Understanding the Composition and Structure of Atmosphere

One of the basic prerequisites for life on this planet is the presence of air. It contains gases that give life to humans and animals and carbon dioxide for plants. Air completely envelops the world and is held in place by the Earth’s gravity. It aids in preventing damaging UV rays and the maintenance of the proper temperature required for life. In general, the atmosphere extends up to 1600 kilometres above the Earth’s surface. However, 99% of the composition and structure of the atmosphere is contained within 32 kilometres of the Earth’s surface. The atmosphere composition is dynamic, changing with the passage of time and location.

Composition of Atmosphere

Different types of gases, water vapour, and dust particles make up the Earth’s atmosphere composition.

• Gases of the Atmosphere

The composition and structure of atmosphere is made up of a variety of gases, such as water vapour and dust particles. The two major gases in the atmosphere are nitrogen and oxygen. These two gases account for 99% of it. The remaining gases in the atmosphere include argon, carbon dioxide, neon, helium, hydrogen, etc. The proportion of gases fluctuates in the upper layers of the atmosphere to the point where oxygen is almost non-existent at altitudes of 120 km.

• Oxygen

Despite accounting for only 21% of the total volume of the composition and structure of the atmosphere, oxygen is an essential gas component. All living things take in oxygen. Oxygen can also interact with other elements to generate useful compounds like oxides. Also, without oxygen, burning is impossible.

• Nitrogen

Nitrogen makes up about 78% of the entire volume of the atmosphere. It’s a moderately innocuous gas found in almost every organic substance. Nitrogen’s primary purpose is to control combustion by diluting oxygen. It also aids in the decomposition of many substances indirectly.

• Carbon Dioxide

A very important gas in meteorology, Carbon dioxide can only be found up to 90 kilometres below the Earth’s surface. It is transparent to insolation (incoming solar energy) but impervious to outgoing terrestrial radiation. The greenhouse effect is mostly caused by carbon dioxide. When the volume of other gases in the earth’s atmosphere composition remains constant, the volume of carbon dioxide in the atmosphere has risen in recent decades, owing primarily to the combustion of fossil fuels. The fundamental cause of global warming is the increase in carbon dioxide levels.

• Ozone Gas

Another essential element of the earth’s atmosphere composition is ozone, which is found primarily between 10 and 50 kilometres above the Earth’s surface. There is very little ozone gas in the atmosphere. It only affects the ozone layer, yet it is extremely significant. It protects living things by absorbing the Sun’s UV radiation. There would have been no living beings or plants on the Earth’s surface if there was no ozone gas in the atmosphere.

• Water Vapour

Evaporation of moisture and water from water bodies, plants, and soil cover provides atmospheric vapour. The amount of vapour in the atmosphere varies from 0% to 5% by volume. It is temperature-dependent, and as a result, it diminishes from the equator poleward as the temperature drops towards the poles. The amount of vapour in the atmosphere decreases as it rises. Up to a height of 5 km, more than 90% of the total atmospheric vapour is detected. Clouds, fog, dew, rainfall, frost, hailstorm, ice, snowfall, and other types of condensation and precipitation are caused by the amount of moisture in the atmosphere.

• Dust particles

Dust particles are most commonly found in the atmosphere’s lower levels. Sand, smoke-soot, sea salt, ash, pollen, and other particles contain these particles. Due to dry winds, dust particles are found in higher densities in temperate and subtropical regions than equatorial and polar regions. These particulates aid the condensation of water vapour. Water vapour condenses in droplets around these dust particles during condensation, resulting in clouds.

Structure of the Atmosphere

Composition, density, pressure, and temperature differences describe the composition of the atmosphere into layers. It is broadly separated into two levels based on its composition and structure of the atmosphere:

• HOMOSPHERE

The Troposphere, Stratosphere, and Mesosphere are the three areas that make up the Homosphere. Even though the air composition is the same in all three regions, air concentration reduces dramatically as height rises. The composition of the gases remains uniform, even though the atmosphere’s density rapidly decreases with height.

• Heterosphere

There are two zones in the Heterosphere: the Thermosphere and the Exosphere. These two areas are referred to as “outer space.” This layer’s gases aren’t equally mixed.  The atmosphere composition and structure can be divided into five strata based on temperature and density differences.

1. The troposphere is the atmosphere’s lowermost layer. It stretches up to 18 kilometres at the equator, 13 kilometres at mid-latitude, and roughly 8 kilometres at the poles. It accounts for roughly 90% of the entire mass of the atmosphere. This layer is where the entire weather event takes place.
2. The stratosphere is located above the troposphere and stretches consistently up to 50 kilometres around the globe. The temperature in this stratum rises in tandem with the height. Temperatures range from -57 to 0 degrees Celsius.
3. Mesosphere spans between 50 and 80 kilometres. The temperature drops again in this stratum, reaching a low of -90o C on average. This temperature, however, is subject to change.
4. The thermosphere (Ionosphere) is a range that varies from 80 to 480 kilometres. It is equipped with a working ionosphere. As the gas molecules absorb the Sun’s short wave energy, the temperature in this layer rises dramatically. The thermosphere can reach temperatures of 1200o C. However, it is not as ‘hot’ as we might imagine despite these high temperatures.
5. The exosphere is the atmosphere’s highest layer. Due to the lack of gravitational force, gases are extremely scarce in this environment. As a result, the air density is very low here.

Conclusion

Without air, life on Earth would be impossible. The atmosphere shields life from incoming ultraviolet (UV) radiation, keeps the globe warm through insulation and prevents temperature extremes between day and night. Changes in the atmosphere’s composition can impact the planet’s habitability, for example, by affecting long-term climate, depleting the ozone layer, changing radiative forcing, or impacting air quality on the ground.