The Atmosphere

Chapter 22

• Atmosphere: A mixture of gasses that surrounds a planet, such as Earth

Chemical composition of the Atmosphere:

Gas Name Chemical Formula Percent Volume

Nitrogen N2 78.08%

Oxygen O2 20.95%

*Water H2O 0 to 4%

Argon Ar 0.93%

*Carbon Dioxide CO2 0.0360%

Neon Ne 0.0018%

Helium He 0.0005%

*Methane CH4 0.00017%

Hydrogen H2 0.00005%

*Nitrous Oxide N2O 0.00003%

*Ozone O3 0.000004%

*Atmosphere made up mostly ofNitrogen 78% and Oxygen 21%.

• The Earth's atmosphere contains several different layers that can be defined according to air temperature or chemical composition

• According to temperature, the atmosphere contains seven different layers

1. troposphere - From the surface of the Earth to approximate 11 kilometers

• 75 % of the total mass of the atmosphere is contained in this layer

• where the majority of our weather occurs.

2. tropopause• an isothermal (temp.

not changing) layer in the atmosphere separates from next layer

• temperature remains constant and where the jet streams occur

3. stratosphere. • temperature

increases with altitude because concentration of ozone layer

• The ozone layer is found in this section

4. stratopause - is

another isothermal layer of separation

5. mesosphere • reaches its coldest

temperatures (about -90° Celsius)

6. mesopause - is another isothermal layer

7. thermosphere. • the hottest layer in the

atmosphere. • Heat is generated from

the absorption of solar radiation by oxygen molecules

• Temperatures can reach 1300 to 1800° Celsius

Earth’s Ozone Layer

• The ozone layer is a region of concentration of the ozone (O3) molecule in the Earth's atmosphere.

• The ozone layer naturally shields us from the harmful effects of the sun's ultraviolet (UV) radiation.

Ozone is created naturally in the stratosphere by the combining of atomic oxygen (O) with molecular oxygen (O2)

• destroyed naturally by the absorption of ultraviolet radiation

Human activities are altering the amount of stratospheric O3.

• A seasonal thinning of the ozone layer primarily at the South Pole is being called the ozone hole.

• The main agent responsible for this destruction was human-made chlorofluorocarbons or CFCs.

Earth’s Solar Budget

Earth’s atmosphere affects incoming solar radiation

• Absorption is defined as a process in which solar radiation is retained by a substance and converted into heat energy.

• Reflection is a process where sunlight is redirect by 180° after it strikes an atmospheric particle.

100% of Solar Radiation is sent from Sun

• 51% makes it to Earth’s Surface• This energy is used to heat the Earth's surface and lower atmosphere • melt and evaporate water• run photosynthesis in plants

• 49 % does not make it all the way to Earth’s surface• 4 % is reflected back to space by the Earth's surface• 26 % is scattered or reflected to space by clouds and atmospheric particles• 19 % is absorbed by atmospheric gases, particles, and clouds.

Solar Budget is closely “balanced”. [51% in, 49% out]

• Too much absorbed or reflected results in Colder temperatures

• Too much allowed to reach surface results in Hot temperatures

• Too much “trapped” by Greenhouse gases results in Global Warming

Greenhouse Effect• Short wavelength rays can enter the Earth’s atmosphere• Outgoing long wavelengths (Infrared heat) cannot escape• Water vapor, methane gas, carbon dioxide gases trap heat• Volcanic eruptions, fossil fuel burning and other activities add these

gases to the atmosphere

Global Warming – global average temperatures steadily increase each year

• The polar ice caps would begin melting and low land flooding occurs

• Rainfall patterns change and affects agriculture • Weather patterns change and cause major destruction

Measuring Atmospheric Pressure

• Barometers used to measure atmospheric pressure

• atmospheres (atm), millimeters or inches of mercury, and millibars (mb).