Layers Of Atmosphere

The Earth’s atmosphere is divided into different layers because of the temperature, pressure, and composition variations with increasing altitude.

These distinct layers have evolved due to the complex interactions between solar radiation, gravity, and the gases that make up the atmosphere.

While Earth’s atmosphere is unique, other planets and celestial bodies in the solar system and beyond also have atmospheres, each with its composition and properties.

For example, Mars has a thin atmosphere primarily composed of carbon dioxide, while Venus has a thick, hot, and inhospitable atmosphere.

What is Atmosphere?

Usually, Earth’s atmosphere is primarily composed of a mixture of gases. The most abundant gases in the Earth’s atmosphere are nitrogen (about 78%) and oxygen (about 21%). Trace gases comprise the remaining percentage, including argon, carbon dioxide, neon, and others.

However, The composition and characteristics of Earth’s atmosphere can vary due to location, altitude, and environmental conditions.

For instance, the atmosphere at higher altitudes has lower pressure and less oxygen, making it challenging for humans to breathe without supplemental oxygen.

Layers of Earth

The Earth’s atmosphere is usually divided into several distinct layers, each with unique characteristics.

However, from the ground up, these layers include the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Each layer has specific properties related to temperature, pressure, and composition. There are five layers of atmosphere.

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Troposphere:

The troposphere is the lowest layer of the atmosphere and is where weather occurs. It extends from the Earth’s surface to an altitude of about 8-15 kilometres (5-9 miles), depending on location and season. Usually, temperature generally decreases with altitude in this layer.

Typically, the troposphere is primarily composed of a mixture of gases, including nitrogen (about 78%), oxygen (about 21%), and trace amounts of other gases, including water vapour, carbon dioxide, and argon.

Water vapour content varies with location and weather conditions and plays a critical role in weather processes.

Generally, temperature in the troposphere decreases with increasing altitude. This temperature decrease is called the “lapse rate” and averages about 6.5 degrees Celsius per kilometre (3.5 degrees Fahrenheit per thousand feet).

This decrease in temperature is why it’s colder at higher altitudes, such as on mountains.

However, many human activities, such as air travel, agriculture, and pollution, directly impact the troposphere.

Besides, this layer of the atmosphere is where aircraft operate, and pollutants released at the surface can be transported and dispersed within this layer.

Besides, The troposphere is vital for sustaining life on Earth. It contains the oxygen we breathe, the water vapour that forms clouds and precipitation, and the atmospheric processes that regulate temperature and weather conditions.

In summary, the troposphere is the layer of the atmosphere closest to the Earth’s surface, where weather processes occur, and it plays a critical role in regulating our climate and supporting life on our planet.

Stratosphere:

The stratosphere is the second major layer of Earth’s atmosphere, located directly above the troposphere and closest to Earth’s surface.  This layer extends from about 15 kilometres (9 miles) to about 50 kilometres (31 miles) above the Earth’s surface.

Further, the Stratosphere include the ozone layer. The ozone layer is characterized by a relatively high concentration of ozone molecules.

The ozone layer absorbs and scatters a significant portion of the Sun’s harmful ultraviolet (UV) radiation. This helps in protecting life on Earth from the harmful effects of excessive UV exposure.

Especially the stratosphere exhibits a unique temperature profile. In the lower stratosphere, temperatures remain relatively constant or may increase slightly with altitude.

This temperature stability is due to ozone molecules’ absorption of solar radiation, creating a warming effect.

Normally, Commercial jet aircraft often operate within the lower stratosphere.

This region is generally characterized by stable and clear air. This layer’s absence of weather-related turbulence makes it an ideal altitude for long-distance air travel.

While the stratosphere is not directly involved in weather patterns, it plays a crucial role in the Earth’s climate system.

Human activities, particularly the release of certain chemicals known as ozone-depleting substances, have led to the depletion of ozone in the stratosphere.

This resulted in the phenomenon known as the ozone hole in certain regions, such as Antarctica. International agreements, such as the Montreal Protocol, have been established to limit the use of these substances and protect the ozone layer.

Under the Environment (Protection) Act of 1986, the Government of India has banned CFC in India. Per this rule, no person may distribute or sell such products in interstate commerce, including import and export banned products.

Mesosphere:

The mesosphere is the third layer of the atmosphere. It extends from about 50 km (31 miles) to 85 km (53 miles) above the surface. In this layer, temperatures decrease with increasing altitude, making it the coldest layer of the atmosphere.

The mesosphere is the layer of Earth’s atmosphere where phenomena such as meteoroid entry and the formation of auroras occur.

While it is less accessible to human activities than lower layers, it is an important area of scientific research for understanding atmospheric processes and interactions in the upper atmosphere.

Usually, The mesopause is the boundary between the mesosphere and the thermosphere. Here temperatures reach their lowest point in the atmosphere.

Besides, it is also a region where chemical reactions occur. This can lead to the formation of noctilucent clouds, the highest clouds in the Earth’s atmosphere. One can sometimes be visible from the ground during twilight.

Generally, The mesosphere is the layer of the atmosphere where meteoroids typically burn up upon entry into the Earth’s atmosphere.

Friction with the air at these altitudes causes the meteoroids to heat up and disintegrate, producing streaks of light known as meteors or “shooting stars.”

Thermosphere:

The thermosphere is characterized by high temperatures due to the absorption of solar radiation. However, it is not as hot as it might seem because this layer’s air density is extremely low.

It extends from about 85 kilometres (53 miles) to the boundary of space, approximately 600 kilometres (372 miles) or more.

Like the other layers of the atmosphere, the thermosphere consists primarily of gases. However, at the high altitudes of the thermosphere, the density of gases is extremely low, and the composition varies with altitude.

The primary gases present are atomic oxygen (O), molecular nitrogen (N₂), and atomic helium (He).

Unlike the lower layers of the atmosphere, where temperature decreases with increasing altitude.

The thermosphere experiences a significant temperature increase with altitude. However, it’s essential to understand that this increase in temperature does not imply that the air in the thermosphere is hot.

Instead, it reflects that individual gas molecules in the thermosphere are highly energetic.

Due to their exposure to solar radiation. As a result, the thermosphere can have some of the highest temperatures in the atmosphere, reaching thousands of degrees Celsius (or Fahrenheit) for individual gas molecules.

However, because the density of the gas is so low, it would not feel hot to a human observer.

The thermosphere is one of the regions where auroras, such as the Northern Lights and Southern Lights, are observed.

These colourful light displays are caused by the interaction of charged particles from the Sun with gases in the upper atmosphere.

Exosphere:

The exosphere is the outermost layer of the atmosphere, transitioning into space. It consists of very thin air and gradually merges with the vacuum of space. Satellites and other spacecraft orbit within the exosphere.

The exosphere, like the layers below it, contains a mixture of gases, including hydrogen (H), helium (He), atomic oxygen (O), and trace amounts of other gases.

However, the density of these gases in the exosphere is extremely low, and they are scattered very sparsely.

However, The exosphere is characterized by an extremely low gas density. This means that there are very few gas molecules per unit volume.

The exosphere is so rarefied that individual gas molecules are separated by large distances, and collisions between them are infrequent.

The temperature in the exosphere can vary widely, ranging from very cold to very hot.

However, the temperature in the exosphere differs from what we typically consider the temperature in everyday life.

Because of the low density of particles, the concept of temperature becomes less meaningful at these altitudes.

In other words, the exosphere doesn’t feel hot or cold to a human observer. Due to the lack of thermal contact with the atmosphere.

Final Thoughts

Lastly, there are layers of atmosphere due to a combination of factors. Such as gravity, temperature variations, the absorption of solar radiation, chemical composition, and dynamic processes.

These layers of atmosphere have distinct properties and purposes, contributing to the complexity and functionality of our atmosphere.