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Composition and Structure of Earth’s Atmosphere

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  • Last Updated : 28 Apr, 2022
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A gaseous blanket that surrounds the Earth and includes the air we breathe is referred to as an atmosphere. The gravitational pull of the earth keeps it close to the planet’s surface. Argon, oxygen, and nitrogen are the three major components of the atmosphere. There is no separation between the atmosphere and outer space. The atmosphere eventually thins and densifies until it merges with space.

Composition of the Atmosphere

A planet’s atmosphere is a layer (or layers) of gas that surrounds it and is held in place by gravity. A planet’s atmosphere is preserved when gravity is high and the temperature of the atmosphere is low.

The atmosphere of the planet is made up of 78 percent nitrogen, 21% oxygen, 0.9 percent argon, 0.04 percent carbon dioxide, and trace gases. Furthermore, there is a variable amount of water vapor in the atmosphere (around 1% at sea level), which decreases with height. The fundamental cause of the greenhouse effect is carbon dioxide gas. Incoming sun energy does not pass through it, but outgoing terrestrial radiation does. Some terrestrial radiation is absorbed, while some are reflected back to the planet’s surface.

Dust particles can also be seen in the air. Sources include fine dirt, smoke-soot, pollen, dust, and dissolved meteoric particles. Dust and salt particles act as hygroscopic nuclei, allowing water vapor to condense and condensate, resulting in clouds.

Structure of Atmosphere

The structure of the atmosphere is divided into five levels based on temperature. These layers are as follows:

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere
  5. Exosphere

Troposphere

The troposphere is the atmosphere’s lowest layer. It rises from ground level to more than ten kilometers above sea level. The border layer of the troposphere is the lowest, and the tropopause is the highest. The troposphere holds 75% of the air in the atmosphere. Because it contains 99 percent of the water vapor in the atmosphere, this layer is where most clouds originate. As you fly higher into the troposphere, the temperature, and air pressure decrease. As it rises, an air packet expands. As it expands, the air cools. Because the air on the Earth’s surface absorbs the sun’s energy, heats up, and then cools down as it rises, the troposphere’s base is warmer than its top.

Stratosphere

The stratosphere is positioned above the troposphere and extends from the top of the troposphere to approximately 50 kilometers above the ground. The ozone layer is found in the stratosphere. The ozone molecules in this layer absorb the Sun’s high-energy ultraviolet (UV) light and convert it to heat. As a result, unlike the troposphere, the stratosphere warms up as one ascends.

Mesosphere

  1. The Mesosphere is located above the stratosphere.
  2. It is the coldest layer in the atmosphere.
  3. The mesosphere extends from 50 to 80 kilometers above the Earth’s surface.
  4. The temperature drops as you travel higher in this stratum.
  5. The temperature decreases to -100 degrees Celsius at 80 kilometers.
  6. Meteors are destroyed in this stratum.
  7. The Mesopause is the highest border between the Mesosphere and the Thermosphere.

Thermosphere

The thermosphere is located above the mesosphere and is characterized by rising temperatures as one ascends. The temperature rises due to the absorption of powerful UV and X-Ray energy from the sun. This layer’s air, on the other hand, is so thin that it appears rather cold to us! Satellites orbit the Earth within the thermosphere. Temperatures in the upper thermosphere can vary from 500 to 2,000 degrees Celsius or more. Northern and Southern Lights, known as Auroras occur in thermosphere.

Ionosphere

The ionosphere, unlike other layers of the atmosphere, is not a distinct layer. The ionosphere is a collection of mesosphere and thermosphere locations where high-energy solar radiation has stripped electrons from their parent atoms and molecules.

Exosphere

  1. It is the atmosphere’s outermost layer.
  2. The exosphere is an area of space from which molecules and atoms can escape.
  3. It can be seen from the top of the thermosphere for a distance of 10,000 kilometers.

Sample Problems

Question 1: What is the greenhouse effect?

Answer:

The greenhouse effect is created by gases in the Earth’s atmosphere trapping solar heat. As a result of this process, the Earth is significantly warmer than it would be in the absence of an atmosphere. One of the variables that contribute to Earth’s comfortable living circumstances is the greenhouse effect.

Question 2: Where does the Earth’s atmosphere end?

Answer:

The earth’s atmosphere does not end at a set point. As we ascend, the atmosphere becomes thinner. The boundary between the atmosphere and outer space is, at best, blurry. 75 percent of the atmosphere may be found within 11 kilometers of the Earth’s surface.

Question 3: The ozone layer is found in which layer of the atmosphere?

Answer:

The stratosphere contains the ozone layer. The stratospheric ozone layer protects the earth by absorbing the majority of UV light from the sun.

Question 4: Which atmospheric layer has very thin air and light gases?

Answer:

The exosphere layer’s air is exceedingly thin, and light gases like helium and hydrogen escape into space from here.

Question 5: What is global warming?

Answer:

When greenhouse gas levels grow due to manufacturing and industry smoke or car fumes, the trapped heat raises the temperature of the earth. This is known as global warming.

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