atmospheric fronts. Cyclones and anticyclones. What is a cyclone and anticyclone? What is an anticyclone definition

Air plays an extremely important role in the life of not only a person, but the whole planet. Atmospheric phenomena have been studied by scientists since the beginning of centuries and continue to be actively investigated today. It is worth saying that, in fact, this is not just a continuous opaque substance, it is divided into masses and fronts, which, moving over various parts, play a key role in the formation of air vortices. Consider what a cyclone and anticyclone are, their main differences.

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Cyclone

A cyclone is an air mass that has the form of a vortex, gigantic in diameter (from 100 to many 1000 km). The cyclone is characterized by low pressure and the movement of air flows clockwise or counterclockwise, in the center, in different directions, depending on the hemisphere in which the vortex operates.

A cyclone differs from an anticyclone by the process of formation. The first has a natural origin: the planet Earth rotates, which causes the air around it to move and form vortices. Considering the physics of the occurrence of these phenomena, we can distinguish two main theories in the formation of the air flow:

• Coriolis force;
• fixed point theorem.

Thanks to these theories, it is possible to explain the appearance of such vortices in the earth-air space and also in the atmospheres of others.

Kinds

There are two main types of vortices that differ in their characteristics.

extratropical

Characteristic for polar or temperate climatic zones. Their diameter usually starts from 1000 km at the beginning and several thousand at the end. They, in turn, are divided into:

• southern - they are characteristic of temperate climatic zones, more precisely their southern parts. These include cyclones in the Balkans, the Mediterranean and the Black Sea coast;
• northern;
• northeastern.

Of these, only the southern ones carry a colossal amount of energy, which usually results in heavy precipitation, winds, lightning storms and other unpleasant natural phenomena.

extratropical cyclone

tropical

Occur only over tropical zones and are small in size. Their diameter is usually estimated at several hundred kilometers (rarely over 1000 km), but they are characterized by strong winds. Because of this, they often become stormy and are distinguished by the “eye of the storm” - this is the central part of the vortex, which is about 30 km in diameter, in which clear weather remains without winds and precipitation.

Important! and the nearest territory to it are the territory in which such natural phenomena never occur.

A cyclone is low pressure in the atmosphere and all that it entails. Meteorologists can timely predict the imminent onset of such an air vortex. What kind of weather does a cyclone bring: with showers and destructive storms, but the warm air temperature remains.

tropical cyclone

Anticyclone

What is an anticyclone - this is part of the air currents in which there is high pressure and wind movement in certain directions. Such an area is distinguished by the fact that the wind is directed clockwise in the territory of the upper hemisphere and counter-clockwise in the lower one.

Anticyclones are divided into two types:

• low - these are predominantly cold air flows, in which up to 1.5 km of the troposphere there are closed isobars, and above there is no high pressure at all;
• high - in such air masses, air is warm and high pressure is present throughout the entire troposphere involved. In such vortices there can be several main centers.

An anticyclone is clear weather without clouds. Moreover, low-lying stratus clouds and fogs with frosts at night in autumn and winter can form, and in summer - cumulus clouds and lack of precipitation, which often leads to forest fires. Such eddies do not exceed several thousand kilometers in diameter and move from west to east at a speed of 30-40 km/h, leaning toward low latitudes.

Signs of the presence of an anticyclone are as follows:

• clear sky;
• little or no clouds;
• no wind and rain with snow;
• sunny stable weather.

The formation of such air currents over areas where the soil is covered with ice is reflected in their strength and characteristics. So, over Antarctica it will be extremely strong, and over Greenland it will be much weaker. The same goes for tropical climates.

Anticyclone

Comparison

The prefix anti itself indicates that an anticyclone is an atmospheric phenomenon that is opposite to a cyclone in its characteristics. If a cyclone is a low atmospheric pressure, then an anticyclone is a high one. This is the most significant difference, drastically changing the weather in the area under these eddies. Their difference lies in the different movements of air currents. How else are they different.

The characteristics of the cyclone and anticyclone are given below.

Characteristic	Cyclone	Anticyclone
Pressure	Low in the center of the vortex	Elevated in the same place
Dimensions	The diameter can be 300-5000 km.	Up to 4000 km at the widest point.
Travel speed (km/h)	On average 30-60.	On average, 20-40 or completely inactive.
Characteristic places	Occur throughout the globe, except for the equator.	Occur predominantly over land covered with an ice layer (Antarctica or the Arctic).
Causes	The natural movement of the earth around its axis. The appearance of an air mass deficit.	The appearance of a cyclone. With an excess of air mass.
Air rotation	Air is directed from the outskirts to the center. As for its direction, in the Northern Hemisphere it moves counterclockwise, and in the Southern Hemisphere, on the contrary, it moves clockwise.	As in general, the movement of air in this vortex is reversed: the air is directed from the center to the outskirts of the vortex, and its direction also depends on the hemisphere: North - clockwise; South is counterclockwise.
Air direction	ascendant	descending
Weather	This natural phenomenon is characterized by a high probability of precipitation and strong wind gusts. Thick clouds form in the sky, and the weather will generally be overcast and humid, but not cold. It often rains in summer, and in winter it snows or rains, but without frost.	It brings with it dry weather, which is not characterized by winds or clouds. Usually in summer it is dry, cloudy weather, without precipitation, and in winter it is cold and frosty.

Thus, the approach of a cyclone indicates that weather is approaching with devastating consequences: heavy rains, winds and snow storms. There will be many clouds and clouds in the sky, strong gusts of wind. In general, the weather will be unstable. Unlike such vortices, anticyclones will bring stability: calm weather will be established, calmness and cloudlessness, it will be warm for a long time.

atmospheric fronts. Cyclones and anticyclones

Cyclone (low pressure area)

Output

Weather-sensitive people often feel the approach of one or another atmospheric phenomenon on themselves: when an anticyclone approaches, atmospheric pressure is high, and blood pressure drops, so dizziness and headaches appear. When a cyclone approaches, the opposite is true: atmospheric pressure decreases, and blood pressure rises.

air masses- these are large air masses of the troposphere and lower stratosphere, which are formed over a certain territory of land or ocean and have relatively uniform properties - temperature, transparency. They move as one unit and in the same direction in the atmosphere system.

Air masses occupy an area of ​​thousands of square kilometers, their thickness (thickness) reaches up to 20-25 km. Moving over a surface with different properties, they heat up or cool down, or become drier. Warm or cold air mass is called, which is warmer (colder) than its environment. There are four types of air masses depending on the areas of formation: equatorial, tropical, temperate, arctic (Antarctic) air masses (Fig. 13). They differ primarily in temperature and humidity. All types of air masses, except for equatorial ones, are divided into maritime and continental, depending on the nature of the surface over which they formed.

The equatorial air mass is formed in the belt. It has rather high temperatures and humidity close to the maximum, both over land and over the sea. Continental tropical air mass is formed in the central part of the continents in. It has high temperature, low humidity, high dust content. Marine tropical air mass is formed over the oceans in tropical latitudes, where rather high air temperatures prevail and high humidity is noted.

Continental moderate air mass is formed over the continents in, dominates the Northern Hemisphere. Its properties change with the seasons. In summer, the temperature and humidity are quite high, precipitation is typical. In winter, low and extremely low temperatures and low humidity. Marine temperate air mass forms over oceans with warm currents in temperate latitudes. It is cooler in summer, warmer in winter, and has significant humidity.

The continental Arctic (Antarctic) air mass is formed over the ice of the Arctic and has extremely low temperatures and low humidity, high transparency. Marine Arctic (Antarctic) air mass is formed over periodically freezing seas and oceans, its temperature is slightly higher, humidity is higher.

Air masses are in constant motion; when they meet, transition zones, or fronts, are formed. - the border zone between two having different properties. The width of the atmospheric front reaches tens of kilometers. Atmospheric fronts can be warm or cold, depending on what kind of air is moving into the territory and what is being displaced (Fig. 14). Most often, atmospheric fronts occur in temperate latitudes, where cold air from polar latitudes and warm air from tropical latitudes meet.

The passage of the front is accompanied by changes in . The warm front moves towards the cold air. It is associated with warming, nimbostratus clouds, bringing drizzling precipitation. The cold front moves towards the warm air. It brings abundant short-term heavy rainfall, often with squally and, and cooling.

Cyclones and anticyclones

In the atmosphere, when two air masses meet, large atmospheric vortices arise -. They are flat air vortices covering thousands of square kilometers at a height of only 15-20 km.

Cyclone- an atmospheric vortex of huge (from hundreds to several thousand kilometers) diameter with reduced air pressure in the center, with a system of winds from the periphery to the center against in the Northern Hemisphere. In the center of the cyclone, ascending air currents are observed (Fig. 15). As a result of ascending air currents, powerful clouds form in the center of cyclones and precipitation falls.

In summer, during the passage of cyclones, the air temperature decreases, and in winter it rises, a thaw begins. The approach of a cyclone causes cloudy weather and a change in wind direction.

Tropical cyclones occur in tropical latitudes from 5 to 25° in both hemispheres. Unlike cyclones of temperate latitudes, they occupy a smaller area. Tropical cyclones occur over the warm sea surface in late summer - early autumn and are accompanied by powerful thunderstorms, heavy rainfall and storm-force winds, which have tremendous destructive power.

In tropical cyclones they are called, in the Atlantic -, off the coast of Australia - willy-willy. Tropical cyclones carry a large amount of energy from tropical to temperate latitudes, which makes them an important component of global atmospheric circulation processes. For their unpredictability, tropical ones are given female names (for example, "Catherine", "Juliet", etc.).

Anticyclone- an atmospheric vortex of huge diameter (from hundreds to several thousand kilometers) with an area of ​​high pressure near the earth's surface, with a system of winds from the center to the periphery clockwise in the Northern Hemisphere. Downdrafts of air are observed in the anticyclone.

Both in winter and in summer, the anticyclone is characterized by a cloudless sky and calmness. During the passage the weather is sunny, hot in summer and very cold in winter. Anticyclones form over the ice sheets of Antarctica, over, over the oceans in tropical latitudes.

The properties of air masses are determined by the areas of their formation. When they move from their places of formation to others, they gradually change their properties (temperature and humidity). Due to cyclones and anticyclones, heat and moisture are exchanged between latitudes. The change of cyclones and anticyclones in temperate latitudes leads to sharp changes in the weather.

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

First, what is a cyclone

A cyclone is a huge atmospheric vortex with low air pressure. In it, the 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 a celestial body. This phenomenon has great power and brings with it the strongest 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 phenomenon is the opposite of a cyclone. It is characterized by the movement of air masses counterclockwise in the southern hemisphere and clockwise in the northern hemisphere.

Anticyclones are able to stabilize the weather. Calm calm weather sets in over the territory after them: in summer it is hot, and in winter it is frosty.

Cyclones and anticyclones

So what is a cyclone and 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 the larger the area of ​​ice, the stronger the anticyclone.

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

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 on the surface above which they are located.
2. Warm ones have more than on the surface where they are located.
3. The local mass is air, the temperature of which is no different from the territory that is located under it.

Air masses are formed over various parts of the Earth, which determines their features and various properties. The area over which air masses form gives them their name.

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

Cyclones

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

In the direction of movement of air masses, scientists can easily determine in which hemisphere it was formed. If its movement coincides with the hour hand, 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 the cyclone, phenomena such as accumulations of cloud masses, sudden changes in temperature, precipitation, thunderstorms, whirlwinds can be observed.

Cyclone born over the tropics

Tropical cyclones are different from those that occur over other areas. Such types of phenomena have a variety of names: hurricanes, typhoons, arcana. Usually tropical eddies are large - up to three hundred miles or more. They are able to drive wind at speeds of over 100 km/h.

A distinctive feature of this atmospheric phenomenon from others is that the wind accelerates throughout the cyclone, and not only in certain zones, as is the case with cyclones that occur in the temperate zone. The main sign of the approach of a tropical cyclone is the appearance of ripples on 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 of the existing five. He had a small wind speed, but the accompanying rain caused the Ganges to overflow the banks, which flooded all the islands, washing away all the settlements. More than 500 thousand people died as a result of this disaster.

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. The storm tide does not exceed two meters.
2. Second category. It is characterized by winds of 50-58 m/s and storm surge up to 3 m.
3. Third category. Wind strength can reach 60 meters per second, and storm tide - 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 with a storm surge of more than 5.5 meters.

One of the most notorious Category 5 tropical hurricanes is Katrina, which has killed nearly 2,000 people. Also, the fifth category received hurricanes: "Wilma", "Rita", "Ivan". During the passage of the latter through the territory of America, more than one hundred and seventeen tornadoes formed.

Stages of cyclone formation

The characteristic of a cyclone is determined during its passage 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 flows. 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. A pressure drop occurs in the central part, a dense ring begins to form around the center, with a radius of about 50 km.
3. maturity stage. It is characterized by the cessation of pressure drop. At this stage, the wind speed reaches its maximum and stops increasing. The storm wind radius is placed on the right side of the cyclone. This stage can be observed from several hours to several days.
4. Attenuation. When the cyclone makes landfall, the attenuation stage begins. During this period, the hurricane can go in two directions at once, or it can gradually fade, turning into lighter tropical eddies.

snake rings

Cyclones (from the Greek "serpent ring") are gigantic eddies, whose diameter can reach thousands of kilometers. They usually form in places where air from the equator collides with cold currents going towards it. The boundary formed between them is called the atmospheric front.

During a collision, warm air does not allow cold air to pass through. In these areas, pushing occurs, and the air mass is forced to rise higher. As a result of such collisions between the masses, the pressure rises: part of the warm air is forced to deviate to the side, yielding to the pressure of the cold one. So there is a rotation of air masses.

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, there are strong jumps in atmospheric pressure. In the very center of the funnel, a lack of air is formed, and in order to somehow make up 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.

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

Types of cyclones

There are various types of vortices, but not every one of them is destructive. For example, where cyclones are weak but very windy, the following phenomena can be observed:

• Perturbations. With 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. In this form, 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 strengthening of tropical cyclones. They become stronger, more dangerous, their activity grows. Because of this, they are found not only in tropical latitudes, but also in European countries, and at an atypical time for them. Most often this phenomenon is observed in late summer and early autumn. So far, cyclones are not observed in spring.

One of the most powerful whirlwinds that swept over the countries of Europe was Hurricane Lothar in 1999. He was very powerful. Meteorologists could not fix it due to the failure of sensors. This hurricane caused the death of hundreds of people and caused serious damage to the forests.

Record cyclones

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

1. Cyclone "Bhola" in 1970, which claimed more than 500 thousand lives, became the record for the number of victims. The potential number of victims could reach a million.
2. In second place is Hurricane Nina, which killed more than a 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 nearly 2,000 lives and caused almost $100 billion in damage.

Hurricane Camila is the only hurricane to make landfall in full force. Wind gusts reached 94 meters per second. Another record holder for wind strength is registered on the island of Guam. The typhoon had a wind force of 105 meters per second.

Among all the recorded eddies, the largest diameter was "Type", spread over more than 2100 kilometers. The smallest typhoon is Marco, which has a wind diameter of only 37 kilometers.

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

Then the air flow rapidly turns into a powerful whirlwind, the wind speed increases significantly and penetrates into the upper layers of the atmosphere. The cyclone captures the adjacent layers of air, dragging them at a speed of up to 50 km / h.

On the distant fronts, a greater speed is achieved than in the center. During this period, due to low pressure, there is a sharp change in the weather.

A developed cyclone passes into the fourth stage and acts for four days or more. The cloud vortex closes in the center and then shifts to the periphery. At this stage, the speed decreases, heavy precipitation falls.

The phenomenon of a cyclone is characterized by a lack of air.

Cold currents come in to replenish it. They push warm air up. As it cools, the water condenses. Clouds appear, from which heavy precipitation falls. Here is what a cyclone is and why the weather changes dramatically when it occurs.

The duration of the vortex is from several days to weeks.

In an area of ​​low pressure, it can last up to a year (for example, the Icelandic or Aleutian cyclone). According to their origin, the types of cyclones differ depending on the place of its occurrence:

• eddies in temperate latitudes
• tropical vortex
• equatorial
• arctic

In the Earth's atmosphere, the movement of masses is constantly formed.

Whirlwinds of various sizes are destroyed all the time in it. Warm and cold air currents collide in temperate latitudes and form areas of high and low pressure, which leads to the formation of vortices.

A tropical cyclone poses a great danger. It forms where the surface temperature of the ocean is at least twenty-six degrees.

Increased evaporation contributes to an increase in humidity. As a result, vertical air masses rush upward.

With a strong impulse, new volumes of air are captured. They have already warmed up enough and become wet above the surface of the ocean.

Rotating at great speed, the air currents turn into hurricanes of destructive force. Of course, not every tropical cyclone brings destruction. When they move to land, they quickly subside.

Movement speed in different stages

1. movement not exceeding 17 m/s is characterized as a disturbance
2. at 17-20 m/s there is some depression
3. when the center reaches 38 m/s, a storm is coming
4. when the forward movement of the cyclone exceeds 39 m/s, a hurricane is observed

In the center of the cyclone, an area of ​​calm weather prevails.

Inside, a warmer temperature is formed than in the rest of the air flow, less humidity is observed. The tropical cyclone is the southernmost one, it is smaller and has a higher wind speed.

For convenience, the phenomena of anticyclones and cyclones were first called numbers, letters, etc. Now they have received female and male names. When exchanging information, this does not create confusion and reduces the number of errors in forecasts.

Each name contains certain data.

The phenomena of anticyclone and cyclone that form over the ocean differ in their properties from those that have arisen over the mainland. Marine air masses are warm in winter and cold in summer compared to continental air.

Tropical cyclones

Tropical cyclones mainly capture areas of the southeast coast of Asia, the eastern part of the island of Madagascar, the Antilles, the Arabian Sea and the Bay of Bengal.

More than seventy powerful cyclones are observed per year.

They are called differently, depending on the place of origin:

• North and Central America - Hurricane
• West coast of Mexico in the Pacific Ocean - cordonaso
• East Asia - typhoon
• Philippines - Baruyo / Baguyo
• Australia - Willy Willy

The properties of temperate, tropical, equatorial and arctic air masses are easily identified by name.

Each tropical cyclone has its own name, such as "Sarah", "Flora", "Nancy", etc.

Conclusion

Vertical-horizontal movements of air masses move in space. The atmosphere is an ocean of air, the winds are its course. Their boundless energy carries heat and moisture across all latitudes, from the oceans to the continents and back.

Moisture and heat on Earth is redistributed due to the constant movement of air masses.

If it were not for the phenomenon of anticyclones and cyclones, then the temperature at the poles would be lower, and at the equator it would be hotter.

The phenomenon of cyclone and anticyclone

The phenomenon of anticyclone and cyclone is a powerful force that can destroy, deposit and transfer rock particles from one place to another.

At first, mills worked from the wind, where they ground grain. On sailboats, he helped to overcome long distances of the seas and oceans. Later, wind turbines appeared, with the help of which people receive electricity.

A cyclone and an anticyclone is a natural “mechanism” that carries air masses and affects weather changes.

More and more delving into the secrets of what cyclones and anticyclones are, perhaps people will learn to use these natural phenomena with maximum benefit and benefit for humanity.

The basic rule for moving baric systems is the leading flow rule:

Rice. 9. Determining the direction of movement of cyclones

and anticyclones along the leading stream

Young mobile cyclones and anticyclones move in the direction of the leading flow, which is observed above their surface centers (Fig.

The speed of movement of cyclones and anticyclones is 80% of the average speed of the leading flow on the AT-700 map or 50% of the average speed of the leading flow on the AT-500 map.

In the cold season, the leading flow is determined, as a rule, according to the AT-700hPa map, in the warm season, according to the AT-500hPa map.

Based on surface weather maps, the movement of baric systems can be determined according to the following rules:

but) Center of the cyclone moves parallel to the isobars of the warm sector, leaving the warm sector to the right of the direction of motion (Fig.

Anticyclone

Rice. 10. Determining the direction of movement

cyclone in the warm sector

b) Center of the cyclone moves parallel to the line connecting the pressure increase center with the drop center, towards the pressure drop center (Fig.

Rice. 11. Determining the direction of movement

cyclone along the centers of growth and pressure drop

Hollow, formed on the periphery of the cyclone, moves along with the cyclone and simultaneously rotates around its center counterclockwise (Fig. 12).

Rice. 12. Determination of direction

hollow movements

Anticyclone moves towards the center of maximum pressure growth, located on its periphery.

If the center of pressure growth is located in the center of the anticyclone, then the anticyclone is stationary.

Rice. 13. Determining the direction of movement

anticyclone

Crest , formed on the periphery of the anticyclone, moves along with the anticyclone and at the same time goes around its center clockwise.

14. Determination of the direction of movement of the ridge

Evolution of pressure systems:

1. If in the center of the cyclone, in the hollow, the pressure drops, i.e. baric tendencies are negative, then the cyclone, the trough deepen (develop), and the weather in these baric systems worsens.

2. If in the center of the cyclone, in the hollow, the pressure increases, i.e. baric tendencies are positive, then the cyclone, the hollow are filled (destroyed) and the weather in these baric systems becomes better.

If the pressure increases in the center of the anticyclone, in the ridge, then the anticyclone, the ridge intensify (develop) and good weather in these baric systems will persist for a long time.

4. If the pressure drops in the center of the anticyclone, in the ridge, then the anticyclone and the ridge collapse, and the weather in these baric systems will worsen.

test questions

1. What meteorological maps are called surface weather maps?

2. What surface charts are called basic (ring) charts, and how often are they made?

3. How are weather data plotted on surface maps?

4. What is the primary analysis (processing) of surface weather maps?

5. What lines are called isobars, for what pressure values ​​and at what intervals are they drawn on weather maps?

What lines are called isallobars, and how are they drawn on weather maps?

7. How are areas of pressure rise and fall identified on weather maps?

8. What color are the main atmospheric fronts (warm, cold, stationary, occlusive front) and secondary atmospheric fronts on color printed weather maps?

9. What ornament on black-and-white weather maps indicate the main and secondary atmospheric fronts?

10. How are zones of overt precipitation distinguished on weather maps?

How are fog zones highlighted on weather maps?

12. How is a thunderstorm distinguished on weather maps (at the time of observation and between periods)?

13. How is the direction of movement of air masses determined on the weather map?

14. What is the transformation of air masses, and what does it depend on?

15. What should be taken into account when analyzing weather conditions if the weather is determined by the air mass?

16. How is the direction of movement of the atmospheric front determined if it is parallel to the isobars (perpendicular or located at an angle not equal to 90 °)?

How does the speed of the front movement depend on the angle of intersection of the front with the isobars and the density of the isobars?

18. How will the nature of the weather change in the atmospheric front zone if the front becomes aggravated (blurred)?

At what values ​​of pressure drop (growth) do atmospheric fronts sharpen (blur)?

20. Why do atmospheric fronts intensify in the center of a cyclone, and erode on its periphery?

21. Why do atmospheric fronts erode in anticyclones and ridges?

22. What happens to atmospheric fronts on the windward and leeward slopes of mountains?

23. At what time of the year and day do warm and cold fronts intensify?

How is the direction and speed of movement of cyclones and anticyclones determined according to the rule of the leading flow?

25. How is the direction of cyclone movement in the warm sector determined?

26. How is the direction of movement of a cyclone along an isallobaric pair determined?

27. How is the direction of movement of the anticyclone determined on surface maps?

How is the direction of ridge movement determined?

29. How is the direction of movement of the hollow determined?

30. In what cases do cyclones (hollows) deepen?

31. When are cyclones (hollows) filled?

32. In what cases are anticyclones (crests) intensified?

When do anticyclones (ridges) collapse?

34. How does the weather change with the deepening of cyclones (hollows)?

35. How does the weather change when cyclones (hollows) fill?

36. How does the weather change when anticyclones (ridges) increase?

37. How does the weather change with the destruction of anticyclones (ridges)?

CYCLONES AND ANTICYCLONES

Cyclones and anticyclones

In the troposphere, eddies of various sizes constantly arise, develop and disappear - from small to giant cyclones and anticyclones.

Cyclone is an area of ​​low pressure in the center. Therefore, the air in the cyclone moves in a spiral from the periphery (from areas of high pressure) to the center (to the area of ​​low pressure) and then rises upwards, forming updrafts. In a cyclone, the air moves along a curved path and is directed counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Cyclones are associated with vast areas of clouds and precipitation, significant temperature changes, and strong winds. However, cyclones are also known that exist throughout the year in constant areas of low pressure: Icelandic cyclone (minimum), located in the North Atlantic in the area of ​​about. Iceland, and Aleutian cyclone (minimum) in the Aleutian Islands in the North Pacific. In addition to temperate latitudes, cyclones are observed in the tropical zone.

Tropical cyclones occur only over the sea, between 10-15 ° N. and y.sh. When moving to land, they quickly fade. These are, as a rule, small cyclones, their diameter is about 250 km, but with very low pressure in the center.

Tropical cyclones move at a speed of 10-20 km / h, mainly from east to west, but their trajectory deviates towards high latitudes (for example, in the Northern Hemisphere they move towards the northwest). These are very powerful whirlwinds with exceptionally strong winds (20-30 m/s, in gusts up to 100 m/s and more), which cause the strongest waves at sea and great destruction on land. On the globe, on average, more than 70 cases of tropical cyclones are recorded per year. They are best known in the Antilles, off the southeast coast of Asia, in the Arabian Sea, the Bay of Bengal, east of about. Madagascar. In different areas they have local names ( cyclone - in the Indian Ocean; Hurricane - in North and Central America; typhoon in East Asia). Cyclones are especially typical for the territory of Europe, where they move from the Atlantic to the east and exist up to 5-7 days, i.e. until the atmospheric pressure equalizes.

Anticyclone is an area with increased pressure in the center. Due to this, the movement of air in the anticyclone is directed from the center (from the region of higher pressure) to the periphery (in the region of lower pressure). In the center of the anticyclone, the air descends, forming descending flows, and spreads in all directions, i.e. from the center to the periphery. At the same time, it also rotates, but the direction of rotation is opposite to the cyclonic one - it occurs clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Anticyclones in temperate latitudes most often follow cyclones, often they take a sedentary (stationary) state and also exist until the pressure equalizes (6-9 days). Due to downward movements in the anticyclone, the air is not saturated with moisture, cloud formation does not occur, and cloudy and dry weather prevails with light winds and calm. In addition to temperate latitudes, anticyclones are most common in subtropical latitudes - in high pressure zones. Here these are permanent atmospheric vortices (high pressure areas) that exist throughout the year: (Azorean) anticyclone (maximum) in the area of ​​the Azores and the South Atlantic anticyclone; North Pacific anticyclone in the Pacific Ocean and South Pacific; Indian anticyclone (maximum) in the Indian Ocean. As you can see, they are all located above the oceans. The only powerful anticyclone over land occurs in winter in Asia with a center over Mongolia - Asian (Siberian) anticyclone.

The sizes of cyclones and anticyclones are comparable: diameter they can reach 3-4 thousand . km, and height - maximum 18-20 km , i.e. they are flat vortices with a strongly inclined axis of rotation. They usually move from west to east at a speed of 20-40 km / h (except for stationary ones).

atmospheric fronts

Air masses, having different physical properties (especially air temperature), are separated from each other by rather narrow transition zones, which are strongly inclined to the earth's surface (less than 1 °).

atmospheric front called the division between air masses with different physical properties. The intersection of the front with the earth's surface is called the front line.

At the front, all the properties of air masses - temperature, wind direction and speed, humidity, cloudiness, precipitation - change dramatically. The passage of the front through the place of observation is accompanied by more or less abrupt changes in the weather. Distinguish fronts associated with cyclones, and climatic fronts. In cyclones, fronts form when warm and cold air meet.

the top of the frontal system, as a rule, is located in the center of the cyclone. Cold air meeting warm air always ends up at the bottom. It leaks under the warm, trying to push it up. Warm air, on the contrary, flows onto cold air and if it pushes it, then it itself rises along the interface plane. Depending on which air is more active, in which direction the front is moving, it is called warm or cold.

warm front moves in the direction of cold air and means the onset of warm air. It slowly pushes cold air out. Being lighter, it flows onto the wedge of cold air, gently rising up along the interface. In this case, an extensive zone of clouds forms in front of the front, from which heavy precipitation falls. The precipitation band in front of the warm front reaches 300, and in cold weather even 400 km. Behind the front line, precipitation stops. The gradual replacement of cold air with warm air leads to a decrease in pressure and an increase in wind. After the passage of the front, a sharp change in the weather is observed: the air temperature rises, the wind changes direction by about 90 ° and weakens, visibility worsens, fogs form, and drizzling precipitation may fall.

cold front moving towards warmer air. In this case, cold air - as denser and heavier - moves along the earth's surface in the form of a wedge, moves faster than warm air and, as it were, lifts warm air in front of it, vigorously pushing it up. Large cumulonimbus clouds form above the front line and in front of it, from which heavy rains fall, thunderstorms arise, and strong winds are observed. After the passage of the front, precipitation and cloudiness significantly decrease, the wind changes direction by about 90 ° and weakens somewhat, the temperature drops, air humidity decreases, its transparency and visibility increase; the pressure is rising.

Climate fronts - fronts of a global scale, which are sections between the main (zonal) types of air masses.

There are five such fronts: arctic, antarctic, two temperate (polar) and tropical. The Arctic (Antarctic) front separates the Arctic (Antarctic) air from the air of temperate latitudes, two temperate (polar) fronts separate the air of temperate latitudes and tropical air. A tropical front forms where tropical and equatorial air meet, differing in humidity rather than temperature.

All fronts, together with the boundaries of the belts, shift towards the poles in summer and towards the equator in winter. Often they form separate branches, spreading over long distances from climatic zones. The tropical front is always in the hemisphere where it is summer.