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- The atmosphere is composed of gases, water vapour and dust particles
- Mixer of dust particle and water vapor are called aerosol
- It receives Incoming solar energy from the sun giving rise to climate.
- We actually live at the bottom of this indefinite layer of atmosphere
- One estimate puts this limit at about 600 miles (950 km) above sea level.
- 99% of the total mass of the atmosphere is confined to the height of 32 km from the earth’s surface.
Composition of Atmosphere
- The proportion of Gases changes in the higher layers of the atmosphere
- Oxygen will be almost in negligible quantity at the height of 120 km.
- Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
- It constituting 2% to 4% of the total volume
- 90% of moisture content in the atmosphere exists within 6 km of the surface of the earth.
- Water vapour plays a significant role in the insulating action, of the atmosphere.
- It absorbs long-wave terrestrial radiation and part of the incoming solar radiation.
- Water vapour is the source of precipitation and clouds.
- It consist of sand particles, pollen grains, small organisms, soot, ocean salts
- These solid particles perform the function of absorbing, reflecting and scattering the radiation.
- It responsible for the orange and red colors at sunset and sunrise
- Blue color of the sky is due to selective scattering by dust particles.
- The Dust particles are an important factor in the formation of clouds, fog and hailstones.
Structure of Atmosphere
- The atmosphere consists of different layers with varying density and temperature.
- Density is highest near the surface of the earth and decreases with increasing altitude.
- The column of atmosphere is divided into 5 different layers depending upon the temperature condition.
- The troposphere is the lowermost layer of the atmosphere.
- Its average height is 13 km
- 8 km near the poles
- 18 km at the equator
- The thickness is greater at the equator because heat is transported to great heights by strong convectional currents.
- The temperature in this layer, as one goes upwards, falls at the rate of 5°C / km
- It reaches -45°C at the poles and -80°C over the equator
- The fall in temperature is called ‘lapse rate’.
- The troposphere is marked by temperature inversion, turbulence and eddies.
- Almost all whether activities like rainfall, fog and hailstorm etc. happens in this layer
- It acts as a boundary between troposphere and stratosphere.
- This layer has a constant temperatures.
- It extend up to an altitude of 50 km from the earth’s surface.
- The temperature rises to reach a level of 0°C at 50 km altitude.
- This rise is due to the presence of ozonosphere
- This layer is ideal for flying airplanes.
- Sometimes, cirrus clouds are present at lower levels in this layer.
- It lies at an altitude between 30 km and 60 km from the earth’s surface
- This layer absorbs ultraviolet radiation.
- The ozonosphere is also called chemosphere
- This layer continues upto an altitude of 80 km from the earth’s surface.
- The temperature gradually falls to -100°C at 80 km altitude.
- Meteorites burn up in this layer on entering from the space.
- In thermosphere temperature rises very rapidly with increasing height.
- Ionosphere is a part of this layer.
- It’s an electrically charged layer
- It extends between 80-400 km.
- Ionosphere helps in radio transmission.
- Thermosphere is also known as exosphere
- Person would not feel warm because of the thermosphere’s extremely low pressure.
- The International Space Station and satellites orbit in this layer.
- Aurora’s are observed in lower parts of this layer.
- Light gases like helium and hydrogen float into the space from here.