What do you mean by mesosphere
Mesosphere: Definition and Detailed Discussion
1. Introduction
The mesosphere is the third layer of Earth's atmosphere, located above the stratosphere and below the thermosphere. It extends from about 50 km to 85 km (31 to 53 miles) above Earth's surface. The mesosphere is the coldest atmospheric layer, where temperatures can drop as low as -90°C (-130°F). This layer is crucial for protecting Earth from meteoroids, as most burn up upon entry due to friction with atmospheric gases.
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2. Location and Structure of the Mesosphere
The mesosphere lies between the stratosphere (below) and the thermosphere (above). The boundaries of the mesosphere are:
Lower boundary: Stratopause (approximately 50 km) – Separates the stratosphere and mesosphere.
Upper boundary: Mesopause (approximately 85 km) – Marks the transition to the thermosphere.
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3. Characteristics of the Mesosphere
3.1 Temperature Profile
Unlike the stratosphere, where temperature increases with altitude due to ozone absorption of ultraviolet (UV) radiation, the mesosphere experiences a decrease in temperature with altitude.
The reason for this cooling is that there is very little ozone to absorb solar radiation, and the mesosphere also loses heat to space.
3.2 Atmospheric Composition
The mesosphere contains the same gases as the lower atmosphere but at extremely low densities.
The primary gases include nitrogen (N₂), oxygen (O₂), and trace amounts of carbon dioxide (CO₂) and water vapor.
Very few molecules exist in this layer due to the decreasing air density with altitude.
3.3 Atmospheric Pressure
Air pressure in the mesosphere is extremely low – about 1/1000th of the pressure at sea level.
The low density of air makes it difficult for aircraft or balloons to operate in this region.
3.4 Winds and Circulation
The mesosphere is known for strong zonal (west-east) winds and atmospheric tides.
It is an important region for gravity waves, which help transfer energy between atmospheric layers.
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4. Role and Importance of the Mesosphere
4.1 Protection from Meteoroids
The mesosphere burns up meteoroids that enter Earth's atmosphere.
The friction between meteoroids and atmospheric particles generates high temperatures, causing the meteors to glow and disintegrate, forming shooting stars or meteors.
4.2 Role in Weather and Climate
The mesosphere affects the movement of atmospheric waves and jet streams, which can influence lower atmospheric weather patterns.
Gravity waves formed in the troposphere dissipate in the mesosphere, transferring energy and impacting global circulation.
4.3 Electrical and Chemical Reactions
The mesosphere contains ions and charged particles that interact with the Earth's magnetic field.
This region plays a role in the formation of sprites and elves, which are electrical discharges caused by thunderstorms.
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5. Phenomena Observed in the Mesosphere
5.1 Noctilucent Clouds (NLCs)
Also known as polar mesospheric clouds, these are thin, bluish-white clouds that appear just after sunset or before sunrise.
They form when water vapor condenses on dust particles at very high altitudes (~80 km).
NLCs are most commonly observed in polar regions during summer.
5.2 Meteors and Meteor Showers
As meteoroids enter Earth's atmosphere, they burn up in the mesosphere due to intense friction, creating streaks of light known as meteors.
Some famous meteor showers include the Perseids (August) and Geminids (December).
5.3 Airglow
A faint glow in the night sky caused by chemical reactions in the mesosphere.
It occurs when oxygen and nitrogen atoms recombine, releasing light.
5.4 Lightning-Related Phenomena (Sprites and Elves)
Sprites: Large, red, jellyfish-like flashes of light that occur above thunderstorms.
Elves: Expanding rings of light that form due to electromagnetic pulses from lightning.
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6. Challenges in Studying the Mesosphere
The mesosphere is one of the least studied atmospheric layers because:
1. Too High for Airplanes and Balloons:
Aircraft and weather balloons cannot reach this altitude due to the thin air.
2. Too Low for Satellites:
Satellites orbit in the thermosphere and exosphere, making direct observations of the mesosphere difficult.
Methods Used to Study the Mesosphere
Rocket-borne instruments (sounding rockets)
Lidar (Light Detection and Ranging) technology
Ground-based radars that detect atmospheric waves and meteors
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7. Comparison with Other Atmospheric Layers
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8. Conclusion
The mesosphere is an important atmospheric layer despite being one of the least understood. It serves as Earth's protective shield against meteoroids, hosts fascinating phenomena like noctilucent clouds and sprites, and plays a role in atmospheric circulation. Due to its low density and extreme cold, direct studies are challenging, but continued research is crucial for understanding its influence on global climate and space weather.
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