Earth’s atmosphere is divided into five different layers. These layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The five layers are distinguished by how temperature changes with altitude. Let’s dive deeper and explore some interesting facts about each layer.
Layers of the atmosphere
1. Troposphere
- It is the lowest and densest layer of the atmosphere, containing about 75% of the total atmospheric mass.
- All weather phenomena (rain, snow, storms, clouds) occur in this layer.
- The thickness of the troposphere varies, being widest at the equator and thinnest at the poles, typically ranging from 8 to 15 km.
- The temperature drops with altitude inside the troposphere.
- The boundary between the troposphere and stratosphere (the next layer) is called the tropopause.
2. Stratosphere
- The stratosphere is the second layer of the atmosphere, extending from the tropopause up to around 50 km above the Earth’s surface.
- The ozone layer, located within the stratosphere, protects us from the sun’s harmful ultraviolet (UV) radiation.
- Unlike the troposphere, the temperature in the stratosphere increases with altitude.
- The stratopause marks the boundary between the stratosphere and the mesosphere, the next layer of the atmosphere.
Why does temperature rise with altitude in the stratosphere?
In the stratosphere, the ozone layer absorbs the Sun’s ultraviolet (UV) radiation, warming the air. Higher portions of the ozone layer absorb more intense UV radiation, causing temperatures to rise with altitude.
3. Mesosphere
- The mesosphere starts after the stratopause and extends to about 85 km.
- The mesosphere is the layer where most meteors burn up upon entering the Earth’s atmosphere.
- In the mesosphere, temperature decreases with altitude.
- The mesopause marks the boundary between the mesosphere and the thermosphere (the next layer).
4. Thermosphere
- The thermosphere begins above the mesopause and extends roughly 500 to 1,000 km above the Earth’s surface.
- Auroras occur in the thermosphere.
- In the thermosphere, temperature increases with altitude.
- The thermopause marks the boundary between the thermosphere and the exosphere (the next layer).
Why does temperature rise with altitude in the thermosphere?
In the thermosphere, temperature rises with altitude because the few air molecules present absorb high-energy solar radiation, including X-rays and extreme ultraviolet (EUV) rays. This absorption increases the kinetic energy of the molecules, raising the temperature. At higher altitudes, molecules absorb more energy, causing temperatures to rise sharply.
5. Exosphere
- The exosphere begins above the thermopause and has no definite outer boundary, gradually merging into outer space.
- The outer boundary of the exosphere is roughly estimated to be about 10,000 km above the Earth’s surface.
Ionosphere
- The ionosphere overlaps portions of the mesosphere, thermosphere, and exosphere, extending roughly from 50 km to 1,000 km above the Earth’s surface. Its total thickness varies depending on the intensity of solar radiation.
- In the ionosphere, atoms are ionized by solar radiation and cosmic rays, losing electrons and becoming positively charged.
- The ionosphere helps in radio communication by reflecting radio waves back to Earth.
- The ionosphere is further divided into D, E, and F regions.
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