The Atmosphere and the Weather

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Composition of the atmosphere

Composition of the Atmosphere near the Earth's Surface
Permanent Gases Variable Gases

Gas Name Chemical
Formula Percent
(by Volume)
Dry Air Gas
(and Particles) Symbol Percent
(by Volume) Parts per
Million (ppm)^*

Nitrogen N₂ 78.08 Water Vapor H₂O 0 to 4

Oxygen O₂ 20.95 Carbon Dioxide CO₂ 0.0383 383

Argon Ar 0.93 Methane CH₄ 0.00017 1.7

Neon Ne 0.0018 Nitrous Oxide N₂O 0.00003 0.3

Helium He 0.0005 Ozone O₃ 0.000004 0.04

Hydrogen H₂ 0.00005 Particles (dust, soot, etc.) 0.00001 0.01-0.15

Xenon Xe 0.000009 Chlorofluorocarbons (CFCs) 0.00000002 0.0002

^*For CO₂, 383 parts per million means that out of every million air molecules, 383 are CO₂ molecules.

Composition of the Atmosphere near the Earth's Surface
Permanent Gases	Variable Gases
Gas Name	Chemical Formula	Percent (by Volume) Dry Air	Gas (and Particles)	Symbol	Percent (by Volume)	Parts per Million (ppm)^*
Nitrogen	N₂	78.08	Water Vapor	H₂O	0 to 4
Oxygen	O₂	20.95	Carbon Dioxide	CO₂	0.0383	383
Argon	Ar	0.93	Methane	CH₄	0.00017	1.7
Neon	Ne	0.0018	Nitrous Oxide	N₂O	0.00003	0.3
Helium	He	0.0005	Ozone	O₃	0.000004	0.04
Hydrogen	H₂	0.00005	Particles (dust, soot, etc.)		0.00001	0.01-0.15
Xenon	Xe	0.000009	Chlorofluorocarbons (CFCs)		0.00000002	0.0002
^*For CO₂, 383 parts per million means that out of every million air molecules, 383 are CO₂ molecules.

The Atmosphere is mostly composed of Nitrogen and Oxygen (99% of the volume of dry atmosphere).

Nitrogen:

Removed from atmosphere by biological processes that involve soil bacteria. Returned to the atmosphere through the decaying of plant and animal matter.

Oxygen:

Removed from atmosphere by when organic matter decays, combines with other substances, or is taken in during breathing. Is added to the atmosphere through photosynthesis by plants.

Water Vapor:

Varies greatly from place to place, and from time to time.
Extremely important gas in our atmosphere because:

Forms into liquid and solid cloud particles that grow in size and fall to earth as precipitation
Redistributes heat energy on earth and is important to the formation of storms
Is a strong greenhouse gas that warms the earth's surface and its atmosphere

Carbon Dioxide:

Natural component of the atmosphere.

Enters the atmosphere through the decay of vegetation, volcanic eruptions, respiration, burning of fossil fuels, and from deforestation. It is removed from the atmosphere by photosynthesis, and the oceans.

Has increased by over 25% in the last three hundred years.

Methane:

Very strong greenhouse gas.

Since 1750, methane concentrations have increased by more than 140%.

The main sources are the breakdown of plant material in rice paddies, domestic grazing animals (biological reactions in their stomach), biological activities of termites.

Nitrous Oxide:

Forms in the soil by bacterial processes and is destroy by ultraviolet light from the sun.

Average concentration of this greenhouse gas is now increasing at a rate of 0.2-0.3% per year

Ozone:

Near the surface and around cities is the primary ingredient of photochemical smog, which is toxic to living organisms.

Most of it is found in the middle atmosphere (the stratosphere) where it forms the ozone layer which protects plants, animals, and humans from the sun's harmfull ultraviolet radiation.