Layers of the Atmosphere

Key Vocabulary Troposphere - Tropopause Stratosphere - Stratopause Ozone Chlorofluorocarbons or CFCs Mesosphere - Mesopause Meteorite Thermosphere/Ionosphere/Exosphere Aurora Borealis  Ions

Troposphere This is the layer that we live in. This is the layer that weather occurs. The troposphere is the most turbulent layer in the atmosphere. The height varies from 6km at the poles to 12km at the equator. The most distinguishing feature & how we tell it apart from Stratosphere, is that the temperature decreases until you reach the tropopause. As The air gets thinner, there are less molecules to absorb energy from the Sun.

Stratosphere The Stratosphere is the next layer and very important layer. The Stratosphere contains the Jet Stream and the Ozone Layer. Temperature rises from the Tropopause to the Stratopause. The temperature rises because the ozone layer absorbs so much ultraviolet radiation. 50 km from Earth to top of Stratosphere.

Jet Stream Jet streams are fast flowing, air currents found in the atmosphere at around 11 kilometers above the surface of the Earth. The major jet streams are westerly winds (flowing west to east) in both the Northern Hemisphere and the Southern Hemisphere. The Jet Steam is used by commercial airlines to help them fly from west to east. Otherwise airliners fly in the Stratosphere to avoid weather and turbulent air.

Ozone It is mainly located in the lower portion of the stratosphere from approximately 15 km to 35 km above Earth's surface. The ozone layer absorbs 97-99% of the sun's high frequency ultraviolet light. Ozone in the earth's stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (O2), splitting them into individual oxygen atoms (atomic oxygen). The atomic oxygen then combines with unbroken O2 to create ozone, O3.

Ozone The O3 is unstable and breaks apart into O2 and atomic oxygen to begin the process over again—creating the ozone-oxygen cycle. Human activity is causing Ozone depletion and holes in the Ozone layer. Compounds in aerosol sprays (chlorofluorocarbons or CFCs), Freon and things like paint fumes break up ozone and destroy our protective layer. Most of these compounds are now banned.

Mesosphere The Mesosphere extends from the Stratopause up to 80 km above the Earth’s surface. The gases in the mesosphere are too thin to absorb much of the Sun's heat. Although the air is still thick enough to slow down meteorites hurtling into the atmosphere. They burn up, leaving fiery trails in the night sky. Temperature drops as you go from Stratopause to Mesopause. Temperature drops because the air molecules become thinner and thinner, absorbing less energy from the Sun.

Thermosphere The Thermosphere extends from the Mesopause up to 300 km. The gases of the thermosphere are even thinner than those in the mesosphere, but there is so much energy available from the sun that the temperature rises to 2000 oC at the top. This layer of the atmosphere would still feel very cold to our skin because of the extremely thin air. The total amount of energy from the very few molecules in this layer is not enough to heat our skin. The Thermosphere is divided into two layers, the Ionosphere and the Exosphere.

Thermosphere - Ionosphere It is made of electrically charged gas particles (ions). The ions get this electric charge by ultraviolet rays of the sun. The ionosphere has the important quality of bouncing radio signals, transmitted from the earth. That’s why places all over the world can be reached via radio. At the north pole, rays from the sun skip off the ionosphere and produce the Northern Lights (Aurora borealis).

Thermosphere--Exosphere The Exosphere is the outermost layer of the atmosphere and extends from 430 miles(700 km) to 500 miles(800 km) above the ground. In this layer gases get thinner and thinner and drift off into space. At the outer edge of the Exosphere we deploy communication satellites.

Summary-Why the Atmosphere has been divided into layers Temperature drops as you go from the surface of the Earth to the Tropopause. Temperature rises from the Tropopause to the Stratopause. Temperature drops as you go from Stratopause to Mesopause. Temperature rises from the Mesopause up through the Thermosphere.