Layers of the Atmosphere

Layers of the Atmosphere

Under the title  Atmosphere : An Introduction , we learned the main points related to the atmosphere. In this topic titled Layers of the Atmosphere, we will learn the important points with detailed about the five different layers of the atmosphere shown below, which we see in the previous topic . 

1. On the Basis of Presence of the gases found in the atmosphere
2. On the basis of various activities and events taking place in the atmosphere

Bardoli Satyagraha : 1928 

1.  On the Basis of Presence of the Gases Found in the Atmosphere

• If we look at the presence or composition of the gases found in the atmosphere, then we can divide the atmosphere into two parts.
• First – Symosphere - This part is also called the samosphere due to the almost uniform mixture of atmospheric gases found up to a height of 80 km from the earth. 
• The troposphere, stratosphere and mesosphere of the atmosphere come under the stratosphere.
• Mainly oxygen and nitrogen are found in the stratosphere.
• Second – Heterosphere - After a height of 80 km from the earth, different molecular layers of different gases are found, such as - molecular layer of oxygen, molecular layer of nitrogen etc. Disparities are found in the chemical and physical properties of these layers, that is why this part is also called heterosphere.
• Mainly four layers of different gases are found in the heterosphere, which are as follows –
• Layer of molecular nitrogen – 90 to 200 km height.
• Molecular oxygen layer – 200 to 1100 km height.
• Helium layer - from 1100 to 3500 km height.
• Layer of molecular hydrogen – 3500 to 10,000 km height.

Lakes and Its Types - Lakes of India and The World

2. On the Basis of Various activities and Events Taking Place in the Atmosphere

• On the basis of various activities and events taking place in the atmosphere, the Atmosphere has been divided into 5 different levels, which are as follows –
1. Troposphere or Convection Zone
2. Stratosphere or Ozone Layer
3. Mesosphere
4. Ionosphere or Thermosphere
5. Exosphere

1. Troposphere or Convection Zone

• This is the lowest level of the atmosphere, in which about 75% of the weight of the entire air is found.
• Its height at the poles is 8 km, while at the equator its height is found to be 18 km due to convection currents. In this way, it becomes thinner from the poles towards the equator. Height and decrease are seen in this part in summer and winter respectively.
• In this circle, there is a decrease of 1^०C in temperature for every 165 meters of height and on an average, there is a decrease of 6.5^०C in temperature for every kilometer of height. This decrease in temperature is called normal temperature lapse rate or normal lapse rate.
• Due to the difference in its height on the equator and the pole, difference in temperature is found at these two places. The temperature at the equator is – 80^०C while the temperature at the pole is – 45^०C.
• All the weather activities taking place in the atmosphere take place in this part. The reason for this is the water vapor and dust particles found in this part, due to the concentration of which clouds are formed and incidents like cyclones and storms occur.
• Due to the weather events occurring in this part, it is not suitable for the operation of aircraft.
• Very fast convection currents or jet streams are found on the upper boundary of the troposphere, that is, the troposphere, due to which this part is also called convection.
• The transition level found between the troposphere and the stratosphere, that is, where the troposphere and the stratosphere meet, is called the Tropopause.

Evolution of the Indian Constitution : Historical Background 

2. Stratosphere or Ozone Layer

• The stratosphere is found above the troposphere, whose height is about 50 km from the surface of the earth.
• Due to the constant temperature in this part, this part is called the stratosphere.
• The concentration of ozone gas is high in the region of 20 km – 35 km of the stratosphere, due to which the stratosphere is also called the ozone sphere. The ozone gas present here absorbs ultraviolet rays. For this reason, the upper part of the stratosphere i.e. at the level of 50 km, the temperature is high, whereas at 20 km, stability is found in the temperature.
• Due to the absence of water vapor and dust particles etc. in the stratosphere, it is free from meteorological phenomena, hence this layer is suitable for the operation of aircraft.
• In the upper part of the stratosphere, where it meets the mesosphere, the transition zone formed at that place is called the stratopause.

Most Route Changing River in India - Kosi or Dormant Kosi River

3. Mesosphere

• As the name suggests, this circle is found in the middle part of the atmosphere. For this reason this part is called the middle circle.
• The height of the middle zone is found from 50 km to 80 km.
• There is a sudden sharp drop in temperature in the mesosphere. The temperature in this part is about – 100^०C, which is the minimum temperature of the atmosphere.
• The upper boundary of this circle, ie the place where it meets the ionosphere, is called the Mesopause.

National War Memorial

4. Ionosphere or Thermosphere

• The height of the ionosphere is between 80 km – 640 km.
• There is an excess of electrically charged particles in this region, due to which this part is called ion region.
• Along with the increase in height in this layer, there is a rapid increase in temperature and on its upper limit the temperature reaches up to 1000^०C. Because of which this circle is also called thermosphere.
• Electrically charged particles found in this region reflect radio waves of different frequencies, which conduct wireless connectivity on Earth.
• On the basis of reflection of rays of different wavelengths, the ionosphere is again divided into four parts, which are as follows –
• D – Layer – Long wavelength ie low frequency radio waves are reflected from this layer.
• E – Layer or Kennelly Heaviside layer – Medium and short wavelength ie medium and high frequency radio waves are reflected from this layer.
• F – Layer or Appleton layer – medium and short wavelength ie radio waves of medium and high frequency are reflected from this layer.
• G – Layer – All types of short, medium and long wavelengths, that is, radio waves of all types of frequency, long, medium and short, are reflected from this part.

Hybridization Experiment of Gregor John Mendel and Mendel

5. Exosphere

• The height of the exosphere is found between 640 km – 1000 km.
• It is the outermost layer of the atmosphere. In this layer, after a height of 1000 km, the air becomes very rarefied, which later merges into space.
• In this part also the predominance of electrically charged particles is found. Here different layers of different gases are found respectively. Like – N₂ , O₂ , He,  Hydrogen etc.
• The temperature on the outer boundary of this circle is found up to about 5568^०C, but heat is not experienced due to the rarefaction.

Bamiyan Buddha : A Dilapidated World Heritage