Class 9 – Chapter 3: Atmosphere and Climate (NCERT BOOK)

-

 Class 9 – Chapter 3: Atmosphere and Climatehttps://link.amazon/B01vdn9oG

1. Atmosphere:- The atmosphere is the blanket of air surrounding the Earth.

  • Held by Earth's gravity.
  • Essential for life because it:
  • Provides oxygen.
  • Protects Earth from harmful UV rays.
  • Maintains Earth's temperature.
  • Controls weather and climate.

2. Composition of Atmosphere:- Gas Percentage

  • Nitrogen 78%
  • Oxygen 21%
  • Argon 0.93%
  • Carbon dioxide 0.04%
  • Other gases 0.03%
  • Other Components
  • Water vapour (0.1–0.4%)
  • Dust particles

Importance

  • Nitrogen helps plant growth.
  • Oxygen supports life.
  • Carbon dioxide is used in photosynthesis.
  • Water vapour forms clouds and rainfall.

Altitude:-  The height of a locationabove mean sea level is called altitude. Usually mesured in meteres or feet. The mean sea level is considered zero.

3. Layers of the Atmosphere

(i) Troposphere

  • Height: 0–12 km
  • Weather changes occur here.
  • Contains air, clouds and water vapour.
  • Temperature decreases with height.
  • Tropopause:- The Troposphere is seperated from the stratosphere by a transition zone known as the tropopause.

(ii) Stratosphere

  • 12–50 km
  • This layer free of clouds or others weather disturbances
  • Aeroplanes fly here.
  • Contains Ozone Layer.
  • Thi layer protect from ultraviolet radiation (UV).

(iii) Mesosphere

  • 50–80 km
  • Meteors burn here.
  • Temperature decreases with height.

(iv) Thermosphere

  • 80–700 km
  • Temperature increases.
  • Gas molecules in this layer absorb the X rays and short-wave ultraviolet radiation
  • Contains Ionosphere.
  • Radio communication and Aurora occur here.
  • Meaning and Origin of AuroraMeaning: Refers to the early morning dawn or the glowing polar lights in the night sky (like the Northern Lights).
  • Word Origin: Comes from Latin (aurora, meaning "dawn") and the ancient Roman goddess of the morning light

(v) Exosphere

  • Outermost layer.
  • Very thin air.
  • Mainly hydrogen and helium gases due to weak gravity. 

4. Weather and Climate

Weather:- Day-to-day condition of the atmosphere. It Changes frequently.

Climate:- Average weather of a place for 30 years or more.

5. Elements of Weather and Climate

Temperature

  • Controlled by Insolation.
  • Decreases from equator to poles.
  • Insolation:- The incoming solar energy from the Sun that is intercepted by the Earth. 

Humidity

  • Amount of water vapour in the air.
  • More humidity → more moisture and discomfort.
  • The level of water vapour in the air are  high, it leads to humidity.

Precipitation:-Forms:

  • Rain
  • Snow
  • Drizzle
  • Sleet
  • Hail

Atmospheric Pressure

  • Pressure exerted by air.
  • It is highest at sea level and decrease with altitude.
  • High pressure → clear weather and sunny skies.
  • Low pressure → cloudy and rainy (wet) weather.
  • Air always moves high pressure area to low pressure areas.

Wind

  • Air moves from high pressure to low pressure.
  • Named after the direction from which it blows.

6. Local Winds

Sea Breeze

  • Blows Sea → Land
  • Occurs during daytime
  • Land heats faster.

Land Breeze

  • Blows Land → Sea
  • Occurs during night
  • Land cools faster.

7. Seasons in India (IMD)

1. Winter

  • December–Early April
  • Coldest month of the year are December and January.
  • North-West temperature:- 10-15 degree.
  • South-East:- 20-25 degree. Temperature increasetowards the equator.
2. Summer (Pre-Monsoon)
  • April–June, or up to july in north-western India.
  • April is the hottest month in western and southern regions.
  • Average temperatur ranges:- 32-40 degree C
  • 3. Monsoon (Advancing)
  • June–September
  • This season dominated by the humid in south-west summer monsoon.
  • Monsoon rain begins to recede from north India at the beginning of October.
  • South India receives more rainfall during this time. 

4. Post-Monsoon (Retreating):- October–December

Traditional Indian Seasons (6 Ṛtus)

  • Vasanta
  • Grīṣhma
  • Varṣhā
  • Śharad
  • Hemanta
  • Śhiśhira

8. Monsoon:- Seasonal reversal of winds. 

A monsoon is a seasonal shift in wind direction that brings heavy rainfall. The word originates from the Arabic word mawsim, which means "season".

lunar mansions nakshatra

  • A nakshatra is a lunar mansion or equal segment of the sky. The sky circle is divided into 27 distinct parts.
  • Definition: A segment of the path of the Moon through the heavens, named after a bright star or group of stars inside or near it.
  • The Moon's Journey: The Moon takes about 27.3 days to circle the Earth, spending roughly one day in each mansion.

South-West Monsoon (Summer Monsoon)

  • June–September. 
  • Winds blow Sea → Land. across the Indian Ocean, the Arbian Sea, and The Bay of Bengal.
  • Brings most rainfall in India.
  • Origin and Moisture: Arises due to intense low pressure over the Indian landmass, bringing heavy moisture-laden winds from the Arabian Sea and the Bay of Bengal.
  • Rainfall: Acts as the primary rainy season, providing about 75% to 80% of India's total annual rainfall.
  • Onset: Starts with a sudden "monsoon burst" over the southern coast of Kerala in the first week of June

North-East Monsoon (Winter Rainfall)

  • October–February
  • Winds blow Land → Sea
  • Origin and Moisture: Arises due to high pressure over the northern landmass and low pressure over the sea; winds are mostly dry except when passing over the Bay of Bengal.
  • Rainfall: Covers a smaller area and brings rain mainly to the southeastern coast of India, particularly Tamil Nadu and parts of Andhra Pradesh.
  • Other Name: Also known as the retreating monsoon as it marks the withdrawal of the southwest monsoon

Gives rainfall mainly to:

  • Tamil Nadu
  • Andhra Pradesh
  • Parts of Karnataka

Importance

  • Agriculture
  • Water supply
  • Economy
  • Rivers and reservoirs

Problems

  • Excess rain → Floods
  • Less rain → Droughts

9. Climate Change:-  Long-term changes in weather caused mainly by human activities.

Causes

  • Burning fossil fuels
  • Deforestation
  • Industrial pollution
  • Greenhouse gases

Effects

  • Global warming
  • Melting glaciers
  • Floods
  • Droughts
  • Rising sea level
  • Loss of biodiversity
  • Ways to Reduce
  • Save electricity
  • Plant trees
  • Use renewable energy
  • Reduce carbon footprint
  • Follow sustainable lifestyle.

10. Carbon Footprint:- Total greenhouse gases released due to human activities.

Reduce by

  • Walking/cycling
  • Using public transport
  • Saving electricity
  • Conserving water
  • Recycling and reducing plastic use.

11. Punjab Floods (2025) – Case Study

Natural Causes

  • Very heavy monsoon rainfall
  • Western disturbances
  • Overflowing rivers

Human Causes

  • Weak embankments
  • Encroachment near rivers
  • Silt in rivers
  • Poor flood warning system

Effects

  • Loss of lives
  • Damage to crops
  • Damage to roads and bridges
  • Disease outbreaks
  • Economic losses.
https://link.amazon/B01vdn9oG:- Imagimake DIY Mandala Art Kit | Art & Craft Kit for Girls Age 8+

Comments

Post a Comment

Popular posts from this blog

Chapter - 3 The Dynamic Atmosphere and Changing Climate (Class- 9)

-
Chapter - 3   The Dynamic Atmosphere and Changing Climate What is Atmosphere:-  The atmosphere is a layer of gases that surrounds the Earth. It is made up of gases like Nitrogen (78%), Oxygen (21%), and small amounts of Carbon dioxide, Argon, and Water vapour. It protects life on Earth and makes it possible for living organisms to survive. Why is the Atmosphere Important:-  The atmosphere plays a very important role: Provides Oxygen – Needed for breathing by humans and animals. Supports Life – Plants use carbon dioxide for photosynthesis. Protects Earth – Shields us from harmful rays of the Sun. Maintains Temperature – Keeps Earth warm enough for life (greenhouse effect). Weather Formation – Clouds, rain, wind, and storms happen in the atmosphere. What is Climate:-  Climate is the average weather condition of a place over a long period of time (years or decades). It includes temperature, rainfall, humidity, and wind patterns. Importance of Climate Affects Agricu...
Read more

Chapter - 4 The Stone Age – The Earliest People

-
 Chapter - 4 The Stone Age – The Earliest People Who were the Earliest People? The earliest humans lived millions of years ago. They are known as hunter-gatherers. They depended on nature for food (hunting animals and gathering fruits, roots, seeds). They lived in caves, rock shelters, or under trees. They had no permanent homes and moved from place to place (nomadic life). Features of Early Humans Use of Stone Tools – For cutting, hunting, and protection Discovery of Fire – Used for cooking, warmth, and safety Group Living – For protection from wild animals No Farming – They did not grow crops initially Simple Life – No writing, no permanent houses Division of the Stone Age The Stone Age is divided into three main periods: 1. Palaeolithic Age (Old Stone Age) Time: About 2 million years ago to 10,000 BCE People used rough, unpolished stone tools Lived in caves and were completely dependent on nature Main activities: Hunting and gathering Discovery of fire Example sites: Bhimbetka (...
Read more

Worksheet: Geography (Class 9) Chapter 2 – Shaping of the Earth

-
 Worksheet: Geography (Class 9) Chapter 2 – Shaping of the Earth Section A – Very Short Answer (1 mark each) (Answer in one or two sentences) What is meant by shaping of the Earth? Name the two main types of forces responsible for shaping the Earth. What are endogenic forces? What are exogenic forces? Which is the outermost layer of the Earth? What is the main composition of the core? What are tectonic plates? Define weathering. Define erosion. Name any one agent of erosion. Section B – Short Answer (2–3 marks each) Differentiate between internal and external forces. Write any two characteristics of the crust. Explain the role of convection currents in the mantle. What happens at a divergent boundary? What is a convergent boundary? Explain physical weathering with an example. How do rivers cause erosion? What are glaciers? How do they shape landforms? Write any two differences between weathering and erosion. What are coastal landforms? Section C – Long Answer (4–5 marks each) Descr...
Read more