Earth’s AtmosphereEarth’s Atmosphere

• The Earth is surrounded by a blanket of air called the atmosphere.

• It extends over 372 miles (560 kilometers) from the surface of Earth

• It protects us from high-energy radiation and the frigid vacuum of space

• The atmosphere absorbs energy from the Sun, recycles water and other chemicals and works with the electrical and magnetic fields of Earth to provide a moderate climate

Composition of the Composition of the AtmosphereAtmosphere

• The atmosphere is made up of a mixture of atoms and molecules of different kinds of gases

• Each type of gas has important uses and roles for our planet

• Nitrogen, oxygen and argon are the primary components

• There are other very influential components including water, “greenhouse” gases or ozone and carbon dioxide

• Four distinct layers have been identified using temperature changes, chemical composition, movement and density:

Troposphere

Stratosphere

Mesosphere

Thermosphere

Layers of the AtmosphereLayers of the Atmosphere

Layers of the AtmosphereLayers of the Atmosphere

• The troposphere starts at the Earth’s surface and extends more than 9 miles above the equator to less than 5 miles above the North and South Poles

• Tropo means “turning” or “changing”

• Most dense part of the atmosphere

• As you climb higher, the temperature drops from about 17 to -52° C

• Almost all weather occurs at levels below 10 miles

The TroposphereThe Troposphere

The StratosphereThe Stratosphere

• The stratosphere extends from the top of the troposphere to about 31 miles above Earth’s surface

• Strato is similar to stratum which means “layer” or “spreading out”

• The lower stratosphere is –60° C

• The upper stratosphere is actually warmer than the lower stratosphere because of a thin layer of ozone, which absorbs energy form the sun which is converted to heat

The MesosphereThe Mesosphere• Above the stratosphere, a drop in temperature marks

the beginning of the next layer, the mesosphere

• Meso means “middle”

• It begins about 31 miles above Earth’ surface and ends at approximately 53 miles high.

• The outer mesosphere is the coldest part of the atmosphere, with temperatures near - 90° C

The ThermosphereThe Thermosphere

• The outermost layer is called the thermosphere, which extends from about 53 miles above Earth’s surface outward into space.– It is actually divided into two separate layers:

Ionosphere and Exosphere

• Thermo means “heat”

• The air is very thin in the thermosphere and extremely hot, up to 1800° C

The ThermosphereThe Thermosphere• The lower layer of the thermosphere is called

the ionosphere and begins about 53 miles above Earth’s surface and ends around 372 miles

• Energy from the sun causes gas molecules to become electrically charged particles called ions– Radio waves bounce off these ions and back

to the Earth

• The brilliant light display of the aurora borealis (Northern Lights) also occurs in the ionosphere

The Thermosphere: The Thermosphere: ExosphereExosphere

• The upper layer of the thermosphere is called the exosphere and extends from 372 miles outward for thousands of miles

• Satellites orbit in the exosphere

Most of the energy that keeps Earth warm comes from the Sun. Some of this energy is reflected or absorbed in the atmosphere. The rest reaches Earth’s surface, where it is reflected or absorbed

Solar energy is mostly visible light

and infrared radiation, and a small amount of

ultraviolet radiation

Clouds, dust and gases in the atmosphere reflect and scatter light

Gases and particles in the atmosphere absorb solar energy

Some energy that reaches the surface is reflected back into the atmosphere

Some of the absorbed energy is then radiated back into the atmosphere

Earth’s surface absorbs solar energy. This energy heats the land and water

Energy in the AtmosphereEnergy in the Atmosphere

Heat Movement in the Heat Movement in the TroposphereTroposphere

• Radiation, conduction and convection work together to heat the troposphere.

• When Earth’s surface absorbs solar energy during the day, the surface becomes warmer than the air.

• The air near the Earth’s surface is warmed by radiation and conduction of heat from the surface to the air.