Tropical latitudes or atmospheric vortex. Classification of hazardous natural phenomena Hazardous meteorological (agrometeorological) phenomena - natural processes and phenomena occurring in the atmosphere - presentation. Air masses and atmospheric fronts

Characteristics of hurricanes, storms, tornadoes

Hurricanes, storms, tornadoes are wind meteorological phenomena , classified as natural disasters, can cause great material damage and lead to loss of life.

Wind- movement of air relative to the earth's surface, resulting from uneven distribution of heat and atmospheric pressure. The main indicators of wind are direction (from a high pressure zone to a low pressure zone) and speed (measured in meters per second (m/s; km/h; miles/hour).

To denote the movement of wind, many words are used: hurricane, storm, gale, tornado... To systematize them, they use Beaufort scale(developed by the English admiral F. Beaufort in 1806) , which allows you to very accurately estimate the strength of the wind in points (from 0 to 12) by its effect on ground objects or on waves at sea. This scale is also convenient because it allows you to quite accurately determine the wind speed without instruments based on the characteristics described in it.

Beaufort scale (Table 1)

Beaufort points		Wind speed, m/s (km/h)	Wind action on land
On the land	On the sea
	Calm	0,0 – 0,2 (0,00-0,72)	Calm. Smoke rises vertically	Mirror smooth sea
	Quiet breeze	0,3 –1,5 (1,08-5,40)	The direction of the wind is noticeable by the direction of the smoke,	Ripples, no foam on the ridges
	Light breeze	1,6 – 3,3 5,76-11,88)	The movement of the wind is felt by the face, the leaves rustle, the weather vane moves	Short waves, crests do not capsize and appear glassy
	Light breeze	3,4 – 5,4 (12,24-19,44)	Leaves and thin branches of trees sway, the wind flutters the upper flags	Short, well-defined waves. The ridges, overturning, form foam, and occasionally small white lambs are formed.
	Moderate breeze	5,5 –7,9 (19,8-28,44)	The wind raises dust and pieces of paper and moves thin tree branches.	The waves are elongated, white caps are visible in many places.
	Fresh breeze	8,0 –10,7 (28,80-38,52)	Thin tree trunks sway, waves with crests appear on the water	The waves are well developed in length, but not very large; whitecaps are visible everywhere.
	Strong breeze	10,8 – 13,8 (38,88-49,68)	Thick tree branches sway, wires hum	Large waves begin to form. White foamy ridges occupy large areas.
	strong wind	13,9 – 17,1 (50,04-61,56)	The tree trunks are swaying, it’s difficult to walk against the wind	The waves pile up, the crests break off, the foam lies in stripes in the wind
	Very strong wind (storm)	17,2 – 20,7 (61,92-74,52)
	Storm (strong storm)	20,8 –24,4 (74,88-87,84)
	Severe storm (full storm)	24,5 –28,4 (88,2-102,2)
		28,5 – 32,6 (102,6-117,3)
	Hurricane	32.7 or more (117.7 or more)	Heavy objects are carried by wind over considerable distances	The air is filled with foam and spray. The sea is all covered with stripes of foam. Very poor visibility.

Characteristics of atmospheric vortices

Atmospheric vortices	Local name	Characteristic
Cyclone (tropical and extratropical) - vortices in the center of which there is low pressure	Typhoon (China, Japan) Bagwiz (Philippines) Willy-Willy (Australia) Hurricane (North America)	Vortex diameter 500-1000 km Height 1-12 km Diameter of calm area ("eye of the storm") 10-30 km Wind speed up to 120 m/s Duration of action - 9-12 days
A tornado is an ascending vortex consisting of rapidly rotating air mixed with particles of moisture, sand, dust and other suspended matter, an air funnel descending from a low cloud onto a water surface or land	Tornado (USA, Mexico) Thrombus (Western Europe)	Height - several hundred meters. Diameter - several hundred meters. Travel speed up to 150-200 km/h Rotation speed of vortices in the funnel up to 330 m/s
Squalls are short-term whirlwinds that occur before cold atmospheric fronts, often accompanied by rain or hail and occurring in all seasons of the year and at any time of the day.	Storm	Wind speed 50-60 m/s Duration up to 1 hour
A hurricane is a wind of great destructive power and considerable duration, occurring mainly from July to October in the zones of convergence of a cyclone and an anticyclone. Sometimes accompanied by showers.	Typhoon (Pacific)	Wind speed more than 29 m/s Duration 9-12 days Width - up to 1000 km
A storm is a wind whose speed is less than a hurricane.	Storm	Duration - from several hours to several days Wind speed 15-20 m/s Width - up to several hundred kilometers

Hurricane

A hurricane is a fast movement of wind, with a speed of 32.7 m/s (117 km/h), although it can exceed 200 km/h (12 points on the Beaufort scale) (Table 1), with a significant duration of several days ( 9-12 days), continuously moving over the oceans, seas and continents and possessing great destructive power. The width of the hurricane is taken to be the width of the catastrophic destruction zone. Often this zone is supplemented with an area of ​​storm force winds with relatively little damage. Then the width of the hurricane is measured in hundreds of kilometers, sometimes reaching 1000 km. Hurricanes occur at any time of the year, but are most common from July to October. In the remaining 8 months they are rare, their paths are short.

A hurricane is one of the most powerful manifestations of nature; its consequences are comparable to an earthquake. Hurricanes are accompanied by precipitation large quantity precipitation and lower air temperatures. The width of the hurricane ranges from 20 to 200 kilometers. Most often, hurricanes sweep over the USA, Bangladesh, Cuba, Japan, the Antilles, Sakhalin, and the Far East.

In half of the cases, the wind speed during a hurricane exceeds 35 m/sec, reaching 40-60 m/sec, and sometimes up to 100 m/sec. Hurricanes are classified into three types based on wind speed:

- Hurricane(32 m/s or more),

- strong hurricane(39.2 m/s or more)

- violent hurricane (48.6 m/s or more).

The reason for such hurricane winds is the emergence, as a rule, on the line of collision of fronts of warm and cold air masses, powerful cyclones with a sharp pressure drop from the periphery to the center and with the creation of a vortex air flow moving in the lower layers (3-5 km) in a spiral to the middle and upwards, in the northern hemisphere - counterclockwise. Forecasters assign each hurricane a name or four-digit number.

Cyclones, depending on the place of their origin and structure, are divided into:

1) Tropical cyclones meet over warm tropical oceans, in the stage of formation usually moves to the west, and after the end of formation they bend towards the poles. A tropical cyclone that has reached unusual strength called:

-tropical storm if he is born in Atlantic Ocean and the adjacent seas. North and South America. Hurricane (Spanish huracán, English hurricane) named after the Mayan god of wind Huracan;

- typhoon – if it originated over the Pacific Ocean. Far East, Southeast Asia;

- cyclone – in the region Indian Ocean.

Rice. Structure of a tropical cyclone

Eye - central part a cyclone in which air descends.

The eye wall is a ring of dense cumulus thunderclouds surrounding the eye.

The outer portion of a tropical cyclone is organized into rain bands—bands of dense thunderstorm cumulus clouds that slowly move toward the center of the cyclone and merge with the eye wall.

One of the most common definitions of cyclone size, which is used in various databases, is the distance from the center of circulation to the outermost closed isobar, this distance is called radius of the outer closed isobar.

2) Temperate latitude cyclones can form both over land and over water. They usually move from west to east. Characteristic feature Such cyclones are characterized by their great “dryness”. The amount of precipitation during their passage is significantly less than in the zone of tropical cyclones.

3) The European continent is affected as tropical hurricanes, originating in the central Atlantic, and cyclones of temperate latitudes.

Rice. Hurricane Isabel of 2003, photograph from the ISS - the characteristic eye of a tropical cyclone, the eye wall and surrounding rain bands can be clearly seen.

Tempest (storm)

Tempest (storm) is a type of hurricane, inferior in strength. Hurricanes and storms differ only in wind speed. A storm is a strong, long-lasting wind, but its speed is less than that of a hurricane 62 - 117 km/h (8 - 11 points on the Beaufort scale). A storm can last from 2-3 hours to several days, covering a distance (width) from tens to several hundred kilometers. A storm that breaks out at sea is called a storm.

Depending on the color of the particles involved in the movement, they distinguish: black, red, yellow-red and white storms.

Depending on the wind speed, storms are classified:

Beaufort points	Verbal definition of wind force	Wind speed, m/s (km/h)	Wind action on land
On the land	On the sea
	Very strong wind (storm)	17,2 – 20,7 (61,92-74,52)	The wind breaks tree branches, it is very difficult to walk against the wind	Moderately high, long waves. Spray begins to fly up along the edges of the ridges. Stripes of foam lie in rows downwind.
	Storm (strong storm)	20,8 –24,4 (74,88-87,84)	Minor damage; the wind tears off smoke hoods and tiles	High waves. The foam falls in wide dense stripes in the wind. The crests of the waves capsize and crumble into spray.
	Severe storm (full storm)	24,5 –28,4 (88,2-102,2)	Significant destruction of buildings, trees are uprooted. Rarely happens on land	Very high waves with long, downward-curving crests. The foam is blown up by the wind in large flakes in the form of thick stripes. The surface of the sea is white with foam. The crash of the waves is like blows. Visibility is poor.
	Fierce storm (fierce storm)	28,5 – 32,6 (102,6-117,3)	Large destruction over a large area. Very rarely observed on land	Exceptionally high waves. Vessels are hidden from view at times. The sea is all covered with long flakes of foam. The edges of the waves are blown into foam everywhere. Visibility is poor.

Storms are divided:

1) Vortex– are complex vortex formations caused by cyclonic activity and spreading over large areas. They are:

- Snow storms (winter) are formed in winter. Such storms are called blizzards, blizzards, and blizzards. Accompanied by severe frost and blizzards, they can move huge masses of snow over long distances, which leads to heavy snowfalls, blizzards, and snow drifts. Snow storms paralyze traffic, disrupt energy supplies, and lead to tragic consequences. The wind helps to cool the body, causing frostbite.

- Squalls – occur suddenly and are extremely short in duration (several minutes). For example, within 10 minutes the wind speed can increase from 3 to 31 m/sec.

2) Stream storms– these are local phenomena of small distribution, weaker than vortex storms. Most often they pass between chains of mountains connecting valleys. Divided into:

- Stock – the air flow moves down the slope from top to bottom.

- Jet – air flow moves horizontally or uphill.

Rice. Storm (storm) Work on the masts of a sailing ship in a storm.

Tornado (tornado)

Tornadoes (in English terminology, tornadoes from Spanish. tornar“twist, twist”) is atmospheric vortex in the form of a dark sleeve with a vertical curved axis and a funnel-shaped expansion in the upper and lower parts. The air rotates at a speed of 50-300 km/h counterclockwise and rises upward in a spiral. Inside the flow, the speed can reach 200 km/h. Inside the column there is a low pressure (rarefaction), which causes suction, lifting up everything encountered along the way (earth, sand, water, sometimes very heavy objects). The height of the sleeve can reach 800 - 1500 meters, the diameter - from several tens above water to hundreds of meters above land. The length of the tornado’s path ranges from several hundred meters to tens of kilometers (40 – 60 km). The tornado spreads following the terrain, the speed of the tornado is 50 - 60 km/h.

A tornado arises in a thundercloud (in the upper part it has a funnel-shaped expansion that merges with the clouds) saturated with charged ions and then spreads in the form of a dark sleeve or trunk towards the surface of the land or sea. When a tornado descends to the surface of the earth or water, its lower part also becomes expanded, similar to an overturned funnel. Tornadoes occur both over the water surface and over land, much more often than hurricanes, usually in the warm sector of a cyclone, often before a cold front. Its formation is associated with a particularly strong instability of the regular distribution of atmospheric air temperatures over altitude (atmospheric stratification). It is often accompanied by thunderstorms, rain, hail, and a sharp increase in wind.

Tornadoes are observed in all regions of the globe. They most often occur in Australia, Northeast Africa, and are most common in America (USA), in the warm sector of a cyclone before a cold front. The tornado moves in the same direction as the cyclone. There are more than 900 of them per year, and most of them originate and bring greatest damage in Tornado Valley.

Tornado Valley extends from West Texas to the Dakotas, 100 miles north to south and 60 miles east to west. Warm, moist air coming from the north from the Gulf of Mexico meets dry, cold wind moving from the south from Canada. Huge clusters of thunderclouds begin to form. The air rises sharply inside the clouds, cools there and descends. These flows collide and rotate relative to each other. A thunderstorm cyclone arises, in which a tornado is born.

Classification of tornadoes

Scourge-like - This is the most common type of tornado. The funnel looks smooth, thin, and can be quite tortuous. The length of the funnel significantly exceeds its radius. Weak tornadoes and tornado funnels that descend into the water are, as a rule, whip-like tornadoes.

Vague- look like shaggy, rotating clouds reaching the ground. Sometimes the diameter of such a tornado even exceeds its height. All large diameter craters (more than 0.5 km) are vague. Usually these are very powerful vortices, often composite. They cause enormous damage due to their large size and very high wind speeds.

Composite- 1957 Dallas composite tornado. May consist of two or more separate clots around a main central tornado. Such tornadoes can be of almost any power, however, most often they are very powerful tornadoes. They cause significant damage over large areas. Most often form on water. These funnels are somewhat related to each other, but there are exceptions.

Fiery- These are ordinary tornadoes generated by a cloud formed as a result of a strong fire or volcanic eruption. It was precisely such tornadoes that were first artificially created by man (the experiments of J. Dessens (Dessens, 1962) in the Sahara, which continued in 1960-1962). They “absorb” tongues of flame that stretch towards the mother cloud, forming a fiery tornado. A fire can spread tens of kilometers. They can be whip-like. Cannot be fuzzy (fire is not under pressure, like whiplash tornadoes).

Mermen- these are tornadoes that formed over the surface of oceans, seas, and in rare cases lakes. They “absorb” waves and water, forming, in some cases, whirlpools that extend towards the mother cloud, forming a waterspout. They can be whip-like. Just like fire ones, they cannot be vague (the water is not under pressure, like in scourge-like tornadoes).

Earthen- these tornadoes are very rare, formed during destructive cataclysms or landslides, sometimes earthquakes above 7 points on the Richter scale, very high pressure drops, very rarefied air. A whip-like tornado is located with the “carrot” (thick part) to the ground, inside a dense funnel, a thin stream of earth inside, a “second shell” of earthen slurry (if there is a landslide). In the case of earthquakes, it lifts stones, which is very dangerous.

Snowy - These are snow tornadoes during a severe snowstorm.

Rice. A tornado and a cavitation cord behind a radial-axial turbine and the distribution of speed and pressure in cross sections these vortex formations.

Whirlwinds in the air. A number of methods for creating vortex movements are known experimentally. The method described above for obtaining smoke rings from a box makes it possible to obtain vortices whose radius and speed are of the order of 10-20 cm and 10 m/sec, respectively, depending on the diameter of the hole and the impact force. Such vortices travel distances of 15-20 m.

The vortices are much bigger size(with a radius of up to 2 m) and higher speeds (up to 100 m/sec) are obtained using explosives. In a pipe, closed at one end and filled with smoke, an explosive charge located at the bottom is detonated. A vortex obtained from a cylinder with a radius of 2 m with a charge weighing about 1 kg travels a distance of about 500 m. Over most of the distance, the vortices obtained in this way are turbulent in nature and are well described by the law of motion, which is set out in § 35.

The mechanism of formation of such vortices is qualitatively clear. When air moves in a cylinder caused by an explosion, a boundary layer forms on the walls. At the edge of the cylinder, the boundary layer breaks off,

As a result, a thin layer of air with significant vorticity is created. Then this layer is folded. A qualitative picture of the successive stages is shown in Fig. 127, which shows one edge of the cylinder and the vortex layer breaking off from it. Other schemes for the formation of vortices are also possible.

At low Reynolds numbers, the spiral structure of the vortex is maintained for quite a long time. At large numbers Reynolds, as a result of instability, the spiral structure is destroyed immediately and turbulent mixing of the layers occurs. As a result, a vortex core is formed, the vorticity distribution in which can be found if we solve the problem posed in § 35, described by the system of equations (16).

However, at the moment there is no calculation scheme that would allow the given parameters of the pipe and the weight of the explosive to determine the initial parameters of the formed turbulent vortex (i.e., its initial radius and speed). The experiment shows that for a pipe with given parameters there is a maximum and minimum charge weight at which a vortex is formed; its formation is strongly influenced by the location of the charge.

Vortexes in the water. We have already said that vortices in water can be obtained in a similar way, by pushing out a certain volume of liquid, tinted with ink, from a cylinder with a piston.

Unlike air vortices, the initial speed of which can reach 100 m/sec or more, in water at an initial speed of 10-15 m/sec, a cavitation ring appears due to the strong rotation of the liquid moving with the vortex. It occurs at the moment of formation of a vortex when the boundary layer is removed from the edge of the Cylinder. If you try to get vortices with speed

more than 20 m/sec, then the cavitation cavity becomes so large that instability occurs and the vortex is destroyed. The above applies to cylinder diameters of the order of 10 cm; it is possible that with an increase in diameter it will be possible to obtain stable vortices moving at high speed.

An interesting phenomenon occurs when a vortex moves vertically upward in water towards a free surface. Part of the liquid, forming the so-called vortex body, flies up above the surface, at first almost without changing shape - the water ring jumps out of the water. Sometimes the speed of the ejected mass in the air increases. This can be explained by the ejection of air that occurs at the boundary of the rotating fluid. Subsequently, the emitted vortex is destroyed under the influence of centrifugal forces.

Drops falling. It is easy to observe the vortices that form when ink drops fall into water. When an ink drop falls into water, a ring of ink is formed and moves downward. A certain volume of liquid moves along with the ring, forming the body of the vortex, which is also colored with ink, but much weaker. The nature of the movement strongly depends on the ratio of the densities of water and ink. In this case, differences in density of tenths of a percent turn out to be significant.

Density clean water less than ink. Therefore, when the vortex moves, it is acted upon by a force directed downward along the direction of the vortex. The action of this force leads to an increase in the momentum of the vortex. Vortex momentum

where Г is the circulation or intensity of the vortex, and R is the radius of the vortex ring, and the speed of the vortex

If we neglect the change in circulation, then a paradoxical conclusion can be drawn from these formulas: the action of a force in the direction of movement of the vortex leads to a decrease in its speed. Indeed, from (1) it follows that with increasing momentum at a constant

circulation, the radius R of the vortex should increase, but from (2) it is clear that with constant circulation, the speed decreases with increasing R.

At the end of the vortex movement, the ink ring breaks up into 4-6 separate clumps, which in turn turn into vortices with small spiral rings inside. In some cases, these secondary rings break apart again.

The mechanism of this phenomenon is not very clear, and there are several explanations for it. In one scheme main role played by gravity and instability of the so-called Taylor type, which occurs when in a gravitational field a more dense liquid is located above a less dense one, and both liquids are initially at rest. The flat boundary separating two such liquids is unstable - it is deformed, and individual clots of a denser liquid penetrate into the less dense one.

As the ink ring moves, the circulation actually decreases and this causes the vortex to stop completely. But the force of gravity continues to act on the ring, and in principle it should fall further as a whole. However, Taylor instability occurs, and as a result, the ring breaks up into separate clumps, which descend under the influence of gravity and in turn form small vortex rings.

Another explanation for this phenomenon is possible. An increase in the radius of the ink ring leads to the fact that part of the liquid moving with the vortex takes the shape shown in Fig. 127 (p. 352). As a result of the action on the rotating torus, consisting of stream lines, of forces similar to the Magnus force, the elements of the ring acquire a speed directed perpendicular to the speed of movement of the ring as a whole. This movement is unstable and disintegrates into separate clumps, which again turn into small vortex rings.

The mechanism for the formation of a vortex when drops fall into water can have a different character. If a drop falls from a height of 1-3 cm, then its entry into the water is not accompanied by a splash and the free surface is slightly deformed. At the boundary between a drop and water

a vortex layer is formed, the folding of which leads to the formation of a ring of ink surrounded by water captured by the vortex. The successive stages of vortex formation in this case are qualitatively depicted in Fig. 128.

When drops fall from a great height, the mechanism of vortex formation is different. Here, a falling drop, deformed, spreads on the surface of the water, imparting an impulse with maximum intensity in the center over an area much larger than its diameter. As a result, a depression forms on the surface of the water, it expands by inertia, and then collapses and a cumulative splash appears - a plume (see Chapter VII).

The mass of this plume is several times greater than the mass of a drop. Falling under the influence of gravity into the water, the plume forms a vortex according to the already disassembled pattern (Fig. 128); in Fig. 129 shows the first stage of a drop falling, leading to the formation of a plume.

According to this scheme, vortices are formed when rare rain with large drops falls on the water - the surface of the water is then covered with a network of small plumes. Due to the formation of such plumes, each

the drop significantly increases its mass, and therefore the vortices caused by its fall penetrate to a fairly large depth.

Apparently, this circumstance can be used as the basis for explaining the well-known effect of dampening surface waves in water bodies by rain. It is known that in the presence of waves, the horizontal components of particle velocity on the surface and at some depth have opposite directions. During rain, a significant amount of liquid penetrating into the depths dampens the wave speed, and currents rising from the depths dampen the speed at the surface. It would be interesting to develop this effect in more detail and build its mathematical model.

Vortex cloud of an atomic explosion. A phenomenon very similar to the formation of a vortex cloud during an atomic explosion can be observed during explosions of conventional explosives, for example, during the detonation of a flat round explosive plate located on dense soil or on a steel plate. You can also arrange the explosive in the form of a spherical layer or glass, as shown in Fig. 130.

A ground-based atomic explosion differs from a conventional explosion primarily in the significantly greater concentration of energy (kinetic and thermal) with a very small mass of gas thrown upward. In such explosions, the formation of a vortex cloud occurs due to the buoyancy force, which appears due to the fact that the mass of hot air formed during the explosion is lighter than the environment. The buoyancy force also plays a significant role during the further movement of the vortex cloud. Just as when an ink vortex moves in water, the action of this force leads to an increase in the radius of the vortex cloud and a decrease in speed. The phenomenon is complicated by the fact that air density changes with altitude. An approximate calculation scheme for this phenomenon is available in the work.

Vortex model of turbulence. Let a flow of liquid or gas flow around a surface that is a plane with indentations limited by spherical segments (Fig. 131, a). In ch. V we showed that in the area of ​​dents zones with constant vorticity naturally arise.

Let us now assume that the vortex zone separates from the surface and begins to move in the main flow (Fig.

131.6). Due to the swirl, this zone, in addition to the speed V of the main flow, will also have a velocity component perpendicular to V. As a result, such a moving vortex zone will cause turbulent mixing in a layer of liquid, the size of which is tens of times larger than the size of the dent.

This phenomenon can apparently be used to explain and calculate movement large masses water in the oceans, as well as the movement of air masses in mountainous areas during strong winds.

Reduced resistance. At the beginning of the chapter, we talked about the fact that air or water masses without shells that move with the vortex, despite their poorly streamlined shape, experience significantly less resistance than the same masses in shells. We also indicated the reason for this decrease in resistance - it is explained by the continuity of the velocity field.

A natural question arises: is it possible to give a streamlined body such a shape (with a moving boundary) and impart to it such a movement that the resulting flow would be similar to the flow during the movement of a vortex, and thereby try to reduce the resistance?

We will give here an example belonging to B. A. Lugovtsov, which shows that such a formulation of the question makes sense. Let us consider a plane potential flow of an incompressible inviscid fluid symmetrical with respect to the x axis, the upper half of which is shown in Fig. 132. At infinity, the flow has a speed directed along the x axis, in Fig. 132 the hatching indicates a cavity in which such pressure is maintained that at its boundary the velocity value is constant and equal to

It is easy to see that if, instead of a cavity, a solid body with a moving boundary is placed in the flow, the speed of which is also equal, then our flow can be considered as an exact solution to the problem of a viscous fluid flowing around this body. In fact, the potential flow satisfies the Navier-Stokes equation, and the no-slip condition at the body boundary is satisfied due to the fact that the velocities of the fluid and the boundary coincide. Thus, thanks to the moving boundary, the flow will remain potential, despite the viscosity, a trace will not appear and full strength, acting on the body, will be equal to zero.

In principle, such a design of a body with a moving boundary can be implemented in practice. To maintain the described motion, a constant supply of energy is required, which must compensate for the dissipation of energy due to viscosity. Below we will calculate the power required for this.

The nature of the flow under consideration is such that its complex potential must be a multivalued function. To isolate its unambiguous branch, we

Let's make a cut along the segment in the flow area (Fig. 132). It is clear that the complex potential maps this region with a cut to the region shown in Fig. 133, a (the corresponding points are marked with the same letters), it also shows images of streamlines (the corresponding points are marked the same numbers). The potential break on the line does not violate the continuity of the velocity field, because the derivative of the complex potential remains continuous on this line.

In Fig. 133b shows an image of the flow area when displayed, this is a circle of radius with a cut along the real axis from the point to the branching point of the flow B, at which the speed is zero, goes to the center of the circle

So, in the plane, the image of the flow region and the position of the points are completely defined. In the plane opposite, you can arbitrarily set the dimensions of the rectangle. Having specified them, you can find by

Riemann's theorem (Chapter I) is the only conformal mapping of the left half of the region in Fig. 133, and on the lower semicircle Fig. 133, b, in which the points in both figures correspond to each other. Due to symmetry, then the entire region of Fig. 133, and will be displayed on a circle with a cut in Fig. 133, b. If you choose the position of point B in Fig. 133, a (i.e., the length of the cut), then it will go to the center of the circle and the display will be completely determined.

It is convenient to express this mapping in terms of the parameter , which varies in the upper half-plane (Fig. 133, c). The conformal mapping of this half-plane onto a circle with a cut in Fig. 133, b with the required correspondence of points can be written out simply.

Some time ago, before the advent of meteorological satellites, scientists could not even think that about one hundred and fifty cyclones and sixty anticyclones form in the Earth’s atmosphere every year. Previously, many cyclones were unknown because they occurred in places where there were no meteorological stations that could record their occurrence.

In the troposphere, the lowest layer of the Earth's atmosphere, vortices constantly appear, develop and disappear. Some of them are so small and unnoticeable that they pass by our attention, others are so large-scale and have such a strong influence on the Earth’s climate that they cannot be ignored (primarily this applies to cyclones and anticyclones).

Cyclones are areas of low pressure in the Earth's atmosphere, in the center of which the pressure is much lower than at the periphery. An anticyclone, on the contrary, is an area of ​​high pressure that reaches in the center of its highest performance. While over the northern hemisphere, cyclones move counterclockwise and, obeying the Coriolis force, try to move to the right. While the anticyclone moves clockwise in the atmosphere and deviates to the left (in the Southern Hemisphere of the Earth everything happens the other way around).

Despite the fact that cyclones and anticyclones are absolutely opposite vortices in their essence, they are strongly interconnected with each other: when pressure decreases in one region of the Earth, its increase is necessarily recorded in another. Also for cyclones and anticyclones is general mechanism, which causes air currents to move: inhomogeneous heating of different parts of the surface and rotation of our planet around its axis.

Cyclones are characterized by cloudy, rainy weather with strong gusts of wind arising from the difference in atmospheric pressure between the center of the cyclone and its edges. An anticyclone, on the contrary, in summer is characterized by hot, windless, partly cloudy weather with very little precipitation, while in winter it causes clear but very cold weather.

Snake Ring

Cyclones (gr. “snake ring”) are huge vortices, the diameter of which can often reach several thousand kilometers. They are formed in temperate and polar latitudes, when warm air masses from the equator collide with dry, cold currents moving towards them from the Arctic (Antarctica) and form a boundary between themselves, which is called an atmospheric front.

Cold air, trying to overcome the warm air flow remaining below, in some area pushes part of its layer back - and it comes into collision with the masses following it. As a result of the collision, the pressure between them increases and part of the warm air turned back, yielding to the pressure, is deflected to the side, beginning an ellipsoidal rotation.

This vortex begins to capture the layers of air adjacent to it, draws them into rotation and begins to move at a speed of 30 to 50 km/h, while the center of the cyclone moves at a lower speed than its periphery. As a result, after some time the diameter of the cyclone ranges from 1 to 3 thousand km, and the height – from 2 to 20 km.

Where it moves, the weather changes sharply, since the center of the cyclone has low pressure, there is a lack of air inside it, and cold air masses begin to flow in to make up for it. They displace warm air upward, where it cools, and the water droplets in it condense and form clouds, from which precipitation falls.

The lifespan of a vortex is usually from several days to weeks, but in some regions it can last about a year: usually these are areas of low pressure (for example, the Icelandic or Aleutian cyclones).

It is worth noting that for equatorial zone Such vortices are not typical, since the deflecting force of the planet’s rotation, necessary for the vortex-like movement of air masses, does not act here.

The southernmost, tropical cyclone, forms no closer to the equator than five degrees and is characterized by a smaller size in diameter, but more high speed wind, often transforming into a hurricane. According to their origin, there are such types of cyclones as the temperate cyclone and the tropical cyclone, which generates deadly hurricanes.

Vortexes of tropical latitudes

In the 1970s, tropical cyclone Bhola hit Bangladesh. Although the wind speed and strength were low and it was assigned only the third (out of five) hurricane category, due to the huge amount of precipitation that fell on the ground, the Ganges River overflowed its banks and flooded almost all the islands, washing away all settlements from the face of the earth.

The consequences were catastrophic: during the rampant disaster, from three hundred to five hundred thousand people died.

A tropical cyclone is much more dangerous than a vortex from temperate latitudes: it is formed where the temperature of the ocean surface is not lower than 26 °, and the difference between air temperatures exceeds two degrees, as a result of which evaporation increases, air humidity increases, which contributes to the vertical rise of air masses.

Thus, a very strong draft appears, capturing new volumes of air that have heated up and gained moisture above the ocean surface. The rotation of our planet around its axis gives the rise of air the vortex-like movement of a cyclone, which begins to rotate at enormous speed, often transforming into hurricanes of terrifying force.

A tropical cyclone is formed only over the ocean surface between 5-20 degrees north and south latitudes, and once on land, it fades out quite quickly. Its dimensions are usually small: the diameter rarely exceeds 250 km, but the pressure at the center of the cyclone is extremely low (the lower, the faster the wind moves, so the movement of cyclones is usually from 10 to 30 m/s, and wind gusts exceed 100 m/s) . Naturally, not every tropical cyclone brings death with it.

There are four types of this vortex:

• Disturbance – moves at a speed not exceeding 17 m/s;
• Depression - the movement of the cyclone is from 17 to 20 m/s;
• Storm - the center of the cyclone moves at a speed of up to 38 m/s;
• Hurricane - a tropical cyclone moves at a speed exceeding 39 m/s.

The center of this type of cyclone is characterized by a phenomenon called the “eye of the storm” - an area of ​​calm weather. Its diameter is usually about 30 km, but if a tropical cyclone is destructive, it can reach up to seventy. Inside the eye of a storm, air masses have more warm temperature and less humidity than in the rest of the vortex.

Calm often reigns here; at the border, precipitation abruptly stops, the sky clears, the wind weakens, thereby deceiving people who, deciding that the danger has passed, relax and forget about precautions. Since a tropical cyclone always moves from the ocean, it drives huge waves in front of it, which, when they hit the coast, sweep everything out of the way.

Scientists are increasingly recording the fact that every year the tropical cyclone becomes more dangerous and its activity is constantly increasing (this is due to global warming). Therefore, these cyclones are found not only in tropical latitudes, but also reach Europe at an atypical time of year for them: they usually form in late summer/early autumn and never occur in spring.

Thus, in December 1999, France, Switzerland, Germany, and the UK were hit by Hurricane Lothar, so powerful that meteorologists could not even predict its appearance due to the fact that the sensors either went off scale or did not work. “Lotar” turned out to be the cause of the death of more than seventy people (they were mainly victims of road accidents and falling trees), and in Germany alone, about 40 thousand hectares of forest were destroyed in a few minutes.

Anticyclones

An anticyclone is a vortex in the center of which there is high pressure and low pressure at the periphery. It is formed in the lower layers of the Earth's atmosphere when cold air masses invade warmer ones. An anticyclone occurs in subtropical and subpolar latitudes, and its movement speed is about 30 km/h.

An anticyclone is the opposite of a cyclone: ​​the air in it does not rise, but descends. It is characterized by the absence of humidity. An anticyclone is characterized by dry, clear, and windless weather, hot in summer and frosty in winter. Significant temperature fluctuations during the day are also characteristic (the difference is especially strong on the continents: for example, in Siberia it is about 25 degrees). This is explained by the lack of precipitation, which usually makes the temperature difference less noticeable.

Names of vortices

In the middle of the last century, anticyclones and cyclones began to be given names: this turned out to be much more convenient when exchanging information about hurricanes and cyclone movements in the atmosphere, since it made it possible to avoid confusion and reduce the number of errors. Behind each name of a cyclone and anticyclone there was hidden data about the vortex, down to its coordinates in the lower layer of the atmosphere.

Before making the final decision on the name of this or that cyclone and anticyclone, a sufficient number of proposals were considered: they were proposed to be designated by numbers, letters of the alphabets, names of birds, animals, etc. This turned out to be so convenient and effective that after a while Over time, all cyclones and anticyclones received names (at first they were female, and in the late seventies tropical vortices began to be called by male names).

Since 2002, a service has appeared that offers anyone who wants to name a cyclone or anticyclone by their name. The pleasure is not cheap: the standard price for a cyclone to be named after a customer is 199 euros, and an anticyclone costs 299 euros, since anticyclones occur less frequently.

Anticyclones. Anticyclones are areas of high atmospheric pressure with closed isobars, with a maximum pressure in the center of up to 1070 mb and a corresponding distribution of air currents. The diameter of the anticyclone can reach several thousand kilometers. Horizontal pressure gradients in anticyclones are directed from the center to the periphery, and the wind, deviating from the pressure gradient in the northern hemisphere to the right, blows clockwise around the center of the anticyclone, and in the southern hemisphere, deviating to the left, is directed counterclockwise.

In the central part of the anticyclone, as a rule, partly cloudy, dry weather with weak wind prevails.
Concept and types, 2018.
Towards the periphery of the anticyclone, cloudiness increases and wind speed increases. The temperature in the western part of the anticyclone, where southern winds dominate (in the northern hemisphere), is usually higher than in the eastern part with its northern winds. In the anticyclone it is sharply expressed diurnal cycle meteorological elements, especially temperature and humidity. In summer, with strong convection in the anticyclone, thunderstorms sometimes occur. In exceptional cases, drizzle, fog and stratus clouds may be observed in the anticyclone.

Cyclones. A cyclone is an area of ​​low pressure with closed isobars, with minimum pressure in the northern hemisphere and clockwise in the southern hemisphere.
Concept and types, 2018.

Cyclones vary in size and depth: one should be about 100 miles in diameter, another over 2000 miles. The pressure at the center of most cyclones ranges from 980 to 1010 mb, but in some cases the pressure drops to 935 mb. and below.

Cyclones can move in almost any direction, but most often they are directed to the northeast in the northern hemisphere and to the southeast in the southern; their speed ranges from 10 to 40 knots, sometimes reaching 60 knots. When cyclones are filled (occluded), their speed decreases.

Tropical cyclones are one of the most dangerous and least studied natural phenomena. They are relatively small in size, ranging from 20 to 600 miles in diameter, but very deep atmospheric vortices. They have high kinetic energy (with low pressure and hurricane force winds, forming a counterclockwise circulation in the northern and clockwise in the southern hemisphere with a slight deviation towards the center). Such a cyclone as a whole (or center) has forward movement and is often the cause of great excitement, much greater than during the most severe storms of temperate latitudes.

The speed of a tropical cyclone varies from 70 to 240 miles per day, increasing with increasing geographical latitude. Atmospheric pressure in a tropical cyclone from the periphery to the center drops to 950-970 mb, and in some cases drops even lower, while the wind speed, on the contrary, increases and reaches its maximum near the central zone of the tropical cyclone highest values, equal to 40-60 m/sec and even more. However, in the very central zone of a tropical cyclone with a diameter of 20 to 30 miles, the wind weakens to calm.

The passage of a tropical cyclone is always accompanied by heavy clouds, very heavy and prolonged downpours and significant waves. In the central zone of a tropical cyclone (the eye of the storm), the sky is usually clear or covered with thin stratus clouds; The excitement here takes on the character of a strong crush. posing a great danger to the ship. Tropical cyclones occur in all oceans.

The main centers of origin and their local names are as follows:

· Caribbean Sea and Gulf of Mexico. The cyclones that arise here are called Antillean hurricanes

· Philippine Islands region, South China Sea tropical cyclones are called typhoons

· Arabian Sea and Bay of Bengal, where tropical cyclones have no local name

· Indian Ocean off the coast of Australia. Here tropical cyclones are called "willy-willy"

· in the Pacific Ocean off the west coast of Mexico - cordonazo

· in the Philippines - baguyo, or baruyo

· In the southern part of the Indian Ocean, east of the island Madagascar.
Posted on ref.rf
The local name for tropical cyclones is ʼʼorcansʼ.

Tropical cyclones often originate in open ocean usually between 5 and 20° latitude, at the edges of the zone of prevailing light winds and calms and in monsoon areas. At the first stage of their movement, tropical cyclones move at a low speed of 10-20 km/h to the west, then the speed increases to 30-40 km/h or more.

Then, increasingly deviating to the right in the northern hemisphere and to the left in the southern hemisphere, they begin to move to the northwest and southwest, respectively. Having reached the border of the trade wind zone, i.e. to approximately 15-30°, northern and southern latitudes, tropical cyclones, if they have not yet filled by that time, change the direction of movement and begin to move to the northeast in the northern hemisphere and to the southeast in the south.
Concept and types, 2018.
Some tropical cyclones, however, do not change direction but continue to move in a northwest or southwest direction until they reach the mainland. As it enters temperate latitudes, the cyclone gradually fills and slows down its movement. But when a cyclone penetrates into a system of colder air (into the region of the polar front), it transforms: it deepens, speed increases (sometimes up to 60 km/h), the zone of storm winds expands, etc. And as an extratropical vortex, it can shift at fairly high latitudes. As the tropical cyclone enters the continent, it quickly weakens and dies out. Tropical cyclones are most often observed in the northern hemisphere from August to September, and in the southern hemisphere in the region Pacific Ocean- from January to July, in the Indian Ocean - from November to April. The exception is Northern part Indian Ocean, where tropical cyclones are more common from May to December.

Tropical cyclones are vortices with low pressure at their center; they are formed in summer and autumn over warm surface ocean.
Typically, tropical cyclones occur only at low latitudes near the equator, between 5 and 20° North and Southern hemispheres.
From here, a vortex with a diameter of approximately 500-1000 km and a height of 10-12 km begins its run.

Tropical cyclones are widespread on Earth, and in different parts of the world they are called differently: in China and Japan - typhoons, in the Philippines - bagwhiz, in Australia - willy-willy, near the coast of North America - hurricanes.
The destructive power of tropical cyclones can rival earthquakes or volcanic eruptions.
In one hour, one such vortex with a diameter of 700 km releases energy equal to 36 hydrogen bombs of average power. In the center of a cyclone there is often the so-called eye of the storm - a small area of ​​calm with a diameter of 10-30 km.
The weather here is partly cloudy, the wind speed is low, heat air and very low pressure, and around, rotating clockwise, winds of hurricane force blow. Their speed can exceed 120 m/s, and heavy clouds occur, accompanied by heavy showers, thunderstorms and hail.

For example, Hurricane Flora, which swept over the islands of Tobago, Haiti and Cuba in October 1963, caused such mischief. The wind speed reached 70-90 m/s. Flooding has begun in Tobago. In Haiti, the hurricane destroyed entire villages, killing 5 thousand people and leaving 100 thousand homeless. The amount of rainfall that accompanies tropical cyclones seems incredible in comparison with the intensity of rainfall from the most severe cyclones in temperate latitudes. Thus, when one hurricane passed through Puerto Rico, 26 billion tons of water fell in 6 hours.
If you divide this amount per unit area, there will be much more precipitation than what falls in a year, for example, in Batumi (on average 2700 mm).

A tornado is one of the most destructive atmospheric phenomena - a huge vertical whirlwind several tens of meters high.

Of course, people cannot yet actively fight tropical cyclones, but it is important to prepare in time for a hurricane, whether on land or at sea. To do this, meteorological satellites maintain a 24-hour watch over the vast expanses of the World Ocean, providing great assistance in forecasting the paths of tropical cyclones.
They photograph these vortices even at the moment of their formation, and from the photograph they can quite accurately determine the position of the center of the cyclone and trace its movement. Therefore, in recent years, it has been possible to warn the population of vast areas of the Earth about the approach of typhoons that could not be detected by ordinary meteorological observations.
A tornado observed in Tampa Bay, Florida in 1964.

A tornado is one of the most destructive and at the same time spectacular atmospheric phenomena.
This is a huge vortex with a vertical axis several hundred meters long.
Unlike a tropical cyclone, it is concentrated in a small area: it’s all there, as if before your eyes.

On the shores of the Black Sea, you can see how a giant dark trunk stretches out from the central part of a powerful cumulonimbus cloud, the lower base of which takes the shape of an overturned funnel, and another funnel rises towards it from the surface of the sea.
If they close together, a huge, rapidly moving column will form, rotating counterclockwise.

Tornadoes are formed when the atmosphere is in an unstable state, when the air in its lower layers is very warm and in the upper layers it is cold.
In this case, a very intense air exchange occurs, accompanied by a vortex of enormous speed - several tens of meters per second.
The diameter of a tornado can reach several hundred meters, and it sometimes moves even at a speed of 150-200 km/h.
A very low pressure is formed inside the vortex, so the tornado draws in everything it encounters on the way: it can carry water, soil, stones, parts of buildings, etc. over a long distance.
For example, “fish” rains are known, when a tornado from a pond or lake, along with the water, pulled in the fish located there.

A ship thrown ashore by the waves.

Tornadoes on land in the USA and Mexico are called tornadoes, in Western Europe- thrombus. Tornado in North America quite a common occurrence - here there are on average more than 250 of them per year. A tornado is the strongest of the tornadoes observed in globe, with wind speeds up to 220 m/s.

Tornado at sea. The diameter of a tornado can reach several hundred meters and move at a speed of 150-200 km/h.

The worst tornado in its consequences swept through the states of Missouri, Illinois, Kentucky and Tennessee in March 1925, where 689 people died. IN temperate latitudes In our country, tornadoes occur once every few years. An exceptionally strong tornado with a wind speed of 80 m/s swept through the city of Rostov Yaroslavl region in August 1953, the tornado passed through the city in 8 minutes; leaving a strip of destruction 500 m wide.
He threw two wagons weighing 16 tons off the railway tracks.

Signs of worsening weather.

Hook-shaped cirrus clouds move from the west or southwest.

The wind does not subside in the evening, but intensifies.

The moon is surrounded by a small corolla (halo).

After the appearance of fast-moving cirrus clouds, the sky becomes covered with a transparent (veil-like) layer of cirrostratus clouds. They are visible in the form of circles near the Sun or Moon.

Clouds of all tiers are simultaneously visible in the sky: cumulus, “lamb”, wavy and cirrus.

If a developed cumulus cloud turns into a thunderstorm and an “anvil” forms in its upper part, then hail should be expected.

Cumulus clouds appear in the morning, grow and take shape by midday tall towers or mountains

Smoke is coming downwards or spreads along the ground.

It is difficult to predict the formation and path of a tornado over land: it moves at enormous speed and is very short-lived. However, a network of observation posts notifies the Weather Bureau of the occurrence of a tornado and its location. There, this data is analyzed and appropriate warnings are transmitted.

Squalls. There was a clap of thunder, a solid black-gray shaft of clouds became even closer - and it was as if everything was mixed up. Hurricane winds broke and uprooted trees and tore roofs off houses. It was a squall.

A squall occurs mainly before cold atmospheric fronts or near the centers of small moving cyclones when cold air masses invade warm ones. When cold air invades, it displaces warm air, causing it to rise quickly, and the greater the temperature difference between the encountered cold and warm air(and it can exceed 10-15°), the greater the strength of the squall. The wind speed during a squall reaches 50-60 m/s, and it can last up to one hour; it is often accompanied by rain or hail. After the squall, a noticeable cooling occurs. A squall can occur in all seasons of the year and at any time of the day, but more often in the summer, when the earth's surface warms up more.

Squalls are a formidable natural phenomenon, especially due to the suddenness of their appearance. Here is a description of one squall. On March 24, 1878, in England, the frigate Eurydice, arriving from a long voyage, was met on the seashore. "Eurydice" has already appeared on the horizon. There were only 2-3 km left to the shore. Suddenly a terrifying squall of snow came. The sea was covered with huge waves. The phenomenon lasted only two minutes. When the squall ended, there were no traces of the frigate left. It was capsized and sank. Winds of more than 29 m/s are called hurricanes.

Hurricane winds are most often observed in the zone of convergence of a cyclone and an anticyclone, that is, in areas with a sharp pressure drop. Such winds are most typical for coastal areas where marine and continental air masses meet, or in the mountains. But they also happen on the plains. At the beginning of January 1969, a cold anticyclone from the north of Western Siberia quickly moved to the south of the European territory of the USSR, where it met a cyclone, the center of which was located over the Black Sea, while very large pressure differences arose in the zone of convergence of the anticyclone and the cyclone: ​​up to 15 mb per 100 km. rose cold wind at a speed of 40-45 m/s. On the night of January 2-3, a hurricane hit Western Georgia. He destroyed residential buildings in Kutaisi, Tkibuli, Samtredia, uprooted trees, and tore out wires. Trains stopped, transport stopped working, and fires broke out in some places. Huge waves of a force twelve storm hit the shore near Sukhumi, and the buildings of the sanatoriums of the Pitsunda resort were damaged. IN Rostov region, Krasnodar and Stavropol Territories, hurricane winds lifted a lot of earth into the air along with snow. The wind tore roofs off houses and destroyed upper layer soil, blew out winter crops. Snow storms covered the roads. Having spread to the Sea of ​​Azov, the hurricane drove water from the eastern coast of the sea to the western. From the cities of Primorsko-Akhtarsk and Azov, the sea retreated 500 m, and in Genichensk, located on the opposite bank, the streets were flooded. The hurricane also hit the south of Ukraine. On the Crimean coast, piers, cranes and beach facilities were damaged. These are the consequences of just one hurricane.

Thunderstorms often accompany volcanic eruptions.

Hurricane winds are frequent on the coasts of the Arctic and Far Eastern seas, especially in winter and autumn during the passage of cyclones. In our country, at the Pestraya Dresva station - on the western shore of Shelikhov Bay - winds of 21 m/s or more are observed sixty times a year. This station is located at the entrance to a narrow valley. Getting into it, weak Eastern wind from the bay, due to the narrowing of the flow, it intensifies to a hurricane.

When at strong wind snow falls, blizzards or blizzards occur. A blizzard is the movement of snow by wind. The latter is often accompanied by whirlwind movements of snowflakes. The formation of blizzards depends not so much on the strength of the wind, but on the fact that snow is a loose and light material that is easily lifted from the ground by the wind. Hence, snowstorms occur at different wind speeds, sometimes starting from 4-6 m/s. Blizzards cover roads and airfield runways with snow and create huge snowdrifts.