Introduction
Imagine standing on a high mountain without any air to breathe. Sounds scary, right? The atmosphere is like a protective blanket of air that surrounds our Earth. It's what makes life possible by providing the air we breathe, protecting us from harmful sun rays, and maintaining the perfect temperature for living beings.
The word "atmosphere" comes from two Greek words: "atmos" meaning vapor and "sphaira" meaning sphere. So, atmosphere literally means "sphere of vapor."
In this article, we’ll explore the composition, layers, and importance of the atmosphere in simple language — useful for students preparing for UPSC, SSC, Railway, and other exams
.
Table of Contents
What is Atmosphere?
The atmosphere is the layer of gases that surrounds our planet Earth, held in place by Earth's gravity. It's composed of a mixture of gases we call "air" and extends hundreds of kilometers above the Earth's surface.
Key Characteristics:
a) It's colorless, odorless, and tasteless
b) It's essential for life on Earth
c) It protects us from meteoroids and harmful solar radiation
d) It helps regulate Earth's temperature
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Composition of the Atmosphere
The atmosphere is made up of different gases mixed together. Just like a dal
khichdi has rice, dal, and spices mixed in specific amounts, the atmosphere has
gases mixed in specific percentages.
Major
Gases in the Atmosphere
|
Gas Name |
Chemical Symbol |
% |
Important Facts |
|
Nitrogen |
N₂ |
78.08% |
Most abundant gas; helps plants grow |
|
Oxygen |
O₂ |
20.95% |
Essential for breathing and burning |
|
Argon |
Ar |
0.93% |
Inactive gas; used in bulbs |
|
Carbon Dioxide |
CO₂ |
0.04% |
Causes greenhouse effect; plants need it |
|
Other Gases (Neon, Helium, Hydrogen, Ozone, etc.) |
Various |
0.002% |
Includes neon, helium, methane |
Example for Exams: If you see a question asking "Which is the most abundant gas in atmosphere?" - the answer is always Nitrogen, not Oxygen. Many students make this mistake.
Variable Components
Some substances in the atmosphere keep changing their amounts:
Water Vapor: Can be 0% to 4% depending on location. Near coastal areas like Mumbai, water vapor is high. In deserts like Rajasthan, it is very low.
Dust Particles: These tiny particles float in air. They help in:
§ Cloud formation (rain clouds need dust to form)
§ Making beautiful sunsets (red and orange colors)
§ Reflecting sunlight back to space
Example: When you see haze in Delhi during
winter, that's because of dust particles and pollution mixing in the
atmosphere.
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Structure of the Atmosphere
The atmosphere is divided into five
main layers, just like a five-story building. Each floor (layer) has different
characteristics.
Layers
of Atmosphere from Bottom to Top
|
Layer Name |
Height from Earth |
Temperature Pattern |
Key Features |
|
Troposphere |
0-12 km |
Decreases with height |
Weather happens here; we live here |
|
Stratosphere |
12-50 km |
Increases with height |
Ozone layer protects us |
|
Mesosphere |
50-80 km |
Decreases with height |
Meteors burn here |
|
Thermosphere |
80-400 km |
Increases with height |
Aurora lights; satellites orbit |
|
Exosphere |
400-10,000 km |
Very thin air |
Merges with space |
1. Troposphere: The Weather Layer
This is the most important layer for us. All human activities happen here.
Key Points:
a.
Contains 75% of atmosphere's total mass.
b. All weather phenomena occur here (rain, clouds, storms).
c. Temperature decreases by 6.5°C for every 1 km height.
d. The boundary between troposphere and stratosphere is called "tropopause".
Example: When you travel from Delhi to Shimla (2000m high), you feel cold because temperature drops as you go higher. This happens in the troposphere.
Exam Tip: The height of troposphere is maximum at the Equator (18
km) and minimum at the Poles (8 km). This question appears frequently in SSC
exams.
2. Stratosphere: The Protective Layer
This layer contains the ozone layer which protects us from harmful sun rays.
Key Points:
a.
Ozone (O₃)
absorbs ultraviolet radiation from the Sun
b. Temperature increases with height because ozone absorbs heat
c. Ideal for aircraft flying (no weather disturbances)
d. CFCs (from old refrigerators and ACs) damage the ozone layer
Example: Commercial airplanes like Boeing 737 fly at 10-12 km height, right at the boundary of troposphere and stratosphere, to avoid weather turbulence.
3. Mesosphere: The Meteor Layer
This is where shooting stars burn up.
Key Points:
a.
Coldest layer with temperatures dropping to -90°C
b. Protects Earth by burning meteors
c. Difficult to study because planes cannot fly so high and satellites orbit
above it
Example: When you see a shooting star during night, it is actually a meteor burning in the mesosphere layer.
4. Thermosphere: The Hot Layer
Despite its name suggesting heat, this layer has very few gas molecules.
Key Points:
a.
Temperature can reach 2000°C, but you won't feel hot because air is very thin
b. Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis)
occur here
c. International Space Station orbits in this layer
d. Radio waves are reflected back to Earth from here
Example: When you listen to All India Radio (AIR) from distant cities, radio waves bounce off the thermosphere and come back to your receiver.
5. Exosphere: The Outer Layer
This
is the outermost layer that gradually merges with space.
Key
Points:
a.
Extremely thin air
b. Satellites orbit here
c. No clear boundary with outer space
Trick
to Remember The Layers:
Use the phrase: "The Smart Man Travels Everyday"
(Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere).
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Functions of the Atmosphere
The atmosphere performs many important jobs that make life possible on Earth.
Protection from Sun's Harmful Rays
The ozone layer acts like sunscreen for Earth. It blocks 99% of harmful UV rays from the Sun.
Example: Countries like Australia have high skin cancer rates because there is an ozone hole above Antarctica. This shows how important the ozone layer is.
Maintaining Earth's Temperature
The atmosphere works like a blanket that keeps Earth warm.
The Greenhouse Effect Process:
1. Sunlight reaches Earth
2. Earth's surface absorbs heat and warms up
3. Earth releases this heat back into space
4. Greenhouse gases trap some of this heat
5. Earth stays warm enough for life
Important Greenhouse Gases:
§ Carbon Dioxide (CO₂)
§ Methane (CH₄)
§ Water Vapor (H₂O)
§ Nitrous Oxide (N₂O)
Example: Venus has a very thick atmosphere with lots of CO₂. Its temperature reaches 450°C. Mars has a very thin atmosphere, so it is freezing cold at -60°C. Earth's atmosphere is just right - this is called the "Goldilocks Zone."
Weather and Climate Formation
All weather events happen in the troposphere layer.
Weather Elements:
§ Temperature: How hot or cold it is
§ Pressure: Weight of air pressing down
§ Humidity: Amount of water vapor
§ Wind: Moving air from high pressure to low pressure
§ Precipitation: Rain, snow, hail
Example: During monsoon in India (June-September), moist winds from the Indian Ocean bring heavy rainfall. This happens because of atmospheric pressure differences.
Supporting Life
The atmosphere provides oxygen for breathing and carbon dioxide for plants.
Example: In Photosynthesis, plants take CO₂ from atmosphere and release O₂. Animals breathe O₂ and release CO₂. This is nature's balance.
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Atmospheric Pressure
Atmospheric pressure is the weight of air pressing down on Earth's surface.
Understanding Pressure Basics
|
Concept |
Explanation |
Example |
|
High Pressure |
Air sinks down; clear skies; no rain |
Desert areas like Rajasthan |
|
Low Pressure |
Air rises up; clouds form; rainfall |
Coastal areas during monsoon |
|
Normal Pressure |
1013.25 millibars at sea level |
Mumbai, Chennai coastal areas |
Important Fact: Atmospheric pressure decreases as we go higher because there is less air above us.
Example: On top of Mount Everest (8848m), atmospheric pressure is only one-third of sea level pressure. That's why climbers need oxygen cylinders.
Pressure Belts on Earth
Earth has seven pressure belts arranged in a pattern:
1. Equatorial Low Pressure Belt (0°-5° latitude)
§ Hot air rises creating low pressure
§ Heavy rainfall throughout the year
§ Example: Amazon rainforest, Congo Basin
2. Subtropical High Pressure Belts (25°-35° latitude)
§ Cool air sinks creating high pressure
§ World's major deserts are located here
§ Example: Sahara Desert, Thar Desert
3. Subpolar Low Pressure Belts (60°-65° latitude)
§ Warm and cold air meet
§ Stormy weather
§ Example: North Atlantic region
4. Polar High Pressure Belts (90° latitude)
§ Extremely cold air sinks
§ Very dry conditions
§ Example: Antarctica, North Pole
Atmospheric Phenomena
Several interesting events happen in the atmosphere that you should know for exams.
Wind Formation
Wind is simply air moving from high pressure areas to low pressure areas.
Types of Winds:
· Trade Winds: Blow from subtropical high to equatorial low
· Westerlies: Blow from subtropical high to subpolar low
· Polar Easterlies: Blow from polar high to subpolar low
Example: In India, during summer (March-May),
hot air over land creates low pressure. Cool air from ocean rushes in, bringing
pre-monsoon showers.
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Monsoon in India
Monsoon is the most important atmospheric phenomenon for India.
Summer Monsoon (June-September):
§ Low pressure over North India due to heat
§ Moisture-laden winds from Indian Ocean
§ Brings 75% of India's annual rainfall
§ Critical for agriculture and economy
Winter Monsoon (December-February):
§ High pressure over North India due to cold
§ Dry winds blow from land to sea
§ Brings rainfall to Tamil Nadu coast
Example: States like Meghalaya receive over 10,000mm rain during monsoon, while Rajasthan receives less than 500mm.
Clouds and Rainfall
Clouds form when water vapor in air condenses into tiny water droplets.
Types of Clouds:
(a)
Cirrus: High
altitude, thin, wispy clouds
(b) Cumulus:
Middle altitude, puffy white clouds
(c) Stratus:
Low altitude, layer clouds bringing drizzle
(d) Nimbus:
Dark rain clouds
Example: Before heavy rain in Mumbai during
monsoon, you see dark nimbus clouds covering the sky.
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Air Pollution
Release of harmful substances into the atmosphere.
Major Pollutants:
§ Particulate Matter (PM 2.5 and PM 10): Causes breathing problems
§ Carbon Monoxide (CO): From vehicle exhaust; poisonous
§ Sulfur Dioxide (SO₂): From factories; causes acid rain
§ Nitrogen Oxides (NOₓ): From vehicles; forms smog
Example: Delhi's Air Quality Index (AQI) reaches 400+ during winter due to stubble burning in Punjab and Haryana, vehicular pollution, and dust.
Global Warming and Climate Change
Increase in Earth's average temperature due to excessive greenhouse gases.
Causes:
§ Burning fossil fuels (coal, petrol, diesel)
§ Deforestation (cutting trees)
§ Industrial emissions
§ Agricultural activities (methane from cattle)
Effects:
§ Melting of glaciers in Himalayas
§ Rising sea levels threatening coastal cities
§ Extreme weather events (floods, droughts)
§ Changes in monsoon patterns
Example: Glaciers in Gangotri (source of Ganga) are retreating by 30 meters every year due to global warming.
Ozone Layer Depletion
Thinning of the ozone layer due to human-made chemicals.
Main Culprits:
§ CFCs from old refrigerators and air conditioners
§ Halons from fire extinguishers
§ Industrial solvents
Montreal Protocol (1987): International agreement to phase out
ozone-depleting substances. India signed it and has been successfully reducing
CFC use.
Mind Map:
❓ FAQs
Q1: What is the most abundant gas in the atmosphere?
Nitrogen is the most abundant gas making up 78.08% of the atmosphere. Many students mistakenly think it is oxygen, but oxygen is only 20.95%.
Q2:
Which layer of atmosphere has the ozone layer?
The ozone layer is located in the stratosphere, between 15-35 km above Earth's surface. It protects us from harmful UV rays.
Q3: Why do mountaineers carry oxygen cylinders?
At high altitudes, atmospheric pressure decreases, which means less oxygen is available. At Mount Everest's peak, oxygen is only one-third of what we get at sea level.
Q4:
What causes the greenhouse effect?
Greenhouse effect is caused by gases like carbon dioxide, methane, and water vapor that trap heat in the atmosphere. It keeps Earth warm, but too much causes global warming.
Q5:
In which layer do weather phenomena occur?
All weather phenomena like rain, clouds, storms, and lightning occur in the troposphere, the lowest layer of the atmosphere where we live.
Q6:
What is atmospheric pressure?
Atmospheric pressure is the weight of air pressing down on Earth's surface. At sea level, it is 1013.25 millibars. It decreases as we go higher.
Q7:
Why is the sky blue?
The sky appears blue because air molecules scatter blue light from the Sun more than other colors. This is called Rayleigh scattering.
Q8:
What is the difference between weather and climate?
Weather is the day-to-day atmospheric conditions (temperature, rain, wind) in a place. Climate is the average weather pattern of a place over 30-35 years.
Q9:
How does monsoon affect India?
Monsoon brings 75% of India's annual rainfall during June-September. It is vital for agriculture, water resources, and overall economy of the country.
Q10:
What are the effects of air pollution?
Air pollution causes breathing problems, lung diseases, reduced visibility, acid rain, and contributes to global warming. Cities like Delhi face severe air pollution during winter.
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Remember, consistent practice and revision are the keys to success in competitive exams. The atmosphere topic can give you easy marks if you prepare it well with proper understanding.
Good
luck with your preparation! Keep learning, keep growing!