Earth’s Atmosphere

Chapter 1: Earth’s Changing Atmosphere

Section 1.2: The sun supplies the atmosphere’s energy.

I. Vocabulary

A. radiation- energy that travels across distances in the form of certain types of waves

B. conduction- the transfer of heat energy from one substance to another by direct contact

C. convection- the transfer of energy from place to place by the motion of a gas or liquid

II. Energy from the sun heats the atmosphere

A. Two things may happen to the sunlight that reaches the Earth

1. Sunlight is reflected (this is how you see things around you)

2. Sunlight is absorbed

B. The sunlight that we see is one type of radiation

1. About 30% of the solar radiation that hits the Earth is reflected

a. Clouds, icecaps are white, so they reflect a lot of light

b. Air reflects light also

2. About 70% of the solar radiation that hits the Earth is absorbed

a. Oceans, landforms, and living things absorb most light

b. Absorbed energy heats Earth’s surface

3. Absorption/reflection breakdown

III. The atmosphere moves energy

A. Radiation- sunlight warms the ground

B. Conduction- the warm ground heats the air

C. Convection- cold, dense air sinks downward and pushes warm air out of the way; warm air rushes energy upward

**Differences in density produce the motion of convection (textbook page 19)

IV. The atmosphere has temperature layers

A. Troposphere

1. Layer of the atmosphere nearest to the Earth’s surface

2. Contains about 80% of the total mass of the atmosphere, and almost all the water vapor

3. Temperature is highest at ground level and decreases 6.5^o C every km you rise

4. All weather occurs in the troposphere

B. Stratosphere

1. Clear, dry layer sitting above the troposphere

2. Contains the ozone layer, which absorbs harmful solar radiation and heats the surrounding air

3. Temperature increases as you go up

C. Mesosphere

1. Layer of extremely thin air above the stratosphere

2. Contains less than 0.1% of the atmosphere’s mass

3. Most meteors that enter the atmosphere burn up here

D. Thermosphere

1. Starts about 56 miles above the Earth’s surface, atop the mesosphere

2. Grows less and less dense, for many miles, until it fades to outer space

3. Air high in this layer is very hot because it absorbs a certain type of solar radiation

4. It would still feel cold to us, though, since molecules are so spread out

5. Temperature here increases as you rise