Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Social Science Guide Pdf Geography Chapter 3 Atmosphere Text Book Back Questions and Answers, Important Questions, Notes.

Tamilnadu Samacheer Kalvi 9th Social Science Solutions Geography Chapter 3 Atmosphere

Samacheer Kalvi 9th Social Science Atmosphere Text Book Back Questions and Answers

I. Choose the best answers

Question 1.
_____ is the most important gas for the survival of living organisms.
(a) Helium
(b) Carbon-di-oxide
(c) Oxygen
(d) Methane
Answer:
(c) Oxygen

Question 2.
The lowest layer of the atmosphere is _______
(a) troposphere
(b) tratosphere
(c) Exosphere
(d) mesosphere
Answer:
(a) troposphere

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 3.
_______ reflects radio waves.
(a) Exosphere
(b) Ionosphere
(c) Mesosphere
(d) Statosphere
Answer:
(c) Mesosphere

Question 4.
The average global surface temperature is .
(a) 12° C
(b) 13° C
(c) 14° C
(d) 15° C
Answer:
(b) 13° C

Question 5.
The process of change of state of water from gaseous to liquid state is called _____
(a) Precipitation
(b) Eveaporation
(c) Transpiration
(d) Condensation
Answer:
(a) Precipitation

Question 6.
The _____ is the chief energy source of the Earth.
(a) Sun
(b) Moon
(c) Stars
(d) Clouds
Answer:
(a) Sun

Question 7.
All types of clouds are found in the ______ .
(a) Troposphere
(b) Ionosphere
(c) Mesosphere
(d) Exosphere
Answer:
(a) Troposphere

Question 8.
_____ clouds are found in the earth
(a) Sun
(b) Moon
(c) Stars
(d) Clouds
Answer:
(a) Sun

Question 9.
The Monsoons are _______
(a) Prevailing winds
(b) Periodic winds
(c) local winds
(d) none of the above.
Answer:
(b) Periodic winds

Question 10.
Dew in the form of ice crystals is called _________
(a) frost
(b) fog
(c) mist
(d) Sleet
Answer:
(a) frost

Question 11.
______ is called the eye of the storm/ cyclone.
(a) Pressure
(b) Wind
(c) Cyclones
(d) Snows
Answer:
(a) Pressure

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 12.
The vertical movement of air is called _____
(a) Wind
(b) Storm
(c) Air current
(d) Drift
Answer:

II. Match the following

  1. Meteorology – (i) wind speed
  2. Climatology – (ii) direction of wind
  3. Anemometer – (iii) cirrus
  4. Wind Vane – (iv) study of climate
  5. Mare’s Tail – (v) study of weather
  6. Leeward side – (vi) Australia
  7. Willy willy – (vii) rain shadow region

Answer:

  1. – v
  2. – iv
  3. – i
  4. – ii
  5. – iii
  6. – vii
  7. – vi

III. Answer the following Briefly:

Question 1.
Define atmosphere.
Answer:

  1. The blanket of air that surrounds the Earth is called the atmospshere.
  2. It is held close to the earth by gravitational attraction.
  3. Atmosphere is a mixture of gases, water vapour and dust particles in different proportions

Question 2.
Name the different atmospheric layers.
Answer:

  1. The atmosphere is thick near the earth surface and thins out until it eventually merges with space.
  2. The five Atmospheric layers are
    • Troposphere
    • Stratosphere
    • Mesosphere
    • Thermosphere
    • Exosphere.

Question 3.
Mention the factors that affect the climate.
Answer:
The factors that affect weather and climate are

  1. Latitude or distance from the equator
  2. Altitude height above the sea level
  3. Nearness to the sea
  4. Nature of the prevailing winds
  5. Mountain barrier
  6. Cloud cover
  7. Ocean currents
  8. Natural vegetatoin

Question 4.
Write short note on Lapse rate.
Answer:
Lapse rate is the rate at which Earth’s atmospheric temperature decreases with an increase in altitude, or increases with the decrease in altitude. Lapse rate arises from the word lapse, in the sense of a gradual change.

Question 5.
What are the processes responsible for heating the atmosphere?
Answer:
Some of the processes that are responsible for atmospheric heat are Radiation, Conduction, Convection and Advection.

Question 6.
Mention the planetary wind system of the earth.
Answer:

  1. The winds which constantly blow in the same direction throughout the year are called the Planetary winds.
  2. They are also called as permanent winds or the prevailing winds.
  3. These winds include Trade winds, Westerlies and Polar Easterlies.

Question 7.
Write short note on:
(a) Trade Winds
(b) Roaring Forties.
Answer:
(a) Trade winds:

  1. Trade winds blow from the subtropical high pressure belt to the Equatorial low pressure belt in both the hemispheres.
  2. They blow with great regularity, force and in a constant direction throughout the year.
  3. These winds were helpful to traders, hence called trade winds.
  4. As they move westwards, they become dry and do not give rainfall.

(b) Roaring Forties:

  1. Westerlies are the permanent winds that blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres.
  2. The velocity of westerlies become so vigorous and fast to be called Roaring Forties at 40°, Furious Fifties at 50° and screaming Sixties at 60° latitudes.

Question 8.
How are clouds formed?
Answer:

  1. Cool moisture laden air gets collected around particles like dust, salt content from the sea, smoke etc and forms clouds.
  2. Sometimes mixing of warmer and cooler air also produces clouds.
  3. A visible mass of condensed water vapour floating in the air above the ground level is called a cloud.

Question 9.
What are the different types of rainfall?
Answer:

  1. Rainfall is the most predominant type of precipitation.
  2. Moisture laden air masses raise upwards, forms clouds and bring rainfall.
  3. Based on the mechanisms of raising the air, there are three types of rainfall.
  4. They are
    • Convectional rainfall
    • Frontal or Cyclonic rainfall
    • Orographic rainfall.

Question 10.
What is Precipitation? What are the different types of precipitation?
Answer:

  1. Falling down of condensed water vapour in different forms is called Precipitation.
  2. When the dew point is reached in the cloud water droplets become saturated and start to fall as Precipitation.
  3. The different types of precipitation are
    • drizzle
    • rain
    • sleet
    • snow
    • hail etc.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 11.
Write short notes on

  1. Drizzle
  2. Rain
  3. Sleet
  4. Snow
  5. Heat

Answer:

  1. Drizzle: Falling of numerous uniform minute droplets of water with diameter of less than 0. 5 is called a driggle.
  2. Rain: Rain is the most wide spread and important form of precipitation in glaces having temperatures above the freezing print.
  3. Sleet: Sleet refers to a precipitation with form of pallets made up of transparent and translucent ice. This is a mixture of snow and rain.
  4. Snow: Snow is formed when condensation occurs below freezing point. It is the precipitation of opaque and semi opaque ice crystals.
  5. Heat: Heat is the energy which makes object hot, while temperature measures the intensity of heat.

Question 12.
How are Cyclones classified?
Answer:

  1. Cyclones are centres of low pressure where, winds from the surrounding high pressure area converge towards the centre in a spiral form.
  2. Cyclones can be classified,into
    • Tropical cyclones
    • Temperate cyclones
    • Extra tropical cyclones.

IV. Give reason

Question 1.
Cyclones cause huge loss of life and property
Answer:

  1. A Tropical cyclone is a rapidly rotating storm system.
  2. It is characterised by a low pressure center, a closed low level atmospheric circulation, strong winds and a spiral arrangement of thunderstorms, that produce heavy rain.
  3. Very strong winds many damage installations, dwellings, communication systems, trees etc.
  4. Therefore, it results in loss of life and property.
  5. Heavy prolonged rains due to cyclones may cause river floods and submergence of low lying areas of rain, causing loss of life and property. .

Question 2.
Cloudy days are warmer than cloudless days.
Answer:

  1. Clouds reflect a large amount of radiation from the sun.
  2. This prevents the entry of heat to the earth’s surface.
  3. So in areas generally of cloudless sky like the deserts, temperature is very high.
  4. On the otherhand under cloudy sky the temperature is low.

Question 3.
Fog is dangerous for traffic
Answer:

  1. Fog is a thick cloud of tiny water droplets suspended in the atmosphere at or near the earth’s surface.
  2. It obscures or restricts visibility to a greater extent than mist.
  3. It strictly reduces visibility to below 1 km.
  4. Many lives are lost each year worldwide from accidents involving fog conditions on the highways, including multiple – vehicle collisions.
  5. The aviation travel industry is affected by the severity of fog conditions.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 4.
Convectional rainfall is also called 4’0 clock rain.
Answer:

  1. In the equatorial regions, convectional rainfall is received almost daily in the afternoon.
  2. It generally happens regularly at 4 p.m. throughout the year.
  3. For this reason it is called 4’o clock rainfall.
  4. This type of rain is common in the hot and wet tropical rain forests of Central Africa, Amazon basin of South America and the islands of South east Asia.
  5. Continuous heating of the earth in the day causes hot convectional currents to raise. Water keeps on evaporating and rising up.
  6. On reaching the upper layers of the atmosphere they cool, condense and form cumulo¬nimbus clouds.
  7. In the late afternoon the clouds burst into a heavy downpour often accompanied by thunder and lightning.
  8. It usually occurs at about 4 p.m, so convectional rain is called 4 o’clock rain and occurs daily in the equatorial regions.

Question 5.
Polar Easterlies are cold and dry. Why it is so?
Answer:

  1. The polar easterlies are the dry, cold prevailing winds that blow from the high pressure areas of the polar highs at the North and South poles towards low pressure areas within the westerlies at high latitudes when air moves near the poles, cold temperatures shrink the air.
  2. These are weak winds flowing from North east direction in the Northern Hemisphere and South east direction in the Southern Hemisphere.

V. Distinguish between the following

Question 1.
Weather and climate
Answer:
Weather:

  1. Weather is the study of atmospheric conditions for short duration over small areas.
  2. The weather changes very often; hour to hour and day to day
  3. A place can experience different types of weather conditions in a day.
    Weather data is collected every day in the observatories
    Study of weather is called Meteorology

Climate:

  1. Climate is the study of the average weather condition observed over a long period of time for a larger area.
  2. Climate is more or less permanent and remains the same always.
  3. A place can experience almost the same type of climate
    Climate is average of weather data
  4. Study of climate is called Climatology

Question 2.
Land breeze and sea breeze
Answer:
Land Breeze:

  1. During the night, the land cools more rapidly than the ocean.
  2. Cool air sinks and forms high pressure
  3. The wind blows from land to sea during the night, this is called land breeze.

Sea Breeze:

  1. During the day, the land masses get heated more rapidly than the oceans.
  2. Heated air ascends and this causes low pressure on the adjoining ocean.
  3. Therefore, the wind blows from ocean to land in the afternoon. This is called sea breeze.

Question 3.
Windward side and Leeward side.
Answer:
Windward Side:

  1. The windward side is the side of a mountain which faces the prevailing wind.
  2. It receives heavy rainfall

Leeward Side:

  1. The leeward side of the mountain is the side sheltered from the wind.
  2. It receives very less rainfall

Question 4.
Tropical cyclones and Temperate cyclones.
Answer:
Tropical Cyclones:

  1. Tropical cyclones develop in the Inter Tropical Convergence Zone (ITCZ)
  2. They are formed due to the differential heating of land and sea.
  3. They are known as ‘cyclones’ in Indian ocean, typhoons in the western pacific ocean, ‘hurricanes’ in the atlantic and eastern Pacific Ocean, ‘baguios’ in-Phillippines and willy willy’ in Australia.
  4. They often cause heavy loss of life and property

Temperate Cyclone:

  1. Temperate cyclones are formed along a front where hot and cold air masses meet in mid – latitudes between 35° and 65° N and S.
  2. Temperate cyclones do not become weak like the tropical cyclones on reaching the land.
  3. They commonly occur over the North Atlantic Ocean, North West Europe, Mediterranean basin.
  4. In India it is called Western disturbances

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

VI. Paragraph Questions

Question 1.
Write a paragraph about the structure of the atmosphere.
Answer:
Atmosphereric layers:

  1. The atmosphere is thick near the earth surface and thins out until it eventually merges with space.
  2. The five atmospheric layers are: Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.

(a) Troposphere:

  1. The lowest layer of the atmosphere is the troposphere.
  2. This layer extends upto 8 kms at the poles and upto 18 kms at the equator.
  3. The temperature decreases with increasing height.
  4. It is called weather making layer.

(b) Stratosphere:

  1. Stratosphere lies above the troposphere.
  2. It extends to a height of about 50 km above earth surface.
  3. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere.
  4. Large jet planes normally fly here.

(c) Mesosphere:

  1. Mesosphere extends between 50 km and 80 km.
  2. The temperature increases with increasing height.
  3. Radial waves transmitted from earth are reflected back to earth from this layer
  4. Most of the meteors nearing the earth, get burned here.

(d) Thermosphere:

  1. Thermosphere exists above the Mesosphere.
  2. It extends to about 600 km.
  3. The composition of gases in the lower thermosphere is more or less uniform, hence it is called ‘Homosphere’.
  4. The upper portion of the thermosphere has uneven composition of gases and hence it is referred as ‘Heterosphere’.

(e) Exosphere:

  1. The uppermost layer of the atmosphere is called exosphere.
  2. This layer is extremely rarefied with gases and gradually merges with the outer space.
  3. This zone is characterised by aurora Australis and aurora borealis.

Question 2.
Explain the different types of permanent winds.
Answer:
The winds which constantly flow in the same direction throughout the year are called Planetary winds. They are also called as Permanent winds or the prevailing winds. These winds include
(a) Tradewinds
(b) Westerlies
(c) Polar Easterlies.

(a) Tradewinds:

  1. Trade winds blow from the subtropical high pressure belt to the equatorial low pressure belt in both the hemispheres.
  2. They blow with great regularity, force and in a constant direction throughout the year.
  3. These winds were very helpful to traders who depended on the winds while sailing in the seas. Hence they are named as Trade winds.
  4. As they travel over vast oceans, they collect more moisture and bring heavy rainfall, to the East Coast of the continents of the tropics.
  5. As they move westwards, they become dry and do not give rainfall.

(b) Westerlies:

  1. Westerlies are the permanent winds that blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres.
  2. They blow from South West to North East in the northern hemisphere and North West to South East in the Southern hemisphere.
  3. The velocity of westerlies become so vigorous and fast to be called Roaring Forties at 40°, Furious Fifties at 50° and Screaming Sixties at 60° latitudes.

(c) Polar Easterlies:

  1. Polar Easterlies are cold and dry polar winds.
  2. They blow from the polar high pressure belt to the sub polar low pressure belt.
  3. These are weak winds blowing from North East-direction in the Northern Hemisphere and South East-direction in the Southern Hemisphere.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 3.
How are clouds classified? Explain them.
Answer:
Clouds are classified, according their height, with following types. They are (a) High clouds (6 – 20 km ht) (b) Middle clouds (2.5 km – 6 km ht) (c) Low clouds (ground surface to 2.5 km ht)

(a) High clouds:

  1. (i) Cirrus: Detached clouds in the form of white, delicate fibrous silky filaments formed at the high sky (8,000 meters to 12,000 meters) are called Cirrus clouds. These clouds are dry and do not give rainfall.
  2. Cirro – Cumulus: They are white patched, sheet or layer like clouds composed of ice crystals.
  3. Cirro – Stratus: Smooth, milky transparent whitish clouds composed of tiny ice crystals.

(b) Middle clouds:

  1. Alto stratus: Thin sheets of grey or blue coloured clouds in uniform appearance, consisting of frozen water droplets.
  2. Alto cumulus: Clouds fitted closely together in parallel bands known as ‘sheep clouds’ or wool pack clouds.
  3. Nimbo Stratus: These are clouds of dark colour very close to the ground surface associated with rain, show or sleet.

(c) low stand

  1. Strato – cumulus: Grey (or) whitish layer of non-fibrous low clouds found in rounded patches at a height of 2500 to 3000 metres, associated with fair or clear weather .
  2. Stratus: Dense, low lying fog – like clouds associated with rain or snow.
  3. Cumulus: Dome shaped with a flat face often resembling a Cauliflower associated with fair weather.
  4. Cumulo Nimbus: Fluffy thick towering thunderstorm cloud capable of producing heavy rain, snow, hailstorm as tornadoes.

Question 4.
How are cyclones formed? How are they classified?
Answer:

  1. Cyclones are centres of low pressure where, winds from the surrounding high pressure area converge towards the centre in a spiral form.
  2. Due to the rotation of the Earth, the cyclonic winds with northern hemisphere move in anti clockwise direction, where as they move in clockwise direction in the southern hemisphere.
  3. Cyclones can be classified as:
    • Tropical cyclones
    • Temperate cyclones and
    • Extra tropical cyclones.

(a) Tropical cyclones:

  1. They develop in the Inter Tropical Convergence Zone (ITCZ).
  2. They are formed due to the differential heating of land and sea.
  3. Tropical cyclones are known as ‘cyclones’ in Indian ocean, typhoons in the western Pacific ocean, hurricanes in the Atlantic and Eastern Pacific ocean.
  4. Tropical cyclones often cause heavy loss of life and property on the coasts and become weak after reaching the land masses.

(b) Temperate cyclones:

  1. These cyclones are formed along a front where hot and cold air masses meet in mid-latitudes between 35° and 65° N and S.
  2. Temperate cyclones do not become weak on reaching the land.
  3. It commonly occurs over the North Atlantic Ocean, North West Europe, Mediterranean basin.
  4. In India, it is called western disturbances.

(c) Extra Tropical cyclone:

  1. It occurs in the latitude between 30° and 60° in both the hemispheres.
  2. They are also called as Mid Latitude Cyclones.
  3. They produce mild showers to heavy gales, thunderstorms, blizzards and tornadoes.

Question 5.
Explain the different forms of precipitation.
Answer:

  1. Falling down of condensed water vapour in different forms is called precipitation.
  2. The climatic conditions / factors influencing the forms of percipitation mainly are:- temperature, altitude, cloud type, atmospheric conditions, precipitation process.
  3. The main forms of precipitation include (a) Drizzle (b) Rain (c) Sleet (d) Snow (e) Hail etc.

(a) Drizzle:

  1. Falling of numerous uniform minute droplets of water with diameter of less than 0.5 mm is called a drizzle.
  2. Drizzle combined with fog reduces visibility.

(b) Rain:

  1. Rain is the most widespread and important form of precipitation in places having temperature above the freezing point.
  2. It occurs only when there is abundant moisture in the air.
  3. The diameter of a raindrop is more than 5 mm.

(c) Sleet:

  1. Sleet refers to a precipitation, in the form of pellets made up of transparent and translucent ice.
  2. This Precipitation is a mixture of snow and rain

(d) Snow:

  1. Snow is formed when
  2. It is the precipitation of opaque and semi opaque ice crystals
  3. When these ice crystels and stocks to gether, it become snowflakes

(e) Hails

  1. Hails are of ice (grater than 2 cm in diameter) falling from the sky, during a rainstrome or thunderstrome

(f) Hailstones:

  1. Hails are a form of a solid percipitation where small pieces of ice fall downwards
  2. These are destructive and dreded forms of solid precipitation beacuse they destroy agriculture human lives

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

VII. Activity

Question 1.
Prepare chart of cloud at various atomosphiric layers.
Answer:
Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 2.
Collecting Proverbs clouds and rain related Proverbs Ans.
Answer:
Proverbs :
Clouds:
Example:

  1. The sun always shines above the clouds – Paul F. Davis
  2. There is divinity in the clouds – Lailah Gifty Akita

Rains:
Example:

  1. After rain comes sunshine. – German Proverb
  2. If a dog’s prayers were answered, bones would rain from the skies.  – Japanese

Question 3.
Poem on ‘clouds’, ‘rain’
Answer:
Clouds in the sky on the deep blue horizon
Sail in the wind and are lit by the sun
As while as the snowfall that lies on the mountain
Changing and moving like avalanche run
In circles they’re rolling by
And differen t patterns form,
For as the pass they rise and fall
Like smoke they dance and play.

Question 4.
Report writing observe the clouds for a week. Write your report about the shape and colours of clouds.
Answer:
Activity to be done by the students them selves

Question 5.
Working models
(a) Rain Gauge
(b) Wind vane
Answer:
Activity to be done by the students themselves

Question 6.
Preparing bar diagram
Answer:
Collect the data of temperature of Kanyakumari, Delhi, Allahabad, and Ifanagar for a day. Also collect the data of rainfall recived by jaisakmer (Rajastan), Mawsynram (Meghalaya), Nagapattinam, Colmbatatore for a day.
Answer:
Activity to be done by the students themselves

Question 7.
Become a budding Meterologisi: Record the local weather condition of your place for a week
Answer:
Activity to be done by the students themselves

Intext Activities

Question 1.
Connect the following places with their latitudes and the temperature observed
Answer:

City Latitude Temperature [In August]
Kanyakumari – Tamil Nadu 8.0883° N 30° C
Delhi-India 28.38N 34° C
Moscow – Russia 55.7558° N 22° C

Question 2.
Connect the following places with Altitude and the temperature
Answer:

City Altitude (height) Temperature [In May]
Madurai- Tamilnadu 101 m 28.8° C
Uthagamandalam – Tamilnadu 2,240 m 36° C
Simla -Himachal Pradesh 2,276 m 2° C

Intext Hots

Question 1.
Why is Troposphere called as weather making layer?
Answer:

  1. The troposphere is the lowest layer of the atmosphere.
  2. In this layer, temperature decreases at the rate of 1 degree C for every 165 m ascent. The troposphere is the densest zone of the atmosphere. Three-fourths of the atmosphere is found within 11 km of the surface of the Earth, including most of the oxygen we need to breathe. –
  3. The average thickness (altitude or height from the surface of the Earth) of the troposphere is 13 km. The thickness varies from about 8 km at the poles to 18 km near the equator. The troposphere is also known as the weather-making zone because all physical processes of weather, like wind, clouds, storms, rainfall, mist, fog and hail, occur here.

Question 2.
Cuddalore and Nagarpattinam are always  affected by cyclones. Why?
Answer:

  1. Cclone is one of the dangerous natural hazards which causes great disasters.
  2. It is a rotating air mass around a low atmospheric pressure point. It creates in low pressure region.
  3. Oceans are the best places for cyclone generation and the plates near the coastal regions are the most cyclone affected regions.
  4. Cuddalore and Nagapattinam are also situated in coastal region of the south India, that’s why these two places are a regular victim of the cyclone.

Samacheer Kalvi 9th Social Science Atmosphere Additional Important Questions and Answers

I. Choose the best answer

The upper limit of the troposphere is called as __________
(a) Tropopause
(b) Stratopause
(c) Mesopause
(d) None of these
Answer:
(a) Tropopause

Question 2.
Large jet planes normally fly here __________
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
(d) Thermosphere
Answer:
(b) Stratosphere

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 3.
This gas is chemically inactive in atmosphere.
(a) Oxygen
(b) Nitrogen
(c) Neon
(d) Helium
Answer:
(b) Nitrogen

Question 4.
The atmospheric layer, which lies beyond the exosphere is __________
(a) Heterosphere
(b) Mesosphere
(c) Magnetosphere
(d) Homosphere
Answer:
(c) Magnetosphere

Question 5.
Daniel Ruthurford discovered __________ in atmosphere.
(a) Oxygen
(b) Nitrogen
(c) Neon
(d) Helium
Answer:
(b) Nitrogen

Question 6.
The Limit of Clouds is upto __________
(a) Statosphere
(b) Homosphere
(c) Troposphere
(d) Mesosphere
Answer:
(c) Troposphere

Question 7.
There is cut off signal when NASA rocket reaches in the region of __________
(a) D-Layer
(b) Stratosphere
(c) Ozone layer
(d) Mesosphere
Answer:
(a) D-Layer

Question 8.
A layer of Ions inside the Mesosphere is called
(a) F-layer
(b) D-Layer
(c) Ozone layer
(d) both (b) and (c)
Answer:
(b) D-Layer

Question 9.
A layer located in stratosphere which absorbs ultraviolet rays of sun called
(a) Ozone layer
(b) F-layer
(c) D-layer
(d) E-layer
Answer:
(a) Ozone layer

Question 10.
The part of atmosphere which is consisted of variable gases with unknown composition is called
(a) Stratosphere
(b) Heterosphere
(c) Homosphere
(d) None of them
Answer:
(b) Heterosphere

Question 11.
The part of atmosphere which contains gases with known composition is called
(a) Homosphere
(b) Thermosphere
(c) Heterosphere
(d) None of these
Answer:
(a) Homosphere

Question 12.
Atmosphere is divided into two main vertical regions the upper portion is Heterospshere and the lower is ______
(a) Troposphere
(b) Mesosphere
(c) Homosphere
(d) None of these
Answer:
(c) Homosphere

Question 13.
When the wind is deflected due to the rotation of the earth, it is called
(a) Geostropic wind
(b) Polar wind
(c) Westerlies
(d) Trade wind
Answer:
(a) Geostropic wind

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 14.
Which one of the following is most destructive?
(a) Cyclone
(b) Tornado
(c) Typhoon
(d) Willy Willy
Answer:
(a) Cyclone

Question 15.
Increase in carbon di-oxide in atmosphere causes
(a) Rise in earth’s temperature
(b) Fall in earth’s temperature
(c) Uniform earth’s temperature
(d) Increase in ultra violet rays
Answer:
(a) Rise in earth’s temperature

Question 16.
Which of the following occur more frequently than the other three in the Indian ocean
(a) Typhoons
(b) Tornado
(c) Hurricanes
(d) Cyclones
Answer:
(d) Cyclones

Question 17.
In the earth’s atmosphere, the atmospheric pressure
(a) increases with height
(b) decreases with height
(c) remains constant
(d) First increases, them decreases with the height
Answer:
(b) decreases with height

Question 18.
The wind system is the equatorial area is known as
(a) Westerlies
(b) trades
(c) Doldrums
(d) Monsoons
Answer:
(b) trades

Question 19.
Hurricanes are cyclonic storms in the
(a) Indian Ocean
(b) South China Sea
(c) West Indies and Gulf of Mexico
(d) West Pacific oceans
Answer:
(c) West Indies and Gulf of Mexico

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 20.
Warm dry winds blowing down the east slopes of Rockies are known as _____
(a) Mistral
(b) Norwesters
(c) Foehn
(d) Chinook
Answer:
(d) Chinook

Question 22.
The Doldrums is an area of ______
(a) Low temperature
(b) Low pressure
(c) Low rainfall
(d) low humidity
Answer:
(b) Low pressure

Question 23.
Which of the following affects atmospheric pressure?
(a) Altitude
(b) Temperature
(c) Earth Rotation
(d) All the above
Answer:
(d) All the above

Question 24.
The weight of water vapour per unit weight of air is _____
(a) Specific gravity
(b) Relative humidity
(c) Absolute humidity
(d) None of the above
Answer:
(a) Specific gravity

Question 25.
Humidity of the atmosphere is measured by
(a) Anemometer
(b) Thermometer
(c) Hygrometer
(d) Windvane
Answer:
(c) Hygrometer

Question 26.
Temperature ______ from the equator to pole.
(a) increases
(b) no change
(c) decreases
(d) stable.
Answer:
(c) decreases

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 27.
The pressure belt extends from 5°N and 5°S latitudes.
(a) Equatorial low
(b) Subtropical high
(c) Sub-polar low
(d) Polar high
Answer:
(a) Equatorial low

II. Match the Following

Question 1.

  1. Oxygen – (i) Insulation
  2. CO2 – (ii) Protects
  3. Nitrogen – (iii) Living organisms
  4. Ozone – (iv) Nuclei
  5. Solid particles – (v) Chemically inactive

Answer:

  1. – (iii)
  2. – (i)
  3. – (v)
  4. – (ii)
  5. – (iv)

Question 2.

  1. Daniel Rutherford – (i) Turn
  2. Joseph Priestly – (ii) Ions
  3. Tropos – (iii) Upper most
  4. Thermosphere – (iv) Oxygen
  5. Exosphere – (ii) Nitrogen

Answer:

  1. – (v)
  2. – (iv)
  3. – (i)
  4. – (ii)
  5. – (iii)

Question 3.

  1. Altitude – (i) Re-Radiation
  2. Trees – (ii) Horizontal movement
  3. Terrestrial radiation – (iii) Lapse Rate
  4. Temperature – (iv) Water Vapour
  5. Advection – (v) Thermometer

Answer:

  1. – (iii)
  2. – (iv)
  3. – (i)
  4. – (v)
  5. – (ii)

Question 4.

  1. Doldrums – (i) Sub tropical High Pressure
  2. Horse latitude – (ii) Horizontal movement
  3. Wind – (iii) Zone of calm
  4. Air current – (iv) Direction of the wind
  5. Windvane – (v) Vertical movement

Answer:

  1. – (iii)
  2. – (i)
  3. – (ii)
  4. – (v)
  5. – (iv)

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 5.

  1. Planetary winds – (i) Screaming Sixties
  2. Waterlies – (ii) India
  3. Polar Easterlies – (iii) Permanent winds
  4. Tropical Monsoon winds – (iv) Coriolis Force
  5. William Ferrel – (v) Cold and Day

Answer:

  1. – (iii)
  2. – (i)
  3. – (v)
  4. – (ii)
  5. – (iv)

Question 6.

  1. Cyclones – (i) Atlantic
  2. Typhoons – (ii) Australia
  3. Hurricanes – (iii) Indian ocean
  4. Baguios – (iv) Western Pacific ocean
  5. Willy willy – (v) Philippines

Answer:

  1. – (iii)
  2. – (iv)
  3. – (i)
  4. – (v)
  5. – (ii)

Question 7.

  1. Thane – (i) Chennai
  2. Vardah – (ii) Mahabalipuram
  3. Ockhi – (iii) Nagapattinam
  4. Roanu – (iv) Cuddalore
  5. Nilam – (v) Kanyakumari

Answer:

  1. – (iv)
  2. – (i)
  3. – (v)
  4. – (iii)
  5. – (ii)

Question 8.

  1. Cirrus – (i) Middle clouds
  2. Nimbo stratus – (ii) Precipitation
  3. Cumulus – (iii) High clouds
  4. Condensed water vapour – (iv) Mixture of Snow and rain
  5. Sleet – (v) Low clouds

Answer:

  1. – (iii)
  2. – (i)
  3. – (v)
  4. – (ii)
  5. – (iv)

III. Consider the statements given below and answer the questions that follow

Question 1.
Statement: The Earth is surrounded by a blanket of air called atmosphere. Reason: Atmosphere is held close to the earth by gravitational attraction. Choose the correct answer based on the Statement and Reason.
(i) Statement and Reason both are wrong.
(ii) Reason is true, Statement is wrong.
(iii) Both statement and Reason are.correct.
(iv) Statement is true, Reason is wrong.
Answer:
(iii) Both statement and Reason are correct

Question 2.
Statement: The Normal Lapse Rate is related to Altitude.
Reason: Places at lower latitudes have a lower temperature.
Choose the correct answer
(i) Both Statement and Reason are true
(ii) Statement is true Reason is wrong
(iii) Statement and Reason are wrong
(iv) Statement is true
Answer:
(ii) Statement is true Reason is wrong

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 3.
Statement I: Temperature measures the intensity of heat Statement II: The Atmosphere acts an insulator Choose the correct answer
(i) Statement I is true, II is wrong.
(ii) Statement II is true, I is wrong.
(iii) Statement I and II are true
(iv) Statement I and II both are wrong.
Answer:
(iii) Statement I and II are true

Question 4.
Statement: Tropical cyclones often cause heavy loss of life and property Reason: In 2016, Vardah devastated Chennai.
Choose the correct answer
(i) Statement is true, Reason is wrong.
(ii) Reason is true, Statement is wrong.
(iii) Statement and Reason are true.
(iv) Statement and Reason are wrong.
Answer:
(iii) Statement and Reason are true

IV. Answer the following briefly

Question 1.
Write about the weather making layer
Answer:

  1. The weather making layer in Troposphere.
  2. Almost all weather phenomenon take place in this layer, hence called weather making layer.
  3. It is the lowest layer of the atmosphere.
  4. Herp the temperature decreases with increasing height.

Question 2.
What is Magnetosphere?
Answer:

  1. Magnetosphere lies beyond the exosphere.
  2. It is the earth’s magnetic belt, where proton and electrons, carrying out from the sun are trapped by the earth.
  3. The magnetic field extends to around 64,000 km above the Earth.

Question 3.
Why is Heterosphere called so?
Answer:

  1. The upper portion of the thermosphere has uneven composition of gases
  2. Hence it is referred as Heterosphere.

Question 4.
Write about the nature of the prevailing winds?
Answer:

  1. The winds change the climate of a place based on from where they blow.
  2. When wind blows from a warm region, it makes the place warm and cold, when blows from a colder region.
  3. The on-shore winds cause rainfall making the place cool where as the off-shore winds bring dry weather.

Question 5.
Write a note on
(a) mountain barriers
(b) ocean currents.
Answer:
(a) Mountain barriers:

  1. The location of the mountains influence the climate of a place.
  2. The mountain chains act as natural barrier for the wind.
  3. Sometimes they prevent the entry of cold winds into the country (or) the escape of monsoon winds, thus having a great influence over the climate.

(b) Ocean currents:

  1. The warm ocean currents raise the temperature of the nearby coastal areas, while the cold current lower the temperature of a place.

Question 6.
What is meant by Albedo?
Answer:
Albedo is the fraction of solar energy reflected from the earth back into space without reaching or heating the earth’s surface.

Question 7.
What is known as heat budget of the earth?
Answer:

  1. There is a balance between insolation and radiation.
  2. This balance is termed as a heat budget of the earth.

Question 8.
What is advection?
Answer:
Advection is the transfer of heat through the horizontal movement of air.

Question 9.
Write about Frigid zone?
Answer:

  1. The Frigid zone is found between Arctic circle (66V20 N) and North Pole (90°N) in the Northern
  2. hemisphere
  3. It stretches out between Antarctic circle (66/2° S) and South Pole (90°s) in the Southern hemisphere.
  4. The sun’s rays fall slanting in this Zone.
  5. These are the coldest regions of the world.
  6. The surface remains permanently frozen under thick snow

Question 10.
Define the atmospheric pressure?
Answer:

  1. The atmospheric pressure is the weight exerted by air or a particular area of the earth surface.
  2. It is measured with a mercury barometer and the unit of measurement is millibar (mb)

Question 11.
What is an isobar?
Answer:

  1. An isobar is an imaginary line drawn through places having equal atmospheric pressure reduced to sea level.
  2. The distribution of atmospheric pressure on the surface of the earth is not uniform. It varies both vertically and horizontally.

Question 12.
What is vertical distribution of air pressure?
Answer:

  1. Air Pressure decreases with altitude above sea level.
  2. At high altitudes the air pressure is less.
  3. Since they are compressed by layers above them.
  4. The air pressure decreases by 34 millibars per 300 metres increase in height.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 13.
What is horizontal distribution of air pressure?
Answer:

  1. The rotation of the earth and the incoming insolation creates a number of pressure belts.
  2. The horizontal distribution of atmospheric air pressure is not uniform.
  3. It varies from time to time and place to place due to
    • air temperature
    • earth’s rotation
    • pressure of water vapour etc.

Question 14.
Write a note on wind.
Answer:

  1. The horizontal movement of air along the surface of the earth is called wind.
  2. The winds always flow from a high pressure area to a low pressure area.
  3. Wind is mostly named after the direction from which it blows.
  4. An anemometer records wind speed whilea ‘wind vane’ measures the direction of the wind.

Question 15.
What is Cariolies effect
Answer:
The rotation of the earth causes ddeflection of winds from their original path

Question 16.
What is Ferrels’ law?
Answer:

  1. Winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere.
  2. This is known as Ferrel’s law.

Question 17.
What are variable winds?
Answer:

  1. The disturbance and the changes in the local weather cause variations in the prevailing winds.
  2. These winds are known as the variable winds.
  3. Variable winds usually end up with the development of cyclones, anticyclones and storms.

Question 18.
What is a Front?
Answer:

  1. A front is the boundary separating warm and cold air masses.
  2. One type of air is usually denser than the other, with different temperatures and humidity.
  3. This meeting of air types causes rain, snow, cold days, hot days and windy days.

Question 19.
What are mid-latitude cyclones?
Answer:

  1. Extra tropical cyclones occur in the latitudes between 30° and 60° in both the hemispheres.
  2. They are also called mid latitude cyclones.
  3. They collect energy from temperature differences which are found in higher latitudes.
  4. Extra tropical cyclones produce mild showers to heavy gales, thunderstorms, blizzards and tornadoes.

Question 20.
How are the cyclones in the Indian ocean region named?
Answer:

  1. Deliberations for naming cyclones in the Indian ocean region began in 2000.
  2. A formula was agreed upon in 2004.
  3. Eight countries in the region Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, SriLanka and Thailand contributed a set of names which are assigned sequentially whenever a cyclonic storm develops.

Question 21.
What are local winds?
Answer:

  1. Local winds are the winds that blow only in a particular locality for a short period of time.
  2. The effect of these local winds are experienced only in that particular area.
  3. They are mostly seasonal and have local names like Foehn (Alps, Europe), Sirocco (North Coast of Africa), Chinook (Rockies – North America), Loo (Thar desert-India), Mistral (Mediterranean sea in France) and Bora (Mediterranean sea in Italy).

Question 22.
Explain the term humidity.
Answer:

  1. Humidity is an important aspect of the atmosphere.
  2. It affects both weather and climate.
  3. The amount of water vapour present in the atmosphere is referred to as humidity.
  4. Humidity of the atmosphere is high when it has large quantities of water vapour.

Question 23.
Explain absolute humidity and relative humidity.
Answer:

  1. The amount of water vapour in the atmosphere is called absolute humidity.
  2. The ratio between the amount of water vapour on the atmosphere and the amount of water vapour it can hold is relative humidity

Question 24.
What are the units used to measure the temperature?
Answer:
Temperature is a measure of the warmth of an object expressed in terms of Celsius or Fahrenheit, measured with thermometer.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 25.
How is the atmospheric pressure measured?
Answer:
The atmospheric pressure is the weight exerted by air on a particular area of the earth’s surface. It is measured with a mercury barometer and the unit of measurement is millibar(mb)

IV. Distinguish between

Question 1.
Distinguish between Equable climate and Continental climate
Answer:
Equable climate:

  1. Places near the coast experience equable climate
  2. Here the winds from the sea influence the climate
  3. The annual and daily range of temperature is low
  4. Mumbai has equable climate

Continental climate:

  1. Places located in the land far from sea experience continental climate.
  2. These places do not experience the moderating influence of the sea.
  3. The annual and daily range of temperature is very high
  4. Delhi has continental or extreme type of climate

Question 2.
Distinguish between Conduction and Convection climate
Answer:
Conduction:

  1. Conduction is a process in which transfer of heat takes place between objects by direct contact
  2. It represents how heat travels between objects in direct contact
  3. The reason is due to temperature difference
  4. It occurs in solids through molecular collisions

Convection:

  1. Convection refers to the form of heat transfer in which energy transition occurs within the fluid
  2. Represents how heat passes through fluids.
  3. The reason is due to density difference.
  4. It occurs in fluids by actual flow of matter

Question 3.
Distinguish between Torrid zone and Temperate zone climate
Answer:
Torrid zone:

  1. It is located between the Tropic of Cancer (23 V2°N) and Tropic of Capricorn 23V2°S).
  2. Torrid zone experiences vertical sun rays almost throughout the year and is hot.

Temperate zone:

  1. The temperate zone stretches out between 1 Tropic of Cancer (23 V2°N) and Arctic circle (66V20N) with Northern Hemisphere and between Tropic of Capricorn (23V2°S) and Antarctic circle (66V2°S) in the southern hemisphere.
  2. The sun’s rays never fall vertical in this region.

Question 4.
Distinguish between The Equatorial Low Pressure Belt and The subtropical High Pressure Belt climate
Answer:
The Equatorial Low Pressure Belt:

  1. This felt extends from equator to 5°S latitudes
  2. At the equator, the earth gets heated by the vertical sun rays and in turn heats the air in contact with it.
  3. The heated air expands and raises upwards resulting in a low pressure belt.

The Sub-tropical High Pressure Belt:

  1. The sub-tropical high pressure belts extend from the tropics to about 35° latitudes in both the hemispheres.
  2. The air that raises with equatorial region, becomes cold and heavy, and starts to descend in the sub-tropical regions.
  3. This results in sub-tropical high pressure belts referred as Horse latitude.

Question 5.
Distinguish between Trade winds and Westerlies
Answer:
Trade winds:

  1. Trade winds blow from the sub-tropical! high pressure belt to the Equatorial low pressure belt in both the hemispheres.
  2. They blow with grant regularity, force and in a constant direction throughout the year,
  3. These winds were very helpful to traders, hence named Trade winds.

Westerlies:

  1. Westerlies blow from the tropical high pressure belt to the
  2. sub polar low pressure belt in both the hemispheres. The velocity of westerlies become vigrous and fast.
  3. Due to their speed they are named as Roaring Forties, Furious Fifties and Screaming Sixties.

Question 6.
Distinguish between Cyclones and Anticyclones
Answer:
Cyclones:

  1. Cyclones are centres of low pressure.
  2. The winds converge towards the centre in a spiral form.
  3. They can be classified’ into Tropical cyclones, Temperate cyclones and Extra tropical cyclones.

Anticyclones:

  1. Anticyclones are an area of high pressure region found in the centre surrounded by low presssure on all sides.
  2. The wind move outwards to the low pressure areas in a spiral form.
  3. Anticyclones are often accompanied by cold and heat waves.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 7.
Distinguish between Convectional Rainfall and Orographic Rainfall
Answer:
Convectional Rainfall:

  1. Convectional rainfall occurs regularly in the equatorial regions.
  2. It is also called 4 o’clock rainfall.
  3. When air near the earth’s surface is heated, it rises and expands resulting in the formation of convectional air currents.

Orographic Rainfall:

  1. When air is forced to rise against a mountain, orographic rainfall takes place.
  2. It is also called Relief rainfall
  3. The mountain barriers lying across the direction of airflow, force the moisture laden air rise along the mountain slope.

V. Give Reasons

Question 1.
Nitrogen and oxygen are called permanent gases of the atmosphere.
Answer:

  1. Atmosphere is a mixture of gases, water vapour and dust particles in different proportions.
  2. Nitrogen (78%) and oxygen (21 %) are permanent gases of the atmosphere.
  3. They constitute 99% of the total composition.
  4. Their percentages always remain the same without any change. Therefore nitrogen and oxygen are called permanent gases of the atmosphere.

Question 2.
Atmosphere is held close to the earth.
Answer:

  1. The blanket of air that surrounds the earth is called the atmosphere.
  2. It is held close to the earth by gravitational attraction.

Question 3.
Exosphere is characterised by aurora Australis and aurora borealis.
Answer:

  1. Exosphere is characterised by aurora Australis and aurora borealis.
  2. An aurora is referred to as polar light. Northern lights (Aurora Borealis) or Southern lights (Aurora Australis) is a natural light display in the Earth’s sky, predominantly seen in the high altitude regions (around the Arctic and Antartic).
  3. Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind due to magnetic storms, that are seen as unique/multicoloured fireworks hanging in the polar sky during mid night.
  4. Most auroras occur in a band known as the auroral zone.

Question 4.
The places near the equator are warmer than the places which are far away from the equator.
Answer:

  1. The sun’s rays fall vertically on the equator.
  2. The rays are inclined on the regions away from the equator and near the poles due to the spherical shape of the earth.
  3. The vertical rays heat up the earth more than the inclined rays.
  4. Thus, the places near the equator are warmer than the places which are far away from the equator.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 5.
The places at higher altitude have a lower temperature.
Answer:

  1. Altitude refers to the height above sea level
  2. The temperature decreases at the rate of 1°C as we cross every 165 meters in height.
  3. This is called Normal lapse rate.
  4. So places at the higher altitude have a lower temperature.

Question 6.
Sub-tropical high pressure belts referred an the Horse Latitudes.
Answer:

  1. In olden days vessels with cargo of horses passing through sub-tropical high pressure belts found difficulty in sailing under-ealm conditions.
  2. With little water and food left for the humans, sailors used to throw the horses into the sea in order to make the vessels lighter.
  3. Henceforth these belts or latitudes are also called horse latitudes.

Question 7.
Cyclonic winds move in anticlockwise direction with northern hemisphere.
Answer:

  1. Cyclones are centres of low pressure, where winds from the surrounding high pressure area converge towards the centre in a spiral form.
  2. Due to the rotation of the earth, the cyclonic winds in the northern hemisphere move in anticlockwise direction.
  3. Where as they move in clockwise direction in the southern hemisphere.

Question 8.
Hailstroms is one of the most feared weather phenomenon.
Answer:

  1. Any thunderstorm which is associated with full of hailstones is known as hailstorm.
  2. Hailstorm is one of the most feared weather phenomenon because it has the potential to destroy plant, trees, crops, animals and human life.

VI. Paragraph Questions

Question 1.
Write about the composition of the Atmosphere.
Answer:

  1. Atmosphere is a mixture of gases, water vapour and dust particles in different proportions.
  2. Nitrogen (78%) and Oxygen (21%) are permanent gases of atmosphere.
  3. They constitute 99% of the total composition and their percentages always remain the same without any change.
  4. The remaining one percentage is occupied by Argon (0.93%) Carbon di-oxide (0.03%), Neon (0.0018%), Helium (0.0005%), Ozone (0.00006%) and Hydrogen (0.00005%).
  5. Krypton, Xenon and Methane are also present in trace.
  6. Water vapour (0-0.4%) is also found in the atmosphere, which plays an important role in predicting weather phenomenon.
  7. The other solid particles present in the atmosphere includes dust particles, salt particles, pollen grains, smoke, soot, volcanic ashes etc.
  8. Oxygen is most important for living organisms
  9. CO2 absorbs heat and keeps the atmosphere warm by insulation and radiation
  10. Nitrogen acts as a diluent and is chemically inactive.
  11. Ozone helps in protecting the earth from radiation.
  12. The solid particles in the atmosphere acts as nuclei on

Question 2.
Explain the factors that influence weather and climate.
Answer:
There are many factors that influence weather and climate. They are given below:

(a) Latitude or the Distance from the Equator:

  1. The vertical rays heat up the earth more than the inclined rays.
  2. Thus the place near the equator where the sun’s rays fall vertically are warmer than the places which are far away from the equator.

(b) Altitude:

  1. Altitude refers to the height above sea level. Temperature decreases at the rate of 1 °C as we cross every 165 metres in height. This is called Normal Lapse Rate.
  2. So places in the higher altitude have a lower temperature.

(c) Nearness to the sea:

  1. The climate of a place varies according to its nearness to the sea.
  2. Places near the coast experience equable climate due to the influence of the winds from the sea.
  3. Places located in the land, far from the sea, does not experience the moderating influence of the sea, such places experience a continental type of climate.

(d) Nature of the prevailing winds:

  1. The winds change the climate of a place based on, from where they blow.
  2. When wind blows from a warm region, it makes the place warm and cold, when blows from a colder region.
  3. The on shore winds cause rainfall making the place and where as the off-shore winds bring dry weather.

(e) Mountain barriers:

  1. The location of the mountains influence the climate of a place.
  2. The mountain chains act as natural barrier for the wind.
  3. Sometimes they prevent the entry of cold winds into the country or the escape of monsoon winds.

(f) Cloud cover:

  1. Clouds reflect a large amount of radiation from the sun.
  2. This prevents the entry of heat to the earth’s surface.
  3. In areas generally of cloudless sky like the deserts, temperature is very high.
  4. On the otherhand under cloudy sky, the temperature is low.

(g) Ocean Currents:

  1. The warm ocean currents raise the temperature of the nearby coastal areas, while the cold current lower the temperature of the place.

(h) Natural vegetation:

  1. The trees release water vapour into the air and makes it cool.
  2. Thus forest areas have lower range of temperature throughout the year in contrast to non- forested areas.

Samacheer Kalvi 9th Social Science Guide Geography Chapter 3 Atmosphere

Question 3.
What are the significance of clouds?
Answer:

  1. Large amount of water evaporates each day from the surface of the sea.
  2. This is the principle source of atmospheric moisture.
  3. Cool moisture laden air, gets collected around particles like dust, salt content from the sea, smoke etc., and forms clouds.
  4. Sometimes mixing of warmer and cooler air also produces clouds.
  5. A visible mass of condensed water vapour floating in the air above the ground level is called a cloud.
  6. The three layers of atmosphere such as troposphere, stratosphere and mesosphere are specific locations of clouds.
  7. According to their height, clouds are classified into the following types
    • High clouds – (6 – 20 km height)
    • Middle clouds (2.5 km – 6 km)
    • Low clouds (Ground surface to 2.5 km height)
  8. These major types of clouds are further divided into different types, based on their shape qnd structure.
  9. Clouds reflect a large amount of radiation from the earth surface.
  10. This prevents entry of heat of the earth’s surface.
  11. So, in areas generally of cloudless sky, like the deserts, temperature is very high.
  12. On the other hand, under cloudy day, the temperature is low.

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