Composition of the Atmosphere

1. Composition of the Atmosphere • A mixture of chemical elements and compounds: • Nitrogen (N2) ~ 78% • Oxygen (O2) ~ 21% • Other gases ~ 1%

2. Layers of the Atmosphere

3. Thermosphere - the atmospheric layer above the mesosphere. • Mesosphere - coldest layer of the atmosphere that extends upward from the stratosphere to an altitude of about 80 km. • Stratosphere - layer of the atmosphere that extends upward from the troposphere to an altitude of 50 km; contains most atmospheric ozone. • Troposphere - atmospheric layer closest to the earth’s surface where nearly all weather occurs.

4. Air Pollution • Temperature Inversion – atmospheric condition in which warm air traps cooler air near the earth’s surface.

5. Conduction, Convection and Radiation • Conduction – type of energy transfer in which vibrating molecules pass heat along to other vibrating molecules by direct contact. • Convection – transfer of heat through the movement of a fluid material. • Radiation - energy that is radiated or transmitted in the form of rays or waves or particles.

6. Units of Standard Atmospheric Pressure: 760 mm 29.92 in of Mg 1 atmosphere 1000 millibars (mb) Mercurial Barometer Barometers

7. Energy Transfer in the Atmosphere • Conduction – direct contact • Convection – movement of a fluid, such as air • Radiation – no direct contact

8. Which is Which?

9. The Atmosphere and Solar Radiation • About 70% of the solar energy that reach Earth is absorbed by land, water, and atmosphere. 30% is reflected back into space. • Scattering – deflection of solar radiation • Albedo – percentage of solar radiation reflected off a surface • Earth’s total albedo = 30%

10. The Greenhouse Effect and Global Warming • How are people speeding up the Greenhouse Effect? • Pollution • Cars • Factories • Increased population • Cutting down trees • Burning fossil fuels • Are people causing global warming and the greenhouse effect?