What is Atmosphere?

Atmosphere is the layer of gas that surrounds a planet. Atmosphere is made up of different layers such as Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere. It consists of gases such as nitrogen, oxygen, carbon dioxide, argon, etc.

In this article, we are going to discuss what is atmosphere, composition of atmosphere, different layers of atmosphere, atmospheric pressure, and importance of atmosphere.

What is Atmosphere?

Atmosphere refers to the layer of gases that surrounds our earth. Atmosphere is also called a blanket of gases. The composition of the gases present in the atmosphere is nitrogen which is 78 %, oxygen is 21 %, argon is 0.93 %, carbon dioxide is 0.04 %, and other gases are present in very small amounts.

The atmosphere protects us from harmful UV radiation emitted by the Sun. Living beings use the gases present in the atmosphere for various purposes. Atmosphere scatters the sunlight entering the earth’s surface. It helps in the regulation of various processes such as the water cycle, regulation of temperature and many other natural process. It maintains the weather of the earth.

Atmosphere Definition

Atmosphere is a mixture of different gases and it envelopes the earth all round. It contains life-giving gases like oxygen for humans and animals and carbon dioxide for plants.

Features of Atmosphere

Atmosphere has many salient features and is very important for human survival. Few of the important features of atmosphere are:

• The atmosphere regulates the temperature by trapping some of the Sun’s energy, preventing it from escaping directly into space.

• Essential gases such as Oxygen and carbon dioxide are present in the atmosphere.

• The most abundant gas present in atmosphere is nitrogen which is 78% of total gases present in the atmosphere.

• Atmosphere is divided into five layers.

• Atmosphere is essential to maintain life on Earth and in controlling the planet’s temperature.

• It also protect us from harmful ultraviolet rays of the sun.

Layers of Atmosphere

There are different layers of atmosphere present on earth. These layers protects us from direct radiation of Sun (UV rays) and other harmful cancer causing radiations. There are five layers of atmosphere namely:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

Troposphere

This is the lowermost layer of the Earth. This layer extends from ground to about 12 kilometer high. This layer contains 75% of all air in the atmosphere and is the densest part of the atmosphere.

The upper part of this layer is known as Tropopause that act as a boundary between troposphere and stratosphere. The temperature in the troposphere decreases with the increase in height. This decreasing temperature is in the order of 6.5 ℃ per km.

Stratosphere

Stratosphere is the second and the most important layer of atmosphere. This layer extends up to 50 kilometers from the ground and is above troposphere. The ozone layer is present in the stratosphere.

The Ozone layer protects us from the harmful UV radiations emitted by Sun. Few clouds are present in this layer. The Aeroplanes and birds fly in the lower level of stratosphere.

Mesosphere

Mesosphere is present just above the Stratosphere. This is the middle layer of atmosphere. Mesosphere extends from about 50 kilometers to the 85 kilometers above the Earth’s surface.

This is the coldest layer of atmosphere as temperature decreases with increase in altitude. The average temperature in mesosphere is about -85 ℃. The ozone concentration in this layer is less than as compared to Stratosphere.

Thermosphere

Thermosphere lies above the mesosphere. The thermos in thermosphere stands for heat, due to its high temperature. The thermosphere extends from about 85 kilometers to the outer edges of the atmosphere to about 700 km above the Earth’s surface. This layer is also known as upper atmosphere.

This layer is very hot with a high temperature range that lies between 500℃ – 2000℃. This layer absorbs the energetic ultraviolet rays emitting from the sun which results in high temperature of this layer. The air density is extremely low in this layer.

Exosphere

Exosphere is the outermost layer of atmosphere. It separates the other layers from the outer space. There is no upper boundary of this layer as it merges out in the space. This layer is about 10,000 km thick. It is also known as the first layer to shield the Earth from meteors, asteroids, and cosmic rays.

Many satellites orbit within the exosphere or below. The pressure in the exosphere is created by solar wind storms that compress it. The air density in this layer is very low because hydrogen is present in this layer and it is the lightest element on earth.

Ionosphere

Ionosphere is a part of upper atmosphere but it is not characterized as a distinct layer of atmosphere. Ionosphere extends from about 80km – 1000km above the earth’s surface and includes thermosphere, and the parts of mesosphere and exosphere.

Ionosphere uses solar radiations to ionize the atoms and molecules resulting in a layer of electrons. It reflects and modifies radio waves used for communication and navigation.

Layers of Atmosphere

Structure of Atmosphere

The different layers of the atmosphere provides the structure of the earth’s atmosphere. The tabular representation of all layers of earth is given below:

Structure of Atmosphere
Layer of Atmosphere	Altitude	Temperature	Characteristics
Troposphere	0km – 12km	-50o C to 200C	First innermost layer Weather is present
Stratosphere	12km- 50km	-50oC to 0oC	Second layer of atmosphere It contains ozone layer
Mesosphere	50km- 85 km	-85oC to -2o C	Middle layer of atmosphere Meteors burn in mesosphere
Thermosphere	85km – 700 km	500oC to 2000oC	Second outermost layer Auroras occur in this layer
Exosphere	700km – 10,000 km	Ranges from 0oC to 1200oC	Outermost layer Less density of air

Composition of Atmosphere

There are several gases present in atmosphere such as nitrogen, oxygen, carbon dioxide, argon, helium, neon, xenon, methane etc. The major composition of gases in atmosphere are:

• Nitrogen – 78%
• Oxygen – 21%
• Argon – 0.93%
• Carbon dioxide – 0.04%

Apart from these, there are traces of other gases, dust particles, water vapours, etc in the atmosphere. Different gases perform different function. The salient features of few important gases of atmosphere are described below:

Nitrogen

• Nitrogen is the most abundant gas of the atmosphere and is about 78% of the total gases present in the atmosphere.
• It is the component of many primary acids such as nitric acid, ammonia etc.
• Nitrogen is used as fertilizers which is helpful in growth of plants.

Oxygen

• Oxygen makes up about 21% of the atmosphere.
• It is the main gas used in respiration by many living beings including human.
• Oxygen is essential for burning.

Argon

• Atmosphere is composed of 0.93% of Argon.
• Argon is used as filler in light bulbs to prevent the oxidation of the filament.
• Argon is used in the process of welding.

Carbon Dioxide

• This gas constitutes of 0.04% of the atmosphere.
• Carbon dioxide is used by plants to make oxygen.
• This gas is also responsible for the greenhouse effect.

Composition of Atmosphere

Read More, Composition of Atmosphere

Atmospheric Pressure

Atmosphere pressure is the pressure exerted by molecules present in atmosphere against a surface. The atmospheric pressure at a point is defined as the force acting normally on a unit area around that point, due to the total height of the air column of the atmosphere above it.

The air pressure keeps on increasing as we move towards the Earth’s surface. Its symbol is P_a and S.I. unit is newton per square meter (Nm^-2) or pascal (Pa). Barometer is the device used to measure the atmospheric pressure of gases. That pressure is referred to as air pressure, atmospheric pressure, or both.

Read More, Atmospheric Pressure

Importance of Atmosphere

Atmosphere is very important part of a planet. The key features of atmosphere are:

• Atmosphere acts as protective layer around our earth surface.
• It protects all living beings from skin cancer and other skin causing diseases caused due to harmful UV radiations emitted by sun.
• Atmosphere protect living beings from harmful greenhouse gases by maintaining the optimal temperature of earth surface.
• The gases present in atmosphere are necessary for survival of living beings and plants on Earth.
• The process by which plants turn sunlight into energy, known as photosynthesis, depends on carbon dioxide in the atmosphere.
• Oxygen is the gas used by human beings for respiration process.
• Layers of atmosphere supports the signals for mobile connection, television and telecommunications.

Read More,

• Composition and Structure of Atmosphere
• Climate and Weather

Atmosphere: Frequently Asked Questions

Is Atmosphere Present on Moon?

Moon has a very thin atmosphere, known as an exosphere that contains helium, argon, neon, ammonia, methane and carbon dioxide.

Is Atmosphere and Air Same?

No, atmosphere and air are not the same. Air is just one of component of atmosphere and atmosphere is the layer of gases around the surface of the Earth.

What is Ozone Layer in Atmosphere?

Ozone layer is the protective layer present in the atmosphere. Ozone protects harmful UV radiations from reaching the earth surface. It absorbs all harmful radiations.

What Would Happen if the Earth’s Atmosphere Disappeared?

If earth’s atmosphere disappear, then there will be no life on Earth. There will be no clouds or rain and the harmful UV rays of the sun will cause a great damage to earth.

Which Instrument is used to Measure Atmospheric Pressure?

Barometer is used to measure the atmospheric pressure.

What are Main Components of Atmosphere?

Main component of atmosphere are its gases. The most abundant gases of atmosphere is Nitrogen which is 78%, followed by oxygen which is 21% and rest of the gases are 1% of the total volume of the atmosphere.

What are Five Layers of Atmosphere?

The Earth’s atmosphere is divided into following layers:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere