Dangerous natural phenomena of meteorological origin. Meteorological phenomena: examples. Dangerous meteorological phenomena. Forecasting natural disasters

Meteorological hazard

natural processes and phenomena that arise in the atmosphere under the influence of various natural factors or their combinations, which have or may have a damaging effect on people, farm animals and plants, economic objects and environment(hurricane, storm, downpour, etc.).

EdwART. Glossary of terms of the Ministry of Emergency Situations, 2010

See what "Meteorological hazard" is in other dictionaries:

Meteorological hazard- natural processes and phenomena that occur in the atmosphere, which have or may have a damaging effect on people, farm animals and plants, economic objects and the surrounding natural environment(hurricane, storm, downpour, etc.) ...

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Dangerous atmospheric phenomena (signs of approach, damaging factors, preventive measures and protective measures)

Meteorological and agrometeorological hazards

Meteorological and agrometeorological hazards are subdivided into:

storms (9-11 points):

hurricanes (12-15 points):

tornadoes, tornadoes;

vertical vortices;

large hail;

heavy rain(shower);

heavy snowfall;

heavy ice;

severe frost;

severe blizzard;

heatwave;

heavy fog;

freezing.

Fog is the concentration of small water droplets or ice crystals in the surface layer of the atmosphere from air saturated with water vapor when it cools. In fogs, horizontal visibility is reduced to 100 m or less. Depending on the horizontal visibility range, a distinction is made between heavy fog (visibility up to 50 m), moderate fog (visibility less than 500 m) and weak fog (visibility is 500 to 1000 m).

Weak air haze with horizontal visibility is called a veil for 1 to 10 km. The veil is strong (visibility 1-2 km), moderate (up to 4 km) and weak (up to 10 km). Distinguish fogs by origin: advective and radiation. Decreased visibility complicates the work of transport - flights are interrupted, timetables and speed changes land transport... Drops of fog, settling on a surface or ground objects under the influence of gravity or air flow, moisturize them. Cases of overlapping insulators of high-voltage power lines as a result of droplets of fog and dew settling on them have been repeatedly noted. Mist drops, like dew drops, provide additional moisture for field plants. By settling on them, the droplets maintain a high relative humidity around them. On the other hand, droplets of fog, settling on plants, contribute to the development of decay.

At night, fogs protect vegetation from excessive cooling as a result of radiation, weaken bad influence frost. During the day, fogs protect vegetation from solar overheating... The deposition of mist droplets on the surface of machine parts leads to deterioration of their coatings and corrosion.

According to the number of foggy days, Russia can be divided into three parts: mountainous regions, the central elevated part and low-lying regions. The frequency of fog increases from south to north. A slight increase in the number of days with fog is observed in spring. Fogs of all types can be observed both at negative and positive temperatures of the soil surface (from 0 to 5 ° C).

Glaze ice is an atmospheric phenomenon that forms as a result of freezing drops of supercooled rain or fog on the surface of the earth and objects. It is a layer of dense ice, transparent or opaque, which builds up on the windward side.

The most significant ice cover is observed during the passage of southern cyclones. When cyclones move eastward from the Mediterranean Sea and fill them over the Black Sea, glaze ice is observed in the south of Russia.

The duration of the ice cover is different - from parts of an hour to 24 hours or more. Formed glaze ice stays on objects for a long time. As a rule, glaze ice forms at night at subzero air temperatures (here 0 ° to - 3 ° C). Ice covered with a strong wind causes significant damage to the economy: under the weight of icing wires break, telegraph poles fall, trees die, traffic stops, etc.

Rime is an atmospheric phenomenon that is the deposition of ice on thin long objects (tree branches, wires). There are two types of rime - crystalline and granular. The conditions of their education are different. Crystalline frost is formed in fog as a result of sublimation (the formation of ice crystals immediately from water vapor without turning it into a liquid state or upon rapid cooling below 0 ° C) water vapor, consists of ice crystals. Their growth occurs on the windward side of objects with a weak wind and temperatures below -15 ° C. The length of crystals does not exceed, as a rule, 1 cm, but can reach several centimeters. Granular rime is snow-like loose ice that grows on objects in foggy, mostly windy weather.

It has sufficient strength. This frost can be many centimeters thick. Most often, crystalline rime occurs in the central part of an anticyclone with a high relative humidity air below the inversion layer. Granular rime, according to the conditions of formation, is close to icy. Rime is observed throughout the territory of Russia, but it is distributed unevenly, since its formation is influenced by local conditions - the height of the area, the shape of the relief, the exposure of slopes, protection from the prevailing moisture-carrying flow, etc.

Due to the low density of frost (bulk density from 0.01 to 0.4), the latter to a greater extent only causes an increase in vibration and sagging of power transmission and communication wires, but can also cause their breaks. The greatest danger for communication lines is frost during strong winds, since the wind creates an additional load on the wires, which sag under the weight of sediments, and the danger of their breakage increases.

A blizzard is an atmospheric phenomenon that is the transfer of snow by the wind over the surface of the earth with a decrease in visibility. There are such blizzards as drifting snow, when most of the snowflakes rise a few centimeters above the snow cover; blowing snow, if snowflakes rise to 2 m or more. These two types of blizzards occur without snow falling from the clouds. And, in the end, the general, or upper, blizzard - snowfall in strong winds. Snowstorms reduce visibility on the roads and interfere with the operation of vehicles.

A thunderstorm is a complex atmospheric phenomenon in which electrical discharges (lightning) occur in large rain clouds and between the clouds and the ground, which are accompanied by a sound phenomenon - thunder, winds and rainstorms, often hail. Lightning strikes damage ground objects, power lines and communications. Thunderstorms and rainstorms, floods and hail accompanying thunderstorm damage agriculture and some areas of industry. There are intra-mass thunderstorms and thunderstorms that occur in the zones of atmospheric fronts. Intra-mass thunderstorms, as a rule, are short-lived and occupy a smaller area than frontal thunderstorms. They arise due to strong heating of the underlying surface. Thunderstorms in the area of ​​the atmospheric front are distinguished by the fact that they often appear in the form of chains of thunderstorm cells that move parallel to each other, covering a significant area.

They occur on cold fronts, fronts of occlusion, and also on warm fronts in warm, humid, tropical air as usual. The zone of frontal thunderstorms is tens of kilometers wide with a front length of hundreds of kilometers. Approximately 74% of thunderstorms are observed in the front zone, other thunderstorms are intra-mass.

During a thunderstorm, you should:

take refuge in the forest among low trees with dense crowns;

hide in a hole, ditch or ravine in the mountains and in open areas;

fold all large metal objects 15-20 m away from you;

having sheltered from the thunderstorm, sit down, bending your legs under you and lowering your head on your legs bent at the knees, connect your feet together;

put under yourself, plastic bag, twigs or spruce branches, stones, clothes, etc. isolating from the soil;

on the way, the group should disperse, walk one at a time, slowly;

in the shelter, change into dry clothes, as a last resort, squeeze out the wet ones thoroughly.

During a thunderstorm, you must not:

take shelter near lonely trees or trees protruding above others;

leaning against or touching rocks and sheer walls;

stop at the edges of the forest, large glades;

walk or stop near bodies of water and in places where water flows;

hide under rocky canopies;

run, fuss, move in a dense group;

be in wet clothes and shoes;

stay on higher ground;

be near watercourses, in crevices and cracks.

blizzard

A snowstorm is one of the types of hurricane, characterized by significant wind speeds, which facilitates the movement of huge masses of snow through the air, has a relatively narrow band of action (up to several tens of kilometers). During a storm, visibility deteriorates sharply, transport links, both intracity and intercity, may be interrupted. The duration of the storm ranges from several hours to several days.

Blizzard, blizzard, blizzard are accompanied by sharp temperature changes and snowfall with strong gusts of wind. Temperature drop, snowfall with rain at low temperatures and strong winds create conditions for icing. Power lines, communication lines, roofs of buildings, various kinds of supports and structures, roads and bridges are covered with ice or sleet, which often causes their destruction. Ice formations on the roads make it difficult, and sometimes even completely impede the operation of road transport. Pedestrian movement will be difficult.

Snow drifts occur as a result of heavy snowfalls and blizzards, which can last from several hours to several days. They cause disruption of transport communications, damage to communication lines and power transmissions, negatively affect economic activity... Snow drifts are especially dangerous when descending snow avalanches from the mountains.

The main damaging factor such natural Disasters is the impact of low temperatures on the human body, causing frostbite, and sometimes freezing.

In case of an imminent threat, the population is alerted, the necessary forces and means, road and communal services are alerted.

A blizzard, blizzard or blizzard can last for several days, therefore it is recommended to create a supply of food, water, fuel in the house in advance, and prepare emergency lighting. You can leave the premises only in exceptional cases and not alone. Restrict movement, especially in rural areas.

Driving a car should only be done on major roads. In the event of a sharp increase in the wind, it is advisable to wait out in locality or near it. If the machine breaks down, do not leave it out of sight. If further movement is impossible, mark a parking lot, stop (with the engine facing upwind), cover the engine from the radiator side. In heavy snow, make sure that the car is not covered with snow, i.e. shovel snow as needed. The car engine must be periodically warmed up to avoid its "defrosting", while not allowing exhaust gases to enter the cab (body, interior), for this purpose, make sure that the exhaust pipe is not blocked by snow. If there are several cars, it is best to use one car as a shelter; the engines of other cars must be drained of water.

In no case should you leave the shelter (car); in heavy snow, landmarks after a few tens of meters may be lost.

A blizzard, blizzard or blizzard can be waited out in a shelter equipped with snow. It is recommended to build a shelter only in open areas, where snow drifts are excluded. Before taking cover, you need to find landmarks on the terrain in the direction of the nearest housing and remember their location.

From time to time it is necessary to control the thickness of the snow cover by piercing the ceiling of the shelter, and to clear the entrance and ventilation hole.

You can find an elevated, stable object in an open and snowless area, hide behind it and constantly throw away and trample the arriving snow mass with your feet.

In critical situations, it is permissible to completely bury yourself in dry snow, for which you put on all warm clothes, sit with your back to the wind, cover yourself with plastic wrap or a sleeping bag, pick up a long stick and let the snow cover you. Constantly clear the ventilation hole with a stick and expand the volume of the formed snow capsule in order to be able to get out of the snow drift. An arrow-reference should be laid out inside the formed shelter.

Remember that a blizzard due to many-meter snow drifts and snowdrifts can significantly change appearance terrain.

The main types of work in case of snow drifts, blizzards, blizzards or blizzards are:

tracing the missing people and providing, if necessary, first aid to them;

clearing roads and areas around buildings;

providing technical assistance to stuck drivers;

elimination of accidents on communal energy networks.

Hail is an atmospheric phenomenon associated with the passage of cold fronts. It occurs with strong ascending air currents during warm seasons. Water droplets falling on great height with streams of air, freeze, and ice crystals begin to grow on them in layers. The drops become heavy and begin to sink down. When falling, they increase in size from merging with drops of supercooled water. Sometimes the hail can reach the size of a hen's egg. Typically, hail falls from large rain clouds during thunderstorms or rainstorms. It can cover the ground with a layer of up to 20-30 cm. The number of days with hail increases in mountainous areas, on hills, in areas with highly rugged terrain. Hail falls mainly in the second half of the day on relatively small areas of several kilometers. The hail usually lasts from a few minutes to a quarter of an hour. The hail causes significant material damage. He destroys crops, vineyards, knocks flowers and fruits from plants. If the size of the hailstones is significant, it can cause destruction of buildings and loss of life. At this time, methods have been developed for determining hail-hazardous clouds, a hail control service has been created. Dangerous clouds are "shot" with special chemicals.

Dry wind - hot and dry wind at a speed of 3 m / s or more, with a high air temperature up to 25 ° С and a low relative humidity up to 30%. Dry winds are observed in low-cloud weather. Most often they occur in the steppes along the periphery of anticyclones, which are formed above North Caucasus and Kazakhstan.

The highest dry wind speeds were observed during the day, the lowest - at night. Dry winds cause great damage to agriculture: they raise the water balance of plants, especially when there is a lack of moisture in the soil, since intensive evaporation cannot be compensated by the intake of moisture through the root system. With prolonged exposure to dry winds, the ground part of the plants turns yellow, foliage curls, their wilting sets in and even the death of field crops.

Dust or black storms - transfer a large number dust or sand in a strong wind. They arise during dry weather due to the waving of sprayed soils over great distances. On the occurrence, recurrence and intensity of dust storms big influence orography, the nature of soils, forest cover and other features of the area.

Most often, dust storms occur from March to September. The most intense and dangerous spring dust storms during a prolonged absence of rain, when the soil dries up, and the plants are still underdeveloped and do not form a continuous cover. At this time, storms blow out the soil over vast areas. Decreases horizontal visibility. S.G. Popruzhenko investigated a dust storm in 1892 in the south of Ukraine. Here is how he described her: "Dry, strong Eastern wind for several days he tore up the earth and drove masses of sand and dust. The crops, which turned yellow from the dry air, were cut to the root like a sickle, but the roots could not survive. The earth was pulled down to 17 cm depth. The channels are backfilled up to 1.5 m.

Hurricane

A hurricane is a wind of destructive force and duration. A hurricane occurs suddenly in areas with a sharp drop in atmospheric pressure. The hurricane speed reaches 30 m / s and more. In terms of its harmful effects, a hurricane can be compared to an earthquake. This is due to the fact that hurricanes carry colossal energy, its amount released by an average hurricane within one hour can be compared with the energy of a nuclear explosion.

A hurricane can cover an area up to several hundred kilometers in diameter and can travel thousands of kilometers. At the same time, a hurricane wind destroys strong and demolishes light buildings, devastates sown fields, breaks wires and knocks down power transmission and communication lines, damages transport highways and bridges, breaks and uproots trees, damages and sinks ships, causes accidents on utility networks ... There were times when a hurricane wind threw trains off the rails and fell factory chimneys. Hurricanes are often accompanied by heavy rains that cause flooding.

A storm is a type of hurricane. The wind speed during a storm is not much less than the speed of a hurricane (up to 25-30 m / s). Losses and destruction from storms are significantly less than from hurricanes. Sometimes violent storm called a storm.

Tornado is a strong small-scale atmospheric vortex with a diameter of up to 1000 m, in which the air rotates at a speed of up to 100 m / s, which has a great destructive force (in the USA it is called a tornado).

On the territory of Russia, tornadoes are noted in the Central region, the Volga region, the Urals, Siberia, Transbaikalia, the Caucasian coast.

Tornado - an upward vortex consisting of extremely rapidly rotating air mixed with particles and moisture, sand, dust and other suspended matter. On the ground, it moves in the form of a dark column of spinning air with a diameter of several tens to several hundred meters.

In the inner cavity of the tornado, the pressure is always low, so any objects that are in its path are sucked in there. average speed tornado moves 50-60 km / h, when it approaches, a deafening rumble is heard.

Strong tornadoes travel tens of kilometers and tear off roofs, uproot trees, lift cars into the air, scatter telegraph poles, and destroy houses. Threat notification is carried out by sending a signal "Attention to all" with a siren and subsequent voice information.

Actions upon receipt of information about an impending hurricane, storm or tornado - you should carefully listen to the instructions of the Civil Emergency Situations Department, which will inform you of the estimated time, the strength of the hurricane and recommendations on the rules of conduct.

Upon receipt of a storm warning, you must immediately begin to carry out preventive work:

strengthen insufficiently strong structures, close doors, dormers and attic spaces, sheathe windows with boards or cover with shields, and glue the glass with strips of paper or cloth, or, if possible, remove;

in order to balance the external and internal pressure in the building, it is advisable to open doors and windows on the leeward side and fix them in this position;

from roofs, balconies, loggias and window sills it is necessary to remove things that, if dropped, can injure people. Objects in the courtyards must be fixed or brought into the room;

it is also advisable to take care of emergency lamps - electric lamps, kerosene lamps, candles. It is also recommended to stockpile water, food and medicine, especially dressings;

extinguish the fire in the stoves, check the condition of electrical switches, gas and water taps;

take pre-prepared places in buildings and shelters (in the case of tornadoes - only in basements and in underground structures). In the room, you need to choose the safest place - in the middle of the house, in the corridors, on the first floor. It is recommended to use built-in wardrobes, sturdy furniture and mattresses to protect against injury from glass splinters.

The safest places during a storm, hurricane, or tornado are shelters, basements, and cellars.

If a hurricane or tornado finds you in an open area, it is best to find any natural depression in the ground (ditch, hole, ravine or any recess), lie down on the bottom of the depression and snuggle tightly to the ground. Leave the vehicle (no matter which one you are in) and take refuge in the nearest basement, shelter or depression. Take measures to protect against heavy rainfall and hail. hurricanes are often accompanied by them.

be on bridges, as well as in the immediate vicinity of objects that use poisonous, potent and flammable substances in their production;

take shelter under freestanding trees, poles, come close to the poles of power lines;

be near buildings from which gusts of wind blow off tiles, slate and other objects;

After receiving a message about the stabilization of the situation, you should leave the house carefully, you need to look around - there are no overhanging objects and parts of structures, broken electrical wires. it is possible that they are energized.

Do not enter damaged buildings unless absolutely necessary, but if such a need arises, then it must be done carefully, making sure that there is no significant damage to stairs, ceilings and walls, fires, breaks in electrical wires, you cannot use the elevators.

The fire cannot be ignited until it is certain that there has been no gas leak. When outdoors, stay away from buildings, pillars, high fences, etc.

The main thing in these conditions is not to panic, to act competently, confidently and reasonably, not to allow yourself and keep others from unreasonable actions, to provide assistance to the victims.

The main types of injury to people in hurricanes, storms and tornadoes are closed injuries to various areas of the body, bruises, fractures, concussions, injuries accompanied by bleeding.

There are two main types of precipitation. The first is precipitation falling over a vast territory as a result of cyclonic activity; it can be subdivided into frontal and non-frontal. Frontal forms when warm air rises above cold air, non-frontal ones - when horizontal convergence occurs and the rising air flows into a low pressure area. Precipitation of the second type falls on a smaller area and represents more intense thunderstorms. showers, in which the warmer air of the lower layers is quickly carried upward by strong convective currents. Convective precipitation can be one of the stages cyclone, and both types of precipitation can be enhanced by additional air rise over high landforms.

Under certain conditions, precipitation falls out of the clouds, i.e. droplets or crystals are large enough that they cannot be suspended in the atmosphere. Rain and snow are the most typical and important, however there are several types of precipitation that differ from the typical forms of rain and snow. Depending on the physical conditions education (on a genetic basis) sediments are subdivided into three types. Clouds of orderly ascending movement (nimbostratus and altostratus) associated with fronts fall heavy precipitation... These are moderate precipitation. They fall out at once over large areas (of the order of hundreds of thousands of square kilometers), spread relatively evenly and last for a fairly long time (about tens of hours). In the area captured by the frontal cloud system, precipitation is recorded at all or most of the stations, and the amount of precipitation at individual stations does not differ too much from one another. The largest percentage in the total amount of precipitation in temperate latitudes is made up of overburden precipitation.

Cloud classification.

1. Cirrus - Cirrus (Ci);
2. Cirrocumulus - Cirrocumulus (Cc);
3. Cirrostratus - Cirrostratus (Cs);
4. Altocumulus - Altocumulus (Ac);
5. Highly layered - Altostratus (As);
6. Nimbostratus - Nimbostratus (Ns);
7. Stratocumulus - Stratocumulus (Sc);
8. Layered - Stratus (St);
9. Cumulus - Cumulus (Cu);
10. Cumulonimbus - Cumulonimbus (Cb).

Cumulonimbus clouds associated with convection receive intense but short-lived rainfall. They can be very intense immediately after the start, but soon break off quickly. Their relatively short duration is explained by the fact that they are associated with individual clouds or narrow cloud zones. In the cold air mass moving above the warm earth's surface, heavy rain at any particular point sometimes lasts only a few minutes. With local convection in summer over land, when the atmosphere is unstable throughout the day and cumulonimbus clouds form continuously or when the fronts pass, showers sometimes last for hours. According to observations in the United States, average area, simultaneously captured by the same heavy rain, about 20 square kilometers. The intensity of rainfall varies greatly. Even during one rain, the amount of precipitation, which fell at a distance of only 1–2 km, can differ by 50 mm. Heavy rainfall is the main type of rainfall in low tropical and equatorial zones... In addition to heavy and heavy rainfall, drizzling precipitation is also distinguished. This is intramass precipitation falling from stratus and stratocumulus clouds typical of warm or local stable air masses. The vertical extent of these clouds is small, therefore, in the warm season, precipitation can fall out of them only as a result of the mutual merging of drops. Falling liquid precipitation - drizzle - consists of very small droplets. In winter, when low temperatures oh, such clouds can contain crystals, then instead of drizzle, small snowflakes and so-called snow grains fall out of them. As a rule, drizzling precipitation does not provide significant daily amounts of moisture. In winter, they do not noticeably increase the snow cover. Only in special conditions for example, in the mountains, drizzle may be more intense and heavy.

Precipitation form.

Distinguish in form the following types precipitation.

Rain

Rain- liquid precipitation, consisting of drops with a diameter of 0.5–6 mm. Drops of larger sizes break into pieces when dropped. In heavy rains, the size of the drops is greater than in heavy rains, especially at the beginning of the rain. At negative temperatures, sometimes supercooled drops can fall out. Contacting the earth's surface, they freeze and cover it with an ice crust.

Drizzle

Drizzle- liquid precipitation, consisting of droplets with a diameter of the order of 0.5–0.05 mm with a very low falling speed. They are easily carried horizontally by the wind.

Snow

Snow- solid precipitation, consisting of complex ice crystals (snowflakes). Their forms are varied and depend on the conditions of education. The main form of snow crystals is a six-pointed star. Stars are obtained from hexagonal plates, because water vapor sublimation occurs most rapidly at the corners of the plates, where the rays grow. On these rays, in turn, ramifications are created. The diameters of falling snowflakes can be very different (on average, on the order of a few millimeters). When falling, snowflakes often merge into large flakes. At temperatures close to zero and above zero, sleet or snow and rain falls. It is characterized by large flakes. At freezing temperatures, nimbostratus and cumulonimbus clouds also produce croup, snowy and icy, - precipitation consisting of icy and heavily grained snowflakes with a diameter of more than 1 mm. Most often, groats are observed at temperatures close to zero, especially in autumn and spring. Snow grains have a snow-like structure: grains are easily compressed with fingers. The nucleoli of the ice grains have an icy surface. It is difficult to crush them; when falling to the ground, they jump. In winter, instead of drizzle, snow grains fall out of stratus clouds - small grains less than 1 mm in diameter, resembling semolina. In winter, at low temperatures, snow needles sometimes fall out of the clouds of the lower or middle tier - precipitation consisting of ice crystals in the form of hexagonal prisms and plates without branching. In severe frosts, such crystals can appear in the air near the earth's surface. They are especially visible on a sunny day, when they sparkle with their faces, reflecting the sun's rays. Clouds of the upper tier are composed of such ice needles. It has a special character freezing rain- precipitation consisting of transparent ice balls (drops of rain frozen in the air) with a diameter of 1–3 mm. Their fallout clearly indicates the presence of temperature inversion. Somewhere in the atmosphere there is a layer of air with a positive temperature, in which the crystals falling from above have melted and turned into drops, and under it is a layer with negative temperature where the drops are frozen. In summer enough hot weather from cumulonimbus clouds sometimes falls hail.

Hail

Hail- precipitation in the form of spherical or irregular ice pieces (hailstones) with a diameter of several millimeters or more. The mass of hailstones in some cases exceeds 300 g. The hailstones consist of a white opaque core and then of successive transparent and cloudy layers of ice. Hail falls from cumulonimbus clouds during thunderstorms and usually with heavy rain. The type and size of the hailstones indicate that during their "life" they are repeatedly dragged up and down by strong convection currents. As a result of collision with supercooled drops, hailstones increase in size.

In descending currents, hailstones descend into layers with positive temperatures, where they thaw from above, then in ascending flows they rise again and freeze from the surface, etc. For the formation of hailstones, a large water content of the clouds is required, therefore hail falls only in the warm season when high temperatures near the earth's surface. Most often, hail falls in temperate latitudes, and with the greatest intensity in the tropics. No hail is observed in polar latitudes. There have been cases when hail lay on the ground for a long time in a layer of several tens of centimeters. Hail often damages crops and destroys them (hail). In some cases, animals and even people can suffer from it.

Thunderstorm

Thunderstorm- an electrical atmospheric phenomenon in which multiple electrical discharges (lightning) accompanied by thunder occur in powerful cumulonimbus clouds or between clouds and the earth's surface. Thunderstorms are usually accompanied by squally winds, heavy rainfall, often with hail.

The average duration of a torrential rain is 25 minutes, mostly heavy rain lasts from 5-15 minutes, then its intensity weakens, and much more slowly than it increases at the beginning of its fall.

According to the conditions of development, thunderstorms are divided into: intramass and frontal.

Intra-mass thunderstorms over the mainland arise as a result of local heating of air from the earth's surface, which leads to the development of upward currents of local convection in it and to the formation of powerful cumulonimbus clouds. Therefore, intramass thunderstorms over land develop mainly in the afternoon hours. Above the seas, the most favorable conditions for the development of convection are observed at night, and the maximum in the diurnal cycle occurs at 4–5 o'clock in the morning.

Frontal thunderstorms appear on the frontal partitions, i.e. at the boundaries between warm and cold air masses and do not have a regular daily variation. Over the continents of the temperate zone, they are most frequent and intense in summer, in arid regions - in spring and autumn. Winter thunderstorms occur in exceptional cases - during the passage of particularly sharp cold fronts.

Thunderstorms on Earth are unevenly distributed: in the Arctic they occur every few years, in temperate at each separate point there are several tens of days with thunderstorms. The tropics and the equatorial region are the most thunderstorm regions of the Earth and are called the "belt of eternal thunderstorms", they have their own "pole" - the Butenzorg region on the island of Java: here thunderstorms rage 322 days a year. In the Sahara Desert, there are almost no thunderstorms at all.

Thunder

Thunder- a sound phenomenon in the atmosphere accompanying lightning. Thunder is caused by vibrations in the air as a result of the rapid heating and expansion of air in the path of lightning. Thunder has the character of long peals and is usually heard at a distance of no more than 15-20 km. The peals of thunder are explained by the reflection of sound from the clouds, as well as by the fact that lightning has a great length, and the sound from different parts of it does not reach the ear of the observer at the same time.

Lightning

Lightning- a giant electric spark discharge in the atmosphere between clouds or between clouds and the earth's surface several kilometers long, tens of centimeters in diameter and tenths of a second long (linear lightning). Occasionally observed ball lightning... Usually lightning is bright flash light, it is accompanied by thunder and contains several repeated discharges, the duration of multiple lightning sometimes exceeds 1 s.

Edward Kononovich

DANGEROUS METEOROLOGISTSCHESKIE JAVL YENIYA, combine meteorological, and often the hydrological phenomena caused by them, which in intensity and duration pose a threat to the safety of people, and can also cause significant damage to sectors of the economy or natural conditions... These include hurricane winds (tropical cyclones, typhoons, etc.), tornadoes (tornadoes), squalls, hail, ice and frost, sleet, blizzards, showers, prolonged rains, snowfalls, fogs, thunderstorms, dust storms, abnormal heat, decreased horizontal and vertical visibility. The latter phenomena are especially dangerous for aviation when the peaks of mountains and hills in the area of ​​flights are shielded by clouds. O. m. I. with the exception of two or three options, they refer to local, or mesoscale phenomena, therefore there is no systematization and reduction of them into a single summary. E.g. rainy and dry periods of tropical monsoons, tornado and tropical cyclone seasons in the Great Plains of the USA, typhoons in Far East... These phenomena are determined by the peculiarities of the processes of the general circulation of the atmosphere and, to a lesser extent, by the peculiarities of the orography and the distribution of water bodies. To the south. districts European territory Russia unfavorable conditions
are created during droughts and dry winds, repeating about 1 time in 10 years. However, due to the irregular nature of the weather on Earth, it is still difficult to predict their onset and duration, and therefore the damage caused. Local-scale phenomena, such as flash or surge floods and floods, are formed both as a result of natural processes and anthropogenic factors. For example, flooding during river floods of residential buildings built in floodplain, irregularly flooded places, runoff from the surrounding slopes, with a natural decrease in filtration deep into the soil, destruction of irrigation facilities, as well as improper maintenance of bridge structures, etc. Below is a typical list O. m. I., Developed by the Hydrometeorological Center of the Russian Federation, on the basis of which the territorial administrations of the hydrometeorological service (UGMS) draw up a list of hazardous phenomena for their service area, updated taking into account local specifics. See table. one.

Table 1. Typical list of dangerous meteorological phenomena for the territory of Russia (2007)

O. m. I. in some cases lead to catastrophic consequences. Floods are especially frequent under their influence. Tropical cyclones are almost always associated with significant amounts of atmospheric precipitation, primarily in the area of ​​the “eye of the storm” wall (see Art. Typhoon) and cyclone rain strips. The “Great Mississippi Flood” occurred in the United States in 1927. After 18 hours of continuous downpours, the Mississippi overflowed its banks and broke through a dam at 145 sites, flooding 70,000 km 2, the spill width reached 97 km, and the depth in flooded areas reached 10 m. 10 states: Kentucky, Arkansas, Illinois, Louisiana, Mississippi, Missouri, Tennessee, Texas, Oklahoma, Kansas. 700,000 people were left homeless, 246 people died, economic losses amounted to $ 400 million.

Main Areas of occurrence of tropical cyclones make up seven virtually isolated continuous zones, which are called basins. The most active is north-west. Pacific Basin, where 25.7 tropics occur annually. cyclone strength of a tropical storm or more (out of 86 in the world). The least active is the North Indian Ocean basin, where only 4–6 tropical cyclones occur annually.

The rise in sea level under the influence of cyclone Bhola in 1970 was catastrophic in terms of the number of victims from tropical cyclones, when 300-500 thousand people died due to a 9-meter storm tide and flooding of the islands of the shallow Ganges delta. in East Pakistan.

Great destruction is caused by hurricane winds and tornadoes (tornadoes) in America. In April 1965, 37 tornadoes, different in power, appeared over the United States at the same time, heights. up to 10 km, diameter approx. 2 km, with wind speeds of up to 300 km per hour, these vortices have caused tremendous destruction in six states. The death toll exceeded 250 people, 2500 people. were injured. See table. 2 and tab. 3.

Interesting incidents related to tornadoes are mentioned. The first news of a tornado in Russia dates back to 1406. The Trinity Chronicle reports that under Nizhny Novgorod the whirlwind lifted the team together with the horse and man into the air and carried it to the other side of the Volga. The next day, the cart and the dead horse were found hanging from a tree, and the man was missing. On June 16 (29), 1904 at 5 p.m., a tornado in Moscow uprooted all the trees (some up to a meter in coverage) of the Annenhof grove, caused damage to Lefortovo, Sokolniki, Basmannaya Street, Mytishchi, drew water from the Moskva River, exposing its bottom ... In 1940, in the village of Meshchera, Gorky Region. there was a rain of silver coins. A thunderstorm rain washed away the treasure with coins, and the tornado lifted the coins into the air and threw them outside the village. "Irving tornado" in the United States on May 30, 1879 lifted a wooden church with parishioners during a church service. Moving it 4 m to the side, the tornado left. The frightened parishioners did not suffer significant damage, apart from injuries from plaster and pieces of wood that fell from the ceiling.

Table 2. Record hurricanes in damage caused

Table 3. Record hurricanes by death toll

These processes and phenomena are associated with various atmospheric processes, and primarily with the processes occurring in the lower layer of the atmosphere - the troposphere. In the troposphere is about 9 / 10 of the entire mass of air. Under the influence of solar heat entering the earth's surface, and the forces of gravity in the troposphere are formed clouds, rain, snow, wind.

Air in the troposphere moves horizontally and vertically. Strongly heated air near the equator expands, becomes lighter and rises. There is an ascending movement of the air-spirit. For this reason, a layer of low atmospheric pressure is formed near the Earth's surface near the equator. At the poles, due to low temperatures, the air cools, becomes heavier and sinks. There is a descending air movement. For this reason, the pressure is high near the Earth's surface near the poles.

In the upper troposphere, on the contrary, above the equator, where ascending air currents prevail, the pressure is high, and above the poles it is low. Air is constantly moving from an area of ​​increased pressure to an area of ​​reduced pressure. Therefore, the air rising above the equator spreads to the poles. But due to the rotation of the Earth around its axis, the moving air does not reach the poles. As it cools, it becomes heavier and sinks around the 30s north and south, forming high pressure areas in both hemispheres.

Large volumes of air in the troposphere with homogeneous properties are called air masses. The properties of air masses depend on the territories over which they were formed. Moving, air masses retain their properties for a long time, and when they meet, they interact with each other. The movement of air masses and their interaction determine the weather in those places where these air masses come. The interaction of various air masses leads to the formation in the troposphere of moving atmospheric vortices - cyclones and anticyclones.

A cyclone is a flat ascending vortex with a low atmospheric pressure in the center. The diameter of the cyclone can be several thousand kilometers. The weather during the cyclone is cloudy with strong winds.

An anticyclone is a flat descending vortex with a high atmospheric pressure with a maximum in the center. In the high pressure area, the air does not rise, but falls. The air spiral spins clockwise in the northern hemisphere. The weather during the anticyclone is slightly cloudy, without precipitation, and the wind is weak.

With the movement of air masses, with their interaction, the appearance of dangerous meteorological phenomena that can cause natural disasters is associated. This iPhones and hurricanes, storms, snowstorms, tornadoes, thunderstorms, drought, severe frosts and fogs.