Class 9 new ncert Chapter 3 SST Solution - Atmosphere and Climate

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Q & A —  6th   7th   8th   9th   10th

Chapter 3 : Atmosphere and Climate

Question 1. What is the atmosphere? Write the composition of the atmosphere.

Answer: The atmosphere is the blanket of air surrounding the Earth. It is a mixture of different gases and is held around the Earth by gravity. It is essential for the survival of all living beings. It also protects Earth from harmful solar radiation and helps regulate its temperature. The atmosphere is mainly made up of:

  • Nitrogen – 78%
  • Oxygen – 21%
  • Argon – 0.93%
  • Carbon dioxide – 0.04%
  • Other gases – about 0.03%

It also contains water vapour and tiny dust particles.

Question 2. Name the major layers of the atmosphere.

Answer: The five major layers of the atmosphere are:

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

Question 3. Why is the troposphere important?

Answer: The troposphere is the most important layer because:

  • We breathe the air present in this layer.
  • Most water vapour and clouds are found here.
  • Almost all weather phenomena occur here.
  • Rainfall, fog and hail occur in this layer.
  • Its average height is about 12 km.

Question 4. Why is the stratosphere suitable for flying aeroplanes?

Answer: The stratosphere is suitable for flying aeroplanes because it is relatively free from clouds and other weather disturbances.

Question 5. What is the importance of the ozone layer?

Answer: The ozone layer is found in the stratosphere. It protects life on Earth by filtering harmful radiation from the Sun, especially ultraviolet radiation.

Question 6. What happens in the mesosphere?

Answer: The mesosphere extends up to about 80 km. Temperature decreases as altitude increases. Most meteorites entering Earth's atmosphere burn up in this layer.

Question 7. What are the important features of the thermosphere?

Answer: The thermosphere extends from about 80 km to 700 km. Temperature increases rapidly with altitude. It helps in radio transmission, and the ionosphere is a part of it. Auroras also occur in this layer.

Question 8. What is an aurora?

Answer: An aurora is a colourful display of light seen in the sky near the Earth's poles. It occurs when charged particles from the Sun interact with gases in the atmosphere.

  • Aurora Borealis occurs in the Northern Hemisphere.
  • Aurora Australis occurs in the Southern Hemisphere.

Question 9. What is the exosphere?

Answer: The exosphere is the uppermost layer of the atmosphere. It has very thin air. Light gases such as helium and hydrogen can escape into space because gravity is weak there.

Question 10. Why do we not feel the pressure of the atmosphere?

Answer: We do not normally feel atmospheric pressure because air presses on our bodies from all sides. The pressure inside our bodies provides counter-pressure, which balances the pressure from outside.

Question 11. What is the weather?

Answer: Weather refers to the hour-to-hour and day-to-day conditions of the atmosphere. It may be hot, cold, humid, rainy, cloudy, sunny or windy. Weather can change significantly from one day to another.

Question 12. What is the climate?

Answer: Climate is the average weather condition of a place over a long period. It generally considers weather conditions and variations over 30 years or more.

Question 13. What are the major elements of weather and climate?

Answer: The major elements are:

  1. Temperature
  2. Precipitation
  3. Humidity
  4. Wind
  5. Atmospheric pressure.

Question 14. What is insolation? How does it affect temperature?

Answer: Insolation means the incoming solar energy received by the Earth. Insolation decreases from the equator towards the poles. Therefore, temperature generally also decreases from the equator towards the poles.

Question 15. What is humidity?

Answer: Humidity refers to the presence of water vapour in the air. When water evaporates from land and water bodies, it becomes water vapour. Warm air can hold more water vapour, resulting in higher humidity.

Question 16. What is precipitation?

Answer: Precipitation occurs when water vapour condenses and falls to the Earth's surface. It includes rain, snow, sleet, hail and drizzle. Rain is the most common form of precipitation.

Question 17. What is atmospheric pressure?

Answer: Atmospheric pressure is the pressure exerted by the weight of air on the Earth's surface.

  • It is highest at sea level.
  • It decreases as altitude increases.
  • Warm air rises and creates low pressure.
  • Cold air sinks and creates high pressure.

Question 18. What is wind? In which direction does it move?

Answer: Wind is the movement of air from a high-pressure area to a low-pressure area. Its direction is also influenced by the rotation of the Earth.

Question 19. What is a land breeze and sea breeze?

Answer: A land breeze is a local wind that blows from land to sea during the night. Land cools faster than the sea at night, causing air to move from land towards the sea.

Remember: Night → Land → Sea

A sea breeze is a local wind that blows from sea to land during the day, especially in the afternoon. During the day, land becomes warmer than the sea and develops low pressure, causing air to move from the sea towards the land.

Remember: Day → Sea → Land

Question 20. What are the four main seasons of India?

Answer: According to the Indian Meteorological Department (IMD), the four main seasons are:

  1. Winter – December to early April
  2. Summer/Pre-monsoon – April to June
  3. Monsoon/Rainy season – June to September
  4. Post-monsoon/Retreating monsoon – October to December

Question 21. What is monsoon? Why is the monsoon important for India?

Answer: Monsoon refers to the seasonal reversal of wind direction during a year. The word monsoon comes from the Arabic word mausim, meaning season.

The monsoon is very important because:

  • Indian agriculture depends greatly on rainfall.
  • It provides water for crops.
  • It helps maintain water in rivers, reservoirs and wells.
  • It affects transport, festivals and employment.
  • It influences the economy and rural livelihoods.

Question 22. Explain the mechanism of the South-West Monsoon.

Answer: The South-West Monsoon is mainly caused by the unequal heating of land and sea.

  1. During summer, the Indian landmass heats faster than the surrounding oceans.
  2. Low pressure develops over the Indian landmass.
  3. The ocean remains relatively cooler and has higher pressure.
  4. Winds move from the high-pressure ocean towards the low-pressure land.
  5. These winds carry moisture from the sea.
  6. They bring rainfall to India.

The South-West Monsoon occurs mainly from June to September and provides most of India's rainfall.

Question 23. Explain the mechanism of the North-East Monsoon.

Answer: During winter, the Indian landmass cools faster than the surrounding oceans.

  1. High pressure develops over the land.
  2. Low pressure develops over the seas.
  3. Cold and dry winds move from land towards the sea.
  4. When these winds cross the Bay of Bengal, they collect moisture.
  5. They bring rainfall mainly to the south-eastern coast.

Tamil Nadu, Andhra Pradesh and parts of Karnataka receive important rainfall from these winds.

Question 24. Differentiate between South-West and North-East Monsoon.

South-West Monsoon North-East Monsoon
Also called summer monsoon. Also called winter monsoon.
Mainly occurs from June to September. Mainly occurs from October to February.
Winds generally move from sea to land. Winds generally move from land to sea.
It brings most of India's rainfall. It gives important rainfall to south-eastern India.
Mainly caused by low pressure over heated land. Mainly caused by high pressure over cooled land.

Question 25. What is climate change? What are the major causes of climate change?

Answer: Climate change means long-term changes in weather patterns such as temperature, rainfall and wind.

The major causes of climate change are:

  1. Burning fossil fuels.
  2. Deforestation.
  3. Industrial pollution.
  4. Increase in greenhouse gases such as carbon dioxide, methane and nitrous oxide.

These gases trap heat in the atmosphere and increase global temperatures.

Question 26. What are the effects of climate change?

Answer: Climate change can cause:

  • More frequent floods and droughts.
  • Melting of glaciers.
  • Rising sea levels.
  • Loss of biodiversity.
  • Damage to ecosystems.
  • Problems for human health.
  • Problems for agriculture.
  • Loss of livelihoods.

Question 27. What is a carbon footprint? How can we reduce our carbon footprint?

Answer: A carbon footprint is the total amount of greenhouse gases released into the atmosphere because of human activities such as energy use, transportation and production of goods and services.

We can reduce our carbon footprint by:

  1. Saving electricity and energy.
  2. Walking or cycling for short distances.
  3. Using public transport or carpooling.
  4. Saving water.
  5. Reusing and recycling materials.
  6. Avoiding single-use plastics.
  7. Using renewable energy.
  8. Protecting forests and planting trees.
  9. Following eco-friendly lifestyles.

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