What is a cyclone? Action and characteristics of an atmospheric cyclone. Movement of extratropical cyclones The maximum speed of movement of a cyclone is

Pressure formations near the Earth's surface in most cases move in the direction of a stable air flow above them at a surface height of AT 700 or AT 500 with a speed proportional to the speed on the corresponding surface, i.e. according to the leading flow rule.

On average, the proportionality coefficient between the speed of the leading flow and the speed of movement of pressure formations is 0.8 for AT 700 and 0.6 for AT 500.

But calculations show that the proportionality coefficient depends on the speed of the leading flow (Table 5):

Table 5. Proportionality coefficient depending on the speed of the leading flow.

The leading flow rule approximately reflects the picture of the movement of pressure formations. Strictly speaking, cyclones and anticyclones, moving in the direction of the leading flow, often deviate from the direction of isohypses on the surface of AT 700 or AT 500.

The speeds at which cyclones move vary widely. In the initial stage of development, low cyclones move at a speed of 40-50 km/h, and in some cases the speed increases to 80-100 km/h.

The active movement of cyclones occurs as long as a stable air flow – the leading flow – remains above them in the middle troposphere. Most often, the cyclone moves from the western half of the horizon to the eastern half, in accordance with the direction of the leading flow. The anomaly in the movement of pressure centers relative to the leading flow, as shown above, is determined by a number of factors, the main one of which is the uneven local change in the geopotential gradient above the moving center.

Thus, in accordance with the main west-east transfer of air masses in the atmosphere, East End the cyclone is its front part, the western part is its rear part. There are deviations from this rule if the direction of the leading flow differs sharply from the west-east direction.

When cyclones become high (starting from the third stage of development), their speed decreases sharply. Filling cyclones are quasi-symmetrical and cold. In the middle troposphere they have closed isohypses, i.e. the leading flow of a certain direction above the center of the cyclone is no longer present, and cyclones, as a rule, become inactive (quasi-stationary). In this case, the cyclonic center sometimes describes a loop.

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P. MANTASHYAN.

We continue to publish the journal version of P. N. Mantashyan’s article “Vortexes: from the molecule to the Galaxy” (see “Science and Life No.”). We will talk about tornadoes and tornadoes - natural formations of enormous destructive power, the mechanism of their occurrence is still not entirely clear.

Science and life // Illustrations

Science and life // Illustrations

A drawing from a book by American physicist Benjamin Franklin, explaining the mechanism of tornadoes.

The Spirit rover discovered that tornadoes occur in the thin atmosphere of Mars and photographed them. Photo from NASA website.

Giant tornadoes and tornadoes that occur on the plains of the southern United States and China are a formidable and very dangerous phenomenon.

Science and life // Illustrations

A tornado can reach a kilometer in height, resting its apex on thunder cloud.

A tornado at sea lifts and draws in tens of tons of water along with marine life and can break apart and sink a small ship. In the era of sailing ships, they tried to destroy a tornado by shooting at it from cannons.

The picture clearly shows that the tornado is rotating, twisting air, dust and rainwater into a spiral.

The city of Kansas City, turned into ruins by a powerful tornado.

Forces acting on a typhoon in the trade wind flow.

Ampere's law.

Coriolis forces on a turntable.

Magnus effect on the table and in the air.

Vortex air movement is observed not only in typhoons. There are vortices larger than a typhoon - these are cyclones and anticyclones, the largest air vortices on the planet. Their sizes significantly exceed the size of typhoons and can reach more than a thousand kilometers in diameter. In a sense, these are antipodal vortices: they have almost everything the other way around. Cyclones of the Northern and Southern Hemispheres rotate in the same direction as the typhoons of these hemispheres, and anticyclones rotate in the opposite direction. A cyclone brings with it inclement weather accompanied by precipitation, while an anticyclone, on the contrary, brings clear, sunny weather. The formation scheme of a cyclone is quite simple - it all starts with the interaction of cold and warm atmospheric fronts. In this case, part of the warm atmospheric front penetrates inside the cold one in the form of a kind of atmospheric “tongue”, as a result of which warm air, lighter, begins to rise, and at the same time two processes occur. Firstly, water vapor molecules under the influence magnetic field The earth begins to rotate and draws all the rising air into rotational motion, forming a gigantic air whirlpool (see “Science and Life” No.). Secondly, the warm air above cools, and the water vapor in it condenses into clouds, which fall as precipitation in the form of rain, hail or snow. Such a cyclone can ruin the weather for a period of several days to two to three weeks. Its “life activity” is supported by the arrival of new portions of moist warm air and its interaction with the cold air front.

Anticyclones are associated with the lowering of air masses, which are adiabatically, that is, without heat exchange with environment, heat up, them relative humidity falls, which leads to the evaporation of existing clouds. At the same time, due to the interaction of water molecules with the Earth’s magnetic field, anticyclonic rotation of the air occurs: in the Northern Hemisphere - clockwise, in the Southern - counterclockwise. Anticyclones bring with them stable weather for a period from several days to two to three weeks.

Apparently, the formation mechanisms of cyclones, anticyclones and typhoons are identical, and the specific energy intensity (energy per unit mass) of typhoons is much greater than that of cyclones and anticyclones, only due to more high temperature air masses heated by solar radiation.

TOrnadoes

Of all the vortices that form in nature, the most mysterious are tornadoes; in fact, they are part of a thundercloud. At first, in the first stage of a tornado, rotation is visible only in the lower part of the thundercloud. Then part of this cloud hangs down in the form of a giant funnel, which becomes increasingly longer and finally reaches the surface of the earth or water. A giant trunk appears, hanging from a cloud, which consists of an internal cavity and walls. The height of a tornado ranges from hundreds of meters to a kilometer and is usually equal to the distance from the bottom of the cloud to the surface of the earth. Feature internal cavity - reduced pressure of the air in it. This feature of a tornado leads to the fact that the cavity of the tornado serves as a kind of pump, which can draw in a huge amount of water from the sea or lake, along with animals and plants, transport them over considerable distances and throw them down along with the rain. A tornado is capable of carrying quite large loads - cars, carts, small ships, small buildings, and sometimes even with people in them. A tornado has gigantic destructive power. When it comes into contact with buildings, bridges, power lines and other infrastructure, it causes enormous destruction.

Tornadoes have a maximum specific energy intensity, which is proportional to the square of the speed of the vortex air flows. According to meteorological classification, when the wind speed in a closed vortex does not exceed 17 m/s, it is called a tropical depression, but if the wind speed does not exceed 33 m/s, then it is a tropical storm, and if the wind speed is 34 m/s and above , then this is already a typhoon. In powerful typhoons, wind speeds can exceed 60 m/s. In a tornado, according to various authors, the air speed can reach from 100 to 200 m/s (some authors point to supersonic air speed in a tornado - over 340 m/s). Direct measurements of the speed of air flows in tornadoes are practically impossible at the current level of technological development. All devices designed to record the parameters of a tornado are mercilessly broken by them at the first contact. The speed of flows in tornadoes is judged by indirect signs, mainly by the destruction they produce or by the weight of the loads they carry. Besides, distinguishing feature classic tornado - the presence of a developed thundercloud, a kind of electric battery that increases the specific energy intensity of the tornado. To understand the mechanism of the emergence and development of a tornado, let us first consider the structure of a thundercloud.

STORM CLOUD

In a typical thundercloud, the top is positively charged and the base is negatively charged. That is, a giant electrical capacitor many kilometers in size floats in the air, supported by rising currents. The presence of such a capacitor leads to the fact that on the surface of the earth or water over which the cloud is located, its electrical trace appears - induced electric charge, having a sign opposite to the sign of the charge of the base of the cloud, that is, the earth's surface will be positively charged.

By the way, the experiment on creating an induced electric charge can be carried out at home. Place small pieces of paper on the surface of the table, comb dry hair with a plastic comb and bring the comb closer to the sprinkled pieces of paper. All of them, looking up from the table, will rush to the comb and stick to it. The result of this simple experiment can be explained very simply. The comb received an electric charge as a result of friction with the hair, and on the piece of paper it induces a charge of the opposite sign, which attracts the pieces of paper to the comb in full accordance with Coulomb's law.

Near the base of a developed thundercloud, there is a powerful upward flow of air saturated with moisture. In addition to dipole water molecules, which begin to rotate in the Earth’s magnetic field, transmitting momentum to neutral air molecules, drawing them into rotation, there are positive ions and free electrons in the upward flow. They can be formed as a result of the influence of solar radiation on molecules, the natural radioactive background of the area and, in the case of a thundercloud, due to the energy of the electric field between the base of the thundercloud and the ground (remember the induced electric charge!). By the way, due to the induced positive charge on the surface of the earth, the number of positive ions in the flow of rising air significantly exceeds the number of negative ions. All these charged particles, under the influence of the rising air flow, rush to the base of the thundercloud. However, the vertical velocities of positive and negative particles in an electric field are different. The field strength can be estimated by the potential difference between the base of the cloud and the surface of the earth - according to researchers’ measurements, it is several tens of millions of volts, which, with a height of the base of the thundercloud of one to two kilometers, gives an electric field strength of tens of thousands of volts per meter. This field will accelerate positive ions and retard negative ions and electrons. Therefore, per unit time, more positive charges will pass through the cross section of the upward flow than negative ones. In other words, an electric current will arise between the earth’s surface and the base of the cloud, although it would be more correct to talk about a huge number of elementary currents connecting earth's surface with the base of the cloud. All these currents are parallel and flow in the same direction.

It is clear that, according to Ampere’s law, they will interact with each other, namely, attract. From the course of physics it is known that the force of mutual attraction per unit length of two conductors with electric currents flowing in the same direction is directly proportional to the product of the forces of these currents and inversely proportional to the distance between the conductors.

The attraction between two electrical conductors is due to Lorentz forces. The electrons moving inside each conductor are influenced by the magnetic field created by the electric current in the adjacent conductor. They are acted upon by the Lorentz force, directed along a straight line connecting the centers of the conductors. But for the force of mutual attraction to arise, the presence of conductors is completely unnecessary - the currents themselves are sufficient. For example, two particles at rest that have the same electric charge repel each other according to Coulomb’s law, but the same particles moving in the same direction are attracted until the forces of attraction and repulsion balance each other. It is easy to see that the distance between particles in the equilibrium position depends only on their speed.

Due to the mutual attraction of electric currents, charged particles rush to the center of the thundercloud, interacting with electrically neutral molecules along the way and also moving them to the center of the thundercloud. The cross-sectional area of ​​the ascending flow will decrease by several times, and since the flow rotates, according to the law of conservation of angular momentum, its angular velocity will increase. The same thing will happen to the upward flow as to a figure skater who, spinning on the ice with her arms outstretched, presses them to her body, causing her rotation speed to sharply increase (a textbook example from physics textbooks that we can watch on TV!). Such a sharp increase in the speed of air rotation in a tornado with a simultaneous decrease in its diameter will lead to a corresponding increase in the linear wind speed, which, as mentioned above, can even exceed the speed of sound.

It is the presence of a thundercloud, the electric field of which separates charged particles by sign, that leads to the fact that the speeds of air flows in a tornado exceed the speeds of air flows in a typhoon. Figuratively speaking, a thundercloud serves as a kind of “electric lens”, in the focus of which the energy of an upward flow of moist air is concentrated, which leads to the formation of a tornado.

SMALL VORTEXES

There are also vortices, the formation mechanism of which is in no way connected with the rotation of a dipole water molecule in a magnetic field. The most common among them are dust devils. They are formed in desert, steppe and mountainous areas. In size they are inferior to classic tornadoes, their height is about 100-150 meters, and their diameter is several meters. For the formation of dust devils, a necessary condition is a desert, well-heated plain. Once formed, such a vortex exists for quite a short time, 10-20 minutes, all this time moving under the influence of the wind. Despite the fact that desert air contains virtually no moisture, its rotational motion is ensured by the interaction of elementary charges with the Earth's magnetic field. Over a plain, strongly heated by the sun, a powerful upward flow of air arises, some of the molecules of which, under the influence of solar radiation and especially its ultraviolet part, are ionized. Solar radiation photons knock out electrons from the outer electron shells of air atoms, forming pairs of positive ions and free electrons. Due to the fact that electrons and positive ions have significantly different masses with equal charges, their contribution to the creation of angular momentum of the vortex is different and the direction of rotation of the dust vortex is determined by the direction of rotation of the positive ions. Such a rotating column of dry air, as it moves, lifts dust, sand and small pebbles from the surface of the desert, which in themselves do not play any role in the mechanism of dust swirl formation, but serve as a kind of indicator of air rotation.

Air vortices, which are quite rare, are also described in the literature. a natural phenomenon. They appear during the hottest time of the day on the banks of rivers or lakes. The lifetime of such vortices is short; they appear unexpectedly and disappear just as suddenly. Apparently, both water molecules and ions formed in warm and humid air due to solar radiation contribute to their creation.

Much more dangerous are water vortices, the formation mechanism of which is similar. The description has been preserved: “In July 1949 in Washington state, on a warm sunny day under a cloudless sky, a high column of water spray appeared on the surface of the lake. It existed for only a few minutes, but had significant lifting power. Approaching the river bank, he lifted a rather heavy motor boat about four meters long, carried it several tens of meters and, hitting the ground, broke it into pieces. Water vortices are most common where the surface of the water is strongly heated by the sun - in tropical and subtropical zones."

Swirling air flows can occur during large fires. Such cases are described in the literature; we present one of them. “Back in 1840, forests were cleared for fields in the United States. A huge amount of brushwood, branches and trees were dumped in a large clearing. They were set on fire. After some time, the flames of individual fires pulled together, forming a column of fire, wide at the bottom, pointed at the top, 50 - 60 meters high. Even higher, the fire was replaced by smoke that went high into the sky. The fire and smoke whirlwind rotated with amazing speed. The majestic and terrifying sight was accompanied by a loud noise, reminiscent of thunder. The force of the whirlwind was so great that it lifted large trees into the air and threw them aside.”

Let's consider the process of formation of a fire tornado. When wood burns, heat is released, which is partially converted into kinetic energy of the ascending flow of heated air. However, during combustion another process occurs - ionization of air and combustion products.

fuel. And although in general heated air and fuel combustion products are electrically neutral, positively charged ions and free electrons are formed in the flame. The movement of ionized air in the Earth's magnetic field will inevitably lead to the formation of a fire tornado.

I would like to note that vortex air movement occurs not only during large fires. In his book “Tornadoes” D.V. Nalivkin asks the questions: “We have already talked more than once about the mysteries associated with small-dimensional vortices, tried to understand why all the vortices rotate? Other questions also arise. Why, when straw burns, the heated air does not rise in a straight line, but in a spiral and begins to swirl. Hot air behaves the same way in the desert. Why doesn't it just go up without any dust? The same thing happens with water spray and splashes when hot air rushes over the surface of the water.”

There are vortices that arise during volcanic eruptions; for example, they were observed over Vesuvius. In the literature, they are called ash vortices - ash clouds erupted by a volcano participate in the vortex movement. The mechanism for the formation of such vortices is in general terms similar to the mechanism for the formation of fire tornadoes.

Let's now see what forces act on typhoons in the turbulent atmosphere of our Earth.

CORIOLIS FORCE

A body moving in a rotating reference frame, for example, on the surface of a rotating disk or ball, is subject to an inertial force called the Coriolis force. This force is determined by the vector product (numbering of formulas begins in the first part of the article)

F K =2M[ VΩ], (20)

Where M- body mass; V is the body velocity vector; Ω - vector of angular velocity of rotation of the reference system, in the case globe- the angular velocity of the Earth's rotation, and [VΩ] - their vector product, which in scalar form looks like this:

F l = 2M | V | | Ω | sin α, where α is the angle between the vectors.

The speed of a body moving on the surface of the globe can be decomposed into two components. One of them lies in a plane tangent to the ball at the point where the body is located, in other words, the horizontal component of the velocity: the second, vertical component is perpendicular to this plane. The Coriolis force acting on a body is proportional to the sine of the geographic latitude of its location. A body moving along a meridian in any direction in the Northern Hemisphere is subject to the Coriolis force directed to the right in its motion. It is this force that causes the right banks of rivers in the Northern Hemisphere to wash away, regardless of whether they flow north or south. In the Southern Hemisphere, the same force is directed to the left in movement and rivers flowing in the meridional direction wash away the left banks. In geography, this phenomenon is called Beer's law. When the river bed does not coincide with the meridional direction, the Coriolis force will be less by the cosine of the angle between the direction of the river flow and the meridian.

Almost all studies devoted to the formation of typhoons, tornadoes, cyclones and all kinds of vortices, as well as their further movement, indicate that it is the Coriolis force that serves as the root cause of their occurrence and that it sets the trajectory of their movement along the surface of the Earth. However, if the Coriolis force were involved in the creation of tornadoes, typhoons and cyclones, then in the Northern Hemisphere they would have a right rotation, clockwise, and in the Southern Hemisphere, a left rotation, that is, counterclockwise. But typhoons, tornadoes and cyclones in the Northern Hemisphere rotate to the left, counterclockwise, and in the Southern Hemisphere - to the right, clockwise. This absolutely does not correspond to the direction of influence of the Coriolis force, moreover, it is directly opposite to it. As already mentioned, the magnitude of the Coriolis force is proportional to the sine of geographic latitude and, therefore, is maximum at the poles and absent at the equator. Consequently, if it contributed to the creation of vortices of different scales, then they would most often appear in polar latitudes, which completely contradicts the available data.

Thus, the above analysis convincingly proves that the Coriolis force has nothing to do with the process of formation of typhoons, tornadoes, cyclones and all kinds of vortices, the formation mechanisms of which were discussed in previous chapters.

It is believed that it is the Coriolis force that determines their trajectories, especially since in the Northern Hemisphere typhoons, as meteorological formations, deviate to the right during their movement, and in the Southern Hemisphere - to the left, which corresponds to the direction of action of the Coriolis force in these hemispheres. It would seem that the reason for the deviation of typhoon trajectories has been found - this is the Coriolis force, but let’s not rush to conclusions. As mentioned above, when a typhoon moves along the surface of the Earth, a Coriolis force will act on it, as a single object, equal to:

F к = 2MVΩ sin θ cos α, (21)

where θ is the geographic latitude of the typhoon; α is the angle between the speed vector of the typhoon as a whole and the meridian.

To find out the true reason for the deviation of typhoon trajectories, let's try to determine the magnitude of the Coriolis force acting on the typhoon and compare it with another, as we will now see, more real force.

THE POWER OF MAGNUS

A typhoon moved by the trade wind will be affected by a force that, to the best of the author’s knowledge, has not yet been considered by any researcher in this context. This is the force of interaction of the typhoon, as a single object, with the air flow that moves this typhoon. If you look at the picture depicting the trajectories of typhoons, you will see that they move from east to west under the influence of constantly blowing tropical winds, trade winds, which are formed due to the rotation of the globe. At the same time, the trade wind not only carries the typhoon from east to west. The most important thing is that a typhoon located in the trade wind is affected by a force caused by the interaction of the air flows of the typhoon itself with the air flow of the trade wind.

The effect of the emergence of a transverse force acting on a body rotating in a flow of liquid or gas impinging on it was discovered by the German scientist G. Magnus in 1852. It manifests itself in the fact that if a rotating circular cylinder flows around an irrotational (laminar) flow perpendicular to its axis, then in that part of the cylinder where the linear speed of its surface is opposite to the speed of the oncoming flow, an area of ​​​​high pressure appears. And on the opposite side, where the direction of the linear velocity of the surface coincides with the speed of the oncoming flow, there is a region low blood pressure. The pressure difference on opposite sides of the cylinder gives rise to the Magnus force.

Inventors have attempted to harness Magnus's power. A ship was designed, patented and built, on which, instead of sails, vertical cylinders rotated by engines were installed. The efficiency of such rotating cylindrical “sails” in some cases even exceeded the efficiency of conventional sails. The Magnus effect is also used by football players who know that if, when hitting the ball, they give it a rotational movement, then its flight path will become curvilinear. With such a kick, which is called a “dry sheet”, you can send the ball into the opponent’s goal almost from the corner of the football field, located in line with the goal. Volleyball players, tennis players, and ping-pong players also spin the ball when hit. In all cases, the movement of a curved ball along a complex trajectory creates many problems for the opponent.

However, let's return to the typhoon, moved by the trade wind.

Trade winds, stable air currents (which blow constantly for more than ten months a year) in the tropical latitudes of the oceans, cover 11 percent of their area in the Northern Hemisphere, and up to 20 percent in the Southern Hemisphere. The main direction of the trade winds is from east to west, but at an altitude of 1-2 kilometers they are supplemented by meridional winds blowing towards the equator. As a result, in the Northern Hemisphere the trade winds move southwest, and in the Southern Hemisphere

To the northwest. The trade winds became known to Europeans after Columbus's first expedition (1492-1493), when its participants were amazed at the stability of strong northeastern winds that carried caravels from the coast of Spain through the tropical regions of the Atlantic.

The gigantic mass of the typhoon can be considered as a cylinder rotating in the air flow of the trade wind. As already mentioned, in the Southern Hemisphere they rotate clockwise, and in the Northern Hemisphere they rotate counterclockwise. Therefore, due to interaction with the powerful flow of trade winds, typhoons in both the Northern and Southern Hemispheres deviate away from the equator - to the north and south, respectively. This nature of their movement is well confirmed by the observations of meteorologists.

(The ending follows.)

AMPERE'S LAW

In 1920, French physicist Anre Marie Ampere experimentally discovered a new phenomenon - the interaction of two conductors with current. It turned out that two parallel conductors attract or repel depending on the direction of the current in them. Conductors tend to move closer together if currents flow in the same direction (parallel), and move away from each other if currents flow in opposite directions (antiparallel). Ampere was able to correctly explain this phenomenon: the interaction of magnetic fields of currents occurs, which is determined by the “gimlet rule”. If the gimlet is screwed in in the direction of current I, the movement of its handle will indicate the direction of the magnetic field lines H.

Two charged particles flying in parallel also form an electric current. Therefore, their trajectories will converge or diverge depending on the sign of the particle charge and the direction of their movement.

The interaction of conductors must be taken into account when designing high-current electrical coils (solenoids) - parallel currents flowing through their turns create large forces that compress the coil. There are known cases when a lightning rod made of a tube, after a lightning strike, turned into a cylinder: it was compressed by the magnetic fields of a lightning discharge current with a force of hundreds of kiloamperes.

Based on Ampere's law, the standard unit of current in SI - ampere (A) - was established. State standard“Units of physical quantities” defines:

“An ampere is equal to the current strength which, when passing through two parallel straight conductors of infinite length and negligibly small cross-sectional area, located in a vacuum at a distance of 1 m from each other, would cause an interaction force equal to 2 on a section of the conductor 1 m long . 10 -7 N.”

Details for the curious

MAGNUS AND CORIOLIS FORCES

Let us compare the effect of the Magnus and Coriolis forces on the typhoon, imagining it to a first approximation in the form of a rotating air cylinder flown by the trade wind. Such a cylinder is acted upon by a Magnus force equal to:

F m = DρHV n V m / 2, (22)

where D is the diameter of the typhoon; ρ - trade wind air density; H is its height; V n > - air speed in the trade wind; V t - linear air speed in a typhoon. By simple transformations we get

Fm = R 2 HρωV n, - (23)

where R is the radius of the typhoon; ω is the angular speed of rotation of the typhoon.

Assuming as a first approximation that the air density of the trade wind is equal to the air density in the typhoon, we obtain

M t = R 2 Hρ, - (24)

where M t is the mass of the typhoon.

Then (19) can be written as

F m = M t ωV p - (25)

or F m = M t V p V t / R. (26)

Dividing the expression for the Magnus force by expression (17) for the Coriolis force, we obtain

F m /F k = M t V p V t /2RMV p Ω sinθ cosα (27)

or F m /F k = V t /2RΩ sinθ cosα (28)

Taking into account that, according to the international classification, a typhoon is considered to be a tropical cyclone in which the wind speed exceeds 34 m/s, we will take this smallest figure in our calculations. Since the geographic latitude most favorable for the formation of typhoons is 16 o, we will take θ = 16 o and, since immediately after their formation typhoons move almost along latitudinal trajectories, we will take α = 80 o. Let's take the radius of a medium-sized typhoon to be 150 kilometers. Substituting all the data into the formula, we get

F m / F k = 205. (29)

In other words, the Magnus force exceeds the Coriolis force by two hundred times! Thus, it is clear that the Coriolis force has nothing to do not only with the process of creating a typhoon, but also with changing its trajectory.

A typhoon in the trade wind will be affected by two forces - the aforementioned Magnus force and the force of the aerodynamic pressure of the trade wind on the typhoon, which can be found from a simple equation

F d = KRHρV 2 p, - (30)

where K is the aerodynamic drag coefficient of the typhoon.

It is easy to see that the movement of the typhoon will be due to the action of the resultant force, which is the sum of the Magnus forces and aerodynamic pressure, which will act at an angle p to the direction of air movement in the trade wind. The tangent of this angle can be found from the equation

tgβ = F m /F d. (31)

Substituting expressions (26) and (30) into (31), after simple transformations we obtain

tgβ = V t /KV p, (32)

It is clear that the resulting force F p acting on the typhoon will be tangent to its trajectory, and if the direction and speed of the trade wind are known, then it will be possible to calculate this force with sufficient accuracy for a specific typhoon, thus determining its further trajectory, which will minimize the damage caused by it. Typhoon path can be predicted step by step method, while the probable direction of the resulting force must be calculated at each point of its trajectory.

In vector form, expression (25) looks like this:

F m = M [ωV p ]. (33)

It is easy to see that the formula describing the Magnus force is structurally identical to the formula for the Lorentz force:

F l = q .

Comparing and analyzing these formulas, we notice that the structural similarity of the formulas is quite deep. Thus, the left sides of both vector products (M& #969; and q V) characterize the parameters of objects (typhoon and elementary particle), and the right sides ( V n and B) - environment (trade wind speed and magnetic field induction).

Physical training

CORIOLIS FORCES ON THE PLAYER

In a rotating coordinate system, for example on the surface of the globe, Newton's laws are not satisfied - such a coordinate system is non-inertial. An additional inertial force appears in it, which depends on the linear velocity of the body and the angular velocity of the system. It is perpendicular to the trajectory of the body (and its speed) and is called the Coriolis force, named after the French mechanic Gustav Gaspard Coriolis (1792-1843), who explained and calculated this additional force. The force is directed in such a way that to align with the velocity vector, it must be rotated at a right angle in the direction of rotation of the system.

You can see how the Coriolis force “works” using an electric record player by performing two simple experiments. To carry them out, cut out a circle from thick paper or cardboard and place it on the disk. It will serve as a rotating coordinate system. Let's make a note right away: the player disk rotates clockwise, and the Earth rotates counterclockwise. Therefore, the forces in our model will be directed in the direction opposite to those observed on Earth in our hemisphere.

1. Place two stacks of books next to the player, just above the platter. Place a ruler or straight bar on the books so that one of its edges fits the diameter of the disk. If, with the disk stationary, you draw a line along the bar with a soft pencil, from its center to the edge, then it will naturally be straight. If you now start the player and draw a pencil along the bar, it will draw a curved trajectory going to the left - in full agreement with the law calculated by G. Coriolis.

2. Build a slide from stacks of books and tape to it a thick paper groove oriented along the diameter of the disk. If you roll a small ball down a groove onto a stationary disk, it will roll along the diameter. And on a rotating disk it will move to the left (if, of course, the friction when it rolls is small).

Physical training

THE MAGNUS EFFECT ON THE TABLE AND IN THE AIR

1. Glue together a small cylinder from thick paper. Place a stack of books not far from the edge of the table and connect it to the edge of the table with a plank. When the paper cylinder rolls down the resulting slide, we can expect that it will move along a parabola away from the table. However, instead, the cylinder will sharply bend its trajectory in the other direction and fly under the table!

Its paradoxical behavior is quite understandable if we recall Bernoulli’s law: the internal pressure in a gas or liquid flow becomes lower, the higher the flow speed. It is on the basis of this phenomenon that, for example, a spray gun works: higher atmospheric pressure squeezes liquid into a stream of air with reduced pressure.

It is interesting that human flows also obey Bernoulli’s law to some extent. In the subway, at the entrance to the escalator, where traffic is difficult, people gather in a dense, tightly compressed crowd. And on a fast-moving escalator they stand freely - the “internal pressure” in the flow of passengers drops.

When the cylinder falls and continues to rotate, the speed of its right side is subtracted from the speed of the oncoming air flow, and the speed of the left side is added to it. The relative speed of air flow to the left of the cylinder is greater, and the pressure in it is lower than to the right. The pressure difference causes the cylinder to abruptly change its trajectory and fly under the table.

The laws of Coriolis and Magnus are taken into account when launching rockets, precision shooting over long distances, calculating turbines, gyroscopes, etc.

2. Wrap the paper cylinder with paper or textile tape several turns. If you now sharply pull the end of the tape, it will spin the cylinder and at the same time give it forward motion. As a result, under the influence of Magnus’s forces, the cylinder will fly, describing loops in the air.

Air masses. An air mass is called a large number of air having relatively uniform properties in horizontal directions, sometimes over thousands of kilometers.

An air mass moving over a warmer underlying surface is called cold; moving over a colder underlying surface - warm; being in thermal equilibrium with the environment - local.

The air mass that forms in the Arctic is called arctic air, which is strongly cooled throughout its thickness, has low absolute and high relative humidity, bringing with it fogs and haze. In temperate latitudes it forms polar air. In winter, masses of such air are close in their properties to Arctic air; In summer, the polar air is very dusty and has reduced visibility. Forming in the subtropics and tropics tropical air very hot, dusty, characterized by high absolute humidity, often causing opalescence phenomena (reddish sun and distant objects in a blue haze). Continental tropical air is unstable during the day (convection, dust devils and storms, tornadoes). Visibility is reduced.

Equatorial air has in general the same properties as tropical air, but some of them are expressed to an even greater extent.

Fronts. The point of contact between two air masses with different physical properties, is called the interface (front). The line of intersection of such a surface with the underlying surface (sea or land) is called the front line. Fronts are divided into mobile and stationary.

The main Arctic front separates the Arctic air from the polar air; main polar front - polar air from tropical; main tropical front - tropical air from the equatorial.

Warm front occurs when a warm air mass creeps onto a cold one. The pressure ahead of such a front drops. Cirrus clouds in the form of “claws” are also a harbinger of a warm front. Prefrontal fogs are observed ahead of the warm front. Crossing the zone of a warm front, the ship finds itself in a wide band of continuous rain or snow with reduced visibility.

Cold front occurs when cold air masses wedge under warm ones. He advances with a “wall” of rain clouds. The pressure ahead of the front drops significantly. When encountering a cold front, the ship finds itself in a zone of showers, thunderstorms, squalls and strong seas. However, if a wedge of cold air “cuts” warm masses slowly, then behind the line of such a cold front the ship finds itself in a zone of heavy precipitation.

Front of occlusion occurs when two air masses interact - warm and cold. If the overtaking mass has a temperature lower than that in front, then the front is called a cold occlusion front; if the overtaking mass has a temperature higher than the one in front - the front of warm occlusion. While passing occlusion fronts, the ship may find itself in conditions of reduced visibility, precipitation, strong winds, accompanied by waves.

Cyclones. A cyclone originates as an area of ​​low pressure at the boundary of two air masses of different temperatures. Usually this is a wave disturbance on the frontal surface. With a length of more than 1000 km, the wave becomes unstable and the cyclone is said to “deepen”: a tongue-shaped sector of warm air is formed between the cold and warm fronts. With further development cold front, moving faster than the warm one, catches up with it; the closure of warm and cold fronts eliminates the warm sector, forming an occlusion front.

The diameter of the cyclone ranges from several hundred to 5000 km; average travel speed is 30-60 km/h. Careful observations of clouds, wind, changes atmospheric pressure and air temperatures allow us to draw important conclusions for navigation:

If isolated small cumulus clouds are moving in the same direction as the wind below, the observer is at the rear of the cyclone and the weather can be expected to improve;

If the direction of movement of the clouds does not coincide with the direction of the wind below, the observer is in the front part of the cyclone and in one or two days one should expect prolonged precipitation and changes in temperature (lowering in summer and increasing in winter);

If the wind increases and its direction changes with the sun, the observer northern hemisphere(southern hemisphere) is located in the right (left) half of the cyclone; if the direction of the increasing wind changes against the sun, the opposite conclusion should be drawn;

If the wind direction does not change, the observer is in the path of the center of the cyclone and should expect a temporary lull, and then increased wind from the opposite side.

Tropical cyclones. Unlike cyclones that originate in temperate latitudes, cyclonic disturbances that occur between the tropics are called tropical cyclones. In the West Indies they are called hurricanes; east of Asia - typhoons; in the Indian Ocean - cyclones; in the southern part Indian Ocean- lasso. Tropical cyclones are typically less than 100 to 300 miles across with a core diameter of 20 to 30 miles. The pressure gradient in a tropical cyclone sometimes exceeds 40 mb, and the wind speed reaches 100 km/h, and these indicators, unlike cyclones of temperate latitudes, persist in almost the entire area of ​​the hurricane (typhoon, etc.).

Rice. 114.

One of the signs that a typhoon is approaching is the appearance of a swell coming from a different direction from which the wind is blowing or was blowing previously. Wind-driven swells can be detected as early as 400 to 600 miles from the center of the typhoon. By the direction of the swell, one can judge the position of the center of the typhoon, and by changing this direction, one can judge the direction of its movement.

As the center of the typhoon approaches, the atmospheric pressure drops sharply, cirrus clouds are replaced by a pile of shower clouds; There comes a pre-storm calm with suffocating heat. Then the air temperature quickly drops and rain begins, turning into a tropical downpour.

A simplified diagram of a tropical cyclone for the northern hemisphere is shown in Fig. 114. As can be seen from the figure, the winds in the typhoon area are deviated from the direction of its center to the right by an average of 60°. Therefore, for an observer with his back to the wind, the center of the typhoon will be ahead, approximately 60° to the left of the wind direction. As the typhoon approaches the center, the angle of wind deviation from the radius increases and reaches 90° in close proximity to the center. In the center of the typhoon, weak winds and even calm conditions are observed in stormy seas. After passing the center of the typhoon (“the eye of the storm”), the wind very quickly intensifies to hurricane force. Force 12 winds persist 30-35 miles from the center or more. Then it gradually weakens. So, at a distance of 50-75 miles from the center of the typhoon, the wind force is 10; at a distance of 100-150 miles - 8-9 points. And only at a distance of 200-250 miles the wind force decreases to 6-7 points. Using the model of a tropical cyclone (see Fig. 114), it is not difficult to establish the position of the ship relative to the path of movement of the center of the tropical cyclone: ​​if the wind direction changes clockwise, then the right half of the cyclone passes through the ship; if the wind direction changes counterclockwise - left half; if the wind direction does not change - the center of the cyclone. Thus,

Rice. 115.

To choose the right course when meeting a tropical cyclone, you must be guided by the following rules:

1) when sailing in the northern hemisphere (Fig. 115, a): when passing the right half of a tropical cyclone, you need to lie down on the starboard tack (bring the wind to the right cheekbone) and maintain this course until the barometer begins to rise;

When passing the left half of a tropical cyclone, you need to lay down on the starboard tack (bring the wind to the stern from the right) and maintain this course until leaving the zone of the tropical cyclone; being in the path of the center of a tropical cyclone, they also lay down on the starboard tack (Fig. 115, a) and hold on as indicated earlier;

2) when sailing in the southern hemisphere (Fig. 115, b):

When passing the left half of a tropical cyclone, lie close-hauled on the port tack, maintaining course until the barometer begins to rise;

When passing the right half of a tropical cyclone, lie on the port tack backstay and hold as indicated earlier; when in the path of a hurricane, also bring the wind into the backstay of the port tack and so steer until leaving the hurricane zone.

Anticyclones- areas of high atmospheric pressure are, like cyclones, stationary and mobile.

An anticyclone penetrating from the north brings lower temperatures, clear weather and good visibility during the cold season; in the warm season there are thunderstorms; the anticyclone coming from the south brings prolonged cloudy weather in the cold season; in warm weather - rains with thunderstorms, and at night - dew and ground fogs. A clear sign Anticyclonic weather is a sharp daily variation in air temperature, humidity and other meteorological elements.

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Cyclones are always moving. By movement we mean the movement of the cyclone as a whole, regardless of the winds blowing in it, which different parts cyclones have different speeds and directions. Move the cyclone like unified system characterized by the movement of its center.

Cyclones move in the direction of the general air transport in the middle and upper troposphere (they also say: in the direction of the leading flow). This general air transfer most often occurs from west to east. Therefore, cyclones most often move from the western half of the horizon to the eastern half.

But it also happens that high, slow-moving cyclones and anticyclones, extending throughout the entire thickness of the troposphere, are located in such a way that isobars and currents at heights deviate from the zonal direction. Then the mobile cyclones, following this non-zonal upper transport, move with a large component to the south or north. In rare cases, the direction of the leading flow is even eastern; then the cyclone moves anomalously, from east to west.

In some cases, the paths of cyclones turn out to be very diverse, and even typical paths over a particular area present a rather complex picture. But on average, cyclones move from west to east with a component directed towards high latitudes. Therefore, the deepest cyclones are observed, as mentioned above, in subpolar latitudes: in the northern hemisphere - in the north of the Atlantic and Pacific Oceans, in the southern hemisphere - near the continent of Antarctica.

The speed of movement of the cyclone is 25-35% less than the speed of the leading flow. On average, it is of the order of magnitude 30-40 km/h. In some cases it can be up to 80 km/h or more. IN late stage life of a cyclone, when it is already filling, the speed of movement decreases, sometimes very sharply.

Although the speeds of cyclones are small, within a few days of its existence a cyclone can move a considerable distance, on the order of several thousand kilometers, changing the weather regime along the way.

As a cyclone passes, the wind increases and its direction changes. If a cyclone passes through a given place on its southern part, the wind changes from south to southwest and northwest. If a cyclone passes through its northern part, the wind changes from southeast to east, northeast and north. Thus, in the front (eastern) part of the cyclone, winds with a southern component are observed, in the rear (western) part - with a northern component. Temperature fluctuations during the passage of a cyclone are also associated with this.

Finally, cyclonic areas are characterized by increased cloudiness and precipitation. In the front part of the cyclone, precipitation is blanket, ascending sliding, falling from the clouds of a warm front or an occlusion front. In the rear part, precipitation is showery, from cumulonimbus clouds, characteristic of a cold front, but mainly of cold air masses flowing in the rear of the cyclone to low latitudes. In the southern part of the cyclone, drizzling precipitation of a warm air mass is sometimes observed.

The approach of a cyclone can often be seen by the drop in pressure and the first clouds appearing on the western horizon. These are frontal cirrus clouds moving in parallel bands. At a glance, due to perspective, these stripes appear to diverge from the horizon. They are followed by cirrostratus clouds, then denser altostratus clouds and, finally, nimbostratus clouds with accompanying nimbostratus clouds. Then, in the rear of the cyclone, pressure increases, and cloudiness takes on a rapidly changing character: cumulus and cumulonimbus clouds often give way to clearings.

Some time ago, scientists could not even think that about two hundred cyclones and about fifty anticyclones form on the surface of the planet, because many of them remained invisible due to the lack of weather stations in the areas where they arise. But now there are satellites that record the changes that occur. What are cyclones and anticyclones, and how do they arise?

First, what is a cyclone

The cyclone is a huge atmospheric vortex with low air pressure. In it, air masses always mix counterclockwise in the north and clockwise in the south.

They say that a cyclone is a phenomenon that is observed on different planets, including the Earth. It arises due to the rotation of the celestial body. This phenomenon is extremely powerful and brings with it strong winds, precipitation, thunderstorms and other phenomena.

Anticyclone

In nature there is such a thing as an anticyclone. It is not difficult to guess that this is the opposite phenomenon of a cyclone. It is characterized by the movement of air masses counterclockwise in the southern hemisphere and clockwise in the northern hemisphere.

Anticyclones can stabilize the weather. After them, calm, quiet weather sets in over the territory: it is hot in summer and frosty in winter.

Cyclones and anticyclones

So what is a cyclone and an anticyclone? These are two phenomena that occur in the upper atmosphere and carry different weather. The only thing these phenomena have in common is that they occur over certain territories. For example, anticyclones most often occur over ice fields. And what larger territory ice, the stronger the anticyclone.

For many centuries, scientists have tried to determine what a cyclone is, what its significance is and what it affects. Key concepts this atmospheric phenomenon air masses and fronts are considered.

Air masses

Over many thousands of kilometers, horizontal air masses have the same properties. They are divided into cold, local and warm:

1. Cold ones have a lower temperature than the surface over which they are located.
2. In warm ones it is greater than on the surface where they are located.
3. Local mass is air whose temperature is no different from the territory that is located underneath it.

Air masses form over very different parts of the Earth, which determines their characteristics and various properties. The area over which air masses form gives them their name.

For example, if they appear over the Arctic, they are given the name Arctic. This air is cold, with fogs and haze. Tropical air masses bring heat and lead to the formation of vortices, tornadoes, and storms.

Cyclones

An atmospheric cyclone is an area of ​​low pressure. It occurs due to two air flows with different temperatures. The center of the cyclone has minimal atmospheric indicators: the pressure in its central part is lower, and at the edges it is high. It seems that air masses are thrown upward, thereby forming upward air currents.

By the direction of movement of air masses, scientists can easily determine in which hemisphere it was formed. If its movement coincides with the clockwise direction, then it originated in the Southern Hemisphere, and if the air moves against it, the cyclone came from the Northern Hemisphere.

In the zone of action of a cyclone, phenomena such as accumulations of cloud masses, sudden temperature changes, precipitation, thunderstorms, and whirlwinds can be observed.

Cyclone born over the tropics

Tropical cyclones are different from those that occur over other areas. These types of phenomena go by a variety of names: hurricanes, typhoons, arcana. Tropical eddies are usually large - up to three hundred miles or more. They are capable of driving winds at speeds of more than 100 km/h.

A distinctive feature of this atmospheric phenomenon from others is that the wind accelerates throughout the entire territory of the cyclone, and not only in certain zones, as is the case with cyclones that occur in the temperate zone. Main sign The approach of a tropical cyclone is the appearance of ripples in the water. Moreover, it goes in the opposite direction from the wind.

In the 70s of the last century, tropical cyclone Bhola hit Bangladesh, which was assigned the third category out of the existing five. It had a low wind speed, but the accompanying rain caused the Ganges River to overflow its banks, which flooded all the islands, washing away all the settlements. As a result of this disaster, more than 500 thousand people died.

Cyclone scales

Any cyclone action is rated on the hurricane scale. It indicates the category, wind speed and storm tide:

1. The first category is considered the easiest. With it, a wind of 34-44 m/s is observed. Storm tide does not exceed two meters.
2. Second category. It is characterized by winds of 50-58 m/s and a storm tide of up to 3 m.
3. Third category. The wind force can reach 60 meters per second, and the storm tide can reach no more than 4 m.
4. Fourth category. Wind - up to 70 meters per second, storm tide - about 5.5 m.
5. The fifth category is considered the strongest. It includes all cyclones with a wind force of 70 meters per second and a storm tide of more than 5.5 meters.

One of the most famous category 5 tropical hurricanes is Katrina, which killed almost 2,000 people. Hurricanes “Wilma”, “Rita”, “Ivan” also received category five. During the passage of the latter through America, more than one hundred and seventeen tornadoes formed.

Stages of cyclone formation

The characteristics of the cyclone are determined as it passes through the territory. At the same time, its stage of formation is specified. There are four in total:

1. First stage. It is characterized by the beginning of the formation of a vortex from air currents. At this stage, deepening occurs: this process usually takes about a week.
2. Young cyclone. A tropical cyclone in its young stage can go in different directions or move in the form of small air masses over short distances. In the central part there is a drop in pressure, and a dense ring with a radius of about 50 km begins to form around the center.
3. Maturity stage. It is characterized by a cessation of pressure drop. At this stage, the wind speed reaches its maximum and stops increasing. The radius of storm winds is located on the right side of the cyclone. This stage can last from several hours to several days.
4. Attenuation. When a cyclone makes landfall, the decay stage begins. During this period, a hurricane can go in two directions at once, or it can gradually fade, turning into lighter tropical whirlwinds.

Snake rings

Cyclones (from the Greek "snake ring") are vortices gigantic size, the diameter of which can reach thousands of kilometers. They usually form in places where air from the equator collides with oncoming cold currents. The boundary formed between them is called the atmospheric front.

During a collision, warm air prevents cold air from passing through. In these areas, pushing back occurs, and the air mass is forced to rise higher. As a result of such collisions between masses, pressure increases: part of the warm air is forced to deviate to the side, yielding to the pressure of cold air. This is how the rotation of air masses occurs.

The resulting vortices begin to capture new air masses, and they begin to move. Moreover, the movement of the cyclone in its central part is less than along the periphery. In those zones where the vortex moves sharply, strong jumps in atmospheric pressure are observed. In the very center of the funnel, a lack of air is formed, and in order to somehow compensate for it, cold masses enter the central part. They begin to displace warm air upward, where it cools, and the water droplets in it condense and form clouds, from which precipitation then falls.

The vortices can live for several days or several weeks. In some regions, cyclones almost a year old have been recorded. This phenomenon is typical for areas with low pressure.

Types of cyclones

There are the most different types vortexes, but not every one of them brings destruction. For example, where cyclones are weak but very windy, the following phenomena may be observed:

• Outrage. During this phenomenon, the wind speed does not exceed seventeen meters per second.
• Storm. In the center of the cyclone, the speed of movement is up to 35 m/s.
• Depression. With this type, the speed of the cyclone is from seventeen to twenty meters per second.
• Hurricane. With this option, the cyclone speed exceeds 39 m/s.

Scientists about cyclones

Every year, scientists around the world record the intensification of tropical cyclones. They become stronger, more dangerous, their activity increases. Because of this, they are found not only in tropical latitudes, but also in European countries, and at atypical times for them. Most often this phenomenon is observed in late summer and early autumn. Cyclones have not yet been observed in the spring.

One of the most powerful whirlwinds that swept over European countries was Hurricane Lothar in 1999. He was very powerful. Meteorologists could not detect it due to sensor failure. This hurricane caused hundreds of deaths and caused serious damage to forests.

Record cyclones

Hurricane Camila occurred in 1969. In two weeks he reached from Africa to America and reached a wind force of 180 km/h. After passing through Cuba, its strength weakened by twenty kilometers, and scientists believed that by the time it reached America, it would weaken even more. But they were wrong. After crossing the Gulf of Mexico, the hurricane gained strength again. “Camila” was assigned the fifth category. More than 300 thousand people were missing and thousands were injured. Here are a few more sad record holders:

1. The Bhola cyclone of 1970 was the record for the number of victims, which claimed more than 500 thousand lives. The potential number of victims could reach a million.
2. In second place is Hurricane Nina, which killed more than one hundred thousand people in China in 1975.
3. In 1982, Hurricane Paul raged in Central America, killing nearly a thousand people.
4. In 1991, Cyclone Thelma hit the Philippines, killing several thousand people.
5. The worst was Hurricane Katrina in 2005, which claimed almost two thousand lives and caused almost one hundred billion dollars in damage.

Hurricane Camila is the only one that made landfall while retaining all its power. Wind gusts reached 94 meters per second. Another record holder for wind strength was registered on the island of Guam. The typhoon had winds of 105 meters per second.

Among all the recorded vortices, “Type” had the largest diameter, stretching over more than 2100 kilometers. The smallest typhoon is Marco, which has a wind diameter of only 37 kilometers.

If we judge by the lifespan of a cyclone, John raged the longest in 1994. It lasted 31 days. He also holds the record for the longest distance traveled (13,000 kilometers).