What is thunderstorm activity? Thunderstorm is a natural phenomenon

August 7, 2014

Thunderstorm - what is it? Where do the lightning that cuts across the entire sky and the menacing peals of thunder come from? A thunderstorm is a natural phenomenon. Lightning, called electrical discharges, can form inside clouds (cumulonimbus) or between the earth's surface and clouds. They are usually accompanied by thunder. Lightning is associated with heavy rain, strong winds, and often hail.

Activity

A thunderstorm is one of the most dangerous natural phenomena. People struck by lightning survive only in isolated cases.

There are approximately 1,500 thunderstorms operating on the planet at the same time. The intensity of the discharges is estimated at a hundred lightning strikes per second.

The distribution of thunderstorms on Earth is uneven. For example, there are 10 times more of them over the continents than over the ocean. The majority (78%) of lightning discharges are concentrated in the equatorial and tropical zones. Thunderstorms are recorded especially often in Central Africa. But the polar regions (Antarctica, Arctic) and the poles of lightning are practically not visible. The intensity of a thunderstorm turns out to be related to the celestial body. In mid-latitudes, its peak occurs in the afternoon (daytime) hours, in the summer. But the minimum was recorded before sunrise. Geographical features are also important. The most powerful thunderstorm centers are located in the Cordillera and Himalayas (mountainous regions). The annual number of “thunderstorm days” also varies in Russia. In Murmansk, for example, there are only four of them, in Arkhangelsk - fifteen, Kaliningrad - eighteen, St. Petersburg - 16, Moscow - 24, Bryansk - 28, Voronezh - 26, Rostov - 31, Sochi - 50, Samara - 25, Kazan and Ekaterinburg - 28, Ufa - 31, Novosibirsk - 20, Barnaul - 32, Chita - 27, Irkutsk and Yakutsk - 12, Blagoveshchensk - 28, Vladivostok - 13, Khabarovsk - 25, Yuzhno-Sakhalinsk - 7, Petropavlovsk-Kamchatsky - 1.

Development of a thunderstorm

How does it go? A thundercloud only forms under certain conditions. There must be upward flows of moisture, and there must be a structure where one fraction of the particles is in an icy state, the other in a liquid state. Convection that will lead to the development of a thunderstorm will occur in several cases.

Uneven heating of surface layers. For example, over water with a significant temperature difference. Over large cities, thunderstorm intensity will be slightly stronger than in the surrounding areas.

When cold air displaces warm air. The frontal convention often develops simultaneously with cover clouds and nimbostratus clouds.

When air rises in mountain ranges. Even low elevations can lead to increased cloud formations. This is forced convection.

Any thundercloud, regardless of its type, necessarily goes through three stages: cumulus, maturity, and decay.

Classification

For some time, thunderstorms were classified only at the observation location. They were divided, for example, into orthographic, local, and frontal. Now thunderstorms are classified according to characteristics depending on the meteorological environments in which they develop. Updrafts are formed due to atmospheric instability. This is the main condition for the creation of thunderclouds. The characteristics of such flows are very important. Depending on their power and size, different types of thunderclouds are formed, respectively. How are they divided?

1. Single-cell cumulonimbus, (local or intramass). Have hail or thunderstorm activity. Transverse dimensions range from 5 to 20 km, vertical dimensions - from 8 to 12 km. Such a cloud “lives” for up to an hour. After a thunderstorm, the weather remains virtually unchanged.

2. Multi-cell cluster. Here the scale is more impressive - up to 1000 km. A multi-cell cluster covers a group of thunderstorm cells that are at various stages of formation and development and at the same time make up one whole. How are they built? Mature thunderstorm cells are located in the center, disintegrating cells are located on the leeward side. Their transverse dimensions can reach 40 km. Cluster multi-cell thunderstorms produce gusts of wind (squally, but not strong), rain, and hail. The existence of one mature cell is limited to half an hour, but the cluster itself can “live” for several hours.

3. Squall lines. These are also multicell thunderstorms. They are also called linear. They can be either solid or with gaps. Wind gusts here are longer (at the leading edge). When approaching, a multi-cell line appears as a dark wall of clouds. The number of streams (both upstream and downstream) here is quite large. That is why such a complex of thunderstorms is classified as multi-cell, although the thunderstorm structure is different. A squall line can produce intense downpours and large hail, but is more often “limited” by strong downdrafts. It often occurs before a cold front. In the photographs, such a system has the shape of a curved bow.

4. Supercell thunderstorms. Such thunderstorms are rare. They are especially dangerous to property and human life. The cloud of this system is similar to the single-cell cloud, since both differ in one zone of updraft. But their sizes are different. The supercell cloud is huge - close to 50 km in radius, height - up to 15 km. Its boundaries may be in the stratosphere. The shape resembles a single semicircular anvil. The speed of upward flows is much higher (up to 60 m/s). A characteristic feature is the presence of rotation. It is this that creates dangerous, extreme phenomena (large hail (more than 5 cm), destructive tornadoes). The main factor for the formation of such a cloud is the surrounding conditions. We are talking about a very strong convention with temperatures from +27 and wind with variable direction. Such conditions arise during wind shears in the troposphere. Precipitation formed in updrafts is transferred to the downdraft zone, which ensures a long life for the cloud. Precipitation is unevenly distributed. Showers occur near the updraft, and hail occurs closer to the northeast. The tail of the storm may shift. Then the most dangerous area will be next to the main updraft.

There is also the concept of “dry thunderstorm”. This phenomenon is quite rare, characteristic of the monsoons. With such a thunderstorm there is no precipitation (it simply does not reach, evaporating as a result of exposure to high temperature).

Movement speed

For an isolated thunderstorm it is approximately 20 km/h, sometimes faster. If cold fronts are active, speeds may reach 80 km/h. In many thunderstorms, old thunderstorm cells are replaced by new ones. Each of them covers a relatively short distance (about two kilometers), but in total the distance increases.

Electrification mechanism

Where do lightning bolts themselves come from? Electric charges around and within clouds are constantly moving. This process is quite complicated. The easiest way to imagine the work of electric charges in mature clouds. The dipole positive structure dominates in them. How is it distributed? The positive charge is placed at the top, and the negative charge is located below it, inside the cloud. According to the main hypothesis (this area of science can still be considered little-explored), heavier and larger particles are charged negatively, while small and light ones have a positive charge. The former fall faster than the latter. This causes spatial separation of space charges. This mechanism is confirmed by laboratory experiments. Particles of ice grains or hail can have strong charge transfer. The magnitude and sign will depend on the water content of the cloud, air temperature (ambient), and collision speed (main factors). The influence of other mechanisms cannot be excluded. Discharges occur between the ground and the cloud (or neutral atmosphere, or ionosphere). It is at this moment that we see flashes cutting across the sky. Or lightning. This process is accompanied by loud peals (thunder).

A thunderstorm is a complex process. It may take many decades, and perhaps even centuries, to study it.

Ministry of Education of the Russian Federation
Kazan State University
Faculty of Geography and Ecology
Department of Meteorology, Climatology and Atmospheric Ecology
Thunderstorm activity in Predkamye
Course work
3rd year student, gr. 259 Khimchenko D.V.

Scientific supervisor Associate Professor Tudriy V.D. ________
Kazan 2007
Content

Introduction
1. Thunderstorm activity
1.1. Characteristics of thunderstorms
1.2. Thunderstorm, its influence on people and the national economy
1.3. Thunderstorms and solar activity
2. Methods for obtaining and processing initial data
2.1. Obtaining starting material
2.2. Basic statistical characteristics
2.3. Statistical characteristics of thunderstorm activity indices
2.4. Distribution of basic statistical characteristics
2.5. Trend analysis
2.6. Regression dependence of the number of days with thunderstorms on Wolf numbers
Conclusion
Literature
Applications
Introduction

The typical development of cumulonimbus clouds and precipitation from them is associated with powerful manifestations of atmospheric electricity, namely with multiple electrical discharges in the clouds or between clouds and the Earth. Such spark discharges are called lightning, and the accompanying sounds are called thunder. The whole process, often accompanied by short-term increases in wind - squalls, is called a thunderstorm.
Thunderstorms cause great damage to the national economy. Much attention is paid to their research. For example, in the main directions of economic and social development of the USSR for 1986-1990. and major events were envisaged for the period up to the year 2000. Among them, research into weather phenomena dangerous to the national economy and the improvement of methods for forecasting them, including thunderstorms and associated downpours, hail and squalls, have acquired particular importance. Nowadays, much attention is also paid to problems associated with thunderstorm activity and lightning protection.
Many scientists from our and foreign countries were involved in thunderstorm activity. More than 200 years ago, B. Franklin established the electrical nature of thunderstorms; more than 200 years ago, M.V. Lomonosov introduced the first theory of electrical processes in thunderstorms. Despite this, there is still no satisfactory general theory of thunderstorms.
The choice fell on this topic not by chance. Recently, interest in thunderstorm activity has been increasing, which is due to many factors. Among them: a more in-depth study of the physics of thunderstorms, improvement of thunderstorm forecasts and lightning protection methods, etc.
The purpose of this course work is to study the temporal features of the distribution and regression dependence of thunderstorm activity with Wolf numbers in different periods and in different regions of the Predkamye region.
Coursework objectives
1. Create a data bank on technical media of the number of days with a thunderstorm with ten-day discretization, as the main characteristics of thunderstorm activity, and Wolf numbers, as the main characteristic of solar activity.
2. Calculate the main statistical characteristics of the thunderstorm regime.
3. Find the equation for the trend in the number of days with thunderstorms.
4. Find the regression equation for the number of days with thunderstorms in Predkamye and Wolf numbers.
Chapter 1. Thunderstorm activity
1.1 Characteristics of thunderstorms

The main characteristics of its thunderstorms are: the number of days with thunderstorms and the frequency of thunderstorms.
Thunderstorms are especially common over land in tropical latitudes. There are areas where there are 100-150 days or more a year with thunderstorms. On the oceans in the tropics there are much fewer thunderstorms, approximately 10-30 days a year. Tropical cyclones are always accompanied by severe thunderstorms, but the disturbances themselves are rarely observed.
In subtropical latitudes, where high pressure prevails, there are much fewer thunderstorms: over land there are 20-50 days with thunderstorms per year, over the sea 5-20 days. In temperate latitudes there are 10-30 days with thunderstorms over land and 5-10 days over the sea. In polar latitudes, thunderstorms are an isolated phenomenon.
The decrease in the number of thunderstorms from low to high latitudes is associated with a decrease in the water content of clouds with latitude due to a decrease in temperature.
In the tropics and subtropics, thunderstorms are most often observed during the rainy season. In temperate latitudes over land, the greatest frequency of thunderstorms occurs in summer, when convection in local air masses develops strongly. In winter, thunderstorms in temperate latitudes are very rare. But over the ocean, thunderstorms that arise in cold air masses heated from below by warm water have a maximum frequency of occurrence in winter. In the far west of Europe (British Isles, coast of Norway) winter thunderstorms are also common.
It is estimated that 1,800 thunderstorms occur simultaneously on the globe and approximately 100 lightning strikes every second. Thunderstorms are observed more often in the mountains than on the plains.
1.2 Thunderstorm, its impact on people and the national economy

A thunderstorm is one of those natural phenomena that the most unobservant person notices. Its dangerous effects are widely known. Less is known about its beneficial effects, although they play a significant role. Currently, the problem of forecasting thunderstorms and associated dangerous convective phenomena seems to be the most pressing and one of the most difficult in meteorology. The main difficulties in resolving it lie in the discreteness of the distribution of thunderstorms and the complexity of the relationship between thunderstorms and the numerous factors influencing their formation. The development of thunderstorms is associated with the development of convection, which is very variable in time and space. Forecasting thunderstorms is also complicated because, in addition to predicting the synoptic situation, it is necessary to predict the stratification and humidity of the air at altitudes, the thickness of the cloud layer, and the maximum speed of the updraft. It is necessary to know how thunderstorm activity changes as a result of human activity. The influence of a thunderstorm on humans, animals, various activities; Issues related to lightning protection are also relevant in meteorology.
Understanding the nature of thunderstorms is important not only for meteorologists. The study of electrical processes in such gigantic volumes compared to the scale of laboratories makes it possible to establish more general physical laws of the nature of high-voltage discharges and discharges in aerosol clouds. The mystery of ball lightning can only be revealed by understanding the processes occurring in thunderstorms.
Based on their origin, thunderstorms are divided into intramass and frontal.
Intramass thunderstorms are observed in two types: in cold air masses moving to the warm earth's surface, and over heated land in the summer (local, or thermal thunderstorms). In both cases, the occurrence of a thunderstorm is associated with the powerful development of convection clouds, and, consequently, with a strong instability of atmospheric stratification and with strong vertical air movements.
Frontal thunderstorms are associated primarily with cold fronts, where warm air is forced upward by advancing cold air. In summer, over land they are often associated with warm fronts. Continental warm air rising above the surface of a warm front in summer can be very unstable stratified, so strong convection can occur over the surface of the front.
The following actions of lightning are known: thermal, mechanical, chemical and electrical.
The temperature of lightning reaches from 8,000 to 33,000 degrees Celsius, so it has a large thermal effect on the environment. In the USA alone, for example, lightning causes about 10,000 forest fires every year. However, in some cases these fires are beneficial. For example, in California, frequent fires have long cleared forests of growth: they were insignificant and not harmful to the trees.
The reason for the occurrence of mechanical forces during a lightning strike is a sharp increase in temperature, pressure of gases and vapors that arise at the point where the lightning current passes. So, for example, when lightning strikes a tree, the tree sap, after current passes through it, turns into a gas state. Moreover, this transition is explosive in nature, as a result of which the tree trunk splits.
The chemical effect of lightning is small and is due to the electrolysis of chemical elements.
The most dangerous action for living beings is electrical action, since as a result of this action a lightning strike can lead to the death of a living being. When lightning strikes unprotected or poorly protected buildings or equipment, it leads to the death of people or animals as a result of the creation of high voltage in individual objects, for this a person or animal only needs to touch them or be near them. Lightning strikes a person even during small thunderstorms, and each direct strike is usually fatal for him. After an indirect lightning strike, a person usually does not die, but even in this case, timely assistance is necessary to save his life.
Forest fires, damaged power and communication lines, damaged aircraft and spacecraft, burning oil storage facilities, agricultural crops destroyed by hail, roofs torn off by storm winds, people and animals killed by lightning strikes - this is not a complete list of the consequences associated with a thunderstorm situation.
The damage caused by lightning in just one year across the globe is estimated at millions of dollars. In this regard, new, more advanced methods of lightning protection and more accurate thunderstorm forecasts are being developed, which, in turn, leads to a more in-depth study of thunderstorm processes.
1.3 Thunderstorms and solar activity

Scientists have been studying solar-terrestrial connections for a long time. They logically came to the conclusion that it is not enough to consider the Sun only as a source of radiant energy. Solar energy is the main source of most physicochemical phenomena in the atmosphere, hydrosphere and surface layer of the lithosphere. Naturally, sharp fluctuations in the amount of this energy affect these phenomena.
The Zurich astronomer R. Wolf (R. Wolf, 1816-1893) was involved in systematizing data on solar activity. He determined that, on an arithmetic average, the period of the maximum and minimum number of sunspots - the maximums and minimums of solar activity - is equal to eleven years.
The growth of the stain-forming process from the point of minimum to maximum occurs in jumps with sharp rises and falls, shifts and interruptions. The jumps are constantly growing and at the moment of maximum they reach their highest values. These jumps in the appearance and disappearance of spots are apparently responsible for many of the effects that develop on Earth.
The most indicative characteristic of the intensity of solar activity, proposed by Rudolf Wolf in 1849, is the Wolf number or the so-called Zurich sunspot number. It is calculated by the formula W=k*(f+10g), where f is the number of spots observed on the solar disk, g is the number of groups formed by them, k is the normalization coefficient derived for each observer and telescope in order to be able to share the relative values found by them Wolf numbers. When calculating f, each core ("shadow") separated from an adjacent core by a penumbra, as well as each pore (a small spot without a penumbra) are considered spots. When calculating g, an individual spot and even an individual pore are considered a group.
From this formula it is clear that the Wolf index is a total index that gives a general characteristic of the sun's sunspot activity. It does not directly take into account the qualitative side of solar activity, i.e. power of spots and their stability over time.
The absolute Wolf number, i.e. counted by a particular observer is determined by the sum of the product of the number ten by the total number of groups of sunspots, with each individual sunspot counted as a group, and the total number of both single and sunspot groups. The relative Wolf number is determined by multiplying the absolute Wolf number by a normalization factor, which is determined for each observer and his telescope.
Restored from historical sources, starting from the mid-16th century, when calculations of the number of sunspots began, the information made it possible to obtain Wolf numbers averaged for each past month. This made it possible to determine the characteristics of solar activity cycles from that time until the present day.
The periodic activity of the Sun has a very noticeable effect on the number and, apparently, the intensity of thunderstorms. The latter are visible electrical discharges in the atmosphere, usually accompanied by thunder. Lightning corresponds to the spark discharge of an electrostatic machine. The formation of a thunderstorm is associated with the condensation of water. vapors in the atmosphere. The rising air masses are cooled adiabatically, and this cooling often occurs to a temperature below the saturation point. Therefore, vapor condensation can occur suddenly, droplets form, creating a cloud. On the other hand, for vapor condensation to occur, the presence of nuclei or condensation centers in the atmosphere is necessary, which, first of all, can be dust particles.
We saw above that the amount of dust in the upper layers of the air may be partly determined by the degree of intensity of the sunspot formation process on the Sun. In addition, during periods of sunspot passage across the solar disk, the amount of ultraviolet radiation from the Sun also increases. This radiation ionizes the air, and the ions also become condensation nuclei.
This is followed by electrical processes in water droplets, which acquire an electrical charge. One of the reasons causing these charges is the adsorption of light air ions by water droplets. However, the significance of this adsorption is secondary and very insignificant. It was also noticed that individual drops merge into a jet under the influence of a strong electric field. Consequently, fluctuations in the field strength and a change in its sign can have a certain effect on the droplets. This is probably how highly charged droplets are formed during a thunderstorm. A strong electric field causes the drops to also become charged with electricity.
The question of the periodicity of thunderstorms was raised in Western literature back in the 80s of the last century. Many researchers devoted their works to clarifying this issue, such as Zenger, Krassner, Bezold, Ridder, etc. Thus, Bezold pointed to the 11-day periodicity of thunderstorms, and then from the processing of thunderstorm phenomena for Southern Germany for 1800-1887. received a period of 25.84 days. In 1900 Ridder found two periods for the frequency of thunderstorms in Ledeberg for 1891-1894, namely: 27.5 and 33 days. The first of these periods is close to the period of rotation of the Sun around its axis and almost coincides with the lunar tropical period (27.3). At the same time, attempts were made to compare the periodicity of thunderstorms with the sunspot formation process. An eleven-year period in the number of thunderstorms was discovered by Hess for Switzerland.
In Russia, D. O. Svyatsky, based on his studies of the periodicity of thunderstorms, obtained tables and graphs, from which both the recurrence periods of so-called thunderstorm waves for vast European Russia are clearly visible, the first - in 24 - 26, the second - in 26 - 28 days, so and the connection between thunderstorm phenomena and sunspot activity. The resulting periods turned out to be so realistic that it became possible to schedule the passage of such “thunderstorm waves” several summer months in advance. The error does not reach more than 1 - 2 days, in most cases a complete match is obtained.
Processing of observations of thunderstorm activity carried out in recent years by Faas shows that for the entire territory of the European part of the USSR, periods of 26 and 13 (half-period) days occur most frequently and annually. The first is again a value very close to the revolution of the Sun around its axis. Research on the dependence of thunderstorm phenomena in Moscow on sun activity has been carried out in recent years by A.P. Moiseev, who, having carefully observed the formation of sunspots and thunderstorms from 1915 to 1926, came to the conclusion that the number and intensity of thunderstorms on average is in direct accordance with the area of sunspots passing through the central meridian of the Sun. Thunderstorms became more frequent and intensified with an increase in the number of sunspots and reached their greatest intensity after the passage of large groups of sunspots through the middle of the solar disk. Thus, the long-term course of the thunderstorm frequency curve and the course of the sunspot number curve coincide quite well. Moiseev then investigated another interesting fact, namely the daily distribution of thunderstorms by hour. The first daily maximum occurs at 12 - 13 pm local time. Then from 14-15 there is a slight decrease, at 15-16 hours the main maximum occurs, and then the curve decreases. In all likelihood, these phenomena are related both to direct radiation from the Sun and ionization of the air, and to temperature variations. From Moiseev’s research it is clear that at the moments of maximum solar activity, as well as near the moment of minimum, thunderstorm activity is most intense, and at the moments of maximum it is much more pronounced. This somewhat contradicts the position supported by Betzold and Hess that the minima of thunderstorm frequency coincide with the maxima of solar activity; Faas, in his treatment of thunderstorms for 1996, indicates that he paid special attention to whether thunderstorm activity increases with the passage of large sunspots through the central meridian of the Sun. For 1926, no positive results were obtained, but in 1923 a very close connection between the phenomena was observed. This can be explained by the fact that during maximum years, sunspots are grouped closer to the equator and pass near the apparent center of the solar disk. In this situation, their disturbing influence on the Earth should be considered greatest. Many researchers have tried to find other periods of thunderstorms, but fluctuations in thunderstorm activity from the materials at our disposal are still too difficult to discern and do not make it possible to establish any general patterns. In any case, this question has attracted the attention of an increasing number of researchers over time.
The number of thunderstorms and their intensity are reflected in a certain way on a person and his property. Thus, from the statistical data cited by Budin, it is clear that the maximums of deaths from lightning strikes fall in the years of maximum stress in the activity of the Sun, and their minimums - in the years of minimum sunspots. At the same time, the Russian forester Tyurin notes that, according to his research carried out on mass material, fires in the Bryansk forest area took on a spontaneous character in 1872, 1860, 1852, 183b, 1810, 1797, 1776 and 1753. In the northern forests, a periodicity of an average of 20 years can also be noted, and the dates of forest fires in the north in many cases coincide with the indicated dates, which shows the influence of the same cause - dry eras, some of them fall on the years of maximum sun activity . It can be noted that a good relationship is also observed in the daily course of thunderstorm activity and in the daily course of the number of fires caused by lightning.
Chapter 2. Methods for obtaining and processing initial data
2.1 Obtaining starting material

This work used meteorological data on thunderstorm activity at seven stations of the Republic of Tatarstan: Tetyushi (1940-1980), Laishevo (1950-1980), Kazan-Opornaya (1940-1967), Kaybitsy (1940-1967), Arsk (1940-1980 ), Agryz (1955-1967) and the meteorological station of Kazan State University (1940-1980). Data are provided with ten-day sampling. The number of days with thunderstorms per decade was taken as indices of thunderstorm activity. As well as monthly data on solar activity - Wolf numbers for 1940-1980.
Based on the data for the indicated years, the main statistical characteristics for thunderstorm activity indices were calculated.
2.2 Basic statistical characteristics

Meteorology deals with huge amounts of observations that need to be analyzed to clarify the patterns that exist in atmospheric processes. Therefore, statistical methods for analyzing large arrays of observations are widely used in meteorology. The use of powerful modern statistical methods helps to present facts more clearly and better discover relationships between them.
The average value of the time series is calculated using the formula
? = ?Gi/N
where 1< i The variance shows the spread of data relative to the average value and is found by the formula
?І = ?(Gi - ?)2 / N, where 1< i A quantity called standard deviation is the square root of the variance.
? = ?(Gi - ?)2 / N, where 1< i The most probable value of a random variable, the mode, is increasingly used in meteorology.
Also, asymmetry and kurtosis are used to characterize meteorological quantities.
If the average value is greater than the mode, then the frequency distribution is said to be positively skewed. If the mean is less than the mode, then it is negatively asymmetric. The asymmetry coefficient is calculated using the formula
A = ?(Gi - ?)3 / N?3, where 1< i Asymmetry is considered small if the asymmetry coefficient |A|?0.25. Asymmetry is moderate if 0.25<|А|>0.5. Asymmetry is large if 0.5<|А|>1.5. Exceptionally large asymmetry if |A|>1.5. If |A|>0, then the distribution has right-sided asymmetry, if |A|<0, то левостороннюю асиметрию.
For frequency distributions that have the same mean values, the asymmetries may differ in the value of kurtosis
E = ?(Gi - ?)? /N?? , where 1< i Kurtosis is considered small if |E|?0.5; moderate if 1?|E|?3 and large if |E|>3. If -0.5?E?3, then the kurtosis approaches normal.
The correlation coefficient is a value that shows the relationship between two correlated series.
The correlation coefficient formula is as follows:
R = ?((Xi-X)*(Yi-Y))/ ?x?y
where X and Y are average values, ?x and ?y are standard deviations.
Properties of the correlation coefficient:
1. The correlation coefficient of independent variables is zero.
2. The correlation coefficient does not change from adding any constant (non-random) terms to x and y, and also does not change from multiplying the values of x and y by positive numbers (constants).
3. The correlation coefficient does not change when moving from x and y to normalized values.
4. Range of change from -1 to 1.
It is necessary to check the reliability of the connection, it is necessary to evaluate the significance of the difference between the correlation coefficient and zero.
If for empirical R the product ¦R¦vN-1 turns out to be greater than a certain critical value, then with reliability S we can assert that the correlation coefficient will be reliable (reliably different from zero).
Correlation analysis makes it possible to establish the significance (non-randomness) of changes in an observed, measured random variable during testing, and allows us to determine the form and direction of existing connections between characteristics. But neither the correlation coefficient nor the correlation ratio provides information about how much a varying, effective characteristic can change when the factorial characteristic associated with it changes.
A function that allows one to find the expected values of another characteristic based on the value of one characteristic in the presence of a correlation is called regression. Statistical analysis of regression is called regression analysis. This is a higher level of statistical analysis of mass phenomena. Regression analysis allows you to predict Y based on X:
Yx-Y=(Rxy* ?y*(X-X))/ ?x (2.1)
Xy-X=(Rxy* ?x*(Y-Y))/ ?y (2.2)
where X and Y correspond to the average, Xy and Yx are partial averages, Rxy is the correlation coefficient.
Equations (2.1) and (2.2) can be written as:
Yx=a+by*X (2.3)
Xy=a+bx*Y (2.4)
An important characteristic of linear regression equations is the mean square error. It looks like this:
for equation (2.3) Sy= ?y*v1-RIxy (2.5)
for equation (2.4) Sx= ?x*v1-RIxy (2.6)
Regression errors Sx and Sy make it possible to determine the probable (confidence) zone of linear regression, within which the true regression line Yx (or Xy) is located, i.e. population regression line.
Chapter 3. Analysis of calculations
3.1 Distribution of main statistical characteristics

Let's consider some statistical characteristics of the number of days with thunderstorms in Predkamye at seven stations (Tables 1-7). Due to the very small number of days with thunderstorms in winter, this work will consider the period from April to September.
Tetyushi station:
In April, the maximum ten-day average value is observed in the 3rd ten-day period of the month? = 0.20. Modal values in all decades are zero, hence weak thunderstorm activity. The maximum dispersion and standard deviation are also observed in the 3rd decade? 2 =0.31; ? =0.56. Asymmetry is characterized by an exceptionally large value in the second decade of A = 4.35. Also in the 2nd decade there is a large value of kurtosis E = 17.79.
In May, due to increased heat influxes, thunderstorm activity increases. The maximum ten-day average value was observed in the 3rd decade and amounted to? =1.61. Modal values in all decades are equal to zero. Are the maximum values of dispersion and standard deviation observed in the 3rd decade? 2 =2.59; ?=1.61. The values of asymmetry and kurtosis decrease from the first decade to the third (in the first decade A = 1.23; E = 0.62; in the third decade A = 0.53; E = -0.95).
In June, the maximum of the average ten-day value occurs in the third ten-day period? = 2.07. There is an increase in the values of dispersion and standard deviation compared to April and May: maximum in the second decade (? 2 = 23.37; ? = 1.84), minimum in the first (? 2 = 1.77; ? = 1.33) . The modal values in the first two decades are equal to zero, in the third decade it was M=2. The asymmetry in all decades is large and positive, in the third decade. Kurtosis in the first two decades is characterized by small values; in the third decade its value increased E = 0.67.
The highest ten-day average value in July? =2.05 in the second decade. The modal values in the first two decades are 1 and 2, respectively, in the third - zero. The maximum values of dispersion and standard deviation are observed in the second decade and amount to? 2=3.15 and?=1.77, respectively, minimum in the first ten days? 2=1.93 and?=1.39 respectively. Asymmetry is characterized by large, positive values: maximum in the first decade A = 0.95, minimum in the second decade A = 0.66. The kurtosis in the second and third decades is small and has a negative value in the second decade; in the first decade there is a maximum of E = 1.28, a minimum in the second decade of E = -0.21.
In August, thunderstorm activity decreases. The highest ten-day average value is observed in the first ten days? =1.78, the smallest is in the third? =0.78. The modal values in the first and third decades are equal to zero, in the second - one. There is a decrease in the values of dispersion and standard deviation: maximum in the first decade (? 2 = 3.33; ? = 1.82), minimum in the third (? 2 = 1.23; ? = 1.11). There is a slight increase in the values of asymmetry and kurtosis from the first decade to the third: maximums in the third decade A = 1.62, E = 2.14, minimums in the second decade A = 0.40, E = -0.82.
In September, the maximum ten-day average value was? =0.63 in the first ten days of the month. Modal values are zero. There is a decrease in the values of dispersion and standard deviation from the first decade to the third (? 2 =0.84; ? =0.92 - in the first decade and ? 2 =0.11;? =0.33 - in the third).
Summarizing the above, we conclude that the values of such statistical characteristics as mode, dispersion and standard deviation increase along with an increase in thunderstorm activity: the maximum values are observed in late June - early July (Fig. 1).
Fig.1
Asymmetry and kurtosis, on the contrary, take on the greatest values during minimal thunderstorm activity (April, September); during the period of maximum thunderstorm activity, asymmetry and kurtosis are characterized by large values, but smaller compared to April and September (Fig. 2).
Fig.2
Maximum thunderstorm activity was observed in late June - early July (Fig. 3).
Fig.3
Let's analyze the remaining stations based on graphs constructed using calculated statistical values at these stations.
Laishevo station:
The figure shows the ten-day average number of days with thunderstorms. The graph shows that there are two maximum thunderstorm activity, occurring at the end of June and the end of July, equal to ?=2.71 and ?=2.52, respectively. One can also note an abrupt increase and decrease, which indicates a strong variability of weather conditions in this area (Fig. 4).
Fig.4
The mode, dispersion and standard deviation are greatest during the period from late June to late July, which corresponds to the period of greatest thunderstorm activity. The maximum dispersion was observed in the third ten days of July and amounted to? 2= 4.39 (Fig. 5).
Fig.5
Asymmetry and kurtosis take their greatest values in the second ten days of April (A = 5.57; E = 31), i.e. during minimal thunderstorm activity. And during the period of maximum thunderstorm activity, they are characterized by low values (A = 0.13; E = -1.42) (Fig. 6).
Fig.6
Kzan-support station:
At this station there is a smooth increase and decrease in thunderstorm activity. The maximum lasts from the end of June to mid-August, with an absolute value of ? = 2.61 (Fig. 7).
Fig.7
The modal values are quite pronounced compared to previous stations. Two main maxima of M=3 are observed in the third ten days of June and in the second ten days of July. At the same time, the dispersion and standard deviation reach their maximums (? 2 = 3.51; ? = 1.87) (Fig. 8).
Fig.8
Maximum asymmetry and kurtosis are observed in the second ten days of April (A=3.33; E=12.58) and the third ten days of September (A=4.08; E=17.87). The minimum was observed in the third ten days of July (A=0.005; E=-1.47) (Fig.9).
Fig.9
Kaybitsy station:
The maximum average value in the second ten days of June? = 2.79. An abrupt increase and smooth decrease in thunderstorm activity is observed (Fig. 10).
Rice. 10
The modal value takes its maximum value in the second ten days of June M=4. At the same time, the dispersion and standard deviation are also maximum (? 2 = 4.99; ? = 2.23) (Fig. 11).
Fig.11
Asymmetry and kurtosis are characterized by exceptionally large values in the second ten days of April (A=4.87; E=24.42) and the third ten days of September (A=5.29; E=28.00). The minimum was observed in the first ten days of June (A = 0.52; E = -1.16) (Fig. 12).
Fig.12
Arsk station:
At this station, two maximum thunderstorm activity is observed, occurring in the second ten days of June and the third ten days of July? = 2.02 (Fig. 13).
Fig.13
The maximum dispersion and standard deviation occur in the second ten days of June, which coincides with the maximum of the average value of thunderstorm activity (? 2 = 3.97; ? = 1.99). The second maximum of thunderstorm activity (the third ten days of July) is also accompanied by large values of dispersion and standard deviation (γ2 = 3.47; δ = 1.86) (Fig. 14).
Fig.14
There are exceptionally large values of asymmetry and kurtosis in the first ten days of April (A=6.40; E=41.00). In September, these values are also characterized by large values (A = 3.79; E = 13.59 in the third ten days of September). The minimum is in the second ten days of July (A = 0.46; E = -0.99) (Fig. 15).
Fig.15
Agryz station:
Due to the small sample size at this station, we can only judge lightning activity conditionally.
An abrupt change in thunderstorm activity is observed. The maximum is reached in the third ten days of July? = 2.92 (Fig. 16).
Fig.16
The modal meaning is well expressed. Three maxima of M=2 are observed in the third ten days of May, in the third ten days of June and in the second ten days of July. The dispersion and standard deviation each have two main maxima, occurring in the second ten days of June and the third ten days of July and equal? 2 =5.08; ? =2.25 and? 2 =4.91; ?=2.22 respectively (Fig. 17).
Fig.17
There are exceptionally large values of asymmetry and kurtosis in all ten days of April (A=3.61; E=13.00). Two main minimums: in the second ten days of May (A=0.42; E=-1.46) and the first ten days of July (A=0.50; E=-1.16) (Fig. 18).
Fig.18
KGU station:
The maximum of the average value occurs in the second ten days of June and is ?=1.90. One can also note a smooth increase and decrease in thunderstorm activity (Fig. 19).
Fig.19
The mode reaches its maximum values in the second ten days of June (M=2) and the first ten days of July (M=2). Dispersion and standard deviation take their greatest values in the third ten days of July (? 2 = 2.75; ? = 1.66) (Fig. 20).
Fig.20
In April and September, asymmetry and kurtosis are characterized by exceptionally large values: in the first ten days of April - A = 6.40; E=41.00, in the third ten days of September - A=4.35; E=17.79. The minimum of asymmetry and kurtosis is in the second ten days of July (A = 0.61; E = -0.48) (Fig. 21).
Fig.21
3.2 Trend analysis

The non-random, slowly changing component of a time series is called a trend.
As a result of data processing, trend equations were obtained at seven stations for monthly data (Tables 8-14). Calculations were carried out for three months: May, July and September.
At the Tetyushi station, an increase in thunderstorm activity in the spring and autumn months and a decrease in July have been noted over a long period of time.
At the station In Laishevo in May over a long-term period there is an increase in thunderstorm activity (b = 0.0093), and in July and September it decreases.
At Kazan-Opornaya, Kaybitsy and Arsk stations, coefficient b is positive in all three months, which corresponds to an increase in thunderstorms.
At the station Agryz, due to the small sample size, it is difficult to talk about the nature of changes in the intensity of thunderstorm activity, but it can be noted that in May and July there is a decrease, and in September there is an increase in thunderstorm activity.
At the station of Kazan State University in May and July, coefficient b is positive, and in September it has a minus sign.
The coefficient b is maximum in July at station. Kaybitsy (b=0.0577), minimal - in July at station. Laishevo.
3.3 Analysis of the regression dependence of the number of days with thunderstorms on Wolf numbers

Calculations were carried out for the central month of summer - July (Table 15), thus, the sample was N = 40 Julys from 1940 to 1980.
Having made the appropriate calculations, we obtained the following results:
The probability of confidence for coefficient a at all stations is practically zero. The probability of trust for coefficient b at most stations also differs little from zero and lies in the range 0.23?b?1.00.
The correlation coefficient at all stations, with the exception of station. Agryz is negative and does not exceed the value of r=0.5, the coefficient of determination at these stations does not exceed the value of r 2 =20.00.
At the station Agryz correlation coefficient is positive and the largest r = 0.51, probability of trust r 2 = 25.90.
Conclusion

As a result, about, etc.................

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Geography of thunderstorms

At the same time, there are about one and a half thousand thunderstorms on Earth; the average intensity of discharges is estimated as 100 lightning strikes per second. Thunderstorms are distributed unevenly across the planet's surface. There are approximately ten times fewer thunderstorms over the ocean than over the continents. About 78% of all lightning discharges are concentrated in the tropical and equatorial zone (from 30° north latitude to 30° south latitude). Maximum thunderstorm activity occurs in Central Africa. In the polar regions of the Arctic and Antarctic and over the poles, there are practically no thunderstorms. The intensity of thunderstorms follows the sun, with maximum thunderstorms occurring in the summer (at mid-latitudes) and during the daytime afternoon hours. The minimum of recorded thunderstorms occurs before sunrise. Thunderstorms are also influenced by the geographical features of the area: strong thunderstorm centers are located in the mountainous regions of the Himalayas and Cordilleras.

Average annual number of days with thunderstorms in some Russian cities:

City	Number of days with thunderstorms
Arkhangelsk	20
Astrakhan	14
Barnaul	32
Blagoveshchensk	28
Bryansk	28
Vladivostok	13
Volgograd	21
Voronezh	26
Ekaterinburg	28
Irkutsk	15
Kazan	28
Kaliningrad	18
Krasnoyarsk	24
Moscow	24
Murmansk	4
Nizhny Novgorod	28
Novosibirsk	20
Omsk	27
Orenburg	28
Petropavlovsk-Kamchatsky	1
Rostov-on-Don	31
Samara	25
Saint Petersburg	16
Saratov	28
Sochi	50
Stavropol	26
Syktyvkar	25
Tomsk	24
Ufa	31
Khabarovsk	25
Khanty-Mansiysk	20
Chelyabinsk	24
Chita	27
Yuzhno-Sakhalinsk	7
Yakutsk	12

Stages of development of a thundercloud

The necessary conditions for the occurrence of a thundercloud are the presence of conditions for the development of convection or another mechanism that creates upward flows of a supply of moisture sufficient for the formation of precipitation, and the presence of a structure in which some of the cloud particles are in a liquid state, and some are in an icy state. Convection leading to the development of thunderstorms occurs in the following cases:

with uneven heating of the surface air layer over different underlying surfaces. For example, over the water surface and land due to differences in temperature of water and soil. Over large cities, the intensity of convection is much higher than in the vicinity of the city.
when warm air rises or is displaced by cold air on atmospheric fronts. Atmospheric convection at atmospheric fronts is much more intense and more frequent than during intramass convection. Often frontal convection develops simultaneously with nimbostratus clouds and blanket precipitation, which masks the developing cumulonimbus clouds.
when air rises in mountainous areas. Even small elevations in the area lead to increased cloud formation (due to forced convection). High mountains create particularly difficult conditions for the development of convection and almost always increase its frequency and intensity.

All thunderclouds, regardless of their type, progress through the cumulus cloud stage, the mature thundercloud stage, and the breakup stage.

Classification of thunderclouds

In the 20th century, thunderstorms were classified according to their formation conditions: intramass, frontal, or orographic. It is now more common to classify thunderstorms according to the characteristics of the thunderstorms themselves, and these characteristics mainly depend on the meteorological environment in which the thunderstorm develops.
The main necessary condition for the formation of thunderclouds is the state of instability of the atmosphere, which forms updrafts. Depending on the size and power of such flows, thunderclouds of various types are formed.

Single cell

Single-cell cumulonimbus (Cb) clouds develop on days with low winds in a low-gradient pressure field. They are also called intramass or local. They consist of a convective cell with an upward flow in its central part, can reach thunderstorm and hail intensity and quickly collapse with precipitation. The dimensions of such a cloud are: transverse - 5-20 km, vertical - 8-12 km, lifespan - about 30 minutes, sometimes up to 1 hour. There are no major weather changes after a thunderstorm.
Cloud formation begins with the formation of a fair-weather cumulus cloud (Cumulus humilis). Under favorable conditions, the resulting cumulus clouds grow rapidly both in the vertical and horizontal directions, while the upward flows are located almost throughout the entire volume of the cloud and increase from 5 m/s to 15-20 m/s. Downdrafts are very weak. The surrounding air actively penetrates into the cloud due to mixing at the boundary and top of the cloud. The cloud enters the mid-cumulus (Cumulus mediocris) stage. The smallest water droplets formed as a result of condensation in such a cloud merge into larger ones, which are carried upward by powerful ascending currents. The cloud is still homogeneous, consisting of drops of water held by an ascending flow - no precipitation falls. At the top of the cloud, when water particles enter the zone of negative temperatures, the drops gradually begin to turn into ice crystals. The cloud enters the stage of a powerful cumulus cloud (Cumulus congestus). The mixed composition of the cloud leads to the enlargement of cloud elements and the creation of conditions for precipitation and the formation of lightning discharges. Such a cloud is called cumulonimbus (Cumulonimbus) or (in particular case) cumulonimbus bald (Cumulonimbus calvus). Vertical flows in it reach 25 m/s, and the summit level reaches a height of 7-8 km.
Evaporating precipitation particles cool the surrounding air, which leads to further intensification of downdrafts. At the maturity stage, both upward and downward air currents are simultaneously present in the cloud.
At the stage of collapse in the cloud, downward flows predominate, which gradually cover the entire cloud.

Multicell cluster thunderstorms

This is the most common type of thunderstorm associated with mesoscale (having a scale of 10 to 1000 km) disturbances. A multicell cluster consists of a group of thunderstorm cells moving as a single unit, although each cell in the cluster is at a different stage of thundercloud development. Mature thunderstorm cells are usually located in the central part of the cluster, and decaying cells are located on the leeward side of the cluster. They have a transverse size of 20-40 km, their peaks often rise to the tropopause and penetrate into the stratosphere. Multicell cluster thunderstorms can produce hail, rain showers and relatively weak squally wind gusts. Each individual cell in a multi-cell cluster remains mature for about 20 minutes; the multi-cell cluster itself can exist for several hours. This type of thunderstorm is usually more intense than a single cell thunderstorm, but much weaker than a supercell thunderstorm.

Multicell linear thunderstorms (squall lines)

Multicell linear thunderstorms are a line of thunderstorms with a long, well-developed gust front at the leading edge of the front. The squall line may be continuous or contain gaps. An approaching multi-cell line appears as a dark wall of clouds, usually covering the horizon on the western side (in the northern hemisphere). A large number of closely spaced ascending/descending air currents allows us to qualify this complex of thunderstorms as multi-cell, although its thunderstorm structure differs sharply from a multi-cell cluster thunderstorm. Squall lines can produce large hail (greater than 2 cm in diameter) and intense downpours, but they are known to produce strong downdrafts and wind shears that are hazardous to aviation. A squall line is similar in properties to a cold front, but is a local result of thunderstorm activity. Often a squall line occurs ahead of a cold front. In radar images, this system resembles a bow echo. This phenomenon is typical for North America; in Europe and the European territory of Russia it is observed less frequently.

Supercell thunderstorms

A supercell is the most highly organized thundercloud. Supercell clouds are relatively rare, but pose the greatest threat to human health and life and their property. A supercell cloud is similar to a single-cell cloud in that both have the same zone of updraft. The difference lies in the size of the supercell: diameter is about 50 km, height - 10-15 km (often the upper boundary penetrates the stratosphere) with a single semicircular anvil. The speed of the upward flow in a supercell cloud is much higher than in other types of thunderclouds: up to 40-60 m/s. The main feature that distinguishes a supercell cloud from other types of clouds is the presence of rotation. A rotating updraft in a supercell cloud (called a mesocyclone in radar terminology) creates extreme weather phenomena such as large hail (2-5 cm in diameter, sometimes more), squalls with speeds of up to 40 m/s and strong destructive tornadoes . Environmental conditions are a major factor in the formation of a supercell cloud. A very strong convective instability of the air is required. The air temperature near the ground (before the thunderstorm) should be +27...+30 and above, but the main necessary condition is a wind of variable direction, causing rotation. Such conditions are achieved with wind shear in the middle troposphere. Precipitation formed in the updraft is carried along the upper level of the cloud by a strong flow into the downdraft zone. Thus, the zones of ascending and descending flows are separated in space, which ensures the life of the cloud for a long period of time. There is usually light rain at the leading edge of a supercell cloud. Heavy rainfall occurs near the updraft zone, and the heaviest precipitation and large hail occurs northeast of the main updraft zone. The most dangerous conditions are found close to the main updraft zone (usually towards the rear of the storm).

Physical characteristics of thunderclouds

Aircraft and radar studies show that a single thunderstorm cell usually reaches an altitude of about 8-10 km and lives for about 30 minutes. An isolated thunderstorm usually consists of several cells in various stages of development and lasts about an hour. Large thunderstorms can be tens of kilometers in diameter, their peak can reach heights of over 18 km, and they can last for many hours.

Upward and downward flows

Updrafts and downdrafts in isolated thunderstorms typically range from 0.5 to 2.5 km in diameter and 3 to 8 km in height. Sometimes the diameter of the updraft can reach 4 km. Near the surface of the earth, streams usually increase in diameter, and their speed decreases compared to higher-lying streams. The characteristic speed of the updraft lies in the range from 5 to 10 m/s and reaches 20 m/s at the top of large thunderstorms. Research aircraft flying through a thundercloud at an altitude of 10,000 m record updraft speeds of over 30 m/s. The strongest updrafts are observed in organized thunderstorms.

Squalls

In some thunderstorms, intense downdrafts of air occur, creating winds of destructive force on the surface of the earth. Depending on their size, such downdrafts are called squalls or microsqualls. A squall with a diameter of more than 4 km can create winds of up to 60 m/s. Microsquals are smaller in size, but create wind speeds of up to 75 m/s. If a squall-generating thunderstorm is formed from sufficiently warm and humid air, then the microsquall will be accompanied by intense rainfall. However, if a thunderstorm forms from dry air, the precipitation may evaporate as it falls (airborne precipitation bands or virga), and the microsquall will be dry. Downdrafts are a serious hazard for aircraft, especially during takeoff or landing, as they create winds close to the ground with strong sudden changes in speed and direction.

Vertical development

In general, an active convective cloud will rise until it loses its buoyancy. The loss of buoyancy is associated with the load created by precipitation formed in a cloud environment, or mixing with the surrounding dry cold air, or a combination of these two processes. Cloud growth can also be stopped by a blocking inversion layer, that is, a layer where the air temperature increases with height. Typically, thunderclouds reach heights of about 10 km, but sometimes reach heights of more than 20 km. When the moisture content and instability of the atmosphere are high, then with favorable winds the cloud can grow to the tropopause, the layer separating the troposphere from the stratosphere. The tropopause is characterized by a temperature that remains approximately constant with increasing altitude and is known as a region of high stability. As soon as the updraft begins to approach the stratosphere, pretty soon the air at the top of the cloud becomes colder and heavier than the surrounding air, and the growth of the top stops. The height of the tropopause depends on the latitude of the area and the season of the year. It varies from 8 km in the polar regions to 18 km and higher near the equator.

When a cumulus convective cloud reaches the blocking layer of the tropopause inversion, it begins to spread outward and forms the “anvil” characteristic of thunderclouds. Winds blowing at anvil height tend to blow cloud material in the direction of the wind.

Turbulence

An airplane flying through a thundercloud (flying into cumulonimbus clouds is prohibited) usually encounters a bump that throws the airplane up, down, and to the sides under the influence of the cloud's turbulent flows. Atmospheric turbulence creates a feeling of discomfort for the aircraft crew and passengers and causes unwanted stress on the aircraft. Turbulence is measured in different units, but more often it is defined in units of g - the acceleration of free fall (1g = 9.8 m/s2). A squall of one G creates turbulence that is dangerous for aircraft. At the top of intense thunderstorms, vertical accelerations of up to three g have been recorded.

Movement

The speed and movement of a thundercloud depends on the direction of the wind, primarily on the interaction of the ascending and descending flows of the cloud with the carrier air currents in the middle layers of the atmosphere in which the thunderstorm develops. The speed of an isolated thunderstorm is usually about 20 km/h, but some thunderstorms move much faster. In extreme situations, a thundercloud can move at speeds of 65-80 km/h during the passage of active cold fronts. In most thunderstorms, as old thunderstorm cells dissipate, new thunderstorm cells emerge in succession. In light winds, an individual cell can travel a very short distance during its life, less than two kilometers; however, in larger thunderstorms, new cells are triggered by the downdraft flowing from a mature cell, giving the appearance of rapid movement that does not always coincide with the direction of the wind. In large multicell thunderstorms, there is a pattern where a new cell forms to the right of the carrier airflow in the northern hemisphere and to the left of the carrier's direction in the southern hemisphere.

Energy

The energy that powers a thunderstorm comes from the latent heat released when water vapor condenses to form cloud droplets. For every gram of water that condenses in the atmosphere, approximately 600 calories of heat are released. When water droplets freeze at the top of the cloud, an additional 80 calories per gram are released. The released latent thermal energy is partially converted into kinetic energy of the upward flow. A rough estimate of the total energy of a thunderstorm can be made based on the total amount of water that fell as precipitation from the cloud. Typical energy is on the order of 100 million kilowatt-hours, which is roughly equivalent to a 20-kiloton nuclear charge (though this energy is released over a much larger volume of space and over a much longer time). Large multi-cell thunderstorms can have tens and hundreds of times more energy.

Weather phenomena under thunderstorms

Downdrafts and squall fronts

Downdrafts in thunderstorms occur at altitudes where the air temperature is lower than the temperature in the surrounding area, and this downdraft becomes even colder when it begins to melt icy precipitation particles and evaporate cloud droplets. The air in the downdraft is not only denser than the surrounding air, but it also carries a horizontal angular momentum that is different from the surrounding air. If a downdraft occurs, for example, at an altitude of 10 km, then it will reach the earth's surface with a horizontal speed noticeably greater than the wind speed at the ground. Near the ground, this air is carried forward before a thunderstorm at a speed greater than the speed of movement of the entire cloud. That is why an observer on the ground will feel the approach of a thunderstorm through the flow of cold air even before the thundercloud is overhead. The downdraft spreading over the ground creates a zone with a depth of 500 meters to 2 km with a distinct difference between the cold air of the flow and the warm, moist air from which a thunderstorm is formed. The passage of such a squall front is easily determined by increased wind and a sudden drop in temperature. In five minutes, the air temperature can drop by 5°C or more. A squall forms a characteristic squall gate with a horizontal axis, a sharp drop in temperature and a change in wind direction.

In extreme cases, the squall front created by the downdraft can reach speeds in excess of 50 m/s, causing destruction to homes and crops. More often, severe squalls occur when an organized line of thunderstorms develops in high wind conditions at mid-levels. At the same time, people may think that this destruction was caused by a tornado. If there are no witnesses who saw the characteristic funnel-shaped cloud of a tornado, then the cause of destruction can be determined by the nature of the destruction caused by the wind. In tornadoes, destruction occurs in a circular pattern, and a thunderstorm squall caused by a downdraft causes destruction primarily in one direction. Cold air is usually followed by rain. In some cases, raindrops completely evaporate as they fall, resulting in a dry thunderstorm. In the opposite situation, typical of severe multicell and supercell thunderstorms, heavy rain and hail occur, causing flash floods.

Tornadoes

A tornado is a strong, small-scale vortex beneath thunderclouds with an approximately vertical but often curved axis. From the periphery to the center of the tornado, a pressure drop of 100-200 hPa is observed. The wind speed in tornadoes can exceed 100 m/s, and theoretically can reach the speed of sound. In Russia, tornadoes occur relatively rarely. The highest frequency of tornadoes occurs in the south of the European part of Russia.

Showers

In small thunderstorms, the five-minute peak of intense precipitation can exceed 120 mm/h, but all other rain has an order of magnitude lower intensity. An average thunderstorm produces about 2,000 cubic meters of rain, but a large thunderstorm can produce ten times that amount. Large organized thunderstorms associated with mesoscale convective systems can produce 10 to 1000 million cubic meters of precipitation.

Electrical structure of a thundercloud

The distribution and movement of electrical charges in and around a thundercloud is a complex, constantly changing process. Nevertheless, it is possible to present a generalized picture of the distribution of electrical charges at the stage of cloud maturity. The dominant positive dipole structure is in which the positive charge is at the top of the cloud and the negative charge is below it within the cloud. At the base of the cloud and below it there is a lower positive charge. Atmospheric ions, moving under the influence of an electric field, form screening layers at the boundaries of the cloud, masking the electrical structure of the cloud from an external observer. Measurements show that, in various geographical conditions, the main negative charge of a thundercloud is located at altitudes with ambient temperatures ranging from −5 to −17 °C. The higher the speed of the upward flow in the cloud, the higher the altitude the center of negative charge is located. The space charge density is in the range of 1-10 C/km³. There is a noticeable proportion of thunderstorms with an inverse charge structure: - a negative charge in the upper part of the cloud and a positive charge in the inner part of the cloud, as well as a complex structure with four or more zones of volumetric charges of different polarities.

Electrification mechanism

Many mechanisms have been proposed to explain the formation of the electrical structure of a thundercloud, and it is still an area of active research. The main hypothesis is based on the fact that if larger and heavier cloud particles are charged predominantly negatively, and lighter small particles carry a positive charge, then the spatial separation of space charges occurs due to the fact that large particles fall at a higher speed than small cloud components. This mechanism is generally consistent with laboratory experiments that show strong charge transfer when ice grains (grains are porous particles made from frozen water droplets) or hail interact with ice crystals in the presence of supercooled water droplets. The sign and magnitude of the charge transferred during contacts depend on the temperature of the surrounding air and the water content of the cloud, but also on the size of the ice crystals, collision speed and other factors. The action of other electrification mechanisms is also possible. When the amount of volumetric electric charge accumulated in the cloud becomes large enough, a lightning discharge occurs between regions charged with the opposite sign. A discharge can also occur between a cloud and the ground, a cloud and the neutral atmosphere, or a cloud and the ionosphere. In a typical thunderstorm, between two-thirds and 100 percent of the discharges are intracloud, intercloud, or cloud-to-air discharges. The remainder are cloud-to-ground discharges. In recent years, it has become clear that lightning can be artificially initiated in a cloud, which under normal conditions does not develop into a thunderstorm. In clouds that have electrified zones and create electric fields, lightning can be initiated by mountains, high-rise buildings, airplanes or rockets that find themselves in a zone of strong electric fields.

Precautions during a thunderstorm

Precautionary measures are due to the fact that lightning strikes mainly higher objects. This happens because the electrical discharge follows the path of least resistance, that is, the shorter path.

During a thunderstorm, you should never:

be near power lines;
hide from the rain under trees (especially tall or lonely ones);
swim in bodies of water (since the swimmer’s head protrudes from the water, in addition, water, thanks to the substances dissolved in it, has good electrical conductivity);
be in open space, in an “open field”, since in this case the person protrudes significantly above the surface;
climb to heights, including the roofs of houses;
use metal objects;
be near windows;
ride a bicycle and motorcycle;
use a mobile phone (electromagnetic waves have good electrical conductivity).

Failure to comply with these rules often results in death or burns and severe injuries.

Thunderstorm - what is it? Where do the lightning that cuts across the entire sky and the menacing peals of thunder come from? A thunderstorm is a natural phenomenon. Lightning, called lightning, can form inside clouds (cumulonimbus), or between clouds. They are usually accompanied by thunder. Lightning is associated with heavy rain, strong winds, and often hail.

Activity

Thunderstorm is one of the most dangerous people. People struck by lightning survive only in isolated cases.

There are approximately 1,500 thunderstorms operating on the planet at the same time. The intensity of the discharges is estimated at a hundred lightning strikes per second.

Development of a thunderstorm

How does it go? is formed only under certain conditions. There must be upward flows of moisture, and there must be a structure where one fraction of the particles is in an icy state, the other in a liquid state. Convection that will lead to the development of a thunderstorm will occur in several cases.

Uneven heating of surface layers. For example, over water with a significant temperature difference. Over large cities, thunderstorm intensity will be slightly stronger than in the surrounding areas.

When cold air displaces warm air. The frontal convention often develops simultaneously with cover clouds and nimbostratus clouds.

When air rises in mountain ranges. Even low elevations can lead to increased cloud formations. This is forced convection.

Any thundercloud, regardless of its type, necessarily goes through three stages: cumulus, maturity, and decay.

Classification

For some time, thunderstorms were classified only at the observation location. They were divided, for example, into orthographic, local, and frontal. Now thunderstorms are classified according to characteristics depending on the meteorological environments in which they develop. are formed due to atmospheric instability. This is the main condition for the creation of thunderclouds. The characteristics of such flows are very important. Depending on their power and size, different types of thunderclouds are formed, respectively. How are they divided?

2. Multi-cell cluster. Here the scale is more impressive - up to 1000 km. A multi-cell cluster covers a group of thunderstorm cells that are at various stages of formation and development and at the same time make up one whole. How are they built? Mature thunderstorm cells are located in the center; disintegrating cells are located in the center. Their transverse dimensions can reach 40 km. Cluster multi-cell thunderstorms produce gusts of wind (squally, but not strong), rain, and hail. The existence of one mature cell is limited to half an hour, but the cluster itself can “live” for several hours.

Movement speed

Electrification mechanism

Where do lightning bolts themselves come from? around the clouds and within them constantly moving. This process is quite complicated. The easiest way to imagine the work of electric charges in mature clouds. The dipole positive structure dominates in them. How is it distributed? The positive charge is placed at the top, and the negative charge is located below it, inside the cloud. According to the main hypothesis (this area of science can still be considered little-explored), heavier and larger particles are charged negatively, while small and light ones have a positive charge. The former fall faster than the latter. This causes spatial separation of space charges. This mechanism is confirmed by laboratory experiments. Particles of ice grains or hail can have strong charge transfer. The magnitude and sign will depend on the water content of the cloud, air temperature (ambient), and collision speed (main factors). The influence of other mechanisms cannot be excluded. Discharges occur between the ground and the cloud (or neutral atmosphere, or ionosphere). It is at this moment that we see flashes cutting across the sky. Or lightning. This process is accompanied by loud peals (thunder).

A thunderstorm is a complex process. It may take many decades, and perhaps even centuries, to study it.

Lightning is a giant electrical discharge in the atmosphere. Lightning occurs as a result of the accumulation of electrical charges in a thundercloud. It is accompanied by a bright glow from a bizarrely curved channel, a shock wave propagating in the surrounding air, turning into a sound wave at some distance. The acoustic manifestation of lightning is called thunder.

Lightning is a formidable natural phenomenon that causes damage to people and their property. This damage is associated with direct damage to people and animals, fires in residential and industrial premises, explosions of dangerous objects, forest fires, generation of a powerful electromagnetic pulse, etc. Lightning's electromagnetic pulse creates electromagnetic compatibility problems.

There are approximately 2000-3000 thunderstorm centers on Earth at the same time, and every second its surface is struck by 100-200 strikes.

Thunderstorms are distributed unevenly across the surface of the globe. The frequency of their formation depends on the time of year, time of day, and terrain. There are approximately 10 times more thunderstorms over land than over oceans. There are more thunderstorms in the evening and at night than during the day. In the mid-latitudes of the northern hemisphere, thunderstorms mainly occur from May to September. This period is called the thunderstorm season. In winter, thunderstorms occur relatively rarely.

In middle latitudes, the earth is struck by 30-40% of the total number of lightning, the remaining 60-70% are discharges between clouds or between differently charged parts of clouds. At equatorial latitudes, the 0 C isotherm is located higher than in middle latitudes. Accordingly, the areas of concentration of charges in the clouds are higher, so discharges into the ground make up an even smaller part.

The intensity of thunderstorm activity in any area is characterized by the average number of thunderstorm hours per year. The number of thunderstorm hours is minimal at high latitudes and gradually increases towards the equator, where increased air humidity and high temperatures, which contribute to the formation of thunderclouds, are observed almost throughout the year.

In some areas (Armenia, Krasnodar crane, Donbass, Carpathians) the annual number of thunderstorm hours reaches 100 or more,

In a number of countries, they use another, less convenient characteristic of thunderstorm activity: the annual number of thunderstorm days (rather than hours). According to the World Meteorological Organization, up to 180 thunderstorm days per year are observed in Central Africa, in Malaysia, Peru, Madagascar - up to 140 days, in Brazil, Central America - 100-120 days.

For practical problems of lightning protection of ground-based structures, the specific density of lightning strikes into the ground is important, i.e. annual number of impacts per 1 km 2 of the earth's surface. Within the annual duration of thunderstorms up to h the specific density of lightning strikes into the ground is almost directly proportional This made it possible to accept in Russia, along with the specific density of lightning strikes, another characteristic of thunderstorm activity: the average number of lightning strikes per 1 km 2 of the earth's surface per 100 thunderstorm hours.

Rice. 9.1. Dependence of the specific number of lightning strikes per 1 km 2 area of the Earth on the number of thunderstorm days per year (dashed lines indicate the area of scatter according to observational data)

If the intensity of thunderstorm activity is expressed by the annual number of thunderstorm days, then the specific density of discharges per 1 km 2 surface per number thunderstorm hours per year can be estimated from Fig. 9.1. However, it should be borne in mind that with the same value, the specific density of lightning strikes into the ground is subject to significant variations due to the influence of terrain and climatic conditions.

For the territory of our country . The greater the number of thunderstorm days in a year, the longer the thunderstorms. It follows from this that the relationship is nonlinear, and therefore thunderstorm activity cannot be characterized simply by the number of lightning strikes per 1 km 2 of the earth's surface per 100 thunderstorm hours.

Objects rising above the surface of the earth, due to the development of counter-leaders from them, collect lightning strikes from an area larger than the occupied territory. However, by taking , we can estimate the number of lightning strikes per 100 thunderstorm hours into a structure of length A, width IN and height N(dimensions in meters) according to the formula