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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.
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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.
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.
Density and the atmosphere • Differences in density are what drive the movement. • The differences in density are caused by solar energy however.
