Atmosphere
The atmosphere can be defined as the gas and the aerosol envelope which extends from the ocean land, and from the ice-covered surface of a planet to space above. The atmosphere density goes on to decrease outward, this happens because of the gravitational attraction of the earth, which pulls the gases and aerosols inward.
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In this context, we will learn about different layers of the atmosphere viz. Stratosphere, Mesosphere, Troposphere, Thermosphere.
Stratosphere and Mesosphere
The stratosphere is typically a layer of the earth’s atmosphere. Moving upward, this will be the second layer of the atmosphere. The bottom of the stratosphere is round about 10 km above the ground situated at the middle latitudes. The top portion of the stratosphere occurs at an altitude of about 50 km. While the height of the bottom of the stratosphere keeps varying with altitude and seasons. The lower boundary of the stratosphere is known as tropopause while the upper boundary is called the stratopause.
The mesosphere is another layer of the Earth's atmosphere. The mesosphere is right above the stratosphere and below the thermosphere layer. This layer extends from about 50 to 85 km above our planet’s earth.
The temperature gradually decreases with the height in the mesosphere. The coldest temperatures in Earth's atmosphere are found near the region of the top of this layer. At the bottom of the mesosphere is the stratopause lies the boundary between the mesosphere and the stratosphere.
The mesosphere is quite difficult to study, so lesser-known facts are available about this layer of the atmosphere than other layers. Weather balloons or other aircraft fail to fly high enough to reach this layer, the mesosphere. Satellites orbit above this layer cannot directly measure their traits.
Troposphere
The troposphere is the lowermost layer of the Earth's atmosphere and this layer is the site of all the weather occurrences on Earth. The tropopause is the boundary on the top of this layer, this separates the troposphere from the stratosphere.
75 percent of the atmosphere's mass comes under this layer. On average, the weight of the molecules present in the air is around 14.7 lb and this covers most of the atmosphere's water vapor. The most dominating gases are nitrogen which is 78 percent and oxygen that is 21 percent, with the remaining 1% as argon and traces of hydrogen ozone (that is formed of oxygen), with other constituents.
Thermosphere
The thermosphere is a layer of the atmosphere that is directly related to the mesosphere and down below the exosphere. This extends from about 90 km (that is 56 miles) to between 500 and 1,000 km (which is 311 to 621 miles) above our planet.
Temperatures rise sharply in the lower thermosphere which is below 200 to 300 km altitude, then level off and hold fairly steady with the increasing altitude above that height. Here the solar activity gets strongly influenced by temperature in the thermosphere. The thermosphere is typical of about 200° C which is hotter in the daytime than at night, and this is roughly 500° C hotter at the time when the Sun is very active than at other times.
Distance of Stratosphere, Ionosphere, Troposphere, and Mesosphere
Troposphere
The troposphere starts right at the Earth's surface which extends 8 to 14.5 kilometers higher (which is 5 to 9 miles). The troposphere is the densest layer of the atmosphere. All-weather types are in this region.
Stratosphere
The stratosphere here starts just above the troposphere which extends up to 50 kilometers that is 31 miles high. This ozone layer functions by absorbing and scattering the solar ultraviolet radiation is in this layer.
Mesosphere
The mesosphere starts immediately above the stratosphere and this extends to 85 kilometers (which is 53 miles) high. Meteors in the space burn up in this layer.
Thermosphere
The thermosphere here starts right above the mesosphere and this extends to 600 kilometers (that is 372 miles) high. The Aurora and satellites occur in this definite layer.
FAQs on Stratosphere and Mesosphere
1. What are the main layers of the Earth's atmosphere in order from the ground up?
The five main layers of the Earth's atmosphere, starting from the ground and moving upwards, are the Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere. Each layer has distinct characteristics regarding temperature, composition, and density.
2. What is the stratosphere and what are its key characteristics?
The stratosphere is the second major layer of the atmosphere, found between approximately 12 and 50 kilometres above the Earth's surface. Its key characteristics include:
- It contains the ozone layer, which absorbs the majority of the sun's harmful ultraviolet (UV) radiation.
- The temperature increases with altitude due to this absorption of UV energy.
- It is a very stable layer with minimal weather, making it the preferred altitude for commercial jet aircraft to fly.
3. What defines the mesosphere and where is it located?
The mesosphere is the atmospheric layer located directly above the stratosphere, from about 50 to 85 kilometres in altitude. It is primarily defined by its extremely cold temperatures, which decrease with increasing altitude. This is the layer where most meteors and space debris burn up upon entering the atmosphere, creating the phenomenon known as shooting stars.
4. What is the main difference between the stratosphere and the mesosphere in terms of temperature?
The primary difference is their temperature profile. In the stratosphere, temperature increases as you go higher because the ozone layer absorbs solar radiation. In contrast, the temperature in the mesosphere decreases as you go higher, making it the coldest layer of the atmosphere, as it has very few gases to absorb heat.
5. Why does temperature increase with altitude in the stratosphere?
Temperature increases with altitude in the stratosphere because this layer contains a high concentration of ozone (O₃) molecules. The ozone layer absorbs high-energy ultraviolet (UV) radiation from the sun. This absorption process converts the UV energy into heat, warming the upper parts of the stratosphere more intensely than the lower parts and creating a temperature inversion.
6. Why is the mesosphere the coldest layer of the Earth's atmosphere?
The mesosphere is the coldest layer, with temperatures dropping to as low as -90°C, mainly because the air is extremely thin, with a very low density of molecules. This means there is very little gas to absorb solar radiation. Furthermore, the few molecules present, such as carbon dioxide, are effective at radiating heat away into space, a process known as radiative cooling.
7. What is the importance of the ozone layer within the stratosphere?
The ozone layer is fundamentally important for protecting life on Earth. It functions as a natural shield by absorbing about 97-99% of the sun's harmful UV-B and UV-C radiation. Without this protective layer, living organisms would be exposed to dangerous radiation levels, which can cause skin cancer, harm plant life, and damage marine ecosystems.
8. What natural phenomena and human activities occur in the stratosphere and mesosphere?
- In the stratosphere, human activities include flying high-altitude jet aircraft and launching weather balloons. The key natural phenomenon is the constant formation and destruction of ozone.
- In the mesosphere, the most famous phenomenon is the burning of meteors. This layer also hosts 'noctilucent clouds' or 'night-shining clouds', which are the highest clouds in our atmosphere.
9. How do the stratopause and mesopause act as boundaries for these atmospheric layers?
The stratopause and mesopause are thin transitional zones that mark the top of their respective layers by a change in temperature trend:
- The stratopause is the boundary above the stratosphere. It is the point of maximum temperature, after which the temperature begins to decrease as one enters the mesosphere.
- The mesopause is the boundary above the mesosphere. It represents the coldest point in the entire atmosphere, after which temperatures begin to rise sharply in the thermosphere.
10. Can commercial aeroplanes fly in the mesosphere? Why or why not?
No, commercial aeroplanes cannot fly in the mesosphere. The primary reasons are:
- The air is far too thin in the mesosphere to provide the necessary aerodynamic lift for an aircraft's wings to function.
- Jet engines rely on oxygen from the air to burn fuel, and the atmosphere in the mesosphere is too sparse in oxygen to support combustion.
Aeroplanes fly in the lower stratosphere to take advantage of its stability while still having enough air for lift and engine operation.
