Atmosphere and Climate Class 9: Notes and Questions

What Atmosphere and Climate is about

Weightage: CBSE has not yet published marks for Class 9 Social Science 2026-27: its syllabus says the course structure "will be provided shortly". Class 9 is a school examination (80 marks annual paper + 20 internal assessment), so your school sets the paper.Source: CBSE Social Science syllabus, Class IX 2026-27

Key concepts

What the atmosphere is and why it matters

NCERT section Atmosphere and Climate

The atmosphere is a blanket of air around the Earth, held in place by gravity. It is a mixture of gases needed by all living beings.

It does three big jobs:

• Protects: it shields us from the Sun's harmful radiation, including ultraviolet rays.
• Keeps us warm: it traps part of the Sun's energy so that it does not all escape to space, regulating the Earth's temperature.
• Makes weather and climate: temperature, humidity and air pressure all depend on it.

A useful fact from the chapter: air presses on us all the time, yet we do not feel it, because it presses from all sides and the pressure inside our bodies is equal and balances it.

Worked example

Why do we not feel the pressure of the atmosphere? (2 marks)

Try it first, then show the solutionSolution

1. Air presses on the body from every side.
2. Pressure inside the body equals atmospheric pressure, so the two cancel out.

Answer: Air presses on our bodies from all sides, and the pressure inside our bodies is equal to the atmospheric pressure outside. The two balance each other, so we do not feel the weight of the air.

Composition of the atmosphere

NCERT section Composition and Structure of the Atmosphere

The air is a mixture. The book's pie chart shows:

• Nitrogen: 78%
• Oxygen: 21%
• Argon: 0.93%
• Carbon dioxide: 0.04%
• Others: 0.03% (helium, neon, krypton, xenon, ozone, hydrogen and so on)

Nitrogen and oxygen are the two main gases essential for life. The air also holds water vapour (generally 0.1 to 0.4 per cent; it forms clouds and rain) and tiny dust particles. The composition also changes with altitude.

Worked example

Name the two most abundant gases in the atmosphere with their percentages, and state why water vapour is important even though it is a small share. (3 marks)

Try it first, then show the solutionSolution

1. Nitrogen 78%, oxygen 21%.
2. Water vapour ranges from about 0.1 to 0.4 per cent.
3. It condenses to form clouds and precipitation.

Answer: Nitrogen (78%) and oxygen (21%). Water vapour is only about 0.1-0.4 per cent of the air, but it condenses to form clouds and falls as rain, snow or hail, so it controls precipitation and supplies most of our groundwater.

Layers of the atmosphere

NCERT section Composition and Structure of the Atmosphere

The layers are defined by changes in temperature and density with height. Air is densest near the ground and thins upward.

Layer	Height	Key features
Troposphere	average about 12 km	Most important layer; air we breathe, most water vapour and clouds; nearly all weather (rain, fog, hail); temperature falls with height. Ends at the tropopause.
Stratosphere	up to 50 km	Free of clouds and weather, so ideal for aeroplanes; contains the ozone layer that filters harmful UV rays. Ends at the stratopause.
Mesosphere	up to 80 km	Temperature falls with height; most meteorites burn up here.
Thermosphere	80 to 700 km	Temperature rises fast (gases absorb X-rays and short-wave UV); reflects radio waves back to Earth; includes the ionosphere; auroras occur here.
Exosphere	top layer	Very thin air; light gases (helium, hydrogen) drift into space because gravity is weak.

Remember: temperature drops with height only in the troposphere and mesosphere.

Auroras: charged particles from the Sun (the solar wind) are guided towards the magnetic poles; as they hit gases, each gas glows in its own colour: Aurora Borealis (north) and Aurora Australis (south).

Worked example

In which layer do aeroplanes fly and why? (2 marks)

Try it first, then show the solutionSolution

1. Identify the layer: stratosphere.
2. Reason: free of clouds and weather disturbances.

Answer: Aeroplanes fly in the stratosphere (above the tropopause) because this layer is free of clouds and other weather disturbances, which makes flying smoother and safer.

Weather and climate

NCERT section Weather and Climate

• Weather = the hour-to-hour and day-to-day condition of the atmosphere. It can change a lot from one day to the next.
• Climate = the sum total of weather conditions and variations over a large area for a long period, usually thirty years or more.

Based on common patterns over weeks or months (hot or cool, wet or dry, windy or calm), the year is divided into seasons.

So 'It is raining in Mumbai today' describes weather; 'Mumbai has heavy rain from June to September every year' describes climate.

Worked example

Classify as weather or climate: (a) A foggy morning in Delhi today. (b) Thiruvananthapuram has nearly the same temperature all year. (2 marks)

Try it first, then show the solutionSolution

1. Short-term condition = weather.
2. Long-term average pattern = climate.

Answer: (a) Weather: it describes a single day's condition. (b) Climate: it describes the long-term average pattern of a place.

Elements of weather and climate

NCERT section Elements of Weather and Climate

Five elements:

• Temperature: varies by day and night and by season. It depends a lot on insolation (incoming solar energy intercepted by the Earth). Insolation falls from the equator to the poles, so temperature does too.
• Humidity: water vapour in the air. Warm air can hold more vapour, so humidity can be higher; on humid days clothes dry slowly and sweat does not evaporate, so we feel uncomfortable.
• Precipitation: when air becomes saturated, vapour condenses and falls as drizzle, rain, snow, sleet or hail. Prevailing winds, mountains and seasons affect it. Rain is the commonest form; it lowers temperature and refills groundwater.
• Atmospheric pressure: the weight of air on the surface; highest at sea level and falls with height. Hot places: air rises → low pressure → cloudy, wet weather. Cold places: air sinks → high pressure → clear, sunny skies.
• Wind: air moving from high to low pressure; its direction is influenced by the Earth's rotation. Winds are named after the direction they come from (a westerly blows from the west).

Worked example

Why is low pressure linked to cloudy, wet weather and high pressure to clear skies? (3 marks)

Try it first, then show the solutionSolution

1. Hot place: air heats, rises, creating low pressure; rising air brings clouds and rain.
2. Cold place: air is heavy and sinks, creating high pressure; skies stay clear.
3. Air flows from high to low pressure as wind.

Answer: Where temperatures are high, air warms and rises, leaving low pressure at the surface; rising moist air forms clouds and brings wet weather. Where temperatures are low, cold, heavy air sinks and builds high pressure, which gives clear, sunny skies. Air then moves from the high-pressure area to the low-pressure area as wind.

Land breeze and sea breeze

NCERT section Elements of Weather and Climate

These are local winds that keep coastal climates moderate.

• Sea breeze (day, especially afternoon): land heats faster than the sea, so a low-pressure area forms over land; wind blows from sea to land.
• Land breeze (night): land cools faster than the sea; wind blows from land to sea. Because the temperature and pressure difference is small at night, the land breeze is gentle.

The same principle, unequal heating of land and water, drives the much larger monsoon.

Worked example

Why does a sea breeze blow during the afternoon on a coast? (2 marks)

Try it first, then show the solutionSolution

1. By afternoon land is warmer than sea; low pressure over land.
2. Air moves from high pressure (sea) to low pressure (land).

Answer: By afternoon the land has heated up more than the sea, so air over the land rises and forms a low-pressure area. Cooler air from the sea, where pressure is higher, flows in towards the land as a sea breeze.

Seasons of India

NCERT section Seasons in India

India's climate is tropical monsoon. The India Meteorological Department (IMD) recognises four seasons:

• Winter (December to early April): December and January are coldest; about 10-15°C in the north-west, rising to 20-25°C in the south-east of mainland India.
• Summer or pre-monsoon (April to June; up to July in the north-west): April is the hottest month in the west and south, May in the north; inland averages 32-40°C.
• Monsoon or rainy, advancing monsoon (June to September): the humid south-west monsoon sweeps across the country from late May or early June.
• Post-monsoon, retreating monsoon (October to December): north-west India has mostly cloudless October-November; the south gets more rain at this time.

The Himalayan states also have autumn and spring. Traditionally India counts six ṛtus of two months each: Vasanta, Grīṣhma, Varṣhā, Śharad, Hemanta, Śhiśhira.

Worked example

Name the four seasons of India recognised by the IMD with their months. (2 marks)

Try it first, then show the solutionSolution

1. List each season with its months.

Answer: Winter (December to early April); summer or pre-monsoon (April to June, up to July in the north-west); monsoon or rainy season (June to September); post-monsoon or retreating monsoon (October to December).

Mechanism of the monsoon

NCERT section Monsoon

Monsoon means the seasonal reversal of wind direction during a year. Arab traders named it from the Arabic mausim ('season'); sailors used the reversing winds to sail to and from India.

South-west (summer) monsoon, June to September:
1. In summer, the Indian landmass heats up faster than the surrounding oceans.
2. A low-pressure area forms over the subcontinent; the cooler Indian Ocean has high pressure.
3. Moist winds blow from sea to land across the Indian Ocean, Arabian Sea and Bay of Bengal, bringing rain. This gives most of India's yearly rainfall.

North-east (winter) monsoon, October to February:
1. The land cools faster than the sea: high pressure over land, low over the sea.
2. Cold, dry winds blow from land to sea, so most of India stays dry.
3. But crossing the Bay of Bengal, they pick up moisture and bring rain to the east coast: Tamil Nadu, Andhra Pradesh and parts of Karnataka.

Why it matters: farming depends on it; a good monsoon fills rivers, reservoirs and wells; it shapes transport, festivals and rural jobs. Too much rain brings floods; a weak monsoon brings drought.

Forecasting: Kṛiṣhiparāśhara and Varāhamihira's Bṛihatsaṁhitā described rainfall prediction; Kālidāsa's Meghadūtam (about 5th century CE) traces monsoon clouds; the Arthaśhāstra records rainfall measurement. Today the National Monsoon Mission and Mission Mausam improve forecasts.

Worked example

Distinguish between the south-west monsoon and the north-east monsoon. (3 marks)

Try it first, then show the solutionSolution

1. Season and months.
2. Pressure pattern and wind direction.
3. Rainfall effect.

Answer: South-west monsoon: June to September; land is hotter than sea, so low pressure over land draws moist winds from sea to land; it brings most of India's rainfall. North-east monsoon: October to February; land is cooler, so high pressure over land sends cold, dry winds from land to sea; it is mostly dry but brings rain to Tamil Nadu, Andhra Pradesh and parts of Karnataka after picking up moisture over the Bay of Bengal.

Climate change and carbon footprint

NCERT section Climate Change

Climate change = long-term changes in weather patterns (temperature, rainfall, wind), caused mainly by human activities: burning fossil fuels, deforestation and industrial pollution.

These raise greenhouse gases (carbon dioxide, methane, nitrous oxide, water vapour), which trap heat and raise global temperatures. Results: more frequent floods and droughts, melting glaciers, rising sea levels and loss of biodiversity, harming health, farming and livelihoods, and affecting women and children greatly.

Carbon footprint = the total greenhouse gases released by a person's or group's activities: energy use, transport, making goods and services.

What helps: reducing carbon footprints, renewable energy, protecting forests, sustainable lifestyles. The book's self-check scores your habits in transport, electricity, water and plastics (low impact 1 point to very high impact 4 points).

Worked example

Define carbon footprint. Suggest three ways a student can reduce it. (3 marks)

Try it first, then show the solutionSolution

1. Definition: total greenhouse gases released by one's activities.
2. Three low-impact choices from transport, electricity, water or plastics.

Answer: Carbon footprint is the total amount of greenhouse gases released into the atmosphere because of a person's activities, such as energy use, transport or the goods they consume. A student can walk, cycle or use public transport; switch off lights and fans when not in use; and reuse or recycle, avoiding single-use plastics.

Atmosphere and Climate in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Composition and Layers of the Atmosphere
• Weather, Elements of Climate, Breezes, Seasons and the Monsoon

Atmosphere and Climate: key facts

Composition of air

• •Nitrogen 78%
• •Oxygen 21%
• •Argon 0.93%
• •CO₂ 0.04%
• •Others 0.03%
• •Water vapour 0.1-0.4% (varies)

Draw as a pie chart for the NCERT question.

Layers bottom to top

1. 1.Troposphere (~12 km)
2. 2.Stratosphere (to 50 km)
3. 3.Mesosphere (to 80 km)
4. 4.Thermosphere (80-700 km)
5. 5.Exosphere

Boundaries: tropopause, stratopause, mesopause.

Temperature with height

Falls: troposphere, mesosphere | Rises: thermosphere

Easy to mix up in true-or-false items.

Pressure and weather

• •Hot → air rises → low pressure → cloudy, wet
• •Cold → air sinks → high pressure → clear, sunny
• •Wind: high → low

Winds are named after where they come from.

Breezes

1. 1.Day: sea
2. 2.land (sea breeze) | Night: land
3. 3.sea (land breeze)

Land heats and cools faster than water.

Monsoon

1. 1.Summer: land hot
2. 2.low pressure over land
3. 3.sea-to-land moist winds (SW) | Winter: land cold
4. 4.high pressure over land
5. 5.land-to-sea dry winds (NE), rain on Tamil Nadu coast

Monsoon = seasonal reversal of winds (Arabic mausim).

Weather vs climate

Weather = day-to-day | Climate = average over 30 years or more over a large area

How the school exam asks Atmosphere and Climate

The question patterns to expect, and the method that works for each.

Tricks to remember Atmosphere and Climate

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Layers in order

  'The Smart Monkey Throws Eggs': Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.

  Use it when: Order of layers.

• Heights

  12-50-80-700: 'a dozen, half a hundred, eighty, seven hundred'.

  Use it when: Upper limits of the first four layers.

• Who does what

  Tropo = Rain, Strato = Planes and Ozone, Meso = Meteors, Thermo = Radio and Auroras, Exo = Exit of gases.

  Use it when: Layer-feature questions.

• Monsoon direction

  Summer Sea-to-land (both S); Winter: land to Water.

  Use it when: SW vs NE monsoon.

• Six ṛtus

  'Very Good Village Shows Happy Sheep': Vasanta, Grīṣhma, Varṣhā, Śharad, Hemanta, Śhiśhira.

  Use it when: Traditional seasons in order from March.

Atmosphere and Climate: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Atmosphere and Climate

The slips examiners see most often, and what to write instead.

• ✗Mistake: Placing the ozone layer in the troposphere

  Students link ozone with 'near us' or with pollution.

  Wrong working

  Ozone, which absorbs UV rays, is found in the troposphere.

  Right working

  The ozone layer is in the stratosphere, where it filters harmful UV radiation.

  ✓Do this: Strato = ozone shield.

  Usually costs: The full mark in an MCQ.

• ✗Mistake: Saying temperature always falls with height

  True in the troposphere, so students generalise.

  Wrong working

  Temperature decreases in all layers as we go up.

  Right working

  It falls only in the troposphere and mesosphere; it rises sharply in the thermosphere.

  ✓Do this: Learn the exception explicitly.

  Usually costs: 1 mark.

• ✗Mistake: Reversing the monsoon pressure pattern

  Students remember 'pressure' but not which side.

  Wrong working

  In summer high pressure over land pulls winds from the sea.

  Right working

  In summer land heats faster and has low pressure; winds blow from high pressure over the sea to low pressure over land.

  ✓Do this: Hot = low pressure; air flows from high to low.

  Usually costs: 1-2 marks in a 3-mark answer.

• ✗Mistake: Naming a wind by where it is going

  It feels natural to name by destination.

  Wrong working

  A wind blowing towards the west is a westerly.

  Right working

  A westerly blows from the west.

  ✓Do this: Winds are named after their source.

  Usually costs: 1 mark.

• ✗Mistake: Calling one week of heat 'climate change'

  Weather and climate are confused.

  Wrong working

  This week is very hot, so the climate has changed.

  Right working

  One hot week is weather; climate change is a long-term shift in patterns over decades.

  ✓Do this: Climate = 30 years or more.

  Usually costs: 1 mark.

NCERT exercise guide: Atmosphere and Climate

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Atmosphere and Climate

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which gas forms about 0.93% of the atmosphere?
   (a) Carbon dioxide (b) Argon (c) Oxygen (d) Helium

   Hint

   The third-largest share.

   Answer

   (b) Argon

2. Q2 · 1 mark · Very short answerExam level

   What is the term for the height of a place above mean sea level?

   Hint

   Mean sea level counts as zero.

   Answer

   Altitude.

3. Q3 · 1 mark · Very short answerExam level

   Name the traditional Indian season that falls in July-August.

   Hint

   The rainy ṛtu.

   Answer

   Varṣhā (months Śhrāvaṇa-Bhādrapada).

4. Q4 · 1 mark · Assertion-reasonHarder exam level

   Assertion (A): The north-east monsoon brings rain to most of India.
   Reason (R): The winter winds blow from land to sea and are cold and dry.
   Choose (a)-(d).

   Hint

   Is A true for most of India?

   Answer

   (d) A is false, R is true: the winter monsoon is dry for most of India; only the east coast gets rain after the winds cross the Bay of Bengal.

5. Q5 · 2 marks · Short answerExam level

   Why does temperature decrease from the equator towards the poles? (2 marks)

   Hint

   Insolation.

   Answer

   Insolation, the solar energy reaching the Earth, is greatest at the equator where sunlight strikes most directly and decreases towards the poles where sunlight comes in at a low angle. So temperature also decreases towards the poles.

6. Q6 · 2 marks · Short answerHarder exam level

   Explain why the land breeze is weaker than the sea breeze. (2 marks)

   Hint

   Size of the pressure difference.

   Answer

   At night, the difference in temperature and air pressure between land and sea is small, so the land breeze is gentle. In the afternoon, the land is much hotter than the sea, so the pressure difference and the sea breeze are stronger.

7. Q7 · 2 marks · Source-basedHOTS / competency

   Using Table 3.3, Delhi gets 67.0 cm of rain and Jodhpur 36.6 cm. Give one likely reason. (2 marks)

   Hint

   How far does the monsoon reach, and how much moisture is left?

   Answer

   The monsoon winds reach Delhi with more moisture than they bring to Jodhpur in the dry west; Jodhpur lies in a desert region that the rain-bearing winds reach late and weakly, so it gets much less rain.

8. Q8 · 3 marks · Short answerHarder exam level

   Explain how human activities cause climate change and give three effects mentioned in the chapter. (3 marks)

   Hint

   Activities → gases → heat → effects.

   Answer

   Burning fossil fuels, cutting forests and industrial pollution add greenhouse gases such as carbon dioxide and methane, which trap heat and raise global temperatures. Effects: more frequent floods and droughts, melting glaciers and rising sea levels (also loss of biodiversity).

9. Q9 · 5 marks · Long answerHOTS / competency

   Suppose your school wants to cut its carbon footprint. Propose a four-point plan using ideas from the chapter. (5 marks)

   Hint

   Transport, electricity, water, waste, trees.

   Answer

   1. Encourage walking, cycling and shared buses instead of private cars. 2. Switch off lights and fans when rooms are empty and fit solar panels (renewable energy). 3. Save water with careful use and rainwater harvesting. 4. Ban single-use plastics, set up recycling, and plant trees on campus. Each step lowers greenhouse gas emissions from daily school life.

10. Q10 · 3 marks · Short answerHOTS / competency

    What would happen if the Earth had no atmosphere? Give three consequences based on the chapter. (3 marks)

    Hint

    Think of the three jobs of the atmosphere.

    Answer

    1. Harmful UV radiation would reach the surface unchecked. 2. Heat would escape to space, so temperatures would swing to extremes. 3. There would be no air to breathe, no clouds or rain, so no weather and no life as we know it.

11. Q11 · 2 marks · Short answerHarder exam level

    Why are auroras seen mostly near the poles? (2 marks)

    Hint

    Solar wind and magnetic poles.

    Answer

    The solar wind's charged particles are directed towards the Earth's magnetic poles; there they strike atmospheric gases in the thermosphere and make them glow, producing the auroras.

12. Q12 · 1 mark · Very short answerExam level

    Name the layer where nearly all weather phenomena such as rain, fog and hail occur.

    Hint

    The lowest layer.

    Answer

    The troposphere.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What holds the atmosphere around the Earth?Show answer

   Gravity.

2. 2.What percentage of air is nitrogen? Oxygen?Show answer

   78% and 21%.

3. 3.Name the boundary between the troposphere and the stratosphere.Show answer

   The tropopause.

4. 4.In which layer do most meteorites burn up?Show answer

   The mesosphere.

5. 5.Which layer reflects radio waves back to the Earth?Show answer

   The thermosphere (its ionosphere part).

6. 6.What is insolation?Show answer

   Incoming solar energy from the Sun intercepted by the Earth.

7. 7.What does the Arabic word mausim mean?Show answer

   Season.

8. 8.Which states get rain from the north-east monsoon?Show answer

   Tamil Nadu, Andhra Pradesh and parts of Karnataka (the east coast).

9. 9.Name four greenhouse gases.Show answer

   Carbon dioxide, methane, nitrous oxide and water vapour.

10. 10.What are the Aurora Borealis and Aurora Australis?Show answer

    Coloured lights in the sky near the north and south poles, caused by the solar wind's charged particles making atmospheric gases glow.

11. 11.Which three rivers' swelling the NCERT case links to the Punjab floods?Show answer

    The Satluj, Beas and Ravi (the Ghaggar was also running high).

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Atmosphere: blanket of air held by gravity; protects from UV, traps heat, makes weather.
• ☐N₂ 78%, O₂ 21%, Ar 0.93%, CO₂ 0.04%; water vapour 0.1-0.4%; dust particles.
• ☐Troposphere ~12 km: weather, clouds; temperature falls; tropopause.
• ☐Stratosphere to 50 km: ozone layer; aeroplanes; stratopause.
• ☐Mesosphere to 80 km: meteors burn; temperature falls.
• ☐Thermosphere 80-700 km: temperature rises; radio waves; ionosphere; auroras.
• ☐Exosphere: very thin air; light gases escape.
• ☐Weather = short term; climate = 30+ years over a large area.
• ☐Elements: temperature (insolation), humidity, precipitation, pressure, wind.
• ☐Hot → low pressure → wet; cold → high pressure → clear; wind high → low.
• ☐Sea breeze by day; land breeze by night.
• ☐IMD seasons: winter, summer, monsoon, post-monsoon; six traditional ṛtus.
• ☐SW monsoon June-Sept: sea to land, most rain; NE monsoon Oct-Feb: land to sea, rain on Tamil Nadu coast.
• ☐Climate change: human-made greenhouse gases; floods, droughts, melting glaciers, sea-level rise.
• ☐Reduce carbon footprint: walk or cycle, save power and water, avoid single-use plastic, renewables.

Atmosphere and Climate: frequently asked questions