What is Cyclone? and Anticyclone [NCERT Geography Notes for UPSC, SSC, Railway Exam]

Cyclone and Anticyclone

• Due to the difference in air pressure, when the condition of the air becomes unstable, the airflow starts in a cyclic form, and by increasing, it takes the form of a severe storm, then it is called cyclone and anticyclones.
• Looking at this cyclic wind, it is as if the air is dancing in the form of a whirlpool around a central axis.
• If there is the low air pressure in the center and high air pressure around it, then that cyclic whirlpool pushes the outside air towards the center.
• The direction of the wind is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The air moving from outside towards the center starts rising.
• This type of air deposit is called a cyclone or depression. In fact, a cyclone is a low-pressure area in which the center of low pressure is surrounded by closely spaced concentric isobars.
• They develop mainly in westerlies, although they are also occasionally produced in trade winds. They move on a fixed path without being static. In westerly winds, they move from west to east.
• An anticyclone is also a circular wind or airflow, but it has high pressure in its center and a low-pressure area around it.
• Its shape is circular or oval and the wind spins and moves outwards from the center.
• The wind direction is to the right (clockwise) in the Northern Hemisphere and to the left (counter-clockwise) in the Southern Hemisphere.

 

Cyclone

• According to the origin, cyclones are of two types-

• Not only is there a difference in the place of origin of these two, but there is also a difference in the method of origin. The origin of temperate cyclones is related to the instability of the air found in the polar front, whereas tropical cyclones arise mainly due to the disparity of temperature and air pressure.
• The words depression and savu are used in English for temperate cyclones. There is no storm in them.
• Tropical cyclones often cause severe storms and for this, the word cyclone is used in English. Tropical cyclones which do not cause storms are kept under depression.
• The size of the cyclone is 1 km. From thousand to two thousand km. Happens till. Its speed is 20 km per hour. from 100 km. can happen till. In this, the speed of wind is faster in the back part than in the next part.
• With this the combination of clouds is necessary. At first, there are light white clouds, but later on, thick clouds start coming and rain starts.
• There is more rainfall in the front. As the center gets closer, the rain becomes dense which sometimes creates a situation of destruction.
• Its center is called the eye of the cyclone. Thunderstorms and thunderstorms occur only on the reverse side of the cyclone, gradually the sky clears, and the temperature drops.

They are found between 30° to 60° latitudes. They move throughout the year between 40° to 60° latitudes and only in winter between 30° to 40° latitudes.

Temperate zone cyclone

• In the Mediterranean region, they are produced in the summer. The size of these cyclones is very large (diameter from 1040 km to 1920 km). Their speed is 300 km per hour. is found up to The reason for their origin is said to be the thermal difference and the union of polar cold and dry and tropical hot and wet winds.
• Norwegian meteorologists have given a satisfactory explanation of its origin, which is called the polar front theory. According to this theory, one cold wind and the other warm wind blow parallel to each other but from opposite directions.
• The tropical wind blows from the south-west to the north-east and the polar wind blows from the north-east to the south-west.
• The front resulting from the union of these two is called a polar front. The tropical warm wind moves towards the pole and mounts on the cold wind.
• SW Due to the speed and strength of the warm wind coming from, the cold wind is pushed backward. For this cold wind to take its place. Turning from here it comes to the back of the tropics.
• As the warm wind advances, the air pressure decreases in the eastern part and due to the development of low air pressure, the winds start moving from all around and move towards the center.
• In place of the tropics, the eye of the cyclone becomes present. The path of movement of temperate cyclones parallels the westerlies.
• Most of the rainfall is received by them in the western part. As they move eastwards, the rain potential decreases when they enter the continents.
• The dominant zone of temperate cyclones is in the southern hemisphere, where they move at a constant speed due to the lack of landmass. There their direction is from west to east. Their main areas in the Northern Hemisphere are-

1. North Pacific Ocean, from where they cross the Rocky Mountain range in winter to reach Canada and the United States.
2. The North Atlantic Ocean, where affects northwestern Europe. In these countries, the British Isles, Norway, Sweden, etc. receive rainfall.
3. The Mediterranean Sea, from where in winter they reach India through Turkey, Iraq, Iran, Afghanistan, Pakistan, affecting southern Europe.
4. By coming here, their humidity decreases, so there is a nominal rainfall, but this rain is very beneficial for the cultivation of wheat, etc.
5. China Sea, where the surrounding areas come under its influence (in winter).

 

Difference between temperate and tropical cyclones

temperate cyclone	tropical cyclone
They are very large in terms of size.	relatively small in size.
Originates in the temperate zone.	Originates in tropical regions.
They are formed on both oceans and continents.	They are made only in the ocean.
are produced in winter.	They are produced in the late summer and autumn.
Be more regular in your construction.	There is a huge difference from year to year.
They get their energy from the asymmetry of the temperature of the air masses.	They get their energy from the latent heat of condensation.
In these, isobars are "V" shaped.	These isobars are circular.
There is a low-temperature gradient.	There are sharp temperature gradients.
Wind speed 10-20 m per second	wind speed 30 m per second is greater.
It rains continuously for several days.	There is heavy and torrential rain for a few hours to a few days.
The flow speed is fast.	Slow-motion

Tropical cyclone

• They originate between the 6° to 15° latitude lines and move towards the poles. They are mainly generated at the end of summer and their speed is 15 km per hour. 25 km from it occurs.
• The speed slows down at the site. Their size is smaller than that of temperate zone cyclones. (Dia. from 80 km to 300 km). They have different names in different places. The reason for their origin is the conduction action.
• Under this process, when the temperature on the sea rises, the air becomes lighter and rises and there is an atmospheric deflection.
• Scholars are also of the opinion that these cyclones arise only in the equatorial calm zone.
• This is the reason that these cyclones originate in this hemisphere only. The extent of these cyclones is less in the Southern Hemisphere. The thermal effect is more important in their origin.
• Indicators of the arrival of these cyclones are blue-sided clouds, the weather becomes calm and warm, gradually the formation of cloudy and layered clouds in the sky and the movement of storms, then rain with thunder. There is usually hail in the back of the cyclone and then the weather becomes pleasant.

The main areas of tropical cyclones are:

1. China Sea where these are known as typhoons. Originating in the east of the Philippines islands, they move in a north-westerly direction and reach Japan via southern China. They run more between June and October. 20 to 30 typhoons have been observed annually.
2. The Bay of Bengal, where their local name is tornadoes. We also call them 'Hurricane'. Mainly they move along the Bay of Bengal. There are three timings of their movement- (a) pre-monsoon, (b) monsoon, and (c) post-monsoon. They have primacy in the first and last time.
3. In the north-east and north-west coast of Australia, they are called willy-willies.
4. The Caribbean Sea, where they are known as hurricanes. Hurricane's area of ​​influence is the Western Islands, Central America, and Florida of the United States, and the SW. is part. Its center is calm and rainless. Its running time is from August to October. This causes immense damage.
5. Much smaller than a hurricane, a tornado is the most destructive hurricane in the world. The wind speed in its center is very strong. The area of ​​the tornado is limited to the intermediate plain in North America.

Wind direction pattern in cyclone and anticyclone

pressure system	pressure at the center	Wind Direction Pattern Northern and Southern Hemisphere
cyclone	Lower	anti-clockwise	clockwise
anticyclone	High	clockwise	anti-clockwise

 

Origin of tropical cyclones

Area	season	native name
The Caribbean Sea, Pacific Coast of Mexico, Florida, Atlantic Coast in America, Gulf of Mexico	June-October	hurricane
China Sea, Philippines Islands, Southern Japan	July-October	typhoon
The northern Indian Ocean, Bay of Bengal, Southern India	April-December	cyclone or cyclone
Southern Indian Ocean - Malamasi	November-April	cyclone or cyclone
South Pacific Ocean, North Coast of Australia	December-April	willy-willy

Extratropical cyclone

• Those cyclonic air systems, which develop away from the tropics, in the middle and high latitudes, are called extratropical or temperate cyclones.
• In the middle and high latitudes, there are sudden rapid changes in meteorological conditions in the area through which they pass.
• Extratropical cyclones form along the polar front. In the beginning, the front is stationary. In the northern hemisphere, cold air blows from the south of the front and cold from the north.
• When the air pressure decreases along the front, the warm air moves northwards and the cold air moves southwards in an anti-clockwise cyclonic circulation.
• From this cyclonic flow, an extratropical cyclone develops which has a warm front and a cold front.
• In this cyclone, the warm air zone or warm section is found between the cold front and the last cold section.
• The warm air moves aggressively over the cold air and in the first part of the warm front, layered clouds appear, and rainfalls. The cold front coming from behind pushes the warm air up, resulting in the formation of cloudy clouds along the cold front.
• The cold front moves faster than the warm front and eventually covers the warm front completely.
• This warm air rises up and has no contact with the surface and forms an occupied front.
• There is a close interrelationship between the processes of air circulation on the surface and at the height. Extratropical cyclones differ from tropical cyclones in many ways.
• Extratropical cyclones have clear front systems, which are not present in tropical cyclones. They are spread over a wide area and they originate both in water and on land.
• Whereas tropical cyclones originate only in the oceans and dissipate when they reach the terrestrial parts.
• Extratropical cyclones affect a wider area than tropical cyclones.
• In tropical cyclones, the wind speed is relatively fast and they are destructive.
• Tropical cyclones move from east to west. Whereas extratropical cyclones move from west to east.

 

Anticyclone

• The wind system in this is opposite to that of a cyclone. The high air pressure remains in the center and the air pressure decreases gradually outwards.
• Isobars in anticyclones are very far apart as compared to cyclones. In this, the wind speed slows down and light winds blow.
• There is no fixed path to proceed in this and they can move in any direction. The weather in this is cool and dry. There is no rain, the sun gets bright. There is often fog in the winter.
• The anticyclone is larger than the cyclone being circular. Its diameter is 3,000 km. is more than that.
• There are two types of anticyclone – one cold and the other hot. In a cold anticyclone, cold air remains up to a height of two kilometers from the surface. This happens due to the cooling of the surface in winter.
• Anticyclones originate in Siberia and Canada only in winter. In a hot anticyclone, the air near the surface is warmer than the air above.
• The permanent anticyclone of the sub-tropics is of this type. The anticyclones affecting Britain move northwards from the sub-tropical region and reach there. Some anticyclones in the UK are generated in other ways as well.
• It is clear from the study of cyclones and anticyclones that heat or heat is exchanged (exchange) by them on the earth.

Difference between anticyclone and cyclone

Symptoms	anticyclone	(cyclone) trough
surface pressure	High	Lower
wind direction	(counterclockwise in the northern hemisphere)	Cyclonic (Northern Hemisphere)
airflow	surface divergence (upward convergence)	Surface convergence (upward divergence)
high wind speed	Concavity	rises up (upward)
wind speed	(weak) emaciated	faster than usual
vision loss	generally dry	humid
cloud cover	cloudless	cloud cover
Stability	still air, concave present, upward inversion	can be unstable.
heat gradient	low-temperature variation	extreme temperature variations, especially near the front
pace of activities	slow or stalled	Mostly moving, moving from west to east.

• When the air masses of the tropics come in the cold or temperate zone, they provide heat there, similarly, when the air masses from the cold zone come towards the tropics, they increase the coolness there.
• The exchange of heat is more in the meeting areas of the air masses and cyclones are generated there.
• The exchange of heat by cyclones takes place over long distances. When water vapor changes into water droplets, the latent heat is released.
• Therefore, not only do air masses of different temperatures exchange heat, but rain also helps in this work by releasing latent heat. Undoubtedly, cyclones and anticyclones are the main methods of heat exchange.
• If the correct information about the route and speed of the air sign is given, then the exact condition of the weather can be told, the weather forecast can be made.

Polar cyclone

• The polar vortex is also called polar cyclone or arctic cyclone. Polar cyclones were first known in the year 1853.
• In the year 1952, new information was obtained on the basis of scientific data about polar storms. Their height can be up to 20 km - that is, the Stratosphere.
• In fact, these cyclones originate at the North and South poles. These polar cyclones are active in the upper part of the troposphere and the lower part of the stratosphere. The belt of high air mass is found in the polar regions.
• The speed of rotation of the atmosphere in the polar regions is much greater than the speed of rotation of the Earth.
• These polar cyclones are surrounded by jet streams.
• The jet-stream enters the Northern Hemisphere towards the south (latitudes of d) making a drift.
• These facts about the jet stream were confirmed in 2006, 2009, 2010, and 2014.

Produce

• Complete information about the origin of polar storms and their effect on Earth has not yet been received, nor has any scientific theory been presented about it.
• Nevertheless, scientists think that from the Stratosphere to the upper part of the Troposphere, the air enters like a vortex in the same way as water is flowing down a slope.
• The origin of the polar storm is believed to be due to such descent of the air sign and the rapid movement of the atmosphere.
• By the way, polar storms originate at both the north and south poles. But their intensity is greater at the South Pole in winter when the steepest temperature gradient is high.
• The diameter of the polar storm is 1000 km. can be up to In the Northern Hemisphere, these winds blow in an anti-clockwise direction and in d. clockwise in the hemisphere In the pole regions, they increase the depletion of the ozone layer.
• The. Their frequency at the pole is high in the spring season (August-September).
• Two major centers of polar cyclones develop in the northern hemisphere-

1. near Baffin Island in Canada, and
2. Near Baikal Lake in the eastern part of Siberia.

• Near the South Pole, 160 ⁰ W is often located on the Ross Ice Shelf.
• Polar storms are stronger at the South Pole than in the Arctic region and only have land at high latitudes (polar regions), due to which Ross B waves flow there. These Ross B winds are helpful in weakening the polar cyclone.
• The weakening of the polar storm leads to an increase in the temperature of the stratosphere. Sometimes the temperature rises up to 30 ⁰ C- 50 ⁰ C within a few days.
• Whenever there is a sudden increase in temperature in the stratosphere, weak polar storms are generated.
• This affects the troposphere, in which low air pressure is generated in the troposphere and the polar cyclone becomes stronger.
• In fact, at an altitude of about 31000 meters, a very low-pressure area would have formed, which also increased the temperature of the troposphere and the lower layer of the mesosphere.

Shape

• Polar storms are elliptical in shape. Its two centers are found in the northern hemisphere, one on Baffin Island located in the north of Canada and the other in Siberia to the northeast of Lake Baikal.
• Sometimes these storms extend to Siberia and the far south of North America. In such a situation, their effect extends to the Gulf of Mexico.
• The air pressure system of the polar regions varies with time and season. When the weather changes, the path of the jet stream also changes.
• The jet stream moves in the upper part of the troposphere from west to east forming meanders. The velocity of air in its core is 300 km. exceeds per hour.
• The height of the polar cyclone (Polo Vortex) is 20 to 30 km. can happen till. The temperature of this type of polar cyclone is very low to zero. The temperature drops to minus 50 ⁰ C, resulting in heavy snowfall.

 

Jetstream

• Huge winds blow from west to east in the upper part of the troposphere. About 8 to 12 km from the ground. The jetstream operates at 160 to 480 km. wide and one km. two km from Is thick The speed of their middle part is 300 km. more than an hour and 110 km on the outskirts. is per hour.
• The jet stream was first reported by pilots participating in the US war that was invading Japan.
• According to him, when pilots move from east to west over the Pacific Ocean, the speed of the aircraft slows down, and when returning from west to east after an attack, the speed of the aircraft increases.

• Jetstreams have a huge impact on global temperature patterns, air masses, wind circulation, and the origin of monsoons.

 

Thank You

Classification of Climate 

Humidity and Precipitation

 

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