Fix the mistake: Structure of the Atmosphere and Ocean

Composition and Layered Structure of the Atmosphere

The atmosphere surrounding Earth is not a simple mixture of gases; it has a layered structure in which temperature, composition, and properties differ greatly with altitude.

Basic Knowledge

Composition of the atmosphere (dry air):
・Nitrogen(N₂): approximately 78%
・Oxygen(O₂): approximately 21%
・Argon(Ar): approximately 0.93%
・Carbon dioxide(CO₂): approximately 0.04%(420 ppm, increasing as of 2024)
・Other gases: neon, helium, methane, water vapor (variable)
Layered structure of the atmosphere(classified according to patterns of temperature change with altitude):
①Troposphere(0〜approximately 12 km): Temperature decreases with altitude (temperature lapse rate approximately 6.5℃/km). Weather phenomena such as water vapor, clouds, and rain occur here. Convection is active.
②Stratosphere(approximately 12〜50 km): The ozone layer(approximately 20〜30 km) absorbs ultraviolet radiation, causing temperature to increase. It is stable, without convection. This is the upper limit of the altitude at which aircraft fly.
③Mesosphere(approximately 50〜80 km): Temperature decreases again. It is the coldest atmospheric layer (approximately -90℃). Meteors can be seen at this altitude.
④Thermosphere(approximately 80 km and above): Temperature rises sharply because of solar radiation (several hundred to more than one thousand℃). However, the air is thin and its heat capacity is small. Auroras occur here. The International Space Station (approximately 400 km) orbits at this altitude.

In Depth

Ozone(O₃) in the stratosphere protects life on Earth's surface by absorbing the Sun's ultraviolet radiation(UV-B). From the 1970s to the 1980s, ozone destruction by chlorofluorocarbons (CFCs) became a problem, and an ozone hole formed above Antarctica. The Montreal Protocol of 1987 regulated the production and use of CFCs, and the ozone layer has shown signs of recovery in recent years.
The average temperature lapse rate in the troposphere is 6.5℃/km, which is smaller than the standard-atmosphere dry adiabatic lapse rate (9.8℃/km). This is because latent heat released when water vapor condenses slows cooling.
Although the thermosphere has a high temperature, it contains few molecules and has extremely small heat capacity, so placing a body there would not feel hot (it is close to a vacuum). The “temperature” experienced by a satellite is direct heating by solar radiation.

Points to Note

① Memorize the order troposphere→stratosphere→mesosphere→thermosphere together with the temperature changes in each layer (decrease・increase・decrease・increase). ② The ozone layer is in the stratosphere(not the troposphere). ③ The “high temperature” of the thermosphere means that molecules have high kinetic energy; it does not mean that it would actually feel hot (there are few molecules).

Practice

1. State the three main components of dry air and their percentages.
2. State the four atmospheric layers in order from the bottom upward.
3. State the name of the layer where the ozone layer exists and the role of the ozone layer.