Definition of Atmosphere :
The atmosphere is the layer of gases that surrounds the Earth. It is held in place by gravity and protects the Earth from harmful solar radiation. The atmosphere is made up of a mixture of gases, including nitrogen, oxygen, argon, carbon dioxide, and water vapor. The composition of the atmosphere varies with altitude.
Composition of Atmosphere :
- Nitrogen (78%): The most abundant gas, crucial for plant growth and various biological processes.
- Oxygen (21% ): Vital for respiration in humans, animals, and combustion processes.
- Argon (0.93%): An inert gas that doesn't readily react with other elements.
- Carbon Dioxide (0.04%): Essential for photosynthesis in plants and a greenhouse gas that regulates Earth's temperature.
- Trace Gases: These include water vapor, neon, helium, methane, and ozone, among others.
Layers of Atmosphere :
Troposphere:
- This is the lowest layer of the atmosphere and is where virtually all weather phenomena, including clouds, rain, snow, and storms, occur in the troposphere.
- It extends from the Earth's surface up to about 12 kilometers (7.5 miles).
- The temperature in the troposphere decreases with altitude, at a rate of about 6.5 degrees Celsius (11 degrees Fahrenheit) per kilometer. This temperature gradient is known as the "lapse rate."
- The troposphere contains about 75% of the mass of the atmosphere.
Stratosphere:
- This layer lies above the troposphere and extends up to about 50 kilometers (31 miles).
- "Planes fly in the lower stratosphere because the air there is stable and less bumpy.
- The temperature in the stratosphere increases with altitude, due to the absorption of ultraviolet radiation by ozone gas.
- The ozone layer is located in the stratosphere and protects life on Earth from harmful ultraviolet radiation.
- Ozone Layer: The stratosphere contains the ozone layer, which absorbs and filters out harmful ultraviolet (UV) radiation from the Sun, protecting life on Earth.
Mesosphere:
- This layer lies above the stratosphere and extends up to about 80 kilometers (50 miles).
- The temperature in the mesosphere decreases with altitude.
- The mesosphere is the coldest layer of the atmosphere.
- Meteoroid Destruction Layer: Meteors entering the Earth's atmosphere burn up in the mesosphere due to friction with air molecules.
Thermosphere / Ionsphere :
- This layer lies above the mesosphere and extends up to about 600 kilometers (373 miles).
- The temperature in the thermosphere increases with altitude, due to the absorption of solar radiation by atmospheric gases.
- The thermosphere is where the aurora borealis (northern lights) and aurora australis (southern lights) occur.
- Ionosphere: Within the thermosphere lies the ionosphere, a region filled with ionized particles. It plays a crucial role in radio communication and the reflection of radio waves.
- International Space Station (ISS): The ISS orbits within the thermosphere, experiencing extreme temperature variations during its 90-minute orbits.
Exosphere:
- This is the outermost layer of the atmosphere and extends beyond 600 kilometers (373 miles).
- The atmosphere gradually fades into space in the exosphere.
- Satellite Orbits: Many artificial satellites, including communication and navigation satellites, orbit within the exosphere.
Revision Points :
The Earth's atmosphere is a thin layer of gases surrounding our planet, held in place by gravity. It serves as a protective shield, regulating temperature, distributing water vapor, and providing essential functions for life. Here are the key points:
1. Protection from Solar Radiation:
- The atmosphere shields Earth from harmful solar radiation, including ultraviolet rays, which can damage living cells.
2. Oxygen Supply:
- It contains approximately 21% oxygen, crucial for respiration and supporting life on Earth.
3. Temperature Regulation:
- The atmosphere traps heat from the sun, maintaining a habitable temperature range on the planet.
4. Water Cycle:
- It facilitates the water cycle by allowing water vapor to rise and form clouds, which eventually release precipitation, essential for life.
5. Sound Transmission:
- Sound waves travel through the atmosphere, enabling communication and our ability to hear.
6. Ozone Layer:
- The stratosphere contains the ozone layer, protecting life from harmful UV radiation.
7. Infrared Reflection:
- It reflects some of the Earth's emitted infrared radiation, helping to keep the planet warm.
8. Climate Change Mitigation:
- The atmosphere absorbs greenhouse gases, mitigating the effects of climate change.
9. Support for Life:
- It provides oxygen for breathing, vital for both plant and animal life.
- It distributes water vapor essential for plant growth.
10. Meteor Protection: - The atmosphere slows down and burns up meteors, preventing them from impacting Earth's surface.
11. Weather and Climate: - Different atmospheric layers interact to create various weather patterns and the overall climate of the planet.
Notable Points :
The atmosphere is a dynamic system and the layers are not always well-defined. The boundaries between the layers can vary depending on factors such as latitude, season, and time of day.
The atmosphere is essential for life on Earth. It provides oxygen for breathing, helps to regulate the Earth's temperature, and protects the Earth from harmful solar radiation. The atmosphere is also important for weather and climate.
The atmosphere is constantly changing, and these changes can have a significant impact on the Earth's climate. Human activities are one of the main causes of changes in the atmosphere. These activities include the burning of fossil fuels, which releases greenhouse gases into the atmosphere. Greenhouse gases trap heat in the atmosphere, which can lead to global warming.
Global warming is a serious problem that is already having a negative impact on the Earth's climate. It is important to take steps to reduce greenhouse gas emissions and mitigate the effects of climate change.
