13.2 Radiation, Conduction &
Convection
Before you learned
The atmosphere supports and protects life
 The atmosphere contains a mixture of
gasses.

78% Nitrogen
 21% Oxygen
 1% Other gasses


The atmosphere is affected by natural
processes.
Now we will learn how
Solar energy heats earth’s surface and
atmosphere.
 The atmosphere moves heat energy
around.
 The layers of the atmosphere play a role in
the movement of energy.

13.2 Key Terms

Radiation


Energy that travels distances in the form of
waves. This can include solar radiation like
UV radiation and visible light.
Conduction

This is the transfer of heat based on direct
contact. You walk on a hot sidewalk or touch
a hot piece of metal.
13.2 Key Terms

Convection

This is the transfer of heat energy from place
to place by the motion of a gas or a liquid.
Think about pouring a hot liquid into a cold
one, or feeling the heat rising off of a fire.
Radiation
Radiation is not always a bad thing!
 Solar radiation constantly is bombarding
earth. Without it, we would not be able to
live.
 Solar radiation provides us with light and
heat.
 However, not all of the radiation from the
sun reaches our planet’s surface.

Radiation and Earth
Of the 100% of solar energy that reaches
our planet, only about 70% is actually
absorbed. Here’s the breakdown;
 70% absorption


40-45% absorbed by Earth’s surface.
 This
radiation can be released as heat from Earth’s
surface, be used to evaporate water, or to create
wind.

25-30% absorbed by Earth’s atmosphere.
Radiation and Earth

30% Reflection
25% by clouds in the atmosphere
 5% by surface objects such as glass & metal
buildings, ice and snow.

Solar Energy and Earth’s
Atmosphere
The atmosphere moves energy

It does this through 3 actions
Radiation
 Conduction
 Convection

Radiation and the atmosphere
The atmosphere as we have already
pointed out, is capable of absorbing some
heat from the sun.
 It absorbs a special kind of energy called
infrared energy.

Conduction & the atmosphere
Conduction is the transfer of energy based
on direct contact.
 When you walk along a hot beach, the
heated atoms in the sand are making
contact with the atoms in your foot. They
transfer energy to your foot and your foot
gets hot.

Conduction & the atmosphere
The atmosphere can be heated by
conduction. You have seen this (and
convection too) if you’ve ever seen air
shimmering and waving over a parking lot
on a hot summers day.
 This transfer of heat by direct contact
causes the air to rise, and cool air rushes
in below to take its place.

Convection and the atmosphere
Convection is the movement of air through
the atmosphere.
 The air movement is driven by energy
gained from radiation or conduction.
 As the air gains energy, the atoms move
more, spreading out.
 As they spread out, they become less
dense, and are squeezed up by colder,
more dense air trying to get under it.

Convection and the atmosphere
Density and the atmosphere

Differences in density are what drive the
movement.

The differences in density are caused by solar
energy however.