9th Std Social Science Term 1 Solution | Lesson.7 Atmosphere

Lesson.7 Atmosphere

Lesson.7 Atmosphere

I. Choose the correct answer

1. …………… is the most important gas for the survival of living organisms.

1. Helium
2. Carbon-di-oxide
3. Oxygen
4. Methane

Ans : c) Oxygen

2. The lowest layer of the atmosphere is

1. Troposphere
2. Stratosphere
3. Exosphere
4. Mesosphere

Ans: a) Troposphere

3. …………… reflects radio waves.

1. Exosphere
2. Ionosphere
3. Mesosphere
4. Stratosphere

Ans: c)

4. The average global surface temperature is ……………

1. 12° C
2. 13° C
3. 14° C
4. 15° C

Ans: b) 13° C

5. The process of change of state of water from gaseous to liquid state is called

1. Precipitation
2. Evaporation
3. Transpiration
4. Condensation

Ans: d) Condensation

6. The …………… is the chief energy source of the Earth.

1. Sun
2. Moon
3. Stars
4. Clouds

Ans: a) Sun

7. The pressure belt extends from 5°N and 5°S latitudes.

1. Equatorial low
2. Subtropical high
3. sub-polar low
4. polar high

Ans: a) Equatorial low

8. All types of clouds are found in the ……………

1. Troposphere
2. Ionosphere
3. Mesophere
4. Exosphere

Ans: a) Troposphere

9. …………… clouds are called ‘Sheep clouds’.

1. Alto-cumulus
2. Alto-Stratus
3. Nimbo-stratus
4. Cirro-stratus

Ans: a) Alto-cumulus

10. The Monsoons are ……………

1. Prevailing winds
2. Periodic winds
3. Local winds
4. None of the above

Ans: d) None of the above

11. Dew in the form of ice crystals is called ……………

1. Frost
2. Fog
3. Mist
4. Sleet

Ans: a) Frost

12. …………… is called the eye of the storm/cyclone.

1. Pressure
2. Wind
3. Cyclones
4. Snow

Ans: c) Cyclones

13. The vertical movement of air is called ……………

1. Wind
2. Storm
3. Air current
4. Drift

Ans: c) Air current

II. Match the following

III. Answer the following Questions Briefly

1. Define atmosphere.

• The blanket of air that surrounds the Earth is called the Atmosphere. It is held close to the Earth by gravitational attraction.
• Atmosphere is a mixture of gases, water various and dust particles in different proportions.
• It is thick near the Earth surface and thins out until it eventually merges with space.

2. Name the different atmospheric layers.

The five atmospheric layers are-

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere and
5. Exosphere.

3. Mention the factors that affect the climate?

The factors that affect the climate are –

• Distance from the equator
• Mountain barrier
• Altitude
• Cloud cover
• Nearness to the sea
• Ocean currents and
• Nature of the prevailing winds
• Natural vegetation

4. What are the units used to measure the temperature?

• The atmosphere acts as an insulator and maintains the temperature of the Earth.
• Temperature is a measure of the warmth of an object expressed in terms of Celsius or Fahrenheit.
• It is measured with thermometer.

5. What is insulation?

The amount of heat received from the sun in the form of short waves is called Insulation or incoming Solar Radiation.

6. What are isotherms?

• Temperature varies from place to place, season to season and continent to continent.
• Isotherms are imaginary lines drawn on maps, connecting points and have equal temperatures.

7. Write short note on Lapse rate.

The temperature decreases at the rate of 65^oC per km of height. This is called Normal lapse
rate.

8. How is the atmospheric Pressure measured?

• The atmospheric pressure is the weight exerted by air on a particular area of the Earth surface.
• It is measured with a mercury barometer and the unit of measurement is millibar(mb).

9. Polar Easterlies are cold and dry. Why it is so?

• Polar Easterlies blow from the polar high pressure belt to the sub polar low pressure belt.
• These are weak winds blowing from North East direction in the Northern Hemisphere and South East direction in the Southern Hemisphere.
• So, Polar Easterlies are cold and dry

10. What are the processes responsible for heating the atmosphere?

The processes that are responsible for atmospheric heat are radiation, conduction, convection and advection.

11. Mention the Planetary wind system of the earth.

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

12. Write short note on: a) Trade winds. B) Roaring Forties

a) Trade winds:

• Trade winds blow from the subtropical high pressure belt on the Equatorial low pressure belt in both the hemispheres.
• They blow with great regularity, fore and in a constant direction throughout the year.
• These winds were very helpful to traders who depended on the winds while sailing in the seas.

b) Roaring forties:

• Westerlies are the permanent winds.
• They blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres.
• They blow from South West to North East in the northern hemisphere and North West to South East in the southern hemisphere.
• The velocity of westerlies becomes so vigorous and fast to be called Roaring forties at 40°.

13. How are clouds formed?

• A visible mass of condensed water vapour floating in the air above the ground level is called a cloud.
• Large amount of water evaporates each day from the surface of the sea. This is the principal source of atmospheric moisture.
• Cool moisture laden air collect particles like dust, salt content from the sea smoke, etc., and forms cloud.
• Sometimes, mixing of warmer and cooler air also produced clouds.

14. What are the different types of rainfall?

Moisture laden air masses raise upwards, forms clouds and bring rainfall. Based on the mechanisms of raising the air, there are three types of rainfall.

They are-

• Conventional rainfall
• Frontal or Cyclonic rainfall and
• Orographic rainfall.

15. What is Precipitation? What are the different forms of precipitation?

• Falling down of condensed water vapour in different forms is called Precipitation.
• The main forms of precipitation in dude drizzle, rain, sleet, snow, hail etc.

16. Write short notes on: a) drizzle b) rain c) sleet d) snow e) heat

a) Drizzle:

Falling of numerous uniform minute droplets of water with diameter of less than 0.5 is called a drizzle.mm. They combined with fog and reduce visibility.

b) Rain:

Rain is the most widespread and important form of precipitation in places having temperature above the freezing point. It occurs only when there is abundant moisture in the air.

c) Sleet:

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

d) Snow:

Snow is formed when condensation occurs below freezing point. It is the precipitation of opaque and semi opaque ice crystals. When these ice crystals collide and stick together, it becomes showflakes.

e) Heat:

• Heat refers to energy that is transferred from a warmer substance or object to a cooler one. Transfer of heat energy is possible only through conduction and radiation.
• As a form of energy, heat has the unit joule (J) in the International System of Units (SI).

17. How are Cyclones classified?

• The term cyclone is a Greek work meaning ‘Coil of a snake’. Cyclones are centres of low pressure where winds from the surrounding high pressure area converge towards the centre in the spiral form.
• Cyclones can be classified into tropical cyclones, temperate cyclones and extra tropical cyclones.

IV. Distinguish between

1. Weather and climate

2. Insulation and temperature

3. Land breeze and sea breeze

4. Windward side and Leeward side.

5. Tropical cyclone and Temperate cyclones.

V. Answer in Paragraph:

1. Write a paragraph about the structure of the atmosphere.

The structure of the atmosphere is-

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Troposphere:

• The lowest layer of the atmosphere is the troposphere. The layer extends up to a 8 km to 18 km at the Equator.
• In this layer, the temperature decreases with increasing height. This layer is also known as Weather making layer

Stratosphere:

• Stratosphere lies above the troposphere. It extends to a height of about 50 km above earth.
• The temperature increases with increase in height in this layer. This layer is also called as Ozonosphere.

Mesosphere:

• It is the third layer of the atmosphere. It extends 50 km and 80 km.
• Radio waves transmitted from earth are reflected back to earth from this layer.
• In this layer also the temperature increases with increasing height.
• Most of the meteors nearing the earth get burned in this layer.

Thermosphere:

• Thermosphere exists above the Mesosphere. It extends to about 600 km.
• Here, the temperature increases with increasing height.
• The upper portion of the Thermosphere is referred as ‘Hetrosphere’ and the lower portion is known as ‘Homosphere’.

Exosphere:

• The uppermost layer of the atmosphere is called exosphere.
• This layer is extremely rarefied with gases and gradually merges with the outer space.

2. Explain the different types of Permanent winds.

Winds are generally classified into four types.

Planetary winds:

• The winds which constantly blow in the same direction throughout the year are called the Planetary Winds.
• They are also called as Permanent Winds of the Prevailing Winds.
• These winds include Trade winds, Westerlies and Polar Easterlies.

Trade Winds:

• Trade winds blow from the subtropical high pressure belt to the Equatorial low pressure belt in both the hemispheres.
• They blow with great regularity, force and in a constant direction throughout the year.
• These winds are very helpful to the traders who sail in the sea.

Westerlies:

• Westerlies blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres.
• They blow from South-west to North-east in the northern hemisphere and North-west to South-east in the southern hemisphere.
• The velocity of westerlies become to vigorous and fast to be called Roaring Forties at 40°, Furious fifties at 50° and screaming sixties at 60° latitudes.

Polar Easterlies:

• Polar easterlies are cold and dry polar winds that blow from the polar high pressure belt to the sub polar low pressure belt.
• These are weak winds blowing from North-east direction in the Northern Hemisphere and South-east direction in the Southern Hemisphere.

3. How are clouds classified? Explain them..

According to their height, clouds are classified into three types such as-

1. High clouds (6 – 20 km height)
2. Middle clouds (2.5 km – 6km height)
3. Low clouds (Ground surface to 2.5 km height)

High Clouds:

High clouds are further classified into

• • i. Cirrus clouds
  • ii. Cirro-cumulus
  • iii. Cirro-stratus.

i) Cirrus :

Detached clouds formed at the high sky (8000 meters to 12,000meters).

These clouds are dry and do not give rainfall

ii) Cirro-cumulus :

White patched, sheet or layer like clouds composed of ice crystals.

iii) Cirro-stratus :

Smooth milky transparent whitish clouds composed of tiny ice crystals.

Middle clouds:

Middle clouds are three types.

They are

• • i) Alto-stratus
  • ii) Alto-cumulus
  • iii) Nimbo stratus.

i) Alto-stratus :

Thin sheets of grey or blue coloured clouds in uniform appearance consisting of frozen water droplets.

ii) Alto-cumulus :

Clouds fitted closely together in parallel bands called as ‘Sheep clouds’ or ‘Wool pack clouds’.

iii) Nimbus stratus :

These are clouds of dark colour very close to the ground surface associated with rain, snow or sleet.

Low clouds:

Four types of Low clouds are

• • i) Strato-cumulus
  • ii) Stratus
  • iii) Cumulus
  • iv) Cumulonimbus.

i) Strato-cumulus :

Grey of whitish layer of non-fibrous low clouds found in rounded patches at an height of 2,500 to 3000 metres associated with fair or clear weather.

ii) Stratus :

Dense, low lying fog like clouds associated with rain or snow.

iii) Cumulus :

Dome-shaped with a flat base resembling a cauliflower, associated with fair weather.

iv) Cumulo-nimbus :

Fluffy thick lowering thunderstorm cloud capable of producing heavy rain, snow, hailstorm or tornadoes.

4. How are cyclones formed? How are they classified?

• The term cyclone is a Greek work meaning ‘Coil of a snake’. Cyclones are centres of low pressure where winds from the surrounding high pressure area converge towards the centre in the spiral form.
• Due to the rotation of the earth, the cyclonic winds in the northern hemisphere move in anti clock wise direction and clockwise direction in the southern hemisphere.
• Cyclones can be classified into
  • i. Tropical cyclones
  • ii. Temperate cyclones
  • iii. Extra tropical cyclones.

i. Tropical cyclones:

• Tropical cyclones develop in the Inter tropical convergence zone. They are formed due to the differential heating of land and sea.
• Tropical cyclones often cause heavy loss of life and property on the coasts and become weak after reaching the landmasses.
• They are known as ‘cyclones’ in Indian ocean, ‘typhoons’ in the western pacific ocean, ‘hurricanes’ in the Atlantic and ‘willy willy’ in Australia.

ii. Temperate cyclones:

• Temperate cyclones are formed where hot and cold air masses meet in mid-latitudes between 35° and 65° N and S.
• The temperature cyclones do not become weak like the tropical cyclones on reaching the land.
• Temperate cyclone commonly occurs over the North Atlantic ocean, North west Europe and Mediterranean basin.
• In India, it is called as ‘Western disturbances’

iii. Extra tropical cyclones:

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

5. Explain the different forms of precipitation.

Falling down of condensed water vapour in different forms is called Precipitation. The main forms of precipitation include-

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

Drizzle

• is a fall of numerous uniform minute droplets of water with diameter of less than 0.5mm.
They combined with fog and reduce visibility.

Rain

is the most widespread and important form of precipitation in places having temperature above the freezing point. It occurs only when there is abundant moisture in the air

Sleet

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

Snow

is formed when condensation occurs below freezing point

Hails

are chunks of ice (greater than 2cm in diameter) failing from the sky during a rain storm or thunder storm.

Hailstones

are a form of solid precipitation where small pieces of ice fall downwards

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