1. Introduction
The atmosphere is the vast envelope of gases that surrounds the Earth. It is essential for life because it provides the gases required by living organisms and helps regulate the temperature of the Earth.
2. Composition of the Atmosphere
The atmosphere consists mainly of nitrogen and oxygen, along with small amounts of other gases and variable quantities of water vapour.
| Gas | Approximate Amount | Importance |
|---|---|---|
| Nitrogen | 78% | Important in the nitrogen cycle and essential for plant growth. |
| Oxygen | 21% | Essential for respiration and combustion. |
| Other gases | About 1% | Includes argon, carbon dioxide and other gases. |
3. Layers of the Atmosphere
On the basis of altitude and changes in temperature, the atmosphere is divided into several layers.
Troposphere
The troposphere is the lowest layer of the atmosphere. Human beings live within this layer. Most weather phenomena, including clouds, rainfall and storms, occur here.
Stratosphere
The stratosphere lies above the troposphere. The ozone layer is found in this region. Ozone absorbs a large part of the harmful ultraviolet radiation coming from the Sun.
Mesosphere
The mesosphere lies above the stratosphere. Temperature generally decreases with height in this layer. Many small meteoroids burn up because of friction in this region.
Thermosphere
The thermosphere is a very high layer of the atmosphere. It is strongly affected by high-energy radiation from the Sun.
Exosphere
The exosphere is the outermost region of the atmosphere. It gradually merges with outer space.
4. Weather and Climate
Weather: The condition of the atmosphere at a particular place and time is called weather.
Climate: The long-term average pattern and characteristics of weather of a place are called its climate.
| Weather | Climate |
|---|---|
| Short-term atmospheric condition | Long-term pattern of weather |
| Can change quickly | Changes relatively slowly |
| Observed over hours or days | Studied using long-term observations |
5. Temperature
Temperature indicates how hot or cold a place or object is. The temperature of the Earth's surface varies from place to place.
Important factors affecting temperature include:
- Latitude
- Altitude
- Distance from the sea
- Distribution of land and water
- Cloud cover
- Winds
- Ocean currents
6. Air Pressure
Air pressure is the pressure exerted by the weight of the atmosphere on the Earth's surface.
7. Winds
The horizontal movement of air from one place to another is called wind. Winds generally move from areas of higher pressure towards areas of lower pressure.
Main Types of Winds
- Permanent or planetary winds
- Seasonal winds
- Local winds
8. Humidity
Humidity refers to the amount of water vapour present in the air. Warm air can generally hold more water vapour than cold air.
9. Condensation and Precipitation
Condensation is the process by which water vapour cools and changes into tiny water droplets or ice particles.
Precipitation is the process through which water falls from clouds to the Earth's surface in forms such as rain, snow or other forms of precipitation.
10. Indian Monsoon
The monsoon is one of the most important features of India's climate. Seasonal changes in wind direction bring moisture from the surrounding seas and contribute to rainfall over large parts of India.
- Provides water for agriculture.
- Helps replenish rivers and reservoirs.
- Supports groundwater recharge.
- Influences India's economy and livelihoods.
11. Climate Change
Climate change refers to significant changes in the long-term patterns of temperature, rainfall and other characteristics of the climate.
Human activities such as burning fossil fuels, deforestation and certain industrial activities can increase the concentration of greenhouse gases in the atmosphere.
12. Greenhouse Effect
Certain gases in the atmosphere absorb and re-emit part of the heat radiated by the Earth's surface. This natural process is known as the greenhouse effect and helps keep the Earth warm enough for life.
13. Carbon Footprint
A carbon footprint refers to the total greenhouse gas emissions associated directly or indirectly with a person, organisation, activity or product.
Ways to Reduce Carbon Footprint
- Save electricity and energy.
- Use public transport when possible.
- Plant and protect trees.
- Promote renewable sources of energy.
- Reduce unnecessary consumption.
- Reuse and recycle materials.
14. Quick Revision
- The atmosphere is the gaseous envelope surrounding Earth.
- Nitrogen and oxygen are the two major gases in the atmosphere.
- Most weather phenomena occur in the troposphere.
- The ozone layer is associated with the stratosphere.
- Weather is a short-term atmospheric condition.
- Climate describes the long-term pattern of weather.
- Winds generally move from high-pressure areas towards low-pressure areas.
- The Indian monsoon is extremely important for agriculture and water resources.
- Human activities can influence climate change through greenhouse gas emissions.
15. Important Terms
| Term | Meaning |
|---|---|
| Atmosphere | The gaseous envelope surrounding the Earth. |
| Weather | The atmospheric condition at a particular time and place. |
| Climate | The long-term pattern of weather of a place. |
| Humidity | The amount of water vapour present in the air. |
| Air Pressure | The pressure exerted by the atmosphere. |
| Condensation | The change of water vapour into liquid water droplets or ice particles. |
| Precipitation | Water falling from clouds to the Earth's surface. |
16. Important Examination Questions
- What is the atmosphere?
- Describe the major layers of the atmosphere.
- Differentiate between weather and climate.
- Explain the major factors affecting temperature.
- Explain the relationship between air pressure and winds.
- What are humidity and condensation?
- Explain the importance of the Indian monsoon.
- What is climate change?
- What is the greenhouse effect?
- What is a carbon footprint? Mention ways to reduce it.
Atmosphere → Layers → Temperature → Air Pressure → Winds → Humidity → Precipitation → Monsoon → Climate Change