RBSE Solutions for Class 11 Physical Geography Chapter 14 Airmasses, Front, Cyclone and Anticyclone

RBSE Solutions for Class 11 Physical Geography Chapter 14 Airmasses, Front, Cyclone and Anticyclone

Rajasthan Board RBSE Class 11 Physical Geography Chapter 14 Airmasses, Front, Cyclone and Anticyclone

RBSE Class 11 Physical Geography Chapter 14 Text Book Questions

RBSE Class 11 Physical Geography Chapter 14 Multiple Choice Questions

Question 1.
What is called the carriage for cyclones and anticyclones?
(a) Front
(b) Air – masses
(c) Turbulence
(d) Hurricane
Answer:
(a) Front

Question 2.
Wind direction of the cyclones in the Northern Hemisphere is:
(a) anti – clockwise
(b) vertical
(c) Clockwise
(d) Oblique
Answer:
(a) anti – clockwise

Question 3.
Hurricane is a:
(a) Temperate Cyclone
(b) Tropical cyclone
(c) Anticyclone
(d) Front
Answer:
(b) Tropical cyclone

Question 4.
Who gave the dynamic theory of the origin of cyclones?
(a) Burkineze
(b) Lam – pert and Shaw
(c) Wagner
(d) Davis
Answer:
(b) Lam – pert and Shaw

Question 5.
Which of the following is not a type of fronts?
(a) Warm Front
(b) Cold Front
(c) Stationary Front
(d) Temporary front
Answer:
(d) Temporary front

RBSE Class 11 Physical Geography Chapter 14 Very Short Answer Type Questions

Question 1.
Describe the types of air – masses based on their region of origin.
Answer:
On the basis of their region of origin, the air – masses are divided into tropical and polar air – masses. On the same basis, continental and oceanic air – masses are found.

Question 2.
What is Warm Front?
Answer:
The warm front is formed by the advancement of warm air over cold air.

Question 3.
What is meant by stationary front ?
Answer:
In the parallel movement of two opposing air – masses, separation and absence of peripheral motion of the air is called stationary front.

Question 4.
Where does the tropical cyclones origin?
Answer:
Tropical cyclones originate from the equatorial region between the Tropic of Cancer and Capricorn.

Question 5.
What is meant by cyclone?
Answer:
Cyclone usually refers to the region of low air pressure, around which the air pressure increases, gradually, due to which the winds flow from all the directions towards the center.

RBSE Class 11 Physical Geography Chapter 14 Short Answer Type Questions

Question 1.
What is front? Describe the types of front.
Answer:
When two opposite – natured air – masses (cold and hot) blow in, they try to retain their identity related to temperature and humidity. In this process, a sloping border develops in between, which is called front.

Types of front:
The fronts are mainly divided into the following parts:

1. Warm Front:
The front which originates by warm air advances over the cold air.

2. Cold Front:
The front which originates by cold air advancing over the warm air.

3. Stationary Front:
Front which originates due to the two opposing fronts being parallel.

4. Occluded Front:
Occluded front is formed when a cold air – mass overtakes a warm air – mass and goes beneath it.

Question 2.
What are the necessary conditions for the origin of the front?
Answer:
The following conditions are necessary for the origin of the front:

1. Air – masses of different nature:
When the opposite variants of air meet, they attempt to enter each other’s area, which creates a wave – type front.

2. The difference in humidity:
Less or more humidity found due to atmospheric conditions is helpful in the formation of fronts.

3. Atmospheric circulation:
Horizontal and vertical movement of winds and their convergence and divergence are helpful in creating fronts.

Question 3.
Explain the difference between cyclones and anticyclones.
Answer:
The following differences are found between cyclones and anticyclones:

Basis of Comparison	Cyclone	Anticyclone
Condition of air pressure	Cyclones are the centers of low air pressure.	Anticyclone are the centers of high air pressure.
Circulation of winds	In a cyclone, winds move from periphery towards the center.	In a anticyclone, winds move from the center towards the periphery.
Size	The shape of the cyclones is usually elliptical, circular or letter ‘V’ shaped.	The shape of the anticyclone is often spherical.
Wind Direction	Winds in the cyclone move in the northern hemisphere in anti – clockwise direction and in clockwise direction in the southern hemisphere.	Winds in the anticyclone move clockwise in the northern hemisphere and in the anti – clockwise direction in the southern hemisphere.

Question 4.
What is Hurricane?
Answer:
The wide tropical cyclones surrounded by several isobars are called hurricanes in the United States. Their speed is usually 120 km/ph. They are very giant and stubborn. Their number is very low and they occur sometimes. These types of hurricanes often occur only in certain parts of the tropical lines. They cause torrential rains. Their direction is from east to west.

Question 5.
What are the theories of origin of cyclones?
Answer:
Following are the major theories of origin of cyclones:

1. Local Warming Theory:
According to this theory, the areas where the heat is high or the temperature is high, the air starts getting heated up fast. Hot air rises and cyclonic conditions arise due to the development of the center of low air pressure.

2. Dynamic Theory:
Vortex is produced in the lower layers of the atmosphere due to several reasons which cause the cyclone to be produced.

3. Polar Front Theory:
According to this theory, the emergence of the cyclones is based on the formation of front. The fronts created by the presence of different air – masses form the cyclone.

RBSE Class 11 Physical Geography Chapter 14 Essay Type Questions

Question 1.
What is meant by front? Describe the types of front along with the conditions essential for their origin.
Answer:
When the two opposite – natured air masses meet, they try to continuously retain their identities of temperature and humidity. In this process, a sloping boundary develops between them, which is called Front. Blair states that, “The surface of the air – masses that are separated by a line are called front”.

The basic conditions essential for the origin of front:
The following conditions are considered necessary for the origin of the front:

1. Air – masses of different nature:
When two differently heated air – masses, or a cold and a hot air – mass meet face – to – face to each other, they attempt to enter each other’s area, due to which a wave – type front is formed.

2. The difference in humidity:
When atmospheric humidity is respectively found to be more or less due to more or less temperature, more humid wind invades upon the lesser humid wind, due to which fronts are formed.

3. Atmospheric circulation:
Horizontal and vertical movements of the winds, and the conditions of divergence and convergence in them are also responsible for the origin of fronts.

Types of front:
The scholar Patterson has divided fronts into the following types:

1. Warm Front:
This is a sloping frontal surface, along which active movement of warm air over cold air takes place.

2. Cold Front:
Such a front is formed when a cold air mass replaces a warm air mass by advancing into it and lifting it up.

3. Stationary Front:
In the parallel movement of two opposing air – masses, separation and absence of peripheral motion of the air masses characterize a Stationary Front.

4. Occluded Front:
Such a front is formed when a cold air – mass overtakes a warm air – mass and goes underneath it. The warm sector diminishes and the cold air – mass completely replaces the warm sector on the ground.

Question 2.
What v is meant by cyclone? Explain the origin cyclones.
Answer:
Cyclone commonly refers to the center of low air pressure, around which the air pressure gradually increases. Because of this the winds flow from all the directions towards the center. Their shape is usually elliptical, circular or ‘V’ oriented.

Origin of temperate cyclone:
Temperate cyclones originate mainly on polar fronts. But their origin can be anywhere outside the tropical zone. Their origin and development is more in the winter season. In the northern hemisphere, these cyclones range from the western coastal parts of the North Pacific Ocean to the Aleutian inland area and from the western shore of the North Atlantic Ocean to the lowlands in Iceland, besides this China, Philippines, Siberia are other major areas. In the southern hemisphere, these cyclones form in both summer and winter in a similar manner. Most cyclones occur around 60° south latitudes here.

Types of temperate cyclones:
These cyclones are divided into the following parts:

1. Thermal Cyclone:
This type of cyclone develops from creation of a low pressure center on the continents due to excessive heat in the temperate regions. In these, the winds move from outside to the center. These are often permanent. These are often formed from low pressure centers over the ocean.

2. Dynamic Cyclone:
The origin of the Cyclones is due to the support obtained from conjunction of fronts of cold polar and warm tropical oceanic air – masses. These cyclones affect wide areas.

3. Migrant Cyclone:
These types of cyclones occur sometimes. These are the results of specific situations.

Question 3.
What is meant by cyclone and anticyclone? Describe their types and characteristics.
Answer:
Cyclones, anticyclones, and their types and characteristics are described as follows:

Meaning of cyclone:
Cyclone is commonly used to refer to the center of low air pressure, around which the air pressure increases gradually. Because of this, the winds flow from all around directions to the center. Their shape is usually elliptical, circular or W shaped.

1. Temperate cyclone:
Such types of cyclones originate in the mid latitudes. At the center of the air-turbulence in mid-latitudes, there is less pressure in center and more pressure is there on the periphery. They are often called low or deep or trough. These cyclones originate from the interaction of the air – masses of opposite nature. The area of these cyclones is found in both the hemispheres between 35° to 65° latitude. Clouds originate in the atmosphere from these cyclones. Under favorable conditions, these cause either rainfall or snowfall.

2. Tropical cyclone:
This type of cyclone is found on both sides of the Equator between the Tropic of Cancer and Capricorn. They appear in many forms. They take a violent and rapid form and create destruction in the areas they hit. As in temperate cyclones, uniformity is not found in these cyclones.

Characteristics of Cyclones:

1. Cyclones are the centers of low air pressure and in which the air pressure increases from the center towards the periphery.
2. Winds move from the periphery to the center.
3. Their shape is similar elliptical, circular, or ‘V’ oriented.
4. They affect the weather.

Meaning of anti – cyclone:
The anti – cyclone is a sequence of circular isobars in which the air pressure is high at the center and it decreases gradually toward the outside.

Types of Anti – cyclones:
Anti – cyclones are divided mainly into the following categories:

1. Cold Anti – cyclone:
These anti – cyclones form in polar regions primarily in arctic regions. These move forward in the east and south – east direction. They are smaller in size than warm anti – cyclones:

2. Warm Anti – cyclone:
These anticyclones are produced in the belt of temperate high air pressure. In this belt, there is divergence of winds. Their size is huge. These are less active.

3. Blocking Anti – cyclone:
This is a new type of anti – cyclone. These cyclones originate due to obstruction of wind circulation in the upper part of the troposphere. Among these, the air system and weather characteristics are similar to warm anti – cyclones. They are smaller and slower in speed.

Characteristics of anti – cyclones:

1. There is high air pressure in the center of every anti – cyclone, which decreases towards the periphery.
2. Winds blow in the clockwise direction in the northern hemisphere, and in the southern hemisphere, in the anti – clockwise direction.
3. Size is larger than cyclones. Their size is often spherical.
4. The weather becomes clear, the sky becomes clean and the wind becomes hot due to the arrival of anti – cyclones.
5. These occur more in sub – tropical high pressure areas.

RBSE Class 11 Physical Geography Chapter 14 Other Important Questions

RBSE Class 11 Physical Geography Chapter 14 Multiple Choice Questions

Question 1.
Monsoon area is:
(a) South – east Asia
(b) North Africa
(c) United States
(d) Europe
Answer:
(a) South – east Asia

Question 2.
Anticyclone areas are:
(a) Arctic Territory
(b) Tropical ocean area
(c) Tropical continental region
(d) Sub – Polar Areas
Answer:
(b) Tropical ocean area

Question 3.
Which air – mass is found in the central part of Australia?
(a) MP
(b) MT
(c) CP
(d) CT
Answer:
(d) CT

Question 4.
Which letter is used for a stable air – mass?
(a) W
(b) K
(c) S
(d)U
Answer:
(c) S

Question 5.
What does MP mean?
(a) Ocean tropical
(b) Continental tropical
(c) Ocean polar
(d) Continental polar
Answer:
(c) Ocean polar

Question 6.
Patterson has divided the fronts into how many categories?
(a) 3
(b) 4
(c) 5
(d) 6
Answer:
(b) 4

Question 7.
When hot air climbs above the cold air with intensity, then the front formed in this manner is:
(a) Warm front
(b) Cold front
(c) Stationary front
(d) Occluded front
Answer:
(a) Warm front

Question 8.
Where do the most temperate cyclones originate?
(a) Near 40° latitude
(b) Near 50° latitude
(c) Near 60° latitude
(d) Near 80° latitude
Answer:
(c) Near 60° latitude

Question 9.
The propounder of polar front theory is:
(a) Davis
(b) Burkineze
(c) Lampert and Shaw
(d) Hackle
Answer:
(b) Burkineze

Question 10.
Who was the first to use the word ‘anticyclone’?
(a) Galton
(b) Burkineze
(c) Hazilk
(d) Odom
Answer:
(a) Galton

Matching Type Questions

Question 1.
Match column A with column B:

Column A (Character used)	Column B (Refers to Air – mass)
(i) T	(a) unstable
(ii) P	(b) stable
(iii) W	(c) polar
(iv) K	(d) warm tropical
(v) S	(e) warm
(vi) U	(f) cold

Answers:

1. (d)
2. (c)
3. (e)
4. (f)
5. (b)
6. (a)

Question 2.
Match column A with column B:

Column A (Type of airmass)	Column B (Related area)
(i) MP	(a) North Africa
(ii) ME	(b) Alaska
(iii) MT	(c) South Pacific
(iv) CT	(d) Central Pacific
(v) CP	(e) North Atlantic

Answers:

1. (e)
2. (c)
3. (d)
4. (a)
5. (b)

RBSE Class 11 Physical Geography Chapter 14 Very Short Answer Type Questions

Question 1.
What is meant by air – mass?
Answer:
The wide and dense part of the atmosphere is called the air – mass, whose physical properties, especially the temperature and humidity, are same nearly identical in horizontal shape.

Question 2.
How do the air – masses originate?
Answer:
When atmospheric conditions are stable on a wide surface plane, the air contains surface humidity and temperature related characteristics, which causes the formation of the air – masses.

Question 3.
What is meant by area of origin of air – mass?
Answer:
The region where air – masses are produced are called the area of their origin.

Question 4.
On which bases are the air – masses classified ?
Answer:
Air – masses have been classified on the basis of difference in their nature, and their area of origin.

Question 5.
How many types of conversions occur in the air – masses?
Answer:
There are two types of conversions in air – masses:

1. Thermodynamic conversion.
2. mechanical conversion.

Question 6.
What does thermodynamic conversion mean?
Answer:
When the air – mass is hot or cold below on its surface due to the exchange of heat between the surface and the base of the air – mass, it is called thermodynamic conversion.

Question 7.
What is meant by mechanical conversion ?
Answer:
The conversion that occurs in the air – mass, which is free from the heating and cooling provided by the surface, is called mechanical conversion.

Question 8.
What is the definition of front according to Blair?
Answer:
According to Blair, “The surface or line by which air – masses remain separated, are called fronts”.

Question 9.
What is cold front?
Answer:
When the hot and light air is lifted by the cold and heavy air, the front so formed is called cold front.

Question 10.
What is meant by occluded front?
Answer:
Occluded front is formed when a cold front overtakes a warm front. When this occurs, the warm air is pushed up and the cold air moves under it over the earth’s surface.

Question 11.
What is the definition of cyclone as given by Triwartha?
Answer:
According to Triwartha, “Cyclones are relatively low air pressure areas, which are surrounded by centric and surrounding isobars.”

Question 12.
How do cyclones affect the weather?
Answer:
When a cyclone arrives, air pressure falls. A halo around the Moon and the Sun is formed, and, it affects the weather by causing heavy rainfall.

Question 13.
Where is the origin of tropical cyclones?
Answer:
Tropical cyclones originate in the oceans between 8° to 15° North latitudes.

Question 14.
What is Tornado?
Answer:
Tornado is the smallest but most terrible and destructive tropical cyclone in terms of its effect, which mainly occurs in the Mississippi Valley of the United States, and in Australia in a minor form.

Question 15.
What types of anticyclone are there?
Answer:
The anticyclones are categorized into mainly three types: the cold anticyclone, the warm anticyclone and the blocking anticyclone.

Question 16.
What is the origin of cold anticyclone?
Answer:
In the Arctic territories, due to excessively high temperature caused by radiation and low insolation, high air pressure is formed during the winter, resulting in the origin of cold anticyclones.

Question 17.
How does Blocking Anticyclone originate?
Answer:
Obstruction of wind circulation in the upper part of the troposphere causes Blocking Anticyclone.

Question 18.
Into how many parts is the jet stream categorized?
Answer:
The jet stream is divided into two parts: Sub – Tropical Jet Stream and the Latitudinal or Polar Front Jet Stream.

Question 19.
Where does the polar front jet stream originate?
Answer:
The polar front jet stream originates in both hemispheres between 40° to 60° latitudes.

Question 20.
What effect does jet stream have on the weather?
Answer:
Jet stream plays an important role in creating, inducing, and magnifying fierce weather events such as cyclones, anticyclones, monsoons, furious winds and storms.

RBSE Class 11 Physical Geography Chapter 14 Short Answer Type Questions (SA-I)

Question 1.
Describe the major characteristics of the air – masses.
Answer:
Air – masses are the atmospheric conditions found in a wide area. They have the following characteristics:

1. Air – masses are extended to hundreds of kilometers.
2. There are many layers in the air – masses.
3. In each horizontal layer of air – masses, there are uniform properties.
4. Once generated, the air – masses do not remain stable in the area of their origin.
5. Air – masses affect the area which comes in their contact.
6. While affecting the area, their own qualities also change.
7. Due to their large size, the change in the air – masses takes place at a lesser speed.

Question 2.
Explain the air – mass classification on any one basis.
Answer:
Air – masses are classified on the following two basis:

1. The nature of the origin area.
2. Conversion of the air – mass.

On the basis of the nature of their area of origin, there are two types of air – masses: the tropical and the polar air – mass. Since the origin area can be either oceans or continents, therefore they can be divided into two sub – classes: sea tropical, continental tropical, sea-polar and continental polar. Due to high humidity in the sea air – masses, they cause excessive rainfall. In contrast, continental air – masses are dry and therefore they cause less rainfall.

Question 3.
Explain the conversion of Air – masses.
Answer:
The process of changes in the characteristics of air – masses after their origin due to their movement in other areas (other than origin area) air – masses is called conversion. The process of conversion in the air – masses has been clarified as follows:

When the air – masses pass through the other area after leaving the area of their origin, they are converted in various sequential steps.

This conversion is of two types:

1. Thermodynamic conversion
2. mechanical conversion.

1. Thermodynamic Conversion:
When the air – mass gets heated up or cooled down from below the surface due to the exchange of heat between the surface and the land surface (Basal plane) of the air – masses, it is called Thermodynamic Conversion.

2. Mechanical Conversion:
The conversion that occurs in the air – masses, which is free from the heating and cooling provided by the surface is called Mechanical Conversion. For example, the conversion of cyclones, anticyclones, and air due to the vertical movement of air.

Question 5.
Explain the characteristics of cyclones.
Or
Explain the physical symptoms found in cyclones.
Answer:
Characteristics of Cyclones:

1. Cyclones are the centers of low air pressure in which the air pressure decreases towards the outside from the center.
2. Winds move from the periphery to the center.
3. The shape of cyclone shape is elliptical, circular, or ‘V’ shaped.
4. Cyclone, affects the weather due to which, decline in air pressure, formation of halo around the Moon and the Sun, the occurrence of heavy rain, etc. take place.
5. In the Northern Hemisphere, the wind blows in the anti – clockwise direction, and clockwise direction in the southern hemisphere.

Question 6.
Describe the characteristics of temperate cyclones.
Or
Explain the various physical symptoms found in temperate cyclones.
Answer:
The various physical traits found in temperate cyclones are as follows:

1. Before the advent of these cyclones, long but thin stripes of white clouds appear in the sky.
2. Before their arrival, the mercury falls continuously in the barometer.
3. The presence of Halo around Sun and Moon is a sign of their coming.
4. Before their arrival, the winds begin to change their direction.
5. Due to the lack of air, if the drains emit a foul smell, than its (cyclone) coming gets confirmed.

Question 7.
Explain the characteristics of tropical cyclones.
Or
What are the symptoms of tropical cyclones?
Answer:
The conditions found in tropical cyclones are as follows:

1. Low air pressure exists in their center and the shape of their isobars is circular.
2. There is a large variation in their speed. At some places their speed is 32 km/h and at other places it is up to 200 km. per hour.
3. There is considerable variation in their size. Normally, their diameter ranges from 80 to 300 km.
4. These cyclones are permanent. They cause rainfall at one place for several days.
5. These cyclones are more destructive.
6. These cyclones move fast over the oceans, but they weaken after coming to the land.

Question 8.
Into how many categories the cold anticyclones have been divided? OR Explain the categorisation of cold anticyclones.
Answer:
The cold anticyclones arising in the polar regions have been divided into the following categories on the basis of activation:

1. Temporary and transient anticyclone.
2. Semi – permanent anticyclone.

1. Temporary and transient anticyclone:
This type of anticyclone ends on their way by themselves. Only a few of these reach the tropics.

2. Semi – permanent anticyclone:
These are more active and the path of these types of anticyclones is also extended.

RBSE Class 11 Physical Geography Chapter 14 Short Answer Type Questions (SA-II)

Question 1.
Where do you find the ideal originating area of the air – masses?
Answer:
The following six ideal generating regions of air – masses are found on the earth:

1. Polar ocean area (the northern region of the Atlantic and Pacific Ocean) – In these areas, the air – masses are produced during the winter.
2. Sub – Polar continental zone (glaciated part of Eurasia and North America and Arctic region) – In these areas, the air – masses arise during the winter period.
3. Monsoon Area (South – East Asia) – This includes India, Bangladesh, Indonesia, Indo – China region.
4. Tropical ocean area (anticyclone area – winter and summer).
5. Tropical continental region (Mississippi Valley Area of North America, Asia and North Africa).
6. Equatorial linear areas – Air – masses originate in these areas due to convectional conditions.

Question 2.
Compare tropical cyclones and temperate cyclones.
Answer:
Following is the difference between Tropical and Temperate cyclones:

Basis of difference	Tropical Cyclones	Temperate cyclones
Area of Origin	Tropical cyclones originate in the mid oceans between 8° to 15° North latitudes.	Temperate cyclones originate mainly on polar region. But they can originate anywhere outside the tropical areas.
Season of origin	Their origin is mainly during summers.	The origin of these cyclones is mainly in the winters.
Isobars	Their isobars are spherical.	Their isobars are often V – shaped.
Air pressure gradient	In these cyclones, pressure gradient is very steep.	The pressure gradient in these cyclones is gentle.
Velocity of air	The velocity of air in these cyclones is intense. Their speed is usually 120 kilometers per hour or more.	The velocity of air is not much in these cyclones.
Flowing direction	The direction of these cyclones is often from east to west.	The direction of this type of cyclone is often from west to east.
Rain conditions	In such cyclones, the rainfall occurs very rapidly.	The rainfall is slow in these cyclones.

Question 3.
Explain the difference between cold anticyclone and warm anticyclone.
Answer:
The following differences are found between cold anticyclones and warm anticyclones:

Basis of difference	Cold Anticyclone	Warm Anticyclone
Area of Origin	These anticyclones are predominant in the arctic regions.	These anticyclones are produced in the belt of high air pressure.
Size	The size of these anticyclones is less than that of warm anticyclones.	The size of these anti – cyclones is large.
Speed	Such types of anti-cyclones move at a faster pace.	This type of anticyclone often moves in slow motion.
Activeness	This type of anticyclone is more active.	The activity of these anticyclones is less.
Cause of origin	The origin of these anticyclone is due to thermal reasons.	This type of cyclone is produced by the divergence of winds.
Rain conditions	In the case of cold anticyclone, clouds cover the sky. Sometimes, it rains.	In such types of anticyclone, the sky is cloud-free and clean.
Transmission area	These types of anticyclones move mainly in Canada and Siaberia.	This type of anticyclones often get more active in the south – eastern        United States and Western European countries.

Question 4.
Explain the difference between the Sub – Tropical Jet Stream and the Polar Front Jet Stream.
Answer:
The distinctions found in the sub – tropical jet stream and polar front jet stream have been explained as follows:

Basis of Difference	Sub – Tropical Jet Stream	Polar Front Jet Stream
Base area	The subtropical jet stream runs between 0° to 30° latitudes in both the northern and southern hemisphere of the earth.	Polar Front Jet Streams run between 40° to 60° latitudes in both the hemispheres.
Height	These winds flow at an altitude of 9 to 12 kilometers.	The polar front jet stream flows at an altitude of 6 to 9 km.
Speed	The speed of the sub -tropical jet stream is less than that of polar front jet stream.	The speed of the polar front jet stream is often more.
Effect	Wind currents rising around the equator descend on 30 ° North and North 30° South latitudes. Some parts of these wind streams take the form of the sub-tropical jet stream.	These winds shift towards the poles in the summer season and towards the equator in the winter season. When they move southwards, they take very cold air in the sub – tropics along with them.
Continuity	These winds often blow continuously.	These winds often stop and then blow intermittently.
Path	These jet streams flow on a relatively lesser wavy path.	This jet stream flows on a relatively move wavy path.

RBSE Class 11 Physical Geography Chapter 14 Essay Type Questions

Question 1.
What is meant by air – masses? Classify the air – masses on various bases.
Answer:
That broad and dense portion of the atmosphere is called air mass, whose physical properties, especially the temperature and humidity, are almost the same in the horizontal plane. Air – masses are often extended to hundreds of kilometers.

The basis of the classification of the air – masses:
Air – masses found in the world are classified mainly on the following bases:

1. On the basis of nature of their region of origin.
2. On the basis of conversion of the air – masses.

On the basis of nature of their region of origin, the air – masses are divided into tropical and polar air – masses. These can again be continental and oceanic. These are again divided into two sub – classes: sea tropical, sea – polar and continental tropical and continental polar region air – masses. Based on these two characteristics, surface and water conditions and the heat of the air – masses, the variants found in the world are shown by the following table:

Areas of main and secondary air – masses found in the world are shown through the following diagrarm:

Question 2.
What is Jet Stream? Explain its types.
Answer:
In the upper layers of the mid-latitudes of the troposphere, near the tropopause, very fast blowing winds are called “Jet Streams”. These are strips of narrow, windy and fast currents. They keep on rotating around the earth. Their width ranges from 40 to 160 km. and thickness is from 2 to 3 km. Their speed is more than 120 km. per hour. Their speed is more intense in winters.

The status of these wind currents varies according to the weather. The path of jet stream shifts towards.the poles in the summer and towards the equator in the winter. The first information about these air currents was obtained during the World War II. After the end of the war, extensive research was done on them. Although weather scientists are unanimous on their places of origin and some other aspects, they are used favorably by the aircraft fliers by taking enough information about them.

Types of Jet Stream:
Jet Stream is divided mainly into the following two categories:

1. Sub – Tropical Jet Stream:
Their location is found in both the hemispheres between 30° to 35° latitudes near the tropopause. It flows throughout the year. Their origin is due to the rotation of the earth. This rotation of the Earth produces maximum motion in the atmosphere above the equatorial zone. As a result, the above – mentioned wind streams in the equatorial zone move upwards towards north and down wards in the south and start blowing at a faster speed.

These wind currents are deflected on the right side of the Northern Hemisphere due to the Coriolis force and to their left side in the southern hemisphere. These same wind streams reach approximately 30° latitude and become sub-tropical jet stream.

2. Latitudinal or Polar Front Jet Stream:
Their origin is due to heat and is closely related to polar front. Their position is between 40° to 60° latitude in both hemispheres. Their condition is more variable than the Sub-Tropical Jet Stream. In summer, they move towards the poles and they shift towards the equator in the winter season. These two types of jet stream are shown with the help of the following diagram.

Importance:
Although the concept of jet stream has not yet been fully understood, however, they have a significant impact on seasonal conditions. These air streams have an important role in creating, inducing and causing fierce weather events such as cyclones, anticyclones, monsoons, furious winds and storms.

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