Question

Give an account of the different layers of the atmosphere.

Answer 1

Hint: The atmosphere is a huge blanket of gases that surrounds Earth. Based on its temperature, the atmosphere can be divided into layers. Our Earth’s atmosphere has five different layers.

Complete answer:
Our Earth’s atmosphere is composed of different layers based on temperature. These layers are the thermosphere, mesosphere, stratosphere, and troposphere. A further region at around 500 km above the Earth's surface is known as the exosphere.
The Troposphere:
This layer is the lowest part of the atmosphere. It is the part we live in. It contains most of our weather -rain, clouds, and snow. In this layer, as the distance above the earth increases, the temperature gets colder by about 6.5 degrees Celsius per kilometer. Depending on the weather, the actual change of temperature with the height varies from day today.
This layer contains about 75 percent of all of the air in the atmosphere and almost all the water vapor that forms clouds and rain. The decrease in temperature with height is a result of decreasing pressure. If a parcel of air moves upwards it starts to expand because of the low pressure. When air expands it cools, hence air higher up is cooler than the air lower down.
The lowest part of the troposphere is known as the boundary layer. This is where air motion is determined by the properties of the Earth's surface. As the wind blows over the Earth's surface, turbulence is generated, and by thermals rising from the land as it is heated by the sun. This turbulence redistributes moisture and heat within the boundary layer, as well as pollutants and many other constituents of the atmosphere.
The tropopause is the top of this layer. This is lowest at the poles, where it is about 7 to 10 km above the Earth's surface. It is the highest around 17 to 18 km, near the equator.
The Stratosphere:
This layer extends upwards from the tropopause to about 50 km. It contains most of the ozone in the atmosphere. Because of the absorption of UV radiation from the sun by this ozone, temperature increases with height. Temperatures in the stratosphere are the lowest over the winter pole and the highest over the summer pole.
By absorbing dangerous ultraviolet radiation, the ozone in the stratosphere protects us from skin cancer and many other health damages. However, chemicals such as freons or CFCs, and halons, which were once used in fire extinguishers, refrigerators, and spray cans have reduced the amount of ozone in the stratosphere, mainly at polar latitudes, leading to the Antarctic ozone hole.
Nowadays, the production of most of the harmful CFCs is stopped, and we expect the ozone hole will eventually recover over the 21st century, but it is a slow process.
The Mesosphere: The region above the stratosphere is called the mesosphere. Here also, the temperature decreases with height, reaching a minimum value of about -90 degree Celsius at the "mesopause".
The Thermosphere and Ionosphere:
This layer lies above the region of mesopause and is a region where the temperatures increase with height. This temperature increase is caused by the absorption of energetic UV and X-Ray radiation from the sun.
The ionosphere is the region of the atmosphere above 80 km, since the energetic solar radiation knocks the electrons off atoms and molecules, making them into ions with positive charge. The temperature of the thermosphere varies between the seasons and between day and night, as do the numbers of electrons and ions which are present. The ionosphere absorbs and reflects radio waves.
 The Exosphere:
The region above 500 km is known as the exosphere. It contains mainly hydrogen and oxygen atoms, but there are few of them that rarely collide - under the influence of gravity they follow ballistic trajectories, and some of them escape right out into space.
The Magnetosphere
Our earth behaves like a huge magnet. It traps protons or positive charges and electrons or negative charges, concentrating them in two bands above the globe about 3,000 and 16,000 km called the Van Allen radiation belts. This outer region surrounding the earth, where the charged particles spiral along magnetic field lines, is known as the magnetosphere.

Note: There is no boundary between outer space and the atmosphere. The atmosphere gets less dense until it blends into outer space.