ATMOSPHERE

ATMOSPHERE

Composition: The Earth’s atmosphere is a mixture of gases such as nitrogen, oxygen, carbon dioxide, hydrogen, helium, and other gases, along with water vapor and dust particles. The two most abundant gases are nitrogen and oxygen, while the others like carbon dioxide, hydrogen, and helium form the rest.

Role of Earth’s Atmosphere:

1. Supplies lifesaving gases: Plants rely on carbon dioxide, and animals (including humans) need oxygen. The atmosphere provides these essential gases for life.
2. Regulates solar radiation: It allows the correct range of solar radiation to pass through, enabling biophysical processes for living organisms. It also protects life by regulating the entry of solar radiation.
3. Maintains temperature: The atmosphere helps maintain temperature within habitable limits, preventing extreme temperature fluctuations between day and night.
4. Protects from UV rays: The ozone layer (in the stratosphere) absorbs harmful ultraviolet (UV) rays, protecting life on Earth.
5. Protects from extraterrestrial objects: The atmosphere (especially the mesosphere) burns up meteors and other extraterrestrial objects through friction as they pass through.
6. Regulates weather: It influences various weather processes, impacting plant growth, agriculture, and human settlements by managing climate and weather patterns.

Layers of the Atmosphere

The atmosphere is structured in layers, each with varying temperatures and densities. From the surface upwards, the layers include:

• Troposphere (0 to 12-18 km)
• Stratosphere (11 to 50 km)
• Mesosphere (50 to 80-90 km)
• Thermosphere (80 to 700 km)
• Exosphere (700 to 3000 km)

TROPOSPHERE

Definition: The lowest region of the atmosphere, extending from the Earth’s surface up to around 8-15 kilometers. It is characterized by a decrease in temperature with increasing altitude.

Significance of the Troposphere:

• Meteorological significance: All weather conditions such as temperature inversion, turbulence, and air eddies occur in this layer.
• Changing sphere: The troposphere is dynamic, with constantly moving air, earning it the name “changing sphere.”
• Rainfall: Most weather phenomena, including rainfall, fog, and hailstorms, occur in this layer.
• Smog formation: Smog forms here, affecting visibility and causing irritation to the eyes and throat.
• Hydrologic cycle: This layer holds around 85% of the atmosphere’s total mass and plays a crucial role in the water cycle (cloud formation, precipitation) and greenhouse effects, influencing meteorology and climate.
• Monsoon onset: Jet streams in the tropopause play a role in the onset of the monsoon in India and other phenomena like polar vortexes.
• Other weather phenomena: Cyclones, thunderstorms, tornadoes, anti-cyclones, heatwaves, cold waves, and local winds also occur here.

STRATOSPHERE

• Definition: The second layer of the atmosphere, extending up to 50 kilometers from the Earth’s surface. This layer is above the troposphere.

Significance of the Stratosphere:

• Ideal for flying aeroplanes: It is largely free from clouds and turbulent weather, making it the perfect zone for flying aircraft. Aircraft typically fly in the lower stratosphere where the weather is calm.
• Protects from UV rays: The stratosphere contains the ozone layer, which absorbs around 90% of the harmful UV radiation from the Sun, thus protecting life on Earth from diseases like skin cancer and sunburn.
• Cooling effect during volcanic eruptions: When volcanoes erupt, the ejected particles can reach the stratosphere, and due to the slow circulation in this layer, volcanic particles remain suspended for a long time, helping cool the Earth’s surface.

MESOSPHERE

• Definition: The third layer of the atmosphere, located above the stratosphere, extending up to a height of 80 kilometers. It is found between the thermosphere and the stratosphere. The mesosphere is the third layer of the atmosphere, found above the stratosphere and below the thermosphere. It extends up to 80 km from the Earth’s surface.

Significance of the Mesosphere:

• Prevents celestial rocks from entering the Earth: The mesosphere protects Earth by burning up meteors and asteroids due to friction with air molecules, creating shooting stars.
• Protection from UV rays: Like the stratospheric ozone layer, the mesosphere also shields us from harmful ultraviolet (UV) radiation.
• Northern Lights: Northern Lights (aurora borealis) and related phenomena occur in this layer, which also has high tourist and economic value in certain regions.
• Helps spacecraft in returning: The mesosphere plays a crucial role when spacecraft re-enter the atmosphere by providing aerodynamic resistance, which assists in braking.
• Climate change study: The supercooling of this layer, due to its low temperature and other factors, helps in studying the changing climate.

THERMOSPHERE

• Definition: The thermosphere is located above the mesosphere, between 80 km and 400 km above the Earth’s surface. It contains ionized particles, and the ionosphere is part of this layer.

Significance of the Thermosphere:

• Helps in radio transmission: The thermosphere contains ionized particles that allow for the reflection of radio waves, enabling radio communication.
• Disintegration of molecules: Meteorites disintegrate as they enter this layer, due to the thermosphere’s composition.
• Aurora Borealis: The northern lights occur in this layer as solar wind particles interact with the Earth’s magnetic field.
• Thermospheric storms: Large magnetospheric storms can produce thermospheric storms, which impact satellite communication and other technologies.

EXOSPHERE

• Definition: The exosphere is the outermost layer of the atmosphere, extending beyond 400 km. It merges with outer space.

Significance of the Exosphere:

• Floating gases: In this layer, the density of gases is very sparse due to minimal gravitational force, allowing light gases such as hydrogen and helium to float into space.
• Formation of outer space: Most of the exosphere’s molecules are pulled back to Earth by gravity, while some escape into space due to low gravity and atmospheric pressure.
• First line of protection: Although the exosphere is the outermost layer of the Earth’s atmosphere, it also serves as the planet’s first line of defense against harmful cosmic rays, asteroids, and meteors.
• Place for satellites: Artificial satellites orbit in the exosphere, gathering data on both outer space and the Earth.
• Pressure by wind storms: The exosphere experiences pressure caused by solar wind storms, which compress this layer.