Air: Atmosphere

Air comprises a mixture of gases that makes up Earth’s atmosphere. Atmosphere comes from Ancient Greek words atmós, meaning’ vapour or steam’, and sphaîra, meaning’ sphere’.

The atmosphere is a mixture of layers of gases that envelop the planet. Hence, the earth’s atmosphere acts as a blanket for the earth. The atmosphere comprises three main constituents- Oxygen, Nitrogen, and Argon. Out of all the gases present in variable concentrations, carbon dioxide, sulphur dioxide, nitrogen dioxide, water vapour are essential. 

The atmosphere, further divided into five layers, is uniform in its composition. This uniformity in the atmosphere’s composition above a height of 90Kms (55 miles) is maintained by mixing the atmospheric motions, which is a diffusional process and plays a vital role in preventing mixing. The barometer is the instrument used for measuring the atmospheric pressure in mm of Hg (mercury).

Features of atmosphere

Location

Around the planet’s surface, the terrestrial atmosphere extends from the ground, reaching about 10,000 kilometres around the planet. The atmosphere forms several layers of more or fewer uniform gases.

Composition

The atmosphere’s composition has changed throughout the history of the planet. As living beings consume certain gases and produce others, they have significantly contributed to this change.

However, it is formed mainly by nitrogen ( around 78%) and oxygen (about 21%). Other essential gases such as hydrogen, ozone, argon, carbon dioxide, and other noble gases have small yet significant contributions. The atmosphere also contains a significant presence of water vapour.

Regions

Earth’s atmosphere is distinguished into two regions:

• Homosphere

It has constant and regular composition, which occupies the first 100 km of the atmosphere from the ground.

• Heterosphere

It is stratified into different layers of gases, which vary according to height and pressure:

80-400 kilometres high: molecular nitrogen (N2).

400-1100 kilometres in height: atomic oxygen (O).

1100-3500 kilometres in height: helium (He).

3500-10,000 kilometres in height: hydrogen (H).

Layers of Atmosphere

The atmosphere is divided into five layers which can be determined if there is a change in temperature and altitude. The five layers of the atmosphere are as follows:

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

1. Troposphere

The troposphere forms the lowest layer of the atmosphere. The topmost layer of the troposphere is called tropopause. Out of total space in the atmosphere, the troposphere comprises a 75% share. Major clouds appear in this layer as 99% of the water vapour is found. The temperature of this layer remains relatively warmer. 

2. Stratosphere

Just above the Troposphere layer lies the stratosphere, which extends the layer of the troposphere to approximately 31 miles. There is an ozone layer that lies above the stratosphere.

Some ozone layer molecules absorb ultraviolet rays directly from the sun and release heat. Hence, as we move upwards, the stratosphere becomes warmer. 

3. Mesosphere

The mesosphere is the layer that lies just above the stratosphere, approximately 53 miles away from the ground. The mesosphere forms the coldest part of the atmosphere as its temperature dips up to -900C. 

4. Thermosphere

The Thermosphere lies just above the mesosphere. Here, the temperature increases significantly due to the sun’s absorption of ultraviolet and X-Rays. The temperature in the Thermosphere can range from 5000 C to 20000 C. Southern and Northern lights appear in the Thermosphere. 

5. Exosphere

The final layer of the atmosphere is the exosphere. The air stored in the exosphere slowly leaks out from the earth’s atmosphere to space. The exosphere does not possess an upper boundary.

6. Ionosphere

This layer is not comparatively different from other layers of the atmosphere. The ionosphere is the part of the mesosphere and Thermosphere wherein high energy radiation passes.

7. Magnetosphere

This name is given to the region of the atmosphere in which the planet’s magnetic field is present, generated by its rotation movement and its heart of cast iron, which acts as a dynamo. This field is also vital as it prevents the entry of solar wind and other forms of electromagnetic radiation into our planet. 

Contamination

Atmospheric pollution is mainly caused by gases, which enhance the greenhouse effect. It further erodes the ozone layer, allowing the entry of solar radiation and increasing the planet’s temperature.

Conclusion

Atmosphere regulates the temperature globally and protects us from solar radiation. The burning of natural gases like coal generates a more significant amount of atmospheric pollution, further deteriorating the ozone layer and increasing global warming. The result of global warming is the overall increase in the earth’s temperature, which causes irreversible effects on both flora and fauna.