3: Atmosphere and Climate
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The Big Questions
(from the book)
1.
What is the composition of the atmosphere?
2.
How do the different layers of the atmosphere affect the planet
Earth?
3.
What is the mechanism of monsoon?
4.
How can we reduce our carbon footprint?
Introduction
When you look up at the sky, you see floating clouds, sunshine,
and feel a breeze. All of these are a result of a blanket of air surrounding
the Earth called the atmosphere.
What is the
Atmosphere?
The atmosphere is a mixture of gases in various
proportions that surrounds the Earth. It is pulled down around the Earth
by gravity. It is vital for the survival of all living beings on
Earth.
Gravity is
a fundamental physical force of attraction between objects that have mass or
energy, such as the Sun and the Earth. The force of attraction that the Earth's
mass exerts on objects on or close to its surface is called Earth's gravity.
Functions of the
Atmosphere
- Shields life from
harmful radiation coming from the Sun, including ultraviolet (UV)
radiation.
- Regulates the
Earth's temperature by trapping some of the
Sun's energy and preventing it from escaping back into space.
- Is a key
component of the Earth's weather and climate systems, influencing
temperature, humidity, and air pressure.
Think
About It: What would happen if there were no atmosphere? Discuss with
your friends and teachers.
Composition and
Structure of the Atmosphere
Composition of the
Atmosphere
The Earth's atmosphere is composed of a mixture of various
gases. The two primary and most abundant gases are:
- Nitrogen — 78%
- Oxygen — 21%
Other gases present in smaller quantities include:
- Carbon dioxide — 0.04%
- Argon — 0.93%
- Others (helium,
neon, krypton, xenon, ozone, hydrogen) — 0.03%
Apart from gases, the atmosphere also contains:
- Water vapour —
generally ranges from 0.2% to 0.4%. It plays a significant role in cloud
formation and precipitation.
- Tiny dust
particles
Note: The
composition of the atmosphere also varies with altitude.
Let's
Recall: How is nitrogen useful for plants? You learnt this in the
chapter 'The Invisible Living World Beyond Our Naked Eyes' in your Grade 8
Science textbook.
Structure of the
Atmosphere
The atmosphere has a layered structure. These layers
are defined on the basis of changes in temperature and density with
increasing altitude.
Altitude is
the height of a location above mean sea level, usually measured in metres or
feet. Mean sea level is considered zero.
- The density
of air is highest near the Earth's surface and decreases with
altitude.
The major layers from the Earth's surface to outer space are:
1. Troposphere
- Average height: About 12
kilometres
- Temperature: Decreases
with increasing altitude
- Contains: The air we
breathe, most of the water vapour, and clouds
- Weather: Nearly all
weather phenomena — rainfall, fog, hail — occur in this layer
- Separated from
the stratosphere by a transition zone called the Tropopause
2. Stratosphere
- Lies above
the troposphere, extending up to 50 kilometres
- Ideal for flying
aeroplanes because
it is free of clouds and other weather disturbances
- Contains
the Ozone Layer, which shields life by filtering the Sun's
harmful radiation, including UV radiation
- The Stratopause marks
the boundary between the stratosphere and mesosphere
3. Mesosphere
- Lies above the
stratosphere, extending up to 80 kilometres
- Temperature
decreases with increasing altitude (like the troposphere)
- Most meteorites entering
from space burn up in the mesosphere
Don't
Miss Out: Temperature decreases with altitude only in
the troposphere and mesosphere.
4. Thermosphere
- Extends
from 80 to 400 km
- Temperature
rises very rapidly with increasing altitude, as
gas molecules absorb X-rays and short-wave ultraviolet radiation from the
Sun
- Helps with radio
transmission by reflecting radio waves transmitted from Earth
back toward it
- The Ionosphere is
a part of the thermosphere
- Auroras (Northern
Lights — Aurora Borealis; Southern Lights — Aurora Australis) occur in
this layer
Aurora: The
word aurora comes from Latin meaning 'dawn' or 'morning light'. It is named
after the Roman goddess Aurora, goddess of dawn. It refers to the colourful
display of light seen in the sky near the poles. Solar wind (charged particles
emitted by the Sun) is directed toward the magnetic poles. As these particles
interact with different atmospheric gases, each gas glows with a particular
colour.
5. Exosphere
- The uppermost
layer of the atmosphere
- Characterised
by very thin air
- Light gases
like helium and hydrogen float into space from this layer
due to weak gravity
Don't
Miss Out: The air above us exerts a significant force on our bodies,
yet we do not feel it. This is because air presses on us from all sides and
our bodies exert a counter pressure in response.
Weather and Climate
Weather
The term weather refers to the hour-to-hour
and day-to-day conditions of the atmosphere. Weather can vary significantly
from day to day. Hot or humid weather may make one irritable, while pleasant or
breezy weather may make one cheerful.
Climate
Climate refers to the sum total of weather conditions and
variations over a large area for an extended period of time —
usually thirty years or more. It is the average weather conditions
of a place over a longer period.
Elements of Weather
and Climate
Various elements influence weather and climate. The major elements
that impact human life are:
1. Temperature
- Temperature
varies between day and night and across seasons (summers
are hotter than winters)
- An important
factor affecting temperature distribution is insolation
Insolation: The
incoming solar energy from the Sun that is intercepted by the Earth.
- The amount of
insolation decreases from the equator towards the poles
- Hence, temperature
also decreases from the equator towards the poles
- This creates
different temperature zones: Torrid Zone (near equator),
Temperate Zones, and Frigid Zones (near poles)
2. Humidity
- When water
evaporates from land and water bodies, it becomes water vapour
- When levels of
water vapour in the air are high, it leads to humidity
- Humidity refers
to the presence of water vapour in the air, creating moisture
- As air gets
warmer, its capacity to hold water vapour increases, leading
to higher humidity
- On a very humid
day, clothes take longer to dry and sweat evaporates more
slowly, leaving us feeling uncomfortable
3. Precipitation
- Occurs when a
part of the atmosphere becomes saturated with water vapour,
which condenses and falls on Earth due to gravity
- Includes: drizzle,
rain, snow, sleet, and hail
- Main factors
affecting precipitation: prevailing winds, mountains, and seasons
- When precipitation
falls in liquid form, it is called rain — the
most common form of precipitation
- Rain lowers
the temperature of a place
- A long absence
of rainfall results in a dry climate
- Most groundwater is
collected from rainwater
4. Atmospheric
Pressure
- The pressure
exerted by the weight of air on the Earth's surface is
called air pressure
- Highest at sea
level and
decreases with altitude
- High Temperature
→ Air heats up → Air rises → Low Pressure Area →
associated with cloudy skies and wet weather
- Low Temperature → Air cools → Air sinks → High Pressure Area →
associated with clear and sunny skies
- Air always moves
from high pressure areas to low pressure areas
5. Wind
- The movement
of air from a high pressure area to a low pressure area is
called wind
- Can be gentle or
strong
- Winds are named
after the direction they blow from (e.g., wind blowing from the
west = westerly)
Wind Speed Categories:
|
Wind |
Speed (km/hr) |
Common Effects |
|
Calm |
0 |
Calm; smoke rises vertically |
|
Light Breeze |
— |
Wind can be felt on the face; leaves rustle; ordinary vane moves |
|
Strong Breeze |
— |
Large branches sway; umbrellas are difficult to use |
|
Storm |
90+ |
Very rarely experienced; usually accompanied by widespread
damage |
Let's
Explore: Find out other categories of wind based on speed and their
common effects.
Land Breeze and Sea
Breeze
Local winds such as the land breeze and sea
breeze affect the weather and climate of a place. They help
create moderate climatic conditions in coastal regions.
|
Sea Breeze |
Land Breeze |
|
|
Direction |
Blows from sea to land |
Blows from land to sea |
|
Time |
During the day (especially afternoon) |
During the night |
|
Cause |
Land becomes warmer than sea → Low pressure over land → Wind flows from sea |
Land cools faster than sea at night → Wind flows from land to
sea |
|
Speed |
Relatively stronger |
Low speed (small temperature difference) |
Seasons in India
The year is divided into seasons based on common
patterns over weeks or months (cool/hot, windy/calm, cloudy/bright, wet/dry).
Let's
Analyse: Note down the weather report from a local newspaper for two
weeks and observe the changes occurring in the weather.
The climate of India can be broadly classified as tropical
monsoon. The Indian Meteorological Department (IMD) has
recognised four distinct seasons in India:
1. Winter (December
to early April)
- The coldest
months are December and January
- Average
temperature in north-west India: around 10°C
- Temperatures
increase toward the equator, reaching around 20–25°C in mainland
India's south-east
2. Summer /
Pre-Monsoon (April to June/July)
- Spans from April
to June (up to July in north-western India)
- In western and
southern regions, the hottest month is April; in northern
regions, it is May
- Average
temperature across most of inland India: 32–40°C
3. Monsoon / Rainy —
Advancing Monsoon (June to September)
- Dominated by
the humid south-west summer monsoon, which slowly sweeps
across the country in late May or early June
- Monsoon rain
begins to recede from north India at the beginning of
October
- South India typically
receives more rainfall during the retreating phase
4. Post-Monsoon —
Retreating Monsoon (October to December)
- In north-western
India, October and November are usually cloudless
- The Himalayan
states, being more temperate, experience two additional seasons —
autumn and spring
Traditional Six
Seasons of India (Ṛtu)
Don't
Miss Out: Traditionally India experiences six seasons,
each about two months long.
|
Season (Ṛtu) |
Months (Indian Calendar) |
Months (Gregorian
Calendar) |
|
Vasanta (Spring) |
Chaitra – Vaishākha |
March – April |
|
Grīshma (Summer) |
Jyeshtha – Āshādha |
May – June |
|
Varsha (Monsoon) |
Shrāvana – Bhādrapada |
July – August |
|
Sharad (Early Autumn) |
Āshvina – Kārtika |
September – October |
|
Hemanta (Late Autumn) |
Mārgashīrsha – Pausha |
November – December |
|
Shishira (Winter) |
Māgha – Phālguna |
January – February |
Think
About It: Hindustani Classical music associates certain rāgas with
specific seasons. Find out which rāgas are connected to each season with the
help of your elders and teachers.
Don't
Miss Out: Kauṭilya's
Arthaśāstra contains records of scientific measurements of rainfall and their
practical application in managing the country's revenue and relief efforts.
Monsoon
What is Monsoon?
Monsoon refers to the seasonal reversal in the wind
direction during a year.
- Sailors who came
to India during ancient times were among the first to notice the
phenomenon of monsoon
- The Arabs,
who came to India as traders, named this seasonal reversal of the wind
system 'monsoon' — derived from the Arabic word mausim,
which literally means 'season'
Don't
Miss Out: Since crop production depended on seasonal monsoon rains,
Indians worked out methods to predict rainfall. Gargasaṃhitā and Bṛhatsaṃhitā describe
such methods. Garga's main technique was based on positions of the Moon and Sun
in the sky. Varāhamihira in his Bṛhatsaṃhitā considered lunar
mansions (nakṣhatras) in
predicting seasonal rainfall. Even today, many farming practices in India are
based on these ancient methods.
Lunar
Mansions (nakṣhatras): Nakṣhatras are a way of dividing
the sky into 27 equal parts along the path the Moon travels. The Moon takes
about 27 days to go around the Earth relative to the stars, so it moves through
one nakṣhatra
each day — like the Moon stays in a different "house" in the sky
every night.
Types of Monsoon
1. South-West Monsoon
(Summer Monsoon)
- Winds blow from
sea to land across the Indian Ocean, Arabian Sea, and Bay of
Bengal
- Occurs
between June and September
- Main
cause: Unequal
heating of land and sea
- During summer,
the landmass of India heats up faster than the
surrounding oceans
- This creates
a low pressure area over the Indian subcontinent
- The Indian
Ocean remains relatively cooler → high
pressure
- Winds move from
high to low pressure → moist
winds blow from ocean to land, bringing rainfall
- Accounts
for most of the rainfall in the country throughout the
year
2. North-East Monsoon
(Winter Monsoon)
- Occurs in India
from October to February
- During this
season, the Indian landmass cools faster than surrounding
oceans
- Creates high
pressure over land and low pressure over seas
- Cold and dry
winds blow from land to sea — generally do not bring rainfall to
most of India
- However, when
north-east monsoon winds pass over the Bay of Bengal, they
pick up moisture and cause rainfall in the eastern coast of India —
especially Tamil Nadu, Andhra Pradesh, and parts of Karnataka
- Thus, the winter
monsoon is important for the rainfall of south-eastern India
Importance of Monsoon
in India
- Most of
India's agriculture depends on monsoon rainfall — farmers
rely on rain for sowing and growing crops
- A good monsoon
ensures sufficient food production and water supply in
rivers, reservoirs, and wells
- Monsoon
affects daily life, transport, festivals, and employment,
especially in rural areas
- Excessive
rainfall →
floods
- Weak monsoon →
droughts
- Monsoon greatly
influences the economy, lifestyle, and livelihoods of
people in India
Let's
Explore: Describe in your own words how monsoon affects the lives of
the people around you.
Don't
Miss Out:
·
Under the National Monsoon Mission (NMM), the Ministry
of Earth Sciences (Government of India) has developed state-of-the-art weather
and climate prediction models to enhance monsoon predictions.
·
Mission Mausam is designed to
position India as a global leader in weather and climate sciences — making the
nation "Weather Ready and Climate Smart" with improved forecasting
for agriculture, disaster management, and rural development.
·
Kālidāsa's Meghadūtam (written
around the 5th century CE) mentions the date of onset of the monsoon over
central India and traces the path of monsoon clouds.
Climate Change
What is Climate
Change?
Climate change refers to long-term changes in
weather patterns — such as temperature, rainfall, and wind — caused
mainly by human activities including:
- Burning of
fossil fuels
- Deforestation
- Industrial
pollution
These activities release gases like carbon dioxide into
the atmosphere.
Greenhouse Effect and
Global Warming
Human activities increase greenhouse gases such
as:
- Carbon dioxide
(CO₂)
- Methane (CH₄)
- Nitrous oxide
(N₂O)
- Water vapour
These gases trap heat in the atmosphere and
raise global temperatures.
Carbon
Footprint: The total amount of greenhouse gases released into the
atmosphere as a result of human activities, such as energy use, transportation,
or the production of goods and services.
Effects of Climate
Change
- More
frequent floods and droughts
- Melting of
glaciers
- Rising sea
levels
- Loss of
biodiversity
- Threats to ecosystems,
human health, agriculture, and livelihoods
- Especially
severe impact on women and children
Solutions / What We
Can Do
- Reduce carbon
footprints
- Use renewable
energy
- Protect forests (stop
deforestation)
- Adopt sustainable
lifestyles
- Every small step
counts — every human being plays a vital role
Let's Explore — My
Carbon Footprint (Activity from the book)
Step 1: My Daily
Habits — Tick what applies to you
A. Transport
- I usually
walk/use a cycle. (Low impact)
- I use public
transport/carpool. (Medium impact)
- I travel by
private car even for short distances. (High impact)
- I take flights
more than twice a year. (Very high impact)
B. Electricity Use
- I always switch
off electrical appliances (lights, fans, etc.) when not in use. (Low
impact)
- I sometimes
forget to switch off appliances. (Medium impact)
- I leave
electrical appliances on frequently. (High impact)
C. Water Use
- I use water
judiciously (e.g., just one bucket for bathing). (Low impact)
- I sometimes
waste water (leaving tap running, long showers). (Medium impact)
- I rarely think
about saving water. (High impact)
D. Waste and Plastics
- I reuse,
recycle, and avoid single-use plastics. (Low impact)
- I sometimes use
disposable plastics (bottles, bags, straws). (Medium impact)
- I often throw
away plastic and do not recycle. (High impact)
Step 2: Score
Yourself
- Low impact = 1
point
- Medium impact =
2 points
- High impact = 3
points
- Very high impact
= 4 points
Add up your total score: _______ points
Step 3: My Climate
Action Pledge
Think about two simple changes you can make to
reduce your score:
Case Study: Punjab
Floods 2025
Background
In 2025, Punjab experienced severe floods due to
heavy monsoon rains and the consecutive swelling of the rivers Sutlej,
Beas, and Ravi. The floods damaged large parts of the state — villages, agricultural
fields, houses, and infrastructure (roads and bridges).
Causes of Punjab
Floods 2025
Natural Causes
- Very heavy
monsoon rains intensified by western disturbances that
brought additional moisture
- Heavy rains in Himachal
Pradesh and Jammu & Kashmir as well
- Major rivers of
Punjab (Sutlej, Beas, Ravi, Ghaggar) were already flowing high before
the heavy rains
- Additional
rainfall caused rivers to overflow, leading to severe flooding
Human-Made Causes
- Weak and old river
embankments (dhīs/bandhs) could not stop the rising
water
- People had
built houses and farms too close to rivers, reducing space for
floodwater to spread safely
- Silt and mud had
accumulated in rivers and dams over time, reducing their capacity to hold
water
- Flood warnings
came late or
were not clearly communicated, leaving people unprepared
Effects of the Floods
in Punjab
- Many
people lost their lives
- Thousands had to
leave their homes and move to relief camps
- Large areas
of farmland were submerged; crops like paddy were
severely damaged
- Poultry and
dairy farms were
damaged; many animals (cows, buffaloes, chickens) got sick or died
- Roads, bridges,
border fences,
and some public buildings were damaged
- Muddy standing
water caused health problems including waterborne
diseases and sanitation concerns
Classroom Discussion
(from the book)
1.
To what extent did natural factors cause these floods compared to
human activities?
2.
Do you think better planning could have reduced the damage? How?
3.
What are the guidelines for the management of floods according to
the National Disaster Management Authority (NDMA)?
4.
What role can students/youth play in helping with disaster
preparedness?
Questions
and Activities
(Exercises
from the Book)
Short Answer
Questions
Q1. What is atmosphere? Explain its composition with the help of a
pie diagram.
Answer: The atmosphere is a blanket of mixed gases surrounding the
Earth, held in place by gravity. It is essential for life and regulates the
Earth's temperature, protects from harmful solar radiation, and drives weather
systems.
Composition:
- Nitrogen — 78% (most
abundant)
- Oxygen — 21%
- Argon — 0.93%
- Carbon Dioxide —
0.04%
- Others (helium,
neon, ozone, etc.) — 0.03%
- Plus water
vapour (0.2%–0.4%) and tiny dust particles
(Draw a pie chart with the above percentages — Nitrogen taking the
largest slice at 78%, Oxygen next at 21%, and the remaining gases in small
slices.)
Q2. Draw a labelled diagram of the structure of atmosphere.
Answer: (Draw a vertical diagram showing the Earth's surface at
the bottom and outer space at the top, with the following layers labelled from
bottom to top:)
|
Layer |
Height |
Key Feature |
|
Troposphere |
0–12 km |
Weather occurs here; temperature decreases with altitude |
|
Tropopause |
Boundary |
— |
|
Stratosphere |
12–50 km |
Ozone layer; aeroplanes fly here |
|
Stratopause |
Boundary |
— |
|
Mesosphere |
50–80 km |
Meteorites burn up here; temperature decreases |
|
Mesopause |
Boundary |
— |
|
Thermosphere |
80–400 km |
Temperature rises; auroras occur here |
|
Exosphere |
400 km+ |
Outermost layer; very thin air; gases escape into space |
Q3. Which are the four main seasons of India?
Answer: According to the Indian Meteorological Department
(IMD), the four main seasons of India are:
1.
Winter — December to early
April (coldest months: December and January)
2.
Summer / Pre-Monsoon —
April to June (hottest months; temperatures reach 32–40°C)
3.
Monsoon / Advancing Monsoon —
June to September (dominated by south-west monsoon; maximum rainfall)
4.
Post-Monsoon / Retreating Monsoon —
October to December (north-east monsoon; south-eastern India gets rainfall)
Q4. Why do you not feel the pressure of the atmosphere?
Answer: The atmosphere exerts a significant pressure on our bodies
from all sides. However, we do not feel it because our bodies exert an equal
counter pressure from inside in response to the atmospheric pressure.
Since the pressure from outside and the pressure from inside our bodies cancel
each other out, we do not feel the weight of the atmosphere pressing on us.
Q5. In which layer of the atmosphere do aeroplanes fly and why?
Answer: Aeroplanes fly in the Stratosphere (the
second layer of the atmosphere, from 12 km to 50 km altitude).
Reasons:
- The stratosphere
is free of clouds and other weather disturbances that are
common in the troposphere
- It
provides calm and stable flying conditions
- There is no
turbulence caused by storms or rainfall in this layer
- This makes it
the safest and most efficient layer for air travel
Q6. Distinguish between the following:
a. The Troposphere and Stratosphere
|
Feature |
Troposphere |
Stratosphere |
|
Height |
0–12 km |
12–50 km |
|
Temperature |
Decreases with altitude |
Increases (warming) due to ozone absorbing UV radiation |
|
Weather |
All weather phenomena (rain, fog, hail) occur here |
Free of clouds and weather disturbances |
|
Ozone |
Not present |
Contains the Ozone Layer (filters UV rays) |
|
Air flights |
Not suitable (turbulence) |
Ideal for aeroplane travel |
|
Boundary |
Upper boundary is the Tropopause |
Upper boundary is the Stratopause |
b. The South-West Monsoon and North-East Monsoon
|
Feature |
South-West Monsoon |
North-East Monsoon |
|
Also known as |
Summer monsoon |
Winter monsoon |
|
Season |
June to September |
October to February |
|
Wind direction |
Sea to land (ocean → India) |
Land to sea (India → ocean) |
|
Cause |
Land heats faster → low pressure over India → moist winds blow in |
Land cools faster → high pressure over land → dry winds blow out |
|
Nature |
Moist, carries heavy rainfall |
Dry for most of India; moist only over Bay of Bengal |
|
Rainfall |
Brings most of India's annual rainfall |
Brings rainfall mainly to Tamil Nadu, Andhra Pradesh,
Karnataka (eastern coast) |
|
Oceans involved |
Arabian Sea + Bay of Bengal + Indian Ocean |
Bay of Bengal (picks up moisture) |
Q7. Do it yourself — Data Activity (Table 3.3)
This is a practical activity. The book provides average
monthly temperatures and rainfall for 10 representative stations
across India. You are required to:
7.1. Re-arrange the 10 stations according to their distance
from the equator (from nearest to farthest):
|
Station |
Latitude |
Distance from Equator |
|
Thiruvananthapuram |
8°29'N |
Nearest |
|
Chennai |
13°4'N |
— |
|
Bengaluru |
12°58'N |
— |
|
Mumbai |
19°N |
— |
|
Nagpur |
21°9'N |
— |
|
Kolkata |
22°34'N |
— |
|
Jodhpur |
26°18'N |
— |
|
Shillong |
24°34'N |
— |
|
Delhi |
29°N |
— |
|
Leh |
34°N |
Farthest |
7.2. Find out:
a. Two stations with the
most extreme climate: → Leh (very
cold, low rainfall — extreme continental climate) and Jodhpur (very
hot, very low rainfall — extreme desert climate) have the most extreme
climates.
b. Two stations influenced
by retreating (north-east) monsoon: → Chennai and Thiruvananthapuram —
located on the eastern/south-eastern coast, they receive most of their rainfall
from the retreating north-east monsoon (October–December).
c. The two hottest stations
in the months of:
- (i)
February: Chennai and Thiruvananthapuram (both
near the equator; warm throughout the year)
- (ii)
June: Jodhpur and Delhi (extreme
summer heat in north and north-west India)
7.3. Now find out:
a. Why does Shillong
experience more rainfall than Kolkata? → Shillong is
located at a high altitude (1461 m) in the Meghalaya plateau (near
Cherrapunji/Mawsynram region), which is one of the wettest regions on Earth.
The Bay of Bengal branch of the south-west monsoon hits the
hilly terrain directly and is forced to rise steeply, causing very heavy orographic
(relief) rainfall. Kolkata, though near the Bay of Bengal, is
on the flat plains and does not receive the same orographic effect. Hence
Shillong gets far more rainfall (225.3 cm annual) than Kolkata (162.5 cm).
b. Why does Delhi receive
more rainfall than Jodhpur? → Delhi is located in the Indo-Gangetic
Plain and is reached by both the Arabian Sea branch and the Bay of
Bengal branch of the south-west monsoon. Jodhpur lies in
the Thar Desert region of Rajasthan. By the time the monsoon
winds reach Jodhpur, they have already lost most of their moisture, resulting
in very little rainfall. Additionally, the Aravalli mountains are roughly
parallel to the Arabian Sea branch of the monsoon and do not obstruct it
effectively. Hence Delhi (67 cm) receives far more rainfall than Jodhpur (36.6
cm).
7.4. Now think why:
a. Thiruvananthapuram has
an equable (moderate) climate: → Thiruvananthapuram is
located close to the southern tip of India at a low latitude
(8°29'N) and is surrounded by the sea on three sides (it is
close to the Kerala coast). The proximity to the sea moderates temperatures —
the sea warms up and cools down slowly, keeping temperatures relatively
constant throughout the year (ranging from about 26°C to 28.7°C). This
maritime influence gives it an equable climate with little
variation between seasons.
b. Chennai has more
rainfall only after the fury of the monsoon is over in most parts of the
country: → Chennai
lies on the eastern (Coromandel) coast of India. During the south-west
monsoon (June–September), Chennai is in the rain shadow of the
Western Ghats — the monsoon winds lose most moisture before crossing the
peninsula, so Chennai gets little rain during this period. However,
during October–December, the north-east (retreating)
monsoon picks up moisture from the Bay of Bengal and
brings heavy rainfall to Tamil Nadu and the eastern coast. So Chennai gets most
of its rainfall from the retreating monsoon, which arrives after the
main monsoon fury is over elsewhere.
c. Leh has moderate
precipitation almost throughout the year: → Leh is
located in the Ladakh region at a very high altitude (3506 m)
in the rain shadow of both the Himalayas and the Karakoram Range.
The south-west monsoon cannot cross the high Himalayan ranges and reach Leh in
significant amounts. The north-east monsoon also barely affects it. Instead,
Leh receives light precipitation spread throughout the year mainly
from western disturbances (westerly winds from the
Mediterranean/Atlantic region) that bring snow and light rain in winter and
spring. This results in low but fairly evenly distributed precipitation (about
8.5 cm annually).
7.5. Despite differences
across regions, is there evidence that monsoons provide climatic unity to the
country? → Yes.
Although India has diverse climatic conditions — the cold deserts of Leh, the
hot Thar Desert, the humid coasts, the temperate Himalayas — the south-west
monsoon arrives almost simultaneously across most of India (advancing
from Kerala in late May/early June to the rest of the country). It brings
a dramatic seasonal shift everywhere — from dry heat to rain —
and determines the agricultural calendar of the entire
country. The monsoon creates a shared rhythm of seasons — the
anticipation of rain, crop sowing, festivals linked to harvest — making it a
powerful unifying climatic experience across India's diverse regions.
Q8. Collect pictures of
houses and clothing of people from different regions of India. Examine whether
they reflect any relationship with the climatic conditions or the relief of
those regions.
Answer (Guidance): This
is a project/observation activity. Here are some relationships to look for:
|
Region |
Climate |
Houses |
Clothing |
|
Rajasthan (Desert) |
Hot and dry |
Thick mud/stone walls to
keep out heat; small windows |
Light cotton clothes;
turbans to protect from sun and dust |
|
Kerala/Coastal |
Hot and humid; heavy
rainfall |
Sloping roofs to drain
rainwater; raised structures |
Light cotton; minimal
layers |
|
Kashmir/Himachal |
Cold, heavy snowfall |
Sloping roofs to shed
snow; wooden construction |
Woollen shawls, phirans,
warm layers |
|
Northeast
(Assam/Meghalaya) |
Heavy rainfall |
Bamboo houses on stilts
to avoid flooding |
Light cotton; traditional
woven fabrics |
|
Punjab/Haryana |
Extreme heat and cold |
Flat-roofed brick homes;
thick walls |
Cotton in summer; heavy
woolens in winter |
Conclusion: The
design of houses and style of clothing in each region are directly adapted to
its local climate and geography, reflecting how human life is
shaped by the environment.
In-Text Activities Summary
📌 Think About It (Page 39)
Task: Can
you imagine what would happen if there were no atmosphere? Discuss your
thoughts with your friends and teachers. (Hint: No air to breathe, no
protection from UV radiation, extreme temperature swings, no weather, no water
cycle, no life.)
📌 Let's Recall (Page 40)
Task: How
is nitrogen useful for plants? (Refer to Grade 8 Science — 'The Invisible
Living World') (Hint: Nitrogen is essential for making proteins and
chlorophyll; plants absorb it through nitrogen-fixing bacteria in the soil.)
📌 Think About It (Page 45)
Task: You
might have noticed that sometimes the wind is so strong it is difficult to walk
against it. Can you think of some other times when strong winds have caused
problems for you? (Personal observation — students write from experience.)
📌 Let's Explore — Wind (Page 46)
Task: Find
out other categories of wind based on speed and their common effects and share
your findings in class. (Refer to the Beaufort Scale for complete wind
categories.)
📌 Let's Analyse — Weather Report (Page
47)
Task: Note
down the weather report from a local newspaper for two weeks and observe the
changes occurring in the weather.
📌 Think About It — Rāgas and Seasons
(Page 48)
Task: Hindustani
Classical music associates certain rāgas with specific seasons. Find out which
rāgas are connected to each season with the help of your elders and
teachers. (Examples: Rāga Megh Malhar — Monsoon; Rāga Basant — Spring;
Rāga Bhairavī — Winter mornings)
📌 Let's Explore — Monsoon and Daily Life
(Page 52)
Task: Describe
in your own words how monsoon affects the lives of the people around you. (Personal/local
observation — students write from experience.)
📌 Let's Explore — Carbon Footprint
Activity (Pages 53–54)
(Described in full above
under the Climate Change section)
📌 Classroom Discussion — Punjab Floods
2025 (Page 56)
(Discussed in full above
under the Case Study section)
Quick Revision: Key Terms at a Glance
|
Term |
Meaning |
|
Atmosphere |
Blanket of mixed gases
surrounding the Earth, held by gravity |
|
Insolation |
Incoming solar energy
intercepted by the Earth |
|
Altitude |
Height above mean sea
level |
|
Troposphere |
Lowest atmospheric layer;
all weather occurs here |
|
Stratosphere |
Second layer; contains
ozone; aeroplanes fly here |
|
Mesosphere |
Third layer; meteorites
burn up here |
|
Thermosphere |
Fourth layer; auroras
occur here; radio waves reflected |
|
Exosphere |
Outermost layer; very
thin air |
|
Weather |
Hour-to-hour/day-to-day
atmospheric conditions |
|
Climate |
Average weather over a
large area for 30+ years |
|
Humidity |
Presence of water vapour
in the air |
|
Precipitation |
Water falling from
atmosphere (rain, snow, hail, etc.) |
|
Monsoon |
Seasonal reversal of wind
direction |
|
Mausim |
Arabic word meaning
'season'; origin of the word 'monsoon' |
|
Nakṣhatras |
Lunar mansions; 27
divisions of the sky used in Indian astronomy |
|
IMD |
Indian Meteorological
Department |
|
NMM |
National Monsoon Mission |
|
Carbon Footprint |
Total greenhouse gases
released by human activities |
|
Climate Change |
Long-term change in
weather patterns due to human activities |
|
NDMA |
National Disaster
Management Authority |
Notes compiled from NCERT
Class IX Social Science Textbook — "Understanding Society: India and
Beyond" (Part 1), First Edition, June 2026.
*******