At
15
15. 1ppt
CH 15 Prentice Hall p.498-501

What is Meteorology?
• The study of weather and the atmosphere.
– Weather- the condition of
Earth’s atmosphere at a particular time and place.

Earth’s Atmosphere
• Atmosphere is from two
Greek words: Atmos and sphaira.
• It makes conditions on the Earth suitable for living things. Contains oxygen and other gases living things need.
• Is constantly changing

Earth’s Atmosphere
• Importance of the atmosphere:
– The atmosphere helps keep the planet warm.
• Allows for liquid water.
– Protects from dangerous radiation.
– Burns up chunks of rocks (meteoroids) from space. (meteors)

Composition of Atmosphere
• Atoms- the smallest unit of a chemical element that retains the properties of that element.
• Molecules- formed by two or more atoms (elements)
– Molecules combine to form
Gases

Composition of Atmosphere
• What gas in the atmosphere makes up the highest percentage of air?
– A. Carbon Dioxide
– B. Oxygen
– C. Argon
– D. Nitrogen

Composition of Atmosphere
• Contains gases, some of which organisms need to live
– Nitrogen
– Oxygen
– Carbon Dioxide
– Water Vapor
– Along with other gasses, particles and liquids.
Nitrogen
Oxygen
Other Gases

• Most abundant (#1) gas in the atmosphere
• One nitrogen molecule contains 2 nitrogen atoms. N
2
• All living organisms need nitrogen in order to grow and repair body cells.

• Nitrogen fixation must occur to convert N
2 into a form that plants can use. (Nitrates)
• Plants absorb the nitrogen from the soil.
• Animals eat the plants.

• The second most abundant (#2) gas O
2
• Oxygen is an important ingredient in the combustion process.
– Burning uses oxygen rapidly.
• Oxygen reacts slowly with metal objects to produce rust.
• Ozone –three oxygen atoms O
–
–
Ozone Layer in Stratosphere
Ozone Hole
3

• One molecule has one atom of carbon and two atoms of oxygen.
• Essential to life.
– Plants must use CO
2
– Animals give off CO
2 to produce oxygen.
as a waste product.

• Fossil fuels increase the amount of CO
2 atmosphere.
in the
• Earth’s temperature rises as a result.

• Nitrogen and
Oxygen make up
99% of the gases in the atmosphere
Other
Gasses
Argon
Carbon Dioxide
Percent by
Volume
0.93
0.036
• Argon and Carbon dioxide make up most of the remaining 1%
(trace gases)
Neon
Helium
Methane
Krypton
Hydrogen
0.0018
0.00052
0.00015
0.00011
0.00005

• Is in the form of a gas.
– It is invisible, not the same thing as steam.
• Varies from place to place.
– Desert, Polar Ice Caps
• Almost no water vapor.
– Tropical Rain Forest
• Five % of the air may be water vapor

• Plays an important role in Earth’s weather.
• Forms clouds when water condenses on particles in the air.
• Leads to precipitation

• Real world air contains tiny solid and liquid particles of:
– Dust
– Smoke
– Salt
– Other chemicals