Layers Of Atmosphere
Composition of the Atmosphere
Do you know that the atmosphere is a mixture of several gases responsible for the life surviving on earth? It contains a huge amount of solid and liquid particles that are collectively known as aerosols. Pure dry air consists mainly of Nitrogen, Oxygen, Argon, Carbon Dioxide, Hydrogen, Helium and Ozone. Besides, water vapour, dust particles, smoke, salts, etc. are also present in the atmosphere.
The atmosphere is composed of:
- Nitrogen (78.09%),
- Oxygen (20.95%),
- Other gases(0.03%)
- Air pressure
- The pressure falls rapidly as we go up the layers of the atmosphere. The air pressure is generally highest at sea level and decreases with height.
- When the areas with high temperature get heated, a low-pressure area is created. Low pressure is associated with cloudy skies and wet weather.
- The lower temperature areas have cold air. Heavy air sinks and creates a high-pressure area. High pressure is associated with clear and sunny skies.
Layers of Atmosphere
- It is the lowest layer of the atmosphere.
- It extends up to a height of 8 Kms at poles and 18 Kms at the Equator.
- All the weather phenomena are confined to Troposphere (e.g. fog, cloud, frost, rainfall, storms, etc.)
- Temperature decreases with height in this layer roughly at the rate of 6.5° per 1000 metres, which is called the normal lapse rate.
- The upper limit of the troposphere is called tropopause which is about 1.5 km.
- Dust particles, water vapour and other impurities are found here
- This layer keeps the earth warn as it absorbs maximum heat radiated by earth’s surface being the densest and lowest layer of atmosphere.
- The air we breathe exists here.
- Tropopause – it is the layer that separates the troposphere from the stratosphere. In the troposphere, the temperature generally decreases with height, whereas above the tropopause, the temperature no longer decreases.
- The stratosphere is more or less devoid of major weather phenomenon but there is a circulation of feeble winds and cirrus cloud in the lower stratosphere.
- It extends up to a height of 50 km.
- Jet aircrafts fly through the lower stratosphere because it provides conducive flying conditions.
- Ozone layer lies within the stratosphere mostly at the altitude of 15 to 35 km above earth’s surface.
- Ozone layer acts as a protective cover as it absorbs ultra-voilet rays of solar radiation.
- Depletion of ozone may result in rise of temperature of ground surface and lower atmosphere.
- Temperature rises from -60°C at the base of the stratosphere to its upper boundary as it absorbs ultra-voilet rays.
- Upper limit of the Stratosphere is called stratopause.
- This is the third layer of the atmosphere and lies above the stratosphere.
- Mesosphere extends to the height of 50 – 90 km.
- Temperature decreases with height. It reaches a minimum of -80°C at an altitude of 80-90 km
- It is the coldest layer of the atmosphere.
- The upper limit is called the menopause.
- Meteorites burn up in this layer on entering from the space.
- It lies at 80 km to 640 km above the earth’s surface.
- It is also known as Ionosphere.
- Temperature increases rapidly with increasing height.
- It is an electrically charged layer. This layer is produced due to the interaction of solar radiation and the chemicals present, thus disappears with the sunset.
- In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
- There are a number of layers in thermosphere e.g. D-layer, E-layer, Flayer and G-layer.
- Radio waves transmitted from earth are reflected back to the earth by these layers.
- This layer contains electrically charged air that protects the Earth from falling meteorites as most of them burn out in this region.
- This is the uppermost layer of the atmosphere extending beyond the ionosphere.
- The density is very low and the temperature becomes 5568°C.
- This layer merges with the outer space.
- Light gases like helium and hydrogen float into space from here.
- It extends from the top of the thermosphere up to 10,000 km (6,200 mi).