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4. Early atmosphere ~4.5 billion years ago Mostly Hydrogen and Helium Escaped into space Outgassing of water vapor and CO2 created a secondary atmosphere with some nitrogen As liquid water formed the oceans and CO2 was removed from atmosphere The atmosphere became dominated by nitrogen. ~ 2 billion years ago oxygen increased in the atmosphere because of plant life and photosynthesis. This allowed for the formation of the stratospheric ozone layer which further enhanced conditions for life on Earth.

5. 78 % Nitrogen N 2 20.95 % Oxygen O 2 0.93 % Argon Ar H 2 O 0 to 4 % Carbon Dioxide CO 2 0 to.037 % (or 370 ppm) Methane CH 4 1.8 ppm Nitrous Oxide N 2 O.3 ppm Ozone 0.04 ppm or 40 ppb) Aerosols (particles) highly variable Click to listen

6. It is important to realize that water vapor is invisible. The clouds you see in this photo are compose of liquid water droplets formed as water vapor condenses into liquid. When we breathe out our breath contains lots of water vapor. This water vapor can becomes visible water drops if we breath onto a cool piece of glass. By far invisible water vapor is the most important atmospheric greenhouse gas.

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8. Carbon Dioxide is the second most significant greenhouse gas.

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10. Methane is another important greenhouse gas. Preindustrial levels were less than half of what they are today. In the early part of the past decade it looked as if methane was stabilizing. More recently is has started to increase again. Click to listen

11. Low density High density Click to listen

12. Mass - quantity of matter Click to listen

13. Weight = mass x gravity Click to listen

14. Density = Mass /volume Click to listen

15. Pressure = Force /Area 300 lbs or 4 sq inches=75 psi 100 lbs or 0.25 sq inches=400 psi Click to listen

16. Standard Sea Level pressure is: 1 Atmosphere 14.7 psi 1013 milli bars Click to listen

17. Air Pressure (& density) drop by 1/2 for every 5.5 km altitude gain.

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20. Lapse Rate is the temperature drop per kilometer height increase Typically about 6 °C/km = 6 °C/1000m Or About 3 °F/1000 ft Click to listen

24. Synoptic Weather map Click to listen

28. Radio Sonde