on maps of SST to investigate whether a thunderstorm–SST relationship is discernible. Weather Research and Forecast model simulations are used to establish what atmospheric changes contribute to the observed distributions of thunderstorms. Maximum convective available potential energy (MCAPE) analysis shows a distinct relationship to the SST distribution. In particular, areas of elevated MCAPE are related to regions of warmer SST with horizontal advection often displacing increased MCAPE downwind of the warmer SST. At short timescales of 3–6 h, the differences in MCAPE become larger and more localised and show a strong correlation with the observed lightning. This suggests that at times the thunderstorms are directly related to the complex structures in the detailed SST dataset. For the damaging Pasha Bulker case, the plume of thunderstorms associated with the coastal damage occurs downwind of the region of enhanced MCAPE on the southern flank of the warm eddy. Based on these results, it is concluded that the particular features of the warm eddy enhanced the thunderstorm potential over the coastal region during this event and helped in localising the area of greatest impact for thunderstorm-related intense rainfall.

An Assessment of Temporal and Spatial Distribution of Thunder Storms in Iran

The main purpose of this study is to investigate temporal and spatial distribution of thunderstorm frequency in Iran. In order to do study, observed statistical data of the present weather codes of thunderstorm (17, 29, 91 - 99) in 50 synoptic stations around the country were used in a 35 years statistic period (1979-2013). The results of the study showed that the phenomenon occurs mostly in southwest, west and northwest regions of Iran. Thunderstorm occurrence reduces when moving toward east. Maku station in northwest of Iran shows the maximum thunderstorm frequency during the statistical period (mean annual of 31). Jask station in southern Iran (mean annual of 2) has shown minimum thunderstorm occurrence during the statistical period. In the eastern regions of Iran, Torbat Heydarieh station revealed higher frequency than the other stations which was because of high mountains like Qaenat. In terms of temporal distribution, spring showed the highest frequency of the phenomenon. In monthly scale, the maximum frequency of hail downfall happens in April and May. In hourly scale, the maximum occurrence of thunderstorm observed at 12 - 18 p.m. for UTC time.

Precipitation changes due to the introduction of eddy-resolved sea surface temperatures into simulations of the “Pasha Bulker” Australian east coast low of June 2007

Weather research and forecast (WRF) model simulations are used to investigate how the distribution of precipitation is related to the distribution of sea surface temperatures (SSTs) during the life cycle of the Australian east coast low of 7–9 June 2007. The focus is placed on investigating changes caused by the introduction of complex ocean eddy and filament structures present in the Bluelink ReANalysis (BRAN) SST data set. In the simulations, enhancement of rainfall is found over and downwind of warmer SSTs and suppression of rainfall over and downwind of cooler SSTs. Specifically, a large warm eddy present during this case is associated with an enhancement of rainfall along its downwind (southern) flank where a strong SST gradient exists. Overall, the model demonstrates considerable skill in simulating the event, although the simulated main rainband propagates southward earlier than observed. However, the maximum one hourly rainfall totals at the stations that received the greatest rainfall are greater and closer to the observed maxima when the BRAN SSTs are used. Global position and tracking system lightning data are overlaid on maps of SST and used to investigate whether a thunderstorm–SST relationship is discernable. An ensemble of WRF simulations is used to establish what atmospheric changes contribute to the observed distributions of thunderstorms. It is concluded that the complex upper ocean heat content structure present during this case significantly influenced the storm’s impact. Therefore, an accurate eddy resolving SST data set may be important for accurate forecasts of future storms of similar nature.

Warm Season Afternoon Thunderstorm Characteristics under Weak Synoptic-Scale Forcing over Taiwan Island

Abstract The spatial and temporal characteristics and distributions of thunderstorms in Taiwan during the warm season (May–October) from 2005 to 2008 and under weak synoptic-scale forcing are documented using radar reflectivity, lightning, radiosonde, and surface data. Average hourly rainfall amounts peaked in midafternoon (1500–1600 local solar time, LST). The maximum frequency of rain was located in a narrow strip, parallel to the orientation of the mountains, along the lower slopes of the mountains. Significant diurnal variations were found in surface wind, temperature, and dewpoint temperature between days with and without afternoon thunderstorms (TSA and non-TSA days). Before thunderstorms occurred, on TSA days, the surface temperature was warmer (about 0.5°–1.5°C) and the surface dewpoint temperature was moister (about 0.5°–2°C) than on non-TSA days. Sounding observations from northern Taiwan also showed warmer and higher moisture conditions on TSA days relative to non-TSA days. The largest average difference was in the 750–550-hPa layer where the non-TSA days averaged 2.5°–3.5°C drier. These preconvective factors associated with the occurrences of afternoon thunderstorms could be integrated into nowcasting tools to enhance warning systems and decision-making capabilities in real-time operations.

Climatological distribution and diurnal variation of mesoscale convective systems over China and its vicinity during summer

The climatological distribution of mesoscale convective systems (MCSs) over China and its vicinity during summer is statistically analyzed, based on the 10-year (1996–2006, 2004 excluded) June–August infrared TBB (Temperature of black body) dataset. Comparing the results obtained in this paper with the distribution of thunderstorms from surface meteorological stations over China and the distribution of lightning from low-orbit satellites over China and its vicinity in the previous studies, we find that the statistic characteristics of TBB less than −52°C can better represent the spatiotemporal distribution of MCSs over China and its vicinity during summer. The spreading pattern of the MCSs over this region shows three transmeridional bands of active MCSs, with obvious fluctuation of active MCSs in the band near 30°N. It can be explained by the atmospheric circulation that the three bands of active MCSs are associated with each other by the summer monsoon over East Asia. We focus on the diurnal variations of MCSs over different underlying surfaces, and the result shows that there are two types of MCSs over China and its vicinity during summer. One type of MCSs has only one active period all day long (single-peak MCSs), and the other has multiple active periods (multi-peak MCSs). Single-peak MCSs occur more often over plateaus or mountains, and multi-peak MCSs are more common over plains or basins. Depending on lifetimes and active periods, single-peak MCSs can be classified as Tibetan Plateau MCSs, general mountain MCSs, Ryukyu MCSs, and so on. The diurnal variation of multi-peak MCSs is very similar to that of MCCs (mesoscale convective complexes), and it reveals that multi-peak MCSs has longer life cycle and larger horizontal scale, becomes weaker after sunset, and develops again after midnight. Tibetan Plateau MCSs and general mountain MCSs both usually develop in the afternoon, but Tibetan Plateau MCSs have longer life cycle and more active MαCSs. Ryukyu MCSs generally develop after midnight, last longer time, and also have more active MαCS. The abundant moisture and favorable large-scale environment over Indian monsoon surge areas lead to active MCSs and MαCSs almost at any hour all day during summer. Due to local mountain-valley breeze circulation over the Sichuan Basin, MCSs are developed remarkably more often during the nighttime, and again there are also more active MαCSs. Because of local prominent sea-land breeze circulation over Guangxi and Guangdong, the MCSs over this region propagate from sea to land in the afternoon and from land to sea after midnight. The statistic characteristics of TBB less than −52°C clearly display the different climatological characteristics of MCSs owing to the thermal difference among water, land and rough terrain. Not only the large-scale atmospheric circulation but also the local atmospheric circulation caused by the thermal difference among water, land and rough terrain, to a great extent, determines the climatological distribution of MCSs over China and its vicinity during summer.

Variations in global thunderstorm activity inferred from the OTD records

We use the data on the planetary distribution of thunderstorms collected by optical transient detector (OTD) to derive the properties of global electric activity. Processing of optical data indicates that modern observations from space confirm the general concept of thunderstorm distribution and motion. Close similarity is demonstrated between the World Meteorological Organization data and modern records including Carnegie curve. Departures noted might be caused by thunderstorms redistribution owing to climate change; the issue deserves a special examination.