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Early atmosphere~4.5 billion years ago Mostly Hydrogen and HeliumEscaped 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.

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 ppmNitrous Oxide N2O .3 ppmOzone 0.04 ppm or 40 ppb)Aerosols (particles) highly variable

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Mass - quantity of matter

Weight = mass x gravity

Density = Mass /volume

Pressure = Force /Area

Standard Sea Level pressure is:

1 Atmosphere

14.7 psi

1013 milli bars

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

Lapse Rate is the temperature drop per kilometer height increase

Typically about 6 °C/km = 6 °C/1000m

Or

About 3 °F/1000 ft

Synoptic Weather map

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