Introduction

We inhale oxygen and exhale carbon dioxide whereas the plants inhale carbon dioxide and exhale oxygen. The air we breathe is all components of the atmosphere. The atmosphere is not just responsible for holding gases, its importance for life on earth is irreplaceable. Earth holds all these glasses with a gravitational pull. The atmosphere, the tropospheric and stratospheric layers play a very vital role. 

Atmosphere

Earth is covered by a thick blanket of gasses that has extended to thousands of kilometres from sea level called the atmosphere. The atmosphere generally stretches up to 1600 kilometres from the earth’s surface. However, within 32 kilometres of the earth’s surface, 99 percent of the Atmosphere’s mass is enclosed. Earth holds all these gasses with a gravitational pull. As altitude increases, the air becomes lighter as air molecules at higher altitudes are loosely packed than at lower altitudes. This phenomenon is due to the pull of the earth’s gravitational force. The air above the earth’s surface exerts pressure because of its weight. This pressure is called atmospheric pressure. This atmospheric pressure influences seasonal and monsoon winds and remains the most important climatic element. The atmosphere contains various gasses like oxygen, carbon dioxide, nitrogen, etc., which are essential for supporting life on earth. The atmosphere helps in maintaining the earth’s temperature under certain limits. Without the atmosphere, temperature extremes would exist between day and night over the earth’s surface. The atmosphere contains different layers with varying densities. Each has characteristic temperatures, pressures, and phenomena. There are five different layers of the earth’s atmosphere. They are:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

Troposphere:

• The lowermost and first layer of the earth’s atmosphere is the troposphere.
• The troposphere extends to 8 km at the poles and 18 km at the equator. The thickness is more significant because warm air rises to greater heights at the equator.
• This layer is the denser layer of all as most of the atmosphere’s mass (about 75-80%) is in the troposphere.
• The troposphere is by far the wettest layer of the atmosphere, with relatively little water vapor in the layers above it.
• This is the layer where clouds are formed and all other climatic changes occur.
• When you climb higher in the atmosphere the temperature drops by 1-degree celsius for every 165 meters of height. This is referred to as a standard lapse rate.
• With increasing altitude the air pressure and density both decrease or drop.
• The rotational friction of the troposphere against the planetary surface affects the flow of the air and results in the formation of the planetary boundary layer (PBL) that varies in height from hundreds of meters up to 2 km.
• The sources of atmospheric water vapor are the bodies of water (oceans, seas, lakes, rivers) on the planetary surface, which humidify the troposphere through the process of evaporation.

Stratosphere

• The stratosphere is the second layer of the earth’s atmosphere. The troposphere and the stratosphere are separated by the tropopause, which remains the boundary between the two layers.
• This layer stretches up to 50 kilometres above sea level.
• Commercial jet aircraft travel in the lower stratosphere to avoid the frequent turbulence in the troposphere.
• The stratosphere is extremely dry and has very little water vapor in the air. This results in the formation of very few clouds in this layer. Almost all the clouds are formed in the lower layer which is a more humid troposphere.
• At the apex of the stratosphere, the air is a thousand times thinner than it is at sea level.
• This layer contains the ozone layer. UV rays are absorbed by the ozone layer, which protects the earth from hazardous radiation.
• The temperature in this layer drops by five °C each kilometer as one ascends, reaching -45°C at the poles and -80°C at the tropopause (the higher fall in temperature above the equator is due to the greater thickness of troposphere – 18 km). Stratospheric temperatures also vary within the stratosphere as the season’s change, reaching particularly low temperatures in the polar night (winter).
• The Stratopause separates the Stratosphere and Mesosphere.
• In the stratosphere the bacterial life survives.

Differentiation Between the Troposphere and Stratosphere: 

• We all know that the troposphere is referred to as the Atmosphere’s lowermost layer, and the second most layer present in the atmosphere above the earth’s surface is referred to as the stratosphere. 

• Up to 50 km, the height of the stratosphere can take off, whereas the height of the troposphere can vary up to 18 km at the equator from 8 km from the poles.

• The stratosphere is also referred to as the zone of non- convection currents, whereas the troposphere is referred to as the convective zone of the atmosphere.

• So, mainly in the stratospheric layer the dust particles, clouds, and water vapors are nonexistent, whereas, in the stratospheric layer clouds, water vapor, and dust particles exist.

• The stratospheric layer is unrestricted from the disturbances of the atmosphere, whereas in the tropospheric layer the disturbances of the atmosphere are restricted. 

Conclusion

We all live in the lower part of the atmosphere. All living organisms live only in the lower layer of the troposphere. The sky is not the limit for the atmosphere as we cannot view the uppermost layer with our naked eyes. Researchers are still exploring the space beyond the atmosphere to check if there are any possibilities for life to survive. The stratosphere is extremely dry and has very little water vapor in the air.