14.1 Characteristics of the Atmosphere

Create a list of ways in which the atmosphere differs from outer space.

Atmosphere A mixture of gases that surrounds Earth.

Atmosphere

Air A mixture of gases that make up the atmosphere. Mostly nitrogen (78%). Oxygen (21 %).

Air Contains liquid water (water droplets). Contains solid water (snow and ice crystals). Contains small particles (Dust, volcanic ash, dirt, smoke).

Air

Air Pressure The measure of the force with which air molecules push on a surface. It’s equal to the weight of the air directly above that point. ( ex: pyramid)

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Why is air pressure highest near Earth’s surface? Air pressure is highest at Earth’s surface because there are a lot of air molecules near the surface and because air at the surface must support the weight of the entire atmosphere above.

Air Temperature Changes as altitude changes. Differences caused from the way that energy is absorbed by gases in the atmosphere.

Layers of the Atmosphere Troposphere Stratosphere Mesosphere Thermosphere

Troposphere The layer of the atmosphere that lies next to Earth’s surface. Contains 90% of atmosphere’s total mass. Contains water vapor, air pollution, and weather. Temperature decreases as altitude increases.

Stratosphere Layer above the troposphere. Air is thin and has little moisture. Temperature rises as altitude increases. Ozone layer – protects life on Earth by absorbing harmful ultraviolet radiation.

Atmosphere

Mesosphere The middle layer of the atmosphere. Coldest layer. Temperature decreases as altitude increases in the mesosphere.

Thermosphere Uppermost atmospheric layer. Temperature increases with altitude.

Why are temperatures high in the stratosphere and thermosphere? In the stratosphere, a layer of gas called ozone absorbs a lot of solar radiation. In the thermosphere, nitrogen and oxygen absorb high-energy radiation.

Review Questions Why does the temperature of different layers of the atmosphere vary? The temperature of the different layers of the atmosphere varies because the gases at different altitudes absorb solar radiation differently. What is air pressure? Air pressure is the measure of the force with which air molecules push on a surface. It is equal to the weight of the air directly above the point.

Why does air pressure decrease as altitude increases? Air pressure decreases as altitude increases because the weight of the overlying atmosphere decreases. 4. Compare the four atmospheric layers. How do temperatures and pressures vary between layers? Air pressure is highest at Earth’s surface and decreases as you move away. The layers of the atmosphere in order of decreasing air pressure are troposphere, stratosphere, mesosphere, and thermosphere. Temperature varies in the atmosphere depending on how gases absorb solar radiation. In the troposphere and mesosphere, temperature decreases as altitude increases. In the stratosphere and the thermosphere, temperature increases as altitude increases.