Introduction to the Atmosphere

Earth's Atmosphere An envelope of air surrounding the planet Earth. How would you define air? What's it made of?

Air is a mixture of solids, liquids, and mostly gases.

Gases in the Atmosphere Permanent Gases: Nitrogen (N2): 78% Oxygen (O2): 21% Argon (Ar): 0.9% Carbon Dioxide (CO2): 0.04% Water Vapor (H2O): 0.0-4.0% Trace Gases (others): 0.01%

Variable Gases Water Vapor (H2O) Carbon Dioxide (CO2) Ozone (O3) Others

Atmospheric pressure decreases with increasing height Atmospheric pressure decreases with increasing height. Since most of the atmosphere's molecules are held close to the earth's surface by the force of gravity, air pressure decreases rapidly at first, then more slowly at higher levels.

Layers of the Atmosphere Troposphere Weather, jets fly here. Stratosphere Ozone Layer Mesosphere Meteors burn up here Thermosphere Ionosphere and Northern Lights Very few particles Exosphere Transition from atmosphere to space

What does the atmosphere do for us? Earth's atmosphere acts as an insulating layer that protects the earth's surface from the intense light and heat of the sun.  Contains oxygen, which we and other living organisms breathe. Medium of transport for various chemicals, including, but not limited to, water (in the form of rain, snow, steam, etc), carbon dioxide and oxygen (for cycling of these chemicals between plants and animals), and nitrogen (which helps plants grow).