Characteristics of the Atmosphere

1. Characteristics of the Atmosphere Pgs. 4 -9

2. What is the Atmosphere? • The atmosphere is a mixture of gases that surrounds the Earth. • It contains oxygen for us to breath. • It protects us from harmful UV rays.

3. Composition of the Atmosphere • Nitrogen = 78% • Oxygen = 21% • Carbon Dioxide, Water Vapor, Argon and others = 1% • Dust, volcanic ash, salts dirt and smoke make up some of the solids in the atmosphere. • Water droplets in the air are the most abundant liquid in the atmosphere.

4. Atmospheric Pressure and Temperature • Air pressure is the measure of the force with which the air molecules push on a surface. • Your ears pop on an airplane or elevator when the air pressure outside your ears changes and then equalize.

5. Pressure • The Earth’s atmosphere is held close to the surface by Earth’s gravity. • Most of the particles in the atmosphere are close to the surface and so pressure is greatest closest to the surface. • As you increase altitude, there are less air particles applying pressure to you and pressure decreases. • Altitude is the height of an object above the Earth’s surface.

6. Air Temperature • Air temperature changes as you increase altitude. • The temperature changes from cooler to warmer based upon how solar energy is absorbed as it moves through the different layers of the atmosphere. • Some layers will absorb more solar energy than others.

7. Troposphere • The lowest layer of the atmosphere is also the densest layer. • It contains 90% of the atmosphere’s total mass. • Most of the Earth’s carbon dioxide, water vapor, clouds, air pollution, weather, and life-forms are in the troposphere.

8. Stratosphere • The stratosphere is the second lowest layer of the atmosphere. • It has very thin air and contains little moisture. • Temperature ranges from -60 – 0. • Temperature rises with altitude due to Ozone molecules that absorb UV radiation. • Ozone is made of 3 Oxygen atoms.

9. Mesosphere • The mesosphere is above the stratosphere and is the coldest layer of the atmosphere. • Temperature decreases with altitude ranging from 0 – (-93) C. • Large wind storms exist in the mesosphere that can exceed 320km/hr winds!

10. Thermosphere • The uppermost atmospheric layer is the thermosphere. • The temperature increases with altitude. • Many gases absorb solar radiation. • Temperatures can reach 1,700 C. • The particles are very spread out and moving very fast, however, it would not feel very warm. • Heat is not transferred because the particles are too spread out.

11. Ionosphere • Within the lower thermosphere and upper mesosphere is an area where x-rays and gamma rays are absorbed. • Here the particles become electrically charged, like ions. • This area is known as the ionosphere. • Ions can radiate different light colors when charged. • The ionosphere can also reflect AM radio waves. • The more reflection that occurs, the clearer the signal.