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3. 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.

4. 78 % Nitrogen N2 20.95 % Oxygen O2 0.93 % Argon Ar H2O 0 to 4 % Carbon Dioxide CO2 0 to .037 % (or 370 ppm) Methane CH4 1.8 ppm Nitrous Oxide N2O .3 ppm Ozone 0.04 ppm or 40 ppb) Aerosols (particles) highly variable Click to listen

10. Mass - quantity of matter Weight = mass x gravity Density = Mass/volume Pressure = Force/Area

11. Standard Sea Level pressure is: 1 Atmosphere 14.7 psi 1013 milli bars

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

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

19. Synoptic Weather map

23. Radio Sonde