Composition and Layers of the atmosphere | Composition and Structure of the Atmosphere

How can we define Atmosphere?

We can define the atmosphere in the following ways:

• Our earth is surrounded by a blanket of air called the atmosphere. 
• The atmosphere is one of the four domains of the earth, the other three are the lithosphere, hydrosphere, and biosphere.
• The atmosphere is a gaseous part of the environment on earth.

Composition of atmosphere:

Earth's atmosphere is comprised of air, dust particle, and water vapors. Dust particle and Water vapors proportion are highly volatile, however, air composition is more or less the same over time. The air Composition of the Atmosphere is listed in the below tables:

Air	% in the Atmosphere
Nitrogen (N2)	78.084 = ~ 78%
Oxygen (O2)	20.946 =~ 21%
Argon (Ar)	0.934=~1%
Carbon Dioxide (Co2)	0.037
Neon(Ne)	0.00182
Helium (He)	0.00052
Krypton (Kr)	0.000114
Hydrogen (H2)	0.00005
Xenon (Xe)	0.000009

Nitrogen ( 78 percent) and Oxygen ( 21 percent) are two gases that make up the bulk of the atmosphere.

Layers of the atmosphere | Structure of the Atmosphere

There are five major layers of our atmosphere. Due to the earth's gravitational force denser and heavier air, dust, and water vapor particles settled near the earth's surface. With altitude density and quantity of air get reduced.

The structure of the atmosphere is comprised of five layers of the atmosphere depending on the temperature and gaseous conditions. The following are five layers of the atmosphere:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere 
• Exosphere

The following image gives us the status of temperature in different layers of the atmosphere.

Layers of Atmosphere

Layers of atmosphere

Troposphere: 

The troposphere is the lowermost layer of the atmosphere. The following are the characteristics of the troposphere:

• The height of the troposphere varies, however average height of the troposphere is about 13 km. It has a rough height of 8 km near the poles and about 18 km at the equator.
• Temperature and Air Pressure decrease with increased height in the troposphere.
• All the weather phenomena such as cloud formation, thundering, etc are found in this layer.
• All the greenhouse gases like carbon dioxide and methane are found in this layer.
• and temperature decrease when we go up from the earth in the troposphere.
• Air also moves vertically due to heating.
• 75% of the air in the atmosphere is found in this layer.
• 99% of the total water vapors of the atmosphere are found in this layer.
• Tropo pause is found at the top of the troposphere.

Stratosphere:

Stratosphere is the second layer of the atmosphere from the earth's surface, it lies above the troposphere. The following are the characteristics of the stratosphere:

• The ozone layer is part of the stratosphere and it is found in the middle part of the stratosphere from 20 to 25 km.
• In this layer, temperature increases with height due to the absorption of UV rays by the ozone layer.
• Polar stratospheric clouds are found in this layer.
• It is known for its calm atmosphere.
• In the lower stratosphere, commercial planes and jets fly due to the calm atmosphere.

Mesosphere:

The following are the characteristics of the Mesosphere:

• This is the third layer and goes up to 80 km.
• Most Meteor burn in this layer
• Temperature decrease with height
• -the 90-degree temperature is in menopause( topmost)

Thermosphere:

The following are the characteristics of the thermosphere:

• It extends from 80 to 1000 km.
• High energy such as X-Ray and UV radiation is absorbed and temperature increase with height
• The temperature reaches up to 1500 degrees but you will not feel cold because of the very low air molecules.
• Colorful Aurora Borealis and Aurora Australia can be seen here.
• The international space station is in this layer.

Exosphere:

• The exosphere extends from Earth to half the distance of the Moon. A very small number of atmospheric molecules, composed mostly of helium and hydrogen, are found in this layer, which absorbs most of the harmful radiation.

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