Layers of the Atmosphere/Troposphere/Stratosphere/Mesosphere/Thermosphere/Exosphere

Layers of the Atmosphere

The Earth’s atmosphere is composed of five distinct layers, each characterized by unique thermal characteristics, chemical composition, movement, and density. These layers are separated by transition zones known as “pauses,” where significant changes in these properties occur.

1. Exosphere

Altitude Range: 600 km to 10,000 km above Earth.

Characteristics: The outermost layer where atoms and molecules escape into space. Satellites orbit within this layer.

Transition: The thermopause marks the lower boundary.

2. Thermosphere

Altitude Range: 85 km to 600 km.

Characteristics: Known as the upper atmosphere. It absorbs high-energy ultraviolet and X-ray radiation from the sun, causing temperatures to rise significantly from -120°C to as high as 2000°C. Despite the high temperatures, it would feel cold due to the thin air.

Transition: The mesopause at the lower boundary.

3. Mesosphere

Altitude Range: 50 km to 85 km.

Characteristics: The layer where temperatures decrease with altitude, reaching about -15°C at its lower boundary. This layer is dense enough to burn up meteors, creating visible trails.

Transition: The stratopause at the lower boundary.

4. Stratosphere

Altitude Range: 6-20 km to 50 km.

Characteristics: Contains 19% of the atmosphere’s gases, with temperature increasing with height due to ozone formation, which heats the layer. Temperature ranges from -51°C to -15°C. The lack of convection prevents vertical air movement.

Transition: The tropopause at the lower boundary.

5. Troposphere

Altitude Range: Surface to 8-18 km.

Characteristics:

a)The lowest layer of the atmosphere, in contact with Earth’s surface, known for vertical mixing and turbulence. The name “troposphere” and “tropopause” derive from the Greek word tropos (“turn”), indicating the overturning of air in this zone. 

b) The depth of the troposphere varies, being deepest over tropical regions and shallowest over the poles. It is also deeper in summer than in winter and changes with the passage of warm and cold air masses.
c) On average, the top of the troposphere is about 18 km above sea level at the equator and about 8 km above sea level over the poles. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.

d) As the density of the gases decreases with height, the air becomes thinner, and temperature drops from around 17°C to -51°C at the tropopause.