13.2 Radiation, Conduction & 13.2 Radiation, Conduction & Convection Convection

Before you learnedBefore you learned

The atmosphere supports and protects lifeThe atmosphere supports and protects lifeThe atmosphere contains a mixture of The atmosphere contains a mixture of

gasses.gasses.78% Nitrogen78% Nitrogen21% Oxygen21% Oxygen1% Other gasses1% Other gasses

The atmosphere is affected by natural The atmosphere is affected by natural processes.processes.

Now we will learn howNow we will learn how

Solar energy heats earth’s surface and Solar energy heats earth’s surface and atmosphere.atmosphere.

The atmosphere moves heat energy The atmosphere moves heat energy around.around.

The layers of the atmosphere play a role in The layers of the atmosphere play a role in the movement of energy.the movement of energy.

13.2 Key Terms13.2 Key Terms

RadiationRadiationEnergy that travels distances in the form of Energy that travels distances in the form of

waves. This can include solar radiation like waves. This can include solar radiation like UV radiation and visible light. UV radiation and visible light.

ConductionConductionThis is the transfer of heat based on direct This is the transfer of heat based on direct

contact. You walk on a hot sidewalk or touch contact. You walk on a hot sidewalk or touch a hot piece of metal.a hot piece of metal.

13.2 Key Terms13.2 Key Terms

ConvectionConvectionThis is the transfer of heat energy from place This is the transfer of heat energy from place

to place by the motion of a gas or a liquid. to place by the motion of a gas or a liquid. Think about pouring a hot liquid into a cold Think about pouring a hot liquid into a cold one, or feeling the heat rising off of a fire. one, or feeling the heat rising off of a fire.

RadiationRadiation

Radiation is not always a bad thing! Radiation is not always a bad thing! Solar radiation constantly is bombarding Solar radiation constantly is bombarding

earth. Without it, we would not be able to earth. Without it, we would not be able to live. live.

Solar radiation provides us with light and Solar radiation provides us with light and heat. heat.

However, not all of the radiation from the However, not all of the radiation from the sun reaches our planet’s surface. sun reaches our planet’s surface.

Radiation and EarthRadiation and Earth

Of the 100% of solar energy that reaches Of the 100% of solar energy that reaches our planet, only about 70% is actually our planet, only about 70% is actually absorbed. Here’s the breakdown;absorbed. Here’s the breakdown;

70% absorption70% absorption40-45% absorbed by Earth’s surface.40-45% absorbed by Earth’s surface.

This radiation can be released as heat from Earth’s This radiation can be released as heat from Earth’s surface, be used to evaporate water, or to create surface, be used to evaporate water, or to create wind.wind.

25-30% absorbed by Earth’s atmosphere.25-30% absorbed by Earth’s atmosphere.

Radiation and EarthRadiation and Earth

30% Reflection30% Reflection25% by clouds in the atmosphere25% by clouds in the atmosphere5% by surface objects such as glass & metal 5% by surface objects such as glass & metal

buildings, ice and snow. buildings, ice and snow.

Solar Energy and Earth’s Solar Energy and Earth’s AtmosphereAtmosphere

The atmosphere moves energyThe atmosphere moves energy

It does this through 3 actionsIt does this through 3 actionsRadiationRadiationConductionConductionConvectionConvection

Radiation and the atmosphereRadiation and the atmosphere

The atmosphere as we have already The atmosphere as we have already pointed out, is capable of absorbing some pointed out, is capable of absorbing some heat from the sun. heat from the sun.

It absorbs a special kind of energy called It absorbs a special kind of energy called infrared energy. infrared energy.

Conduction & the atmosphereConduction & the atmosphere

Conduction is the transfer of energy based Conduction is the transfer of energy based on direct contact. on direct contact.

When you walk along a hot beach, the When you walk along a hot beach, the heated atoms in the sand are making heated atoms in the sand are making contact with the atoms in your foot. They contact with the atoms in your foot. They transfer energy to your foot and your foot transfer energy to your foot and your foot gets hot.gets hot.

Conduction & the atmosphereConduction & the atmosphere

The atmosphere can be heated by The atmosphere can be heated by conduction. You have seen this (and conduction. You have seen this (and convection too) if you’ve ever seen air convection too) if you’ve ever seen air shimmering and waving over a parking lot shimmering and waving over a parking lot on a hot summers day. on a hot summers day.

This transfer of heat by direct contact This transfer of heat by direct contact causes the air to rise, and cool air rushes causes the air to rise, and cool air rushes in below to take its place.in below to take its place.

Convection and the atmosphereConvection and the atmosphere

Convection is the movement of air through Convection is the movement of air through the atmosphere. the atmosphere.

The air movement is driven by energy The air movement is driven by energy gained from radiation or conduction. gained from radiation or conduction.

As the air gains energy, the atoms move As the air gains energy, the atoms move more, spreading out. more, spreading out.

As they spread out, they become less As they spread out, they become less dense, and are squeezed up by colder, dense, and are squeezed up by colder, more dense air trying to get under it. more dense air trying to get under it.

Convection and the atmosphereConvection and the atmosphere

Density and the atmosphereDensity and the atmosphere

Differences in density are what drive the Differences in density are what drive the movement.movement.The differences in density are caused by solar The differences in density are caused by solar

energy however.energy however.