The AtmosphereThe Atmosphere

Chapter 6Chapter 6

About the PhotoAbout the Photo Imagine climbing a mountain and taking only one out Imagine climbing a mountain and taking only one out of three breaths! As altitude increases, the density of of three breaths! As altitude increases, the density of the atmosphere decreases. At the heights shown in this the atmosphere decreases. At the heights shown in this picture, the atmosphere is so thin that it contains only picture, the atmosphere is so thin that it contains only 30% of the amount of oxygen found in the atmosphere 30% of the amount of oxygen found in the atmosphere at sea level. So, most mountaineers carry part of their at sea level. So, most mountaineers carry part of their atmosphere with them—in the form of oxygen tanks.atmosphere with them—in the form of oxygen tanks.

Characteristics of the Characteristics of the AtmosphereAtmosphere

The The atmosphereatmosphere is a mixture of gases is a mixture of gases that surrounds Earth. In addition to that surrounds Earth. In addition to containing the oxygen you need to containing the oxygen you need to breathe, the atmosphere protects you breathe, the atmosphere protects you from the sun's damaging rays. The from the sun's damaging rays. The atmosphere is always changing. Every atmosphere is always changing. Every breath you take, every tree that is breath you take, every tree that is planted, and every vehicle you ride in planted, and every vehicle you ride in affects the atmosphere's composition.affects the atmosphere's composition.

Composition of the Composition of the AtmosphereAtmosphere

Water is also found in the Water is also found in the atmosphere.atmosphere.

Liquid waterLiquid water (water (water droplets) and droplets) and solid watersolid water (snow and ice crystals)(snow and ice crystals) are are found in clouds. found in clouds. But most But most water in the atmosphere water in the atmosphere exists as an invisible gas exists as an invisible gas called called water vaporwater vapor.. When When atmospheric conditions atmospheric conditions change, water vapor can change, water vapor can change into solid or liquid change into solid or liquid water,water, and and rain or snowrain or snow might fall from the sky.might fall from the sky.

  Describe the three physical states of Describe the three physical states of water in the atmosphere. water in the atmosphere.

1.1. 2.2. 3.3.

Atmospheric Pressure and Atmospheric Pressure and TemperatureTemperature

What would carrying a column of air What would carrying a column of air that is 700 km high feel like? You may that is 700 km high feel like? You may be surprised to learn that you carry this be surprised to learn that you carry this load every day. While air is not very load every day. While air is not very heavy, its weight adds up. At sea level, a heavy, its weight adds up. At sea level, a square inch of surface area is under square inch of surface area is under almost 15 lb of air. Carrying that much almost 15 lb of air. Carrying that much air on such a small surface area is like air on such a small surface area is like carrying a large bowling ball on the tip carrying a large bowling ball on the tip of your finger!of your finger!

As in a human pyramid, air As in a human pyramid, air pressure pressure increasesincreases closer to closer to

the Earth's surface.the Earth's surface.   

                                                                                                                          

                         

Atmospheric Pressure and Temperature

• The atmosphere is held around the Earth by gravity. Gravity pulls gas molecules in the atmosphere toward the Earth’s surface, causing air pressure.

• As altitude increases (distance from the earth’s surface), air pressure decreases.

• Air temperature decreases as altitude increases too. Lower parts of the atmosphere are warmer because they contain a high percentage of gases that absorb solar energy.

Atmospheric Composition Atmospheric Composition Affects Air TemperatureAffects Air Temperature

Air temperature also changes as Air temperature also changes as altitude increases. The altitude increases. The temperature differences result temperature differences result mainly from the way solar mainly from the way solar energy is absorbed as it moves energy is absorbed as it moves through the atmosphere. Some through the atmosphere. Some parts of the atmosphere are parts of the atmosphere are warmer because they contain a warmer because they contain a high percentage of gases that high percentage of gases that absorb solar energy. Other absorb solar energy. Other parts of the atmosphere contain parts of the atmosphere contain less of these gases and are less of these gases and are cooler.cooler.

Layers of the AtmosphereLayers of the Atmosphere

                                                                                                      

                                             

The layers of the atmosphere are defined by changes in temperature.

Which layer of the atmosphere is closest to Earth?

Troposphere

-sphere-sphere means "ball," which suggests that means "ball," which suggests that each layer of the atmosphere surrounds the each layer of the atmosphere surrounds the Earth like a hollow ball.Earth like a hollow ball.

Tropo-Tropo- means "turning" or "change," and the means "turning" or "change," and the troposphere is the layer where gases turn troposphere is the layer where gases turn and mix. and mix.

Strato-Strato- means "layer," and the stratosphere means "layer," and the stratosphere is the sphere where gases are layered and do is the sphere where gases are layered and do not mix very much. not mix very much.

Meso-Meso- means "middle," and the mesosphere means "middle," and the mesosphere is the middle layer. Finally, is the middle layer. Finally,

thermo-thermo- means "heat," and the thermosphere means "heat," and the thermosphere is the sphere where temperatures are is the sphere where temperatures are highest.highest.

What does the name of What does the name of each atmospheric layer each atmospheric layer

mean? mean? -sphere-sphere Tropo-Tropo- Strato-Strato- Meso-Meso- thermo-thermo-

The Troposphere: The Layer The Troposphere: The Layer in Which We Livein Which We Live

The lowest layer of the atmosphere, which lies The lowest layer of the atmosphere, which lies next to the Earth's surface, is called the next to the Earth's surface, is called the tropospheretroposphere..

the densest atmospheric layer and contains the densest atmospheric layer and contains almost almost 90%90% of the atmosphere's total mass. of the atmosphere's total mass.

Has almost all of the Earth's gases, weather, Has almost all of the Earth's gases, weather, and and life-formslife-forms. .

Temperatures vary greatly here Temperatures vary greatly here Differences in air temperature and density Differences in air temperature and density

cause gases in the troposphere to mix cause gases in the troposphere to mix continuously.continuously.

As altitude increases in the As altitude increases in the troposphere, temperature decreases. troposphere, temperature decreases. Snow remains all year on this Snow remains all year on this mountain.mountain.

                                                             

              

The Stratosphere: Home of The Stratosphere: Home of the Ozone Layerthe Ozone Layer

The atmospheric layer above the tropo sphere is called The atmospheric layer above the tropo sphere is called the the stratospherestratosphere..

Gases in the stratosphere are layered and do not mix as Gases in the stratosphere are layered and do not mix as much as gases in the troposphere. much as gases in the troposphere.

The air is also very thin in the stratosphere and contains The air is also very thin in the stratosphere and contains little moisture. little moisture.

The lower stratosphere is extremely cold. The lower stratosphere is extremely cold. Unlike the troposphere temperature Unlike the troposphere temperature risesrises as altitude as altitude

increases in the stratosphere. This rise happens because increases in the stratosphere. This rise happens because ozoneozone in the stratosphere absorbs ultraviolet radiation in the stratosphere absorbs ultraviolet radiation from the sun, which warms the air. from the sun, which warms the air.

Almost all of the ozone in the stratosphere is contained Almost all of the ozone in the stratosphere is contained in the ozone layer. in the ozone layer.

The The ozone layerozone layer protects life on Earth by protects life on Earth by absorbingabsorbing harmful ultraviolet radiation.harmful ultraviolet radiation.

How does temperature change within the stratosphere?

For the first few kilometers, the

temperature remains fairly constant. Then,

the temperature begins rising steeply and levels off again toward the top

of the layer.

This photograph of Earth's atmosphere was taken from space. The troposphere is the yellow layer; the stratosphere is the

white layer.

The Mesosphere: The The Mesosphere: The Middle LayerMiddle Layer

Above the stratosphere is the Above the stratosphere is the mesosphere. The mesosphere. The mesospheremesosphere is the is the middle layer of the atmosphere.middle layer of the atmosphere.

It is also the coldest layer. It is also the coldest layer. Like the troposphere, the Like the troposphere, the

temperature decreases as altitude temperature decreases as altitude increases in the mesosphere. increases in the mesosphere.

The Thermosphere: The Edge of the The Thermosphere: The Edge of the AtmosphereAtmosphere

The uppermost atmospheric layer is called the The uppermost atmospheric layer is called the thermospherethermosphere.. In the thermosphere, In the thermosphere, temperature again increases with altitude. Atoms temperature again increases with altitude. Atoms of nitrogen and oxygen absorb high-energy solar of nitrogen and oxygen absorb high-energy solar radiation and release thermal energy, which radiation and release thermal energy, which causes temperatures in the thermosphere to be causes temperatures in the thermosphere to be 1,000°C or higher.1,000°C or higher.Although the thermosphere has very high temperatures, it does Although the thermosphere has very high temperatures, it does not feel hot. not feel hot. TemperatureTemperature is different from is different from heatheat. . TemperatureTemperature is a measure of the average energy of is a measure of the average energy of particles in motion.particles in motion. The high temperature of the The high temperature of the thermosphere means that particles in that layer are moving very thermosphere means that particles in that layer are moving very fastfast. . HeatHeat, however, is the transfer of thermal energy , however, is the transfer of thermal energy between objects of different temperatures.between objects of different temperatures. Particles Particles must touch one another to transfer thermal energy. The space must touch one another to transfer thermal energy. The space between particles in the thermosphere is so great that particles do between particles in the thermosphere is so great that particles do not transfer much energy. In other words, the density of the not transfer much energy. In other words, the density of the thermosphere is so low that particles do not often collide and thermosphere is so low that particles do not often collide and transfer energy.transfer energy.

Temperature in the Troposphere and the Thermosphere 

Which atmospheric layer has the greatest temperature range?

Thermosphere.

Why doesn’t it feel hot?

The Ionosphere: Home of The Ionosphere: Home of the Aurorasthe Auroras

Charged particles in the ionosphere cause auroras, or northern and southern lights. 

Explain how density affects the transfer of thermal energy.

The less dense the air is, the less effective it is at transferring thermal energy. Particles must

collide with one another to transfer energy. Particles

farther apart are less likely to collide with other particles than

particles that are close together.

Section SummarySection Summary

Nitrogen and oxygen make up most of Earth's Nitrogen and oxygen make up most of Earth's atmosphere. atmosphere. ••

Air pressure decreases as altitude increases. Air pressure decreases as altitude increases. •• The composition of atmospheric layers affects The composition of atmospheric layers affects

their temperature. their temperature. •• The troposphere is the lowest atmospheric The troposphere is the lowest atmospheric

layer. It is the layer in which we live. layer. It is the layer in which we live. •• The stratosphere contains the ozone layer, The stratosphere contains the ozone layer,

which protects us from harmful UV radiation. which protects us from harmful UV radiation. ••

The mesosphere is the coldest atmospheric The mesosphere is the coldest atmospheric layer. layer. ••

The thermosphere is the uppermost layer of The thermosphere is the uppermost layer of the atmosphere.the atmosphere.

Section QuizSection Quiz

Write the letter of the correct answer in the space provided._____ 1. Which answer best describes Earth’s atmosphere?a. mostly oxygen with about 21% nitrogenb. mostly nitrogen with about 21% oxygenc. mostly carbon dioxide with about 21% oxygend. mostly nitrogen with about 21% carbon dioxide_____ 2. What causes differences in air temperatures at different altitudes?a. mainly the way air radiates solar energyb. mainly the way gases radiate lightc. mainly the way gases absorb solar energyd. mainly the way moisture moves through the atmosphere_____ 3. What are the two highest layers of the atmosphere?a. troposphere, mesosphereb. thermosphere, mesospherec. stratosphere, thermosphered. troposphere, stratosphere_____ 4. Auroras are caused by electrically charged particles in thea. mesosphere.b. troposphere.c. hemisphere.d. ionosphere.

Match the correct definition with the correct term. Write the letter in the spaceprovided._____ 5. layered gases, thin air, little moisture_____ 6. coldest layer, temperature decreases asaltitude increases_____ 7. lack of particle density, little thermalenergy transfer_____ 8. densest layer, contains almost 90% ofthe atmosphere’s massa. troposphereb. thermospherec. stratosphered. mesosphere