Layers of the Atmosphere

Science  Notes - 4th Quarter


Lesson 1 - Layers of the Atmosphere

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The Atmosphere


The atmosphere constantly maintains the temperature of Earth. This means that the atmosphere prevents large differences in temperature between day and night. 


  • The atmosphere protects Earth from harmful solar radiation during the day, and traps heat to keep Earth warm during the night.


  • The atmosphere is made up of five main layers, based on temperature gradients, hovering up to more than 400 km above Earth's crust. 



Troposphere

The troposphere is the layer of the atmosphere closest to Earth's surface. Its name comes from the Greek word tropos, which means change.


  • This is the layer humans are in direct contact with, and where most of the weather phenomena occurs. It extends from the ground to about 10 to 14 km above sea level, with slight variation in the equator and the poles.


  • At the equator where the air is warmer, the troposphere is thicker and can extend as high as 18 to 20 km. In contrast, at the north and south poles, where the air is colder, the troposphere is thinner reaching from 6 to 9 km.


  • About 75% of the mass of air, and 99% of water vapor in the atmosphere is found in the troposphere. Weather systems occur within the troposphere, including the formation of thunder and lightning.


  • Because of the dynamic interplay of weather forces, airplanes flying within the troposphere experience turbulence.


  • Temperature in the troposphere decreases as altitude increases.


Stratosphere


The stratosphere is a layer of Earth's atmosphere that lies above the troposphere. Its name comes from the Greek word, strat, which means layer because it is subdivided into layers based on air temperature. 


  • In contrast with the troposphere, the temperature in the stratosphere increases with altitude. The stratosphere is about 35 km thick. 


  • Within the stratosphere, about 15 to 30 km above Earth, is a thin layer called the ozone layer. This layer absorbs the harmful ultraviolet radiation from the sun, which explains why temperature in the stratosphere increases with altitude. 


  • The highest point in the atmosphere where supersonic jet planes can reach is within the stratosphere. 


Mesosphere 


The mesosphere is a layer of Earth's atmosphere, about 35 km thick, that lies above the stratosphere. The name is derived from the Greek word meso, which means middle.


  • It is the highest layer of the atmosphere where the gases are mixed up, regardless of their masses. Gas molecules in the mesosphere are closely packed, constantly colliding with each other, causing friction on passing meteoroids and asteroids.



Lesson 1 - Layers of the Atmosphere

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Mesosphere 


  • Friction causes these high-speeding space rocks to burn into fire balls as they pass through. Meteor showers are observed in the mesosphere. You cannot breathe the air in the mesosphere because it is too thin.


  • The temperature in the mesosphere decreases with altitude. It is the coldest layer of the atmosphere, with temperature ranges of about -2.5 to -90°C. 


  • The boundary between the mesosphere and the thermosphere above it is called the mesopause.



Thermosphere


The thermosphere is a layer of Earth's atmosphere that lies above the mesosphere. It is named after the Greek word thermos, which means heat. In the thermosphere, temperature greatly increases with altitude; the temperature in the upper thermosphere could reach up to 2200°C.


  • The International Space Station (ISS) of the National Aeronautics and Space Agency (NASA), as well as the Maya cube satellites (400 km) of the Philippine Space Agency (PSA), orbit within the thermosphere.


  • Within the thermosphere and mesosphere is an overlapping ion-rich layer called the ionosphere, where electrically charged particles are ionized due to radiation from the sun. 


  • The Northern Lights are produced in the thermosphere. The boundary between the upper thermosphere and the exosphere above is called the thermopause.



Exosphere


The exosphere is the outermost layer and edge of Earth's atmosphere. It is named after the Greek word exo, which means outside. This sphere is about 10000 km thick and blends with interplanetary space. 


  • The exosphere is mostly composed of hydrogen and helium atoms that are widely spaced out. There is no breathable air in the exosphere, and the temperature could reach up to 1500°C.