The results of the interaction of certain atmospheric processes, which are characterized by certain combinations of several meteorological elements, are called atmospheric events.

Atmospheric phenomena include: thunderstorm, blizzard, dusty brown, fog, tornado, polar lights, etc.

All meteorological phenomena observed at meteorological stations are divided into the following groups:

hydrometeors , are a combination of rare and solid or both particles of water suspended in the air (clouds, fogs) that fall in the atmosphere (precipitation); which settle on objects near the earth's surface in the atmosphere (dew, hoarfrost, ice, frost); or raised by the wind from the surface of the earth (blizzard);

lithometeors , are a combination of solid (non-aqueous) particles that are lifted by the wind from the earth's surface and are transported to a certain distance or remain suspended in the air (dust drift, dust storms, etc.);

electrical Phenomena, which are the manifestations of the action of atmospheric electricity, which we see or hear (lightning, thunder);

optical phenomena in the atmosphere, which arise as a result of reflection, refraction, scattering and diffraction of solar or monthly light (halo, mirage, rainbow, etc.);

unclassified (miscellaneous) phenomena in the atmosphere, which are difficult to attribute to any of the types indicated above (squall, whirlwind, tornado).

Vertical inhomogeneity of the atmosphere. The most important properties of the atmosphere

According to the nature of temperature distribution with height, the atmosphere is divided into several layers: troposphere, stratosphere, mesosphere, thermosphere, exosphere.

Figure 2.3 shows the course of temperature change with distance from the earth's surface in the atmosphere.

А – altitude 0 km, t = 15 0 С; B - height 11 km, t = -56.5 0 С;

C – altitude 46 km, t = 1 0 С; D - height 80 km, t = -88 0 С;

Figure 2.3 - The course of temperature in the atmosphere

Troposphere

The thickness of the troposphere in our latitudes reaches 10-12 km. The main part of the mass of the atmosphere is concentrated in the troposphere, therefore, various weather phenomena are most clearly manifested here. In this layer, there is a continuous decrease in temperature with height. It averages 6 0 C for every 1000 g. The sun's rays strongly heat the earth's surface and the adjacent lower layers of air.

The heat that comes from the earth is absorbed by water vapor, carbon dioxide, dust particles. Above, the air is more rarefied, there is less water vapor in it, and the heat radiated from below has already been absorbed by the lower layers - therefore the air is colder there. Hence the gradual drop in temperature with height. In winter, the surface of the earth is very cold. This is facilitated by the snow cover, which reflects most of the sun's rays and at the same time radiates heat into the higher layers of the atmosphere. Therefore, the air near the surface of the earth is very often colder than at the top. The temperature rises slightly with altitude. This so-called winter inversion (temperature reversal). In the summer, the earth is heated by the sun's rays strongly and unevenly. From the most heated areas rise air streams, whirlwinds. In place of the air that has risen, air flows in from the less heated areas, in turn, being replaced by air that descends from above. Convection occurs, which causes the atmosphere to mix in the vertical direction. Convection destroys fog and reduces dust in the lower atmosphere. Thus, due to vertical movements in the troposphere, there is a constant mixing of air, which ensures the constancy of its composition at all altitudes.

The troposphere is the place where clouds, precipitation and other natural phenomena constantly form. Between the troposphere and the stratosphere there is a thin (1 km) transitional layer called the tropopause.

Stratosphere

The stratosphere extends up to a height of 50-55 km. The stratosphere is characterized by an increase in temperature with height. Up to a height of 35 km, the temperature rises very slowly; above 35 km, the temperature rises rapidly. The increase in air temperature with height in the stratosphere is associated with the absorption of solar radiation by ozone. At the upper boundary of the stratosphere, the temperature fluctuates sharply depending on the time of year and the latitude of the place. The rarefaction of the air in the stratosphere causes the sky there to be almost black. There is always good weather in the stratosphere. The sky is cloudless and mother-of-pearl clouds appear only at an altitude of 25-30 km. There is also intensive air circulation in the stratosphere and its vertical movements are observed.

Mesosphere

Above the stratosphere is a layer of the mesosphere, up to approximately 80 km. Here the temperature drops with height to several tens of degrees below zero. Due to the rapid drop in temperature with height, there is highly developed turbulence in the mesosphere. At altitudes close to the upper boundary of the mesosphere (75-90 km), noctilucent clouds are observed. It is most likely that they are composed of ice crystals. At the upper boundary of the mesosphere, the air pressure is 200 times less than at the earth's surface. Thus, in the troposphere, stratosphere and mesosphere together, up to a height of 80 km, there is more than 99.5% of the total mass of the atmosphere. The higher layers have a small amount of air.

Thermosphere

The upper part of the atmosphere, above the mesosphere, is characterized by very high temperatures and is therefore called the thermosphere. It differs, however, in two parts: the ionosphere, which extends from the mesosphere to heights of about a thousand kilometers, and the exosphere, which is located above it. The exosphere passes into the earth's corona.

The temperature here increases and reaches + 1600 0 C at an altitude of 500-600 km. Gases are very rarefied here, molecules rarely collide with each other.

The air in the ionosphere is extremely rarefied. At altitudes of 300-750 km, its average density is about 10 -8 -10 -10 g/m 3 . But even with such a low density of 1 cm 3, air at an altitude of 300 km still contains about one billion molecules or atoms, and at an altitude of 600 km - over 10 million. This is several orders of magnitude greater than the content of gases in interplanetary space.

The ionosphere, as the name itself says, is characterized by a very strong degree of air ionization - the content of ions here is many times greater than in the lower layers, despite the large overall rarefaction of the air. These ions are mainly charged oxygen atoms, charged nitrogen oxide molecules, and free electrons.

In the ionosphere, several layers or regions with maximum ionization are distinguished, especially at altitudes of 100-120 km (layer E) and 200-400 km (layer F). But even in the intervals between these layers, the degree of ionization of the atmosphere remains very high. The position of the ionospheric layers and the concentration of ions in them change all the time. The concentration of electrons in a particularly high concentration is called electron clouds.

The electrical conductivity of the atmosphere depends on the degree of ionization. Therefore, in the ionosphere, the electrical conductivity of air is generally 10-12 times greater than that of the earth's surface. Radio waves undergo absorption, refraction and reflection in the ionosphere. Waves longer than 20 m cannot pass through the ionosphere at all: they are reflected by electron clouds in the lower part of the ionosphere (at altitudes of 70-80 km). Medium and short waves are reflected by the higher ionospheric layers.

It is due to reflection from the ionosphere that long-range communication at short waves is possible. Multiple reflection from the ionosphere and the earth's surface allows short waves to zigzag to propagate over long distances, skirting the surface of the globe. Since the position and concentration of the ionospheric layers are constantly changing, the conditions for absorption, reflection and propagation of radio waves also change. Therefore, reliable radio communication requires continuous study of the state of the ionosphere. Observation of the propagation of radio waves is the means for such research.

In the ionosphere, auroras and a glow of the night sky close to them in nature are observed - a constant luminescence of atmospheric air, as well as sharp fluctuations in the magnetic field - ionospheric magnetic storms.

Ionization in the ionosphere takes place under the influence of ultraviolet radiation from the sun. Its absorption by molecules of atmospheric gases leads to the appearance of charged atoms and free electrons. Fluctuations in the magnetic field in the ionosphere and auroras depend on fluctuations in solar activity. Changes in the flux of corpuscular radiation that goes from the Sun into the Earth's atmosphere are associated with changes in solar activity. Namely, corpuscular radiation is of fundamental importance for these ionospheric phenomena. The temperature in the ionosphere increases with height to very high values. At altitudes close to 800 km, it reaches 1000°.

Speaking about the high temperatures of the ionosphere, they mean that particles of atmospheric gases move there at very high speeds. However, the density of air in the ionosphere is so low that a body that is in the ionosphere, such as a satellite, will not be heated by heat exchange with air. The temperature regime of the satellite will depend on the direct absorption of solar radiation by it and on the return of its own radiation to the surrounding space.

Exosphere

Atmospheric layers above 800-1000 km are distinguished by the name of the exosphere (outer atmosphere). The velocities of gas particles, especially light ones, are very high here, and due to the extremely rarefied air at these heights, the particles can circle the Earth in elliptical orbits without colliding with each other. In this case, individual particles can have velocities sufficient to overcome the force of gravity. For uncharged particles, the critical speed will be 11.2 km/s. Such particularly fast particles can, moving along hyperbolic trajectories, fly out of the atmosphere into outer space, "slip out", and dissipate. Therefore, the exosphere is also called the scattering sphere. Hydrogen atoms are predominantly susceptible to slipping.

Recently, it was assumed that the exosphere, and with it the earth's atmosphere in general, ends at altitudes of the order of 2000-3000 km. But observations from rockets and satellites have shown that hydrogen that slips out of the exosphere forms a so-called terrestrial corona around the Earth, which extends to more than 20,000 km. Of course, the density of gas in the Earth's corona is negligible.

With the help of satellites and geophysical rockets, the existence of the Earth's radiation belt in the upper part of the atmosphere and near-Earth space, which begins at an altitude of several hundred kilometers and extends for tens of thousands of kilometers from the earth's surface, has been established. This belt consists of electrically charged particles - protons and electrons, captured by the Earth's magnetic field, which move at very high speeds. The radiation belt constantly loses particles in the earth's atmosphere and is replenished by fluxes of solar corpuscular radiation.

The composition of the atmosphere is divided into homosphere and heterosphere.

The homosphere extends from the earth's surface to a height of about 100 km. In this layer, the percentage of the main gases does not change with height. The molecular weight of air also remains constant.

The heterosphere is located above 100 km. Here oxygen and nitrogen are in the atomic state. The molecular weight of air decreases with height.

Does the atmosphere have an upper boundary? The atmosphere has no boundaries, and, gradually rarefied, passes into interplanetary space.

Storms and hurricanes

The uneven heating of the atmosphere leads to a change in atmospheric pressure and, as a result, causes a general circulation of air in the atmosphere, which determines the climate, weather, and the possibility and frequency of meteorological emergencies.

The area of ​​low atmospheric pressure with a minimum in the center is called a cyclone. A cyclone in diameter reaches several thousand kilometers. Cyclones form cloudy weather with strong winds.

Storms and hurricanes occur during cyclones. The wind speed near the earth's surface exceeds 20 m/s and can reach 100 m/s.

The danger of these natural phenomena is created as a result of dynamic load from the flow of air masses. The destruction of buildings, structures and other objects, the defeat of people occurs as a result of the action of high-speed air pressure, which causes significant pressure on objects.

To characterize the strength of the wind, the 12-point Beaufort scale is often used, which is based on the characteristic consequences of the action of the wind on the earth's surface (Table 2.2).

Table 2.2 - Beaufort scale

Points	Wind speed m/s	Wind characteristic	Effects of the wind
	0-0,5	calm	the leaves on the trees do not move, the smoke from the chimneys rises vertically
	0,5-1,7	quiet	the smoke deviates a little, the wind is almost not felt
	1,7-3,3	easy	feel the slight breeze
	3,3-5,2	weak	swaying small branches
	5,2-7,4	moderate	dust rises, branches of medium thickness sway
	7,4-9,8	big enough	thin trees and thick branches sway, ripples form on the water
	9,8-12	strong	swaying thick tree trunks
	12,0-15,0	very strong	big trees sway, it's hard to go against the wind
	15,0-18,0	extremely strong	thick tree trunks break
	18,0-22,0	storm	destroyed light buildings, fences
	22,0-25,0	heavy storm	rather strong buildings are destroyed, the wind uproots trees
	25,0-29,0	fierce storm	significant damage, overturned wagons, cars
	over 29	Hurricane	destroyed brick houses, stone fences

Storms divided into vortex, dust and stream (storm at sea) - wind force of 9-11 points, wind speed of 20-32 m / s causes damage to buildings, uproots trees, overturns cars, destroys overhead communication lines and power lines. The defeat of people occurs as a result of damage to buildings, overturning machines and mechanisms, falling trees.

Hurricane - wind force 12 points, wind speed 32-60 m / s, sometimes up to 100 m / s - destroys and devastates everything in its path.

For security during a storm and a hurricane, a "Storm Warning" is announced. According to this report, the access to the sea of ​​floating craft is limited, tower cranes and other large-sized construction mechanisms are secured by a "storm", the movement of vehicles is limited, logging, field work, etc. are stopped. In addition, preventive measures at enterprises provide for the strengthening of structures, buildings, cleaning or securing objects that can injure people, take measures to preserve equipment.

Doors and windows are tightly closed in private houses, apartments and industrial premises. Objects are taken from roofs, loggias, balconies, which, due to gusts of wind, can fall down and injure people. Items located in the yards are fixed or brought into the room.

A storm (hurricane) may be accompanied by a thunderstorm. At the same time, it is necessary to avoid situations in which the possibility of lightning strikes increases.

Forecasting and warning about a storm (hurricane) is carried out by the hydrometeorological service using modern instruments, including meteorological satellites, which record the occurrence of extreme meteorological phenomena, after which the possible direction of their movement, probable power and time of approach to a certain area are calculated. The administrative bodies of regions, districts, civil protection headquarters, agricultural, forestry and industrial facilities are notified of the approach of a hurricane (storm). Local authorities notify the population, and the heads of enterprises and the headquarters of the PP - workers. This makes it possible to alert the formations of civil protection in time, to carry out preventive work in areas of possible action of a hurricane or storm, and to effectively eliminate the consequences of a natural disaster.

In the area of ​​a hurricane, storm, tornado, civil protection formations and the population must be prepared for:

Carrying out the evacuation of the population and material assets from dangerous areas;

Rescuing people; search and release of victims from under destroyed buildings and structures;

The provision of first aid and the delivery of victims to medical institutions;

extinguishing fires;

Elimination of accidents at production facilities and utility networks.

hail

Hail - atmospheric precipitation in the form of ice particles of irregular shape. Intense hail destroys agricultural crops, and especially large hail leads to the destruction of roofs, damages cars, can cause serious injury or even death.

Smog

Chemical reactions that occur in the air lead to the formation of smoky fogs. Smog occurs under the following conditions: firstly, atmospheric pollution as a result of intense intake of dust, smoke, exhaust and industrial gases, and other products in the form of fine particles that cities emit into the air, and secondly, the long existence of anticyclones, in which pollutants accumulate in the surface layer of the atmosphere. Great smoke, which in its effect is similar to smog, also occurs during large forest fires. Smog and smoke cause exacerbation of chronic lung diseases in people, deterioration of well-being, cause certain material damage associated with the removal of plaque on equipment located on the street, windows, and the like.

There are three layers of smog:

Lower, located in the surface layers of air. It is formed mainly from the exhaust gases of transport and the redistribution of dust raised into the air;

The second layer is formed due to emissions from heating systems, located at a height of about 20-30 m above the ground;

The third layer is located at a height of 50-100 m or more and is formed mainly as a result of emissions from industrial enterprises. Smog is quite toxic.

Lightning

Lightning and discharges are to some extent associated with matter in the plasma state. Lightning is linear and ball.

Linear lightning occurs when the electric field strength between the clouds and the ground increases. Linear lightning parameters:

Length - no more than 10 km;

Channel diameter - up to 40 cm;

Current strength - 105-106 A;

Time of one lightning discharge - 10 -4 s;

The temperature in the lightning channel is up to 10,000°K.

A lightning strike, as a result of its thermal and electrodynamic action, can cause injury and death of people, destruction of structures, fire. The greatest damage occurs from lightning strikes to ground objects in the absence of a lightning rod or other good conductors between the strike site and the ground. When a lightning strikes, from an electrical breakdown in the material, channels appear in which a high temperature is formed and part of the material evaporates, followed by an explosion and fire. In addition to the direct action of lightning, during a strike, a significant difference in electrical potentials between individual objects may occur, which can lead to electric shock to people.

Protection against lightning is carried out with the help of lightning rods, which are equipped with all houses and buildings. The degree of protection depends on the purpose of the house or structure, the intensity of thunderstorm activity in the area and the expected reliability of the object being struck by lightning.

Ball lightning is generated when powerful linear lightning strikes, they have a diameter of about 30 cm, their light emission is approximately equal to 100 W of a light bulb, the luminous flux is ~ 1400 lumens, the thermal radiation is small, the speed of movement is 3-5 m/s, sometimes up to 10 m/s, the energy released during the explosion is about 10,000 J. Ball lightning is often attracted to metal objects, its decay occurs in most cases by an explosion, but it can also simply fade and fall apart. The explosion of ball lightning is not powerful, but it can cause burns, objects torn off by the explosion are dangerous. The result of the action of ball lightning can be a fire.

Personal safety during an encounter with ball lightning, you need to sit or stand still, watching it. If the lightning approaches, you can blow on it - the lightning will fly away. In any case, it is necessary to move as far as possible from ball lightning, since the "behavior" of lightning is unpredictable.

Natural disasters.

A natural disaster is a catastrophic natural phenomenon (or process) that can cause numerous casualties, significant material damage and other severe consequences.

Natural disasters include earthquakes, volcanic eruptions, mudflows, landslides, landslides, floods, droughts, cyclones, hurricanes, tornadoes, snowdrifts and avalanches, prolonged heavy rains, severe persistent frosts, extensive forest and peat fires. Epidemics, epizootics, epiphytoties, and the mass spread of pests in forestry and agriculture are also classified as natural disasters.

Over the last 20 years of the 20th century, more than 800 million people in the world suffered from natural disasters (over 40 million people a year), more than 140 thousand people died, and the annual material damage amounted to more than 100 billion dollars.

Three natural disasters in 1995 provide clear examples.

1) San Angelo, Texas, USA, May 28, 1995: tornadoes and hail hit a city of 90,000 people; the damage caused is estimated at 120 million US dollars.

2) Accra, Ghana, July 4, 1995: The heaviest rainfall in almost 60 years caused severe flooding. About 200,000 residents lost all their possessions, more than 500,000 more could not get into their homes, and 22 people died.

3) Kobe, Japan, January 17, 1995: An earthquake that lasted only 20 seconds killed thousands of people; tens of thousands were injured and hundreds were left homeless.

Natural emergencies can be classified as follows:

1. Geophysical hazards:

2. Geological hazards:

3. Marine hydrological hazards:

4. Hydrological hazards:

5. Hydrogeological hazards:

6. Natural fires:

7. Infectious incidence of people:

8. Infectious incidence of farm animals:

9. Damage to agricultural plants by diseases and pests.

10. Meteorological and agrometeorological hazards:

storms (9 - 11 points);

hurricanes and storms (12 - 15 points);

tornadoes, tornadoes (a kind of tornado in the form of a part of a thundercloud);

vertical vortices;

large hail;

heavy rain (shower);

heavy snowfall;

heavy ice;

severe frost;

strong blizzard;

heatwave;

heavy fog;

frosts.

Hurricanes and Storms

Storms are long-term movement of wind, usually in one direction at high speed. By their appearance, they are divided into: snowy, sandy. And according to the intensity of the wind along the width of the band: hurricanes, typhoons. Movement and wind speed, intensity is measured on the Beaufort scale in points.

Hurricanes are winds of force 12 on the Beaufort scale, i.e. winds that exceed 32.6 m/s (117.3 km/h).

Storms and hurricanes occur during the passage of deep cyclones and represent the movement of air masses (wind) at great speed. During a hurricane, the air speed exceeds 32.7 m/s (more than 118 km/h). Sweeping over the earth's surface, the hurricane breaks and uproots trees, rips off roofs and destroys houses, power lines and communications, buildings and structures, disables various equipment. As a result of a short circuit in the power grid, fires occur, the supply of electricity is disrupted, the operation of objects stops, and other harmful consequences may occur. People may find themselves under the rubble of destroyed buildings and structures. Fragments of destroyed buildings and structures and other objects flying at high speed can cause serious injuries to people.

Reaching the highest stage, the hurricane goes through 4 stages in its development: tropical cyclone, baric depression, storm, intense hurricane. Hurricanes tend to form over the tropical North Atlantic, often off the west coast of Africa, and gain strength as they move west. A large number of incipient cyclones develop in this manner, but on average only 3.5 percent of them reach the tropical storm stage. Only 1-3 tropical storms, usually over the Caribbean Sea and the Gulf of Mexico, reach the east coast of the United States each year.

Many hurricanes originate off the west coast of Mexico and move northeast, threatening coastal Texas.

Hurricanes usually exist from 1 to 30 days. They develop over overheated areas of the oceans and transform into supertropical cyclones after a long passage over the cooler waters of the North Atlantic Ocean. Once on the underlying land surface, they quickly go out.

The conditions necessary for the birth of a hurricane are not completely known. There is the Storms Project, which is designed by the US government to develop ways to defuse hurricanes at their source. Currently, this set of problems is being studied in depth. The following is known: an intense hurricane is almost correctly rounded in shape, sometimes reaching 800 kilometers in diameter. Inside the pipe of superwarm tropical air is the so-called "eye" - an expanse of clear blue sky with a diameter of about 30 kilometers. It is surrounded by the "wall of the eye" - the most dangerous and restless place. It is here that swirling inward, moisture-saturated air rushes upward. In doing so, it causes condensation and the release of dangerous latent heat - the source of the storm's strength. Rising kilometers above sea level, the energy is released to the peripheral layers. In the place where the wall is located, the upward air currents, mixing with condensation, form a combination of maximum wind force and violent acceleration.

Clouds spiral around this wall parallel to the direction of the wind, thus giving the hurricane its characteristic shape and changing from heavy rain at the center of the hurricane to tropical downpour at the edges.

Hurricanes typically move at 15 kilometers per hour along a westerly path and often pick up speed, usually drifting toward the north pole at a line of 20-30 degrees north latitude. But often they follow a more complex and unpredictable pattern. In any case, hurricanes can cause enormous destruction and tremendous loss of life.

Prior to the approach of a hurricane wind, equipment, individual buildings are fixed, doors and windows are closed in industrial premises and residential buildings, and electricity, gas, and water are turned off. The population takes shelter in protective or buried structures.

Modern methods of weather forecasting allow several hours or even days to warn the population of a city or an entire coastal region about an impending hurricane (storm), and the civil defense service can provide the necessary information about the possible situation and the required actions in the current conditions.

The most reliable protection of the population from hurricanes is the use of protective structures (metro, shelters, underpasses, building basements, etc.). At the same time, in coastal areas, it is necessary to take into account the possible flooding of low-lying areas and choose protective shelters in elevated areas.

A hurricane on land destroys buildings, communication and power lines, damages transport communications and bridges, breaks and uproots trees; when propagating over the sea, it causes huge waves with a height of 10-12 m or more, damages or even leads to the death of the ship.

After a hurricane, the formations, together with the entire able-bodied population of the facility, carry out rescue and emergency recovery work; they rescue people from overwhelmed protective and other structures and provide assistance to them, restore damaged buildings, power and communication lines, gas and water pipes, repair equipment, and carry out other emergency recovery work.

In December 1944, 300 miles east of about. Luzon (Philippines) ships of the US 3rd Fleet were in the area near the center of the typhoon. As a result, 3 destroyers sank, 28 other ships were damaged, 146 aircraft carriers and 19 seaplanes on battleships and cruisers were wrecked, damaged and washed overboard, more than 800 people died.

From hurricane winds of unprecedented strength and gigantic waves that hit the coastal regions of East Pakistan on November 13, 1970, a total of about 10 million people were affected, including about 0.5 million people who died and went missing.

Tornado

A tornado is one of the cruel, destructive phenomena of nature. According to V.V. Kushina, a tornado is not a wind, but a “trunk” of rain twisted into a thin-walled pipe, which rotates around an axis at a speed of 300-500 km / h. Due to centrifugal forces, a vacuum is created inside the pipe, and the pressure drops to 0.3 atm. If the wall of the "trunk" of the funnel breaks, bumping into an obstacle, then outside air rushes into the funnel. Pressure drop 0.5 atm. accelerates the air secondary flow to speeds of 330 m / s (1200 km / h) and more, i.e. to supersonic speeds. Tornadoes are formed in an unstable state of the atmosphere, when the air in the upper layers is very cold, and in the lower layers it is warm. There is an intense air exchange, accompanied by the formation of a vortex of great strength.

Such whirlwinds arise in powerful thunderclouds and are often accompanied by thunderstorms, rain, and hail. Obviously, it cannot be said that tornadoes arise in every thundercloud. As a rule, this happens on the edge of the fronts - in the transition zone between warm and cold air masses. It is not yet possible to predict tornadoes, and therefore their appearance is unexpected.

The tornado does not live long, since rather soon the cold and warm air masses mix, and thus the reason supporting it disappears. However, even in a short period of its life, a tornado can cause enormous damage.

The physical nature of a tornado is very diverse. From the point of view of a meteorological physicist, this is twisted rain, a previously unknown form of the existence of precipitation. For a physicist-mechanic, this is an unusual form of a vortex, namely: a two-layer vortex with air-water walls and a sharp difference in the velocities and densities of both layers. For a physicist and heat engineer, a tornado is a giant gravitational-thermal machine of enormous power; in it, powerful air currents are created and maintained due to the heat of the water-ice phase transition, which is released by water captured by a tornado from any natural reservoir when it enters the upper layers of the troposphere.

Until now, the tornado is in no hurry to reveal its other secrets. So, there are no answers to many questions. What is a tornado funnel? What gives its walls a strong rotation and tremendous destructive power? Why is the tornado stable?

It is not only difficult to study a tornado, but also dangerous - upon direct contact, it destroys not only the measuring equipment, but also the observer.

Comparing the descriptions of tornadoes (tornadoes) of the past and present centuries in Russia and other countries, one can see that they develop and live according to the same laws, but these laws have not been fully elucidated and the behavior of a tornado seems unpredictable.

During the passage of tornadoes, of course, everyone hides, runs, and people are not up to observing, and even more so measuring the parameters of tornadoes. The little that we managed to find out about the internal structure of the funnel is due to the fact that the tornado, breaking away from the ground, passed over people's heads, and then it could be seen that the tornado is a huge hollow cylinder, brightly lit inside by the brilliance of lightning. A deafening roar and buzzing is heard from within. It is believed that the wind speed in the walls of the tornado reaches the sound.

A tornado can suck in and lift up a large portion of snow, sand, etc. As soon as the speed of snowflakes or grains of sand reaches a critical value, they will be thrown out through the wall and can form a kind of case or cover around the tornado. A characteristic feature of this case-cover is that the distance from it to the wall of the tornado is approximately the same along the entire height.

Let us consider, as a first approximation, the processes occurring in thunderclouds. Abundant moisture entering the cloud from the lower layers releases a lot of heat, and the cloud becomes unstable. Rapid ascending currents of warm air arise in it, which carry masses of moisture to a height of 12-15 km, and equally rapid cold descending currents that fall down under the weight of the formed masses of rain and hail, strongly cooled in the upper layers of the troposphere. The power of these streams is especially great due to the fact that two streams simultaneously arise: ascending and descending. On the one hand, they do not experience environmental resistance, because the volume of air going up is equal to the volume of air going down. On the other hand, the expenditure of energy by the flow to lift water up is completely replenished when it falls down. Therefore, flows have the ability to accelerate themselves to enormous speeds (100 m/s or more).

In recent years, another possibility has been identified for the rise of large masses of water into the upper troposphere. Often, when air masses collide, vortices are formed, which, for their relatively small size, are called mesocyclones. The mesocyclone captures a layer of air at a height of 1-2 km to 8-10 km, has a diameter of 8-10 km and rotates around a vertical axis at a speed of 40-50 m/s. The existence of mesocyclones has been reliably established, and their structure has been studied in sufficient detail. It has been found that in mesocyclones a powerful thrust arises on the axis, which ejects air to heights of up to 8-10 km and above. Observers have found that it is in the mesocyclone that a tornado sometimes originates.

The most favorable environment for the origin of the funnel is fulfilled when three conditions are met. First, the mesocyclone must be formed from cold, dry masses of air. Secondly, the mesocyclone must enter the area where a lot of moisture has accumulated in the surface layer 1-2 km thick at a high air temperature of 25-35 ° C. The third condition is the ejection of masses of rain and hail. The fulfillment of this condition leads to a decrease in the flow diameter from the initial value of 5–10 km to 1–2 km and an increase in velocity from 30–40 m/s in the upper part of the mesocyclone to 100–120 m/s in the lower part.

In order to have an idea of ​​the consequences of tornadoes, we will briefly describe the Moscow tornado in 1904 and the Ivanovo tornado in 1984.

On June 29, 1904, a strong whirlwind swept over the eastern part of Moscow. His path lay not far from three Moscow observatories: the University observatory in the western part of the city, the Land Survey Institute in the eastern part and the Agricultural Academy in the northwestern part, so the recorders of these observatories recorded valuable material. According to the weather map at 7 o'clock in the morning of this day in the east and west of Europe there were areas of high pressure (more than 765 mm Hg). Between them, mainly in the south of the European part of Russia, there was a cyclone with a center between Novozybkov (Bryansk region) and Kyiv (751 mm Hg). At 1 pm it deepened to 747 mm Hg. and shifted to Novozybkov, and at 21 h - to Smolensk (pressure in the center dropped to 746 mm Hg). Thus, the cyclone moved from SSE to NW. At about 17:00, when the tornado passed through Moscow, the city was on the northeastern flank of the cyclone. In the following days, the cyclone went to the Gulf of Finland, where it caused storms in the Baltic. If we dwell only on this synoptic description, then the cause of the tornado does not clearly appear.

The picture becomes clearer if we analyze the distribution of temperatures and air masses. The warm front went from the center of the cyclone to Kaluga, Zametchino and Penza, and the cold front - from the center of the cyclone to Kursk, Kharkov, Dnepropetrovsk and further south. Thus, the cyclone had a well-defined warm sector with masses of warm moist air at daytime temperatures of 28–32 ° C. Dry cold air with a temperature of 15–16 ° C was located in front of the warm front. In the frontal zone, the temperature is slightly higher. The temperature contrast is very large. The calculation shows that the warm front was moving to the north at a speed of 32-35 km/h. The formation of the Moscow tornado occurred before a warm front, where, with the participation of tropical air, there is always a threat of the emergence of severe thunderstorms and squalls.

On that day, strong thunderstorm activity was noted in four districts of the Moscow region: in Serpukhov, Podolsky, Moskovsky and Dmitrovsky, almost for 200 km. Thunderstorms with hail and storm were observed, in addition, in the Kaluga, Tula and Yaroslavl regions. Starting from the Serpukhov region, the storm turned into a hurricane. The hurricane intensified in the Podolsk region, where 48 villages were affected and there were casualties. The most terrible devastation was brought by a tornado that arose southeast of Moscow in the area of ​​​​the village of Besedy. The width of the thunderstorm area in the southern part of the Moskovsky region was determined to be 15 km; here the storm moved from south to north, and the tornado arose in the eastern (right) side of the thunderstorm band.

The tornado caused great destruction on its way. The villages of Ryazantsevo, Kapotnya, Chagino were destroyed; then the hurricane flew into the Lublin grove, uprooted and broke up to 7 hectares of forest, then destroyed the villages of Graivoronovo, Karacharovo and Khokhlovka, entered the eastern part of Moscow, destroyed the Annenhof grove in Lefortovo, planted under Tsaritsa Anna Ioannovna, tore off the roofs of houses in Lefortovo , went to Sokolniki, where he felled a centuries-old forest, headed to Losinoostrovskaya, where he destroyed 120 hectares of large forest, and disintegrated in the Mytishchi region. Further, there was no tornado, and only a strong storm was noted. The length of the tornado's path is about 40 km, the width all the time fluctuated from 100 to 700 m.

In appearance, the vortex was a column, wide at the bottom, gradually narrowing in the form of a cone and expanding again in the clouds; in other places, sometimes it took the form of just a black spinning pillar. Many eyewitnesses mistook it for rising black smoke from a fire. In those places where the tornado passed through the Moskva River, it captured so much water that the channel was exposed.

Among the mass of fallen trees and the general chaos, in some places it was possible to find a certain sequence: for example, near Lyublino there were three regularly arranged rows of birches: the north wind knocked down the lower row, the second one fell over it, felled by the east wind, and the upper row fell down with the south wind. Therefore, this is a sign of vortex motion. When the tornado passed from south to north, it captured this area on the right side, judging by the change in the wind, and its rotation was cyclonic, i.e. counterclockwise when viewed from above. The vertical component of the vortex was unusually large. The torn roofs of buildings flew through the air like shreds of paper. Even stone walls were destroyed. Half of the bell tower in Karacharovo has been demolished. The whirlwind was accompanied by a terrible rumble; its destructive work lasted from 30 s to 1-2 min. The crackling of falling trees was drowned out by the roar of the whirlwind.

In some places, swirling air movements are clearly visible by the nature of the windbreak, but in most cases, fallen trees, even in small spaces, lay in all possible directions. The picture of the destruction of the Moscow tornado turned out to be very complex. An analysis of its tracks led us to believe that on June 29, 1904, several tornadoes rushed through Moscow. In any case, by the nature of the destruction, the existence of two funnels can be noted, one of which moved in the direction of Lyublino - Rogozhskaya Zastava - Lefortovo - Sokolniki - Losinoostrovskaya-Mytishchi, and the second - Conversations - Graivoronovo - Karacharovo - Izmailovo - Cherkizovo. The width of the path of both funnels was from a hundred to a thousand meters, but the boundaries of the paths were clear. Buildings at a distance of several tens of meters from the boundaries of the path remained intact.

The accompanying phenomena are also characteristic of strong tornadoes. When the funnel approached, it became completely dark. The darkness was accompanied by a terrible noise, a roar and a whistle. Electrical phenomena of unusual intensity have been recorded. Due to frequent lightning strikes, two people died, several were burned, and fires broke out. Ball lightning was observed in Sokolniki. The rain and hail were also of extraordinary intensity. Hailstones with a chicken egg were noted repeatedly. Individual hailstones were star-shaped and weighed 400-600 g.

The destructive power of tornadoes is especially great in gardens, parks and forests. Here is what the Moscow Leaflet wrote (1904, No. 170). At Cherkizovo “... suddenly a black cloud completely descended to the ground and covered the metropolitan garden and grove with an impenetrable veil. All this was accompanied by a terrible noise and whistling, thunderclaps and the incessant crash of a large falling hail. There was a deafening blow, and a huge linden tree fell onto the terrace. Her fall was extremely strange, as she got onto the terrace through the window and with her thick end forward. The hurricane threw it 100 meters through the air. The grove was especially affected. In three or four minutes it turned into a clearing, completely covered with fragments of huge birches, in places uprooted from the ground and thrown over considerable distances. The brick fence around the grove was destroyed, and some bricks were thrown a few sazhens.

Actions of the population under threat and during hurricanes, storms and tornadoes.

Upon receiving a signal of an impending danger, the population begins urgent work to improve the security of buildings, structures and other places where people are located, prevent fires and create the necessary reserves to ensure life in extreme emergency conditions.

On the windward side of buildings, windows, doors, attic hatches and ventilation openings are tightly closed. Glasses of windows are pasted over, windows and show-windows are protected by shutters or boards. In order to equalize the internal pressure, doors and windows on the leeward side of buildings are opened.

It is advisable to fix fragile institutions (country houses, sheds, garages, stacks of firewood, toilets), dig in with earth, remove protruding parts or disassemble, crushing the disassembled fragments with heavy stones, logs. It is necessary to remove all things from balconies, loggias, window sills.

It is necessary to take care of the preparation of electric lamps, kerosene lamps, candles, camping stoves, kerosene stoves and stoves in places of shelter, the creation of stocks of food and drinking water for 2-3 days, medicines, bedding and clothes.

At home, residents should check the placement and condition of electrical panels, gas and water main taps and, if necessary, be able to shut them off. All family members must be taught the rules of self-rescue and first aid for injuries and concussion.

Radios or TVs must be on at all times.

When informed of the imminent approach of a hurricane or severe storm, the inhabitants of the settlements take their previously prepared places in buildings or shelters, preferably in basements and underground structures (but not in the flood zone).

While in the building, you should beware of injuries from broken glass. In case of strong gusts of wind, it is necessary to move away from the windows and take a place in the niches of the walls, doorways or stand close to the wall. For protection, it is also recommended to use built-in wardrobes, durable furniture and mattresses.

When forced to stay in the open air, it is necessary to be away from buildings and occupy ravines, pits, ditches, ditches, road ditches for protection. In this case, you need to lie on the bottom of the shelter and press tightly to the ground, grab the plants with your hands.

One of the chronicles found on the territory of Belarus reported a hurricane in Borisov. The people who worked in the fields were "worn over the trees." Those who managed to grab hold and hold on tight remained alive. “And others on the field, powerfully grasping the stubble and holding on, if they didn’t let the wind under them…”

Any protective actions reduce the number of injuries caused by the throwing action of hurricanes and storms, and also provide protection from flying fragments of glass, slate, tiles, bricks and various objects. You should also avoid being on bridges, pipelines, in places in close proximity to objects that have highly toxic and flammable substances (chemical, oil refineries and storage bases).

During storms, avoid situations that increase the likelihood of electric shock. Therefore, you can not hide under separate trees, poles, come close to power transmission towers.

During and after a hurricane or storm, it is not recommended to enter susceptible buildings, and if necessary, this should be done with caution, making sure that there are no significant damage to stairs, ceilings and walls, fires, gas leaks, or broken electrical wires.

During snow or dust storms, it is allowed to leave the premises in exceptional cases and only as part of a group. At the same time, relatives or neighbors must be informed of the route and time of return. In such conditions, it is allowed to use only pre-prepared vehicles capable of moving with snow, sand drifts, and sleet. If it is impossible to move further, mark the parking lot, completely close the blinds and cover the engine from the side of the radiator.

When receiving information about the approach of a tornado or detecting it by external signs, you should leave all modes of transport and take cover in the nearest basement, shelter, ravine, or lie down on the bottom of any recess and cling to the ground. When choosing a place of protection against a tornado, it should be remembered that this natural phenomenon is often accompanied by heavy rainfall and large hail. In such cases, it is necessary to take measures to protect against damage by these hydrometeorological phenomena.

After the end of the active phase of the disaster, rescue and recovery work begins: dismantling the rubble, searching for the living, the wounded and the dead, providing assistance to those who need it, restoring housing, roads, businesses and a gradual return to normal life.

QUESTIONS:

1) What is often accompanied by vortices in powerful thunderclouds?

Whirlwinds in powerful thunderclouds are often accompanied by thunderstorms, rain, and hail.

2) What does a vortex look like?

In appearance, the vortex is a column, wide at the bottom, gradually narrowing in the form of a cone and expanding again in the clouds.

3) What can a tornado suck up and lift up?

A tornado can suck in and lift up a large portion of snow and sand.

4) What is the speed of hurricanes?

Hurricanes are winds that exceed 32.6 m/s (117.3 km/h).

5) What is the most reliable protection of the population from hurricanes?

The most reliable protection of the population from hurricanes is the use of protective structures (metro, shelters, underpasses, building basements, etc.).

6) On what scale is movement and speed measured?

Movement and wind speed, intensity is measured on the Beaufort scale in points.

Lecture

Natural emergencies and measures to reduce the possible impact from them

1. Theoretical provisions

2. Natural phenomena of meteorological origin

3. Natural phenomena of geophysical origin

4. Natural phenomena of geological origin

5. Natural phenomena of cosmic origin

6. Natural phenomena of biological origin

Theoretical Provisions

Natural emergencies have threatened the inhabitants of our planet since the beginning of civilization. The amount of damage depends on the intensity of natural phenomena, the level of development of society and living conditions. Natural phenomena can be extreme, extraordinary and catastrophic. Catastrophic natural phenomena are called natural disasters. Disaster is a catastrophic natural phenomenon that can cause numerous human casualties and cause significant material damage. The total number of natural disasters worldwide is constantly increases. Natural phenomena most often sudden and unpredictable and also they can wear explosive and fast paced. Natural phenomena can happen regardless from each other (for example, avalanches and wildfires) and during interaction(eg earthquake and tsunami). Mankind is not so helpless in the face of the elements. Some phenomena can be predicted, and some can be successfully resisted. To effectively counteract natural emergencies, it is necessary to know composition of the event, historical chronicle and local characteristics of natural hazards. Protection from natural hazards can be active(for example, construction of engineering structures) and passive(the use of shelters, hills. Due to the occurrence of natural phenomena, they are currently divided into six groups.

Natural phenomena of meteorological origin

Meteorology is the science that studies changes in the Earth's atmosphere. These are temperature, humidity, atmospheric pressure, air currents (wind), changes in the Earth's magnetic field. The movement of air relative to the earth is called wind. Wind strength is estimated on a 12-point Beaufort scale (at a standard height of 100 meters above an open flat surface).

Storm - long and very strong wind, the speed of which exceeds 20 m/s.

Hurricane - wind of great destructive power and considerable duration, the speed of which is 32 m/s (120 km/h). A hurricane-force wind accompanied by heavy rainfall is called a typhoon in Southeast Asia.

Tornado - or tornado - an atmospheric vortex that occurs in a thundercloud, and then spreads in the form of a dark sleeve or trunk towards the land or sea surface. The principle of operation of a tornado resembles the operation of a vacuum cleaner.

dangers for people during such natural phenomena are the destruction of houses and structures, overhead power lines and communications, ground pipelines, as well as the defeat of people by fragments of destroyed structures, glass fragments flying at high speed. During snow and dust storms, snow drifts and accumulations of dust on fields, roads and settlements, as well as water pollution, are dangerous. The movement of air is directed from high pressure to low pressure. An area of ​​low pressure is formed with a minimum in the center, which is called cyclone. The cyclone in diameter reaches several thousand kilometers. The weather during a cyclone is cloudy, with an increase in wind. Weather-sensitive people during the passage of a cyclone complain of a deterioration in well-being.

Very coldy - characterized by a decrease in temperature for several days by 10 or more degrees below the average for the area.

Ice - a layer of dense ice (several centimeters) that forms on the surface of the earth, sidewalks, the carriageway of streets and on objects and buildings when supercooled rain and drizzle (fog) freeze. Ice is observed at temperatures from 0 to 3 C. As an option - freezing rain.

Black ice - This is a thin layer of ice on the surface of the earth, formed after a thaw or rain as a result of a cold snap, as well as freezing of wet snow and raindrops.

Dangers. Increase in the number of accidents and injuries among the population. Violation of life activity during icing of power lines, contact networks of electric transport, which can lead to electrical injuries and fires.

Blizzard(blizzard, blizzard) is a hydrometeorological disaster. Associated with heavy snowfall, with wind speeds above 15 m/s and snowfall duration of more than 12 hours

dangers for the population consist in drifts of roads, settlements and individual buildings. The drift height can be more than 1 meter, and in mountainous areas up to 5-6 meters. It is possible to reduce visibility on the roads to 20-50 meters, as well as the destruction of buildings and roofs, power outages and communications.

Fog - the accumulation of small water droplets or ice crystals in the surface layer of the atmosphere, reducing visibility on the roads.

dangers. Reduced visibility on the roads disrupts the operation of transport, which leads to accidents and injuries among the population.

Drought - prolonged and significant lack of precipitation, more often at elevated temperatures and low humidity.

Heatwave - characterized by an increase in the average annual temperature of the ambient air by 10 or more degrees for several days

Lecture topic: "Natural hazards and protection against them".

Plan.

General patterns and classification of natural hazards.

Geological hazards.

meteorological hazards.

hydrological hazards.

natural fires.

Space dangers.

1. To natural hazards include natural phenomena that pose a direct threat to human life and health (for example, floods, earthquakes, etc.).

Dangers of a natural nature have threatened the inhabitants of the Earth since the beginning of civilization.

Despite profound differences, all natural hazards are subject to certain general patterns:

Each type of hazard is characterized by a certain spatial confinement.

It has been established that the greater the intensity (power) of the danger, the less often it happens.

Each type of danger is preceded by some specific signs (harbingers).

Despite the unexpectedness of a natural hazard, its manifestation can be predicted and protective measures provided.

There is a relationship between natural hazards (one phenomenon can be the cause of another).

Anthropogenic influence can lead to increased hazardous impacts.

A prerequisite for successful protection against natural hazards is the study of their causes and mechanisms. Knowing the essence of the processes, it is possible to predict them. A timely and accurate forecast is an important prerequisite for effective protection.

By localization, natural hazards are conditionally divided into groups:

geological (earthquakes, volcanic eruptions, landslides, mudflows, avalanches);

meteorological (storms, hurricanes, tornadoes, showers, frosts, hail);

hydrological (floods, tsunamis);

natural fires (forest, fires of steppe and grain massifs, peat, underground fires of fossil fuels);

space (falling meteorites).

2. earthquakes - these are tremors and vibrations of the earth's surface, resulting from sudden displacements and ruptures in the earth's crust or the upper part of the mantle and transmitted over long distances in the form of elastic vibrations.

Earthquake science - seismology.

earthquake source- this is a certain volume in the thickness of the Earth, within which energy is released. The center of the focus is a conditional point called hypocenter. The projection of the hypocenter onto the Earth's surface epicenter around which the greatest damage occurs.

Hundreds of thousands of earthquakes are recorded every year on the globe. Approximately every 30 seconds there is one earthquake. Most of them are weak and we do not notice them.

The strength of earthquakes is estimated a) by seismic energy and b) by the intensity of destruction on the Earth's surface.

In 1935, C. Richter (professor at the California Institute of Technology) proposed to estimate the energy of an earthquake magnitude. Richter proposed a 9-magnitude scale (Japan uses a 7-magnitude scale). The magnitude value is determined from observations at seismic stations. Ground vibrations are recorded by special devices - seismographs.

According to the international scale MSK-64 (Medvedev-Sponheier-Kernik), the strength of earthquakes is estimated in points depending on the intensity of destruction occurring on the Earth's surface (12-point scale). This scale is accepted in Russia.

The magnitude is indicated by Arabic numerals, and the intensity - by Roman ones (for example, the intensity of the earthquake that occurred on December 7, 1988 in Spitak was estimated at IX-X points).

Earthquakes are distributed over the earth's surface very unevenly. The analysis of seismic and geographic data makes it possible to outline the areas where earthquakes should be expected in the future and to assess their intensity. The seismic zoning map is an official document that design organizations should be guided by. In areas prone to earthquakes, earthquake-resistant or anti-seismic construction is carried out.

Currently, two seismic belts are known:

Mediterranean-Asian (Portugal, Italy, Greece, Turkey, Iran, Northern India)

Pacific (Sakhalin, Kuril ridge).

In Russia, the most dangerous areas are located in the Baikal region, Kamchatka, the Kuril Islands, South Siberia and the North Caucasus.

Anti-seismic measures:

A) preventive, preventive, carried out before a possible earthquake - the study of the nature of earthquakes, the mechanism, the identification of precursors (the growth of weak shocks, the rise of water in wells, an increase in radiation levels, restless behavior of animals); development of forecast methods, public education, earthquake-resistant or anti-seismic construction, training of rescue services;

B) activities carried out immediately before, during and after an earthquake, i.e. actions in an emergency - emergency rescue operations.

Actions of the population during an earthquake

Do not panic, act calmly and prudently.

Move away from tall buildings and power lines.

With the beginning of the earthquake, people in the houses should urgently leave the premises (in 25-30 seconds) and go to an open place ( It is forbidden to use the elevator!).

If it is impossible to leave the building, stand in the doorway of the main internal wall. Turn off gas, light, water. After the cessation of tremors, leave the premises.

Get involved in saving people.

Volcanic activity.

Volcanic activity occurs as a result of constant active processes occurring in the depths of the Earth. About 200 million people live dangerously close to active volcanoes.

The set of phenomena associated with the movement of magma in the earth's crust and on its surface is called volcanism.

Magma- this is a glorified mass of predominantly silicate composition, formed in the deep zones of the Earth. Reaching the earth's surface, magma erupts in the form of lava. Lava differs from magma in the absence of gases escaping during an eruption. Volcanoes are geological formations that arise above channels and cracks in the earth's crust, through which magma erupts onto the earth's surface. Magma chambers are located in the mantle at a depth of 50-70 km.

Volcanoes are divided into:

Active;

Asleep;

Extinct.

To asleep Volcanoes are those whose eruptions are not known, but they have retained their shape and local earthquakes occur under them.

Extinct are volcanoes without any volcanic activity.

Volcanic eruptions are long and short-term.

There is a relationship between volcanic activity and earthquakes. Seismic shocks usually mark the beginning of an eruption. At the same time, lava fountains, hot lava flows, hot gases are dangerous. Explosions of volcanoes can initiate landslides, avalanches, collapses, and tsunamis on the seas and oceans.

Preventive actions.

Actions include changing land use patterns, building dams to divert lava flows, and bombarding lava flows to mix the lava with the ground and reduce it to a less liquid mass.

At the beginning of volcanic activity, which can be predicted with the help of modern equipment, it is necessary to evacuate the nearby population.

Landslide - this is a sliding displacement down the slope under the action of gravity of the soil masses that form the slopes of hills, mountains, river, lake and sea terraces. The triggers of landslide processes are earthquakes, volcanic eruptions, construction work, precipitation, weathering, etc. The danger of landslides is that huge masses of soil, suddenly shifting, can lead to the destruction of buildings and structures and great casualties.

The most tragic landslide was in 1920 in China. After a strong earthquake in the mountains, thousands of cubic meters of forests filled up valleys, covered cities and villages, which led to the death of 200 thousand people

Protection measures:

arrangement of engineering structures (retaining walls);

protective and restrictive measures (prohibition of construction, blasting, etc.).

In dangerous places, a system for monitoring and warning the population, as well as emergency rescue services, is provided.

sat down - short-term rapid floods on mountain rivers, having the character of mud-stone flows. Mudflows can be caused by earthquakes, heavy snowfalls, downpours, and intense snowmelt. The main danger is the huge kinetic energy of mud streams, the speed of which can reach 15 km/h.

Mudflows occur suddenly, grow rapidly and usually last from 1 to 3 hours, sometimes 6-8 hours. Mudflows are predicted based on the results of observations over the past years and weather forecasts.

To preventive anti-mudflow measures include: the construction of hydraulic structures (mudflow-retarding and mudflow-directing), melt water discharge, afforestation, forest felling regulation, etc.

In mudflow-prone areas, automatic mudflow warning systems are being created and appropriate action plans are being developed.

snow avalanche - this is a snowfall, a mass of snow falling or sliding from the mountain slopes under the influence of some kind of influence and entraining new masses of snow on its way. Snow avalanches are common in mountainous areas. The danger of an avalanche lies in the high kinetic energy of the avalanche mass, which has tremendous destructive power. Avalanche speed can reach 100 m/s, 20-30 m/s on average.

Protection methods: the use of snow-retaining shields, planting a forest, artificially provoking an avalanche at a pre-selected time and subject to safety measures (directional explosions, strong sound sources), etc.

3. Weather hazards:

strong wind (including storm, hurricane, tornado);

heavy rain (with precipitation of 50 mm or more for 12 hours or more);

heavy snowfall (with precipitation of 20 mm or more in 12 hours);

strong blizzards (at a wind speed of 15 m/s or more);

large hail (hailstone diameter 20 mm or more);

• frosts (when the air temperature during the growing season on the soil surface drops below 0 0 С);

  severe frost or extreme heat;

Wind is the movement of air relative to the ground. The movement of air is directed from high pressure to low pressure. The area of ​​low pressure in the atmosphere with a minimum in the center is a cyclone. The weather during a cyclone is more cloudy, with strong winds. An anticyclone is an area of ​​high pressure with a maximum in the center. The anticyclone is characterized by cloudy, dry weather and light winds.

To assess the strength of the wind in points according to its effect on ground objects or on waves at sea, the English Admiral F. Beaufort in 1805 developed a conditional scale, which, after changes and clarifications in 1963, was adopted by the World Meteorological Organization and is widely used in synoptic practice (12-point scale). On this scale 0 b. - calm, wind speed 0-0.2 m/s.

9 b. - a storm or a strong storm, wind speed 20.8-24.4 m/s, the wind breaks the tiles, minor damage.

12 b. – hurricane, wind speed of 32.7 m/s or more, wind of great destructive force.

Flurries– short-term increases in wind speed up to 20-30 m/s.

Typhoons- hurricanes that occur over the Pacific Ocean. The average duration is 9-12 days.

Tornado- this is an atmospheric vortex that occurs in a thundercloud and propagates in the form of a dark sleeve or trunk towards the land or sea surface. In the upper part it has a funnel-shaped extension that merges with the clouds. Like hurricanes, tornadoes are identified by weather satellites. Often occur suddenly, they are difficult to predict.

In the USA, tornadoes over land are called tornado.

4. Flood - this is a significant flooding of the area with water as a result of a rise in the water level in a river, lake or sea, caused by various reasons. Flooding is the most common natural hazard.

The causes of flooding are:

high water; - flood; - storm; - congestion; - gluttonous; - mudflows; - surge; - in case of accidents at hydraulic structures.

high water- a relatively long increase in the flow of rivers, which is repeated annually in the same season, accompanied by an increase in the water level. It occurs due to the spring melting of snow and ice in the mountains.

high water- a relatively short-term and non-periodic rise in the water level. Occurs due to rains, winter thaws with wet snow.

Floods are often caused by blocking the channel with large pieces of ice during ice drift - congestion(it happens at the end of winter or in spring.) or clogging of the channel with internal loose ice under a fixed ice cover and the formation of an ice plug - congestion(occurs at the beginning of winter).

Sometimes floods occur under the influence of winds that drive water from the sea and cause an increase in the level due to the delay at the mouth of the water brought by the river - surge floods.

Tsunami- these are gravitational waves of very long length, resulting from the upward or downward displacement of extended sections of the bottom during strong underwater earthquakes (less often volcanic eruptions).

Actions of the population during a flood

The most effective method of protection is evacuation. Before evacuation, it is necessary to turn off electricity, gas, water in the houses; take a supply of food, medicines, documents and depart along the indicated route. In the event of a sudden flood, you must urgently leave the house and take the nearest safe elevated place, posting a signal white or colored flag.

After the water subsides, when returning home, you must follow safety measures: do not come into contact with electrical wiring, do not use food that has fallen into the water. At the entrance to the house to carry out ventilation. It is forbidden to turn on gas and electricity.

5 . Among natural fires allocate:

• fires of steppe and grain massifs;

  peat;

  underground fires of fossil fuels.

In 90-97 cases out of 100, the perpetrators of a fire are people who do not exercise due care when using fire in places of work and recreation. Lightning fires account for 2% of the total.

Forest fires are uncontrolled burning of vegetation, spontaneously spreading through the forest area. Large forest fires develop during a period of extreme danger in the forest, with a long and severe drought. Their development is facilitated by windy weather and cluttered forests.

Depending on the nature of the fire and the composition of the forest, fires are divided into grassroots, riding, soil. Almost all fires at the beginning of their development are in the nature of grassroots and, if certain conditions are created, they turn into crown and soil fires. According to the speed of the spread of fire, grassroots and upland fires are divided into stable and runaway fires from 0.02 m/s to 2 m/s. The intensity of burning depends on the state of the stock of combustible materials, the slope of the terrain, the time of day and especially the strength of the wind.

Runaway ground fires are characterized by the rapid advance of the edge of the fire, when dry grass and fallen leaves are burning. They occur more often in the spring, usually do not damage mature trees, but often pose a threat of crown fire. With stable ground fires, the edge moves slowly, a lot of smoke is formed, which indicates a heterogeneous nature of combustion. They are typical for the second half of summer.

Peat(underground) fire - when it burns a peat layer of waterlogged and swampy soils. Spreading speed – 1-3 m/min. A characteristic feature is the flameless combustion of peat with the release of a large amount of heat. Occur from lightning, spontaneous combustion of peat under adverse weather conditions (high air temperature, drought).

6 . Among the serious dangers that threaten a person and all life on Earth, one should single out those associated with collisions of the planet with cosmic bodies: asteroids, comets, meteorites.

asteroids- These are small planets revolving around the Sun, the diameter of which varies between 1-1000 km.

Comet- a relatively small, compared with an asteroid, celestial body. Most comets move around the Sun in elongated ellipses: when approaching the Sun, under the influence of its heat, they emit gases that form a luminous shell around the nucleus - the head of the comet, and develop a tail directed in the opposite direction from the Sun. As the comet moves away from the Sun, the tail gradually disperses into outer space.

Meteorite- a small solid body that flew into the Earth's atmosphere at a speed of tens of km / s and did not have time to completely evaporate or disperse in the Earth's atmosphere.

fireball- a very bright meteor with a long luminous tail; the flight of a fireball is sometimes accompanied by a strong sound and ends with a meteorite falling onto the earth's surface.

Currently, about 300 space bodies are known that can cross the Earth's orbit. In total, according to astronomers' forecasts, there are ≈ 300 thousand asteroids and comets in space. The encounter of the Earth with such celestial bodies poses a serious threat to the entire biosphere. According to calculations, the impact of an asteroid with a diameter of about 1 km is accompanied by the release of energy ten times greater than the entire nuclear potential available on Earth.

The main means of struggle is nuclear missile technology. It is proposed to develop a planetary protection system against asteroids and comets, which is based on changing the trajectory of a dangerous space object or destroying it into several parts. For this purpose, it is planned to use intercontinental ballistic missiles with a nuclear warhead.

Lecture "Biological and social emergencies"

Biological emergencies include epidemics, epizootics and epiphytoties.

An epidemic is a widespread infectious disease among people, significantly exceeding the incidence rate usually recorded in a given area.

A pandemic is an unusually large spread of morbidity both in terms of level and scale of distribution, covering a number of countries, entire continents and even the globe.

Infectious diseases are divided into:

infections of internal organs (viral hepatitis (Botkin's disease), brucellosis, typhoid fever, dysentery, salmonellosis);

respiratory tract infections (tuberculosis, various pneumoconiosis);

bloodborne or transmissible (HIV);

infections of the external integument (dermatitis, eczema, psoriasis, fungal diseases).

The general biological classification of infectious diseases is based on their division, primarily in accordance with the characteristics of the pathogen (anthroponoses, zoonoses), as well as the division into transmissible and non-transmissible. Infectious diseases by type of pathogen - viral diseases, rickettsiosis, bacterial infections, protozoal diseases, helminthiases, tropical microses, diseases of the blood system.

Epizootics are infectious diseases of animals. These diseases have such signs as the presence of a specific pathogen, cyclical development, the ability to be transmitted from an infected animal to a healthy one and to take epizootic spread.

An epizootic focus is the location of a source of an infectious agent in a certain area of ​​the area where, in a given situation, the transmission of pathogens to susceptible animals is possible.

According to the breadth of distribution, the epizootic process occurs in three forms: sporadic morbidity, epizootic, panzootic.

Sporadia - single, accidental manifestations of an infectious disease that are not interconnected by a single source of the infectious agent (the lowest degree of intensity of the disease).

With an epizootic, an average degree of intensity of the disease is observed, which is accompanied by the spread of diseases in the economy, district, region. Such diseases are characterized by a common source of the infectious agent, the simultaneity of the lesion, periodicity, seasonality.

According to the epizootic classification, all infectious animal diseases are divided into 5 groups:

Group 1 - alimentary infections, transmitted through soil, feed, water. The organs of the digestive system are mainly affected. The pathogen is transmitted through infected feed, manure, soil (anthrax, foot and mouth disease, glanders, brucellosis).

Group 2 - respiratory infections (aerogenic) damage to the mucous membranes of the respiratory tract and lungs. The main route of transmission is airborne (avian influenza, exotic pneumonia, sheep and goat pox, canine distemper).

Group 3 - transmissible infections, transmitted by blood-sucking arthropods (encephalomyelitis, tularemia, infectious anemia of horses).

Group 4 - infections transmitted through the outer integument without the participation of carriers (tetanus, rabies, cowpox).

Group 5 - infectious diseases with unexplained ways of infection.

Panzootic is the highest degree of epizootic development, characterized by an unusually wide spread of the disease, covering one state, several countries, the mainland.

To assess the scale of plant diseases, such concepts as epiphytoty and panphytoty are used.

Epiphytoty is the spread of infectious plant diseases over considerable distances over a certain period of time.

Panphytotia is a mass disease covering several countries or continents.

The most dangerous diseases are stem rust of cereals and potato late blight.

Plant diseases are classified according to the following criteria:

Place or phase of development in plants (diseases of seeds, seedlings, seedlings, mature plants);

Place of appearance (local, local, general);

Current (acute, chronic);

Affected culture;

Cause (infectious or not).

All pathological changes in plants manifest themselves in various forms: rot, mummification, wilting, raids, growths.