Structure & Composition of the Atmosphere

Structure & Composition

of the Atmosphere

• The earth is surrounded by many different gases that reach up to a height of many kilometers.
• According to Strahler, 97% of the earth’s atmosphere found at the height of 29km but the limit of atmospheric height goes at the height of 10,000km.
• Earth’s atmosphere works like a big glass ball in which the short wave of radiation coming from the sun is allowed to enter but the terrestrial long wave is absorbed by the atmospheric gases such as co2 and much more.

Gases	% in Atmosphere
Nitrogen	78.08
Oxygen	20.24
Argon	0.93
Carbon dioxide	0.03
other gases	0.01856

• The Air pressure at the surface of the ocean is near about 1034 gram per square centimeter
• 50 % of the atmospheric portion found at 5.6km above sea level.
• Nitrogen, Oxygen, and Carbon dioxide gases are found at the lower level of the atmosphere at the height of less than 100 km above sea level, and gases like helium, neon, and much more are found at the upper level of the atmosphere.
• The amount of water vapor in the atmosphere is 4 to 5% of its total volume.
• The percentage of water vapor decrease when the height of the atmosphere increases.
• 90 % of water vapor found at a height of 8 km above sea level.

Structure of the Atmosphere

Earth’s atmospheric structure is divvied into main 5 layers which are following:

1. Troposphere layers
2. Stratosphere layers
3. Mesosphere layers
4. Ionosphere layers
5. Exosphere layers

1. Troposphere layers
   • Lower and densest layer of the atmosphere which Containing 75% of the total air volume.
   • All human activity takes place here.
   • Weather phenomena, such as storms, clouds, rain, and much more happen in this layer.
   • Here the temperature decreases with the increasing the elevation fig 1.Decreasing rate of temperature is 1 degree Celsius per 165m which is known as the normal lapse rate.
   • The troposphere is thickest in the equatorial and tropical regions, where it stretches from sea level to about 16 km (10 mi). It thins toward the poles, where it is only about 6 km (4 mi) thick.
   • The troposphere gives way to the stratosphere at the tropopause.

2. Stratosphere
   • The upper layer above the troposphere is known as the stratosphere. One of the very important layers because of the presence of the ozone layer.
   • Height of the stratosphere 50km above sea level.
   • Air present in the stratosphere began warmer as altitude increases.
   • The stratosphere is the home of strong, persistent winds that flow from west to east.
   •  Stratosphere holds a very little amount of water vapor.
   • The ozone layer comes under the stratosphere, the ozone layer is like a shield of earth life from intense, harmful ultraviolet radiation that comes from space.
   • Presence of ozone molecules in the stratosphere layer warm, causing the temperature to increase with altitude because they hold or absorb the sun’s radiation.
   • The temperature stops when increasing with altitude at the stratopause.

3. Mesosphere
   • Stratosphere layer at stratopause and the other atmospheric layer named mesosphere starts.
   • The mesosphere lies between the height of 50 to 80km above sea level.
   • Temperature decreases with the altitude in this layer.
   • The temperature at 80km is near about 100-degree Celcius.
   • This layer ends at the mesopause, the level at which temperature stops falling with altitude.

4. Ionosphere / Thermosphere
   • The layer lies between the height of 80km to 400km
   • In the ionosphere, the temperature increases with altitude again, but because the density of air is very thin in this layer, the air holds little heat.
   • Air present in this layer is an energy absorber, which causes the Aurora activity on the poles to occur in that layer (Aurora Borealis north pole & Aurora Australis South pole).
   • Radioactive waves return on the earth from reflected in this layer.

5. Exosphere
   • The most upper layer of the atmosphere.
   • The air in this layer is very thick and separates the rest of the atmosphere from outer space.
   • The exosphere is the very edge of our atmosphere.
   • It’s about 6,200 miles (10,000 kilometers) thick.
   • The exosphere has gases like hydrogen and helium, but they are very spread out. There is a lot of empty space in between. There is no air to breathe, and it’s very cold.