Short note on the composition and structure of atmosphere
Answers
Structure of atmosphere
Based primarily on the temperature pattern, earth's atmosphere can be roughly divided into four major zones:-
1. The troposphere:
The zone immediately above earth's surface is known as the troposphere which extends upto a height of about 20 kms above the equator and about 8 kms over the poles. The temperature in this zone drops with height being as low as - 60°C at its upper extremity.
2. The stratosphere:
The layer next to troposphere is called the stratosphere. It is about 30 kms in thickness and is a very important zone of atmosphere as it contains the vital ozone layer. The temperature in this zone rises from - 60°C to about 0°C in its upper layers. The rise in temperature is due to the formation of ozone under the influence of ultra-violet radiation.
3. The mesosphere:
It is a zone of about 40 kms in thickness which lies next to the stratosphere. This zone is characterised by gradual decline in temperatures to about - 90°C.
4. The Thermosphere:
It is the zone next to mesosphere in which temperature increases with height. Most of the constituents of this zone are in ionized state.
The troposphere
The troposphere contains over 80% of the mass of the atmosphere, along with nearly all of the water vapor. This layer contains the air we breathe, the winds we observe, and the clouds that bring our rain. All of what we know as weather occurs in the troposphere, the name of which means “changing sphere.” All of the cold fronts, warm fronts, high and low pressure systems, storm systems, and other features seen on a weather map occur in this lowest layer. Severe thunderstorms may penetrate the tropopause.
Stratosphere
Stratosphere is found just above the troposphere.
It extends up to a height of 50 km.
The temperature remains almost the same in the lower part of this layer up to the height of 20 km. After this, the temperature increases slowly with the increase in the height. The temperature increases due to the presence of ozone gas in the upper part of
The mesosphere is a layer of Earth's atmosphere. The mesosphere is directly above the stratosphere and below the thermosphere. It extends from about 50 to 85 km (31 to 53 miles) above our planet.