1. Atmosphere

2. Composition of the Atmosphere
The atmosphere is composed of two basic gases: nitrogen (78%) and oxygen (21%).
Gas
Volume
Nitrogen (N2)
780,840 ppmv (78.084%)
Oxygen (O2)
209,460 ppmv (20.946%)
Argon (Ar)
9,340 ppmv (0.9340%)
Carbon dioxide (CO2)
387 ppmv (0.0387%)
Neon (Ne)
18.18 ppmv ( %)
Helium (He)
5.24 ppmv ( %)
Methane (CH4)
1.79 ppmv ( %)
Krypton (Kr)
1.14 ppmv ( %)
Hydrogen (H2)
0.55 ppmv ( %)
Nitrous oxide (N2O)
0.3 ppmv ( %)
Xenon (Xe)
0.09 ppmv (9 × 10−6 %)
Ozone (O3)
0.0 to 0.07 ppmv (0% to 7 × 10−6 %)
Nitrogen dioxide (NO2)
0.02 ppmv (2 × 10−6 %)
Iodine (I)
0.01 ppmv (1 × 10−6 %)
Carbon monoxide (CO)
0.1 ppmv ( %)
Ammonia (NH3)
trace
Water vapor (H2O)
~0.40% over full atmosphere, typically 1%-4% at surface
*** ppmv: parts per million by volume

3. Variable Components of the Atmosphere
Water vapor, dust particles and ozone in the atmosphere vary in their amounts.
The amount of water vapor in the air varies from practically none to about 4 percent by volume.
Like carbon dioxide, water vapor has the ability to absorb heat energy given off by the earth .
Dust particles are most numerous in the lower atmosphere, but dust is also carried to great heights by rising currents of air.
Dust is essential to the formation of clouds and fog. Dust acts as a surface for water vapor to condense.

4. Ozone
Ozone is a form of oxygen that combines three oxygen atoms in to each molecule (O3).
There is very little ozone in the lower atmosphere. Most ozone is concentrated between 10 and 50 km (6 and 31 miles) above the surface.
In this altitude range, oxygen molecules (O2) are split into single oxygen (O) when they absorb ultraviolet radiation emitted by the sun. Ozone is then created when a single oxygen (O) collides with an oxygen molecule (O2).
The presence of the ozone layer is crucial to life on Earth because it absorbs the potentially harmful ultraviolet radiation from the sun.
Humans are affecting the ozone layer by the pollutants that we are adding to it.

5. Layers of the Earth’s Atmosphere
There are four major layers in the atmosphere: troposphere, stratosphere, mesosphere, thermosphere.
The majority of the air is found closest to the earth.
The atmosphere rapidly thins as you move away from the earth.
At sea level, the average pressure is slightly more than 1,000 millibars. This corresponds to a weight of slightly more than 1 kilogram per square centimeter (14.7 pounds per square inch).

6. Troposphere
The layer of the atmosphere closest to the earth is called the troposphere.
The troposphere contains 75% of the atmosphere.
All weather occurs in the troposphere.

7. The troposphere extends about 8 kilometers (5 miles) above the earth’s surface at the poles and 16 kilometers (10 miles) at the equator.
Temperatures in the troposphere are warmest near the earth and get colder with altitude.
The top of the troposphere is marked by the tropopause.

8. Stratosphere
The second layer in the atmosphere is called the stratosphere.
The stratosphere extends from about 16 kilometers (10 miles) to about 50 kilometers (31 miles).
The temperature of the stratosphere increases due to ozone absorbing heat energy.

9. The stratosphere is where …
the jet stream is found
large planes fly
the ozone layer is found

10. Mesosphere The third layer of the atmosphere is the mesosphere.
The mesosphere is the coldest layer of the atmosphere .
It extends from 50 km (31 miles) to 80 km (50 miles).

11. The mesosphere is the layer of the atmosphere where meteoroids start to burn and become meteors.

12. Thermosphere
The outermost atmospheric layer is called the thermosphere.
It extends from about 85 kilometers (31 + miles) into outer space.

13. The thermosphere is the warmest part of the atmosphere due to the absorption of very short-wave, high-energy solar radiation by atoms of oxygen and nitrogen.
Temperatures rise to extremely high values of more than 1000 degrees Celsius. But these temperatures are not comparable to those near the earth’s surface. Temperature is defined as the average speed at which molecules move. Since the gases of the thermosphere are moving at very high speeds, the temperature is very high. But the gases are sparse and possess only an insignificant quantity of heat.

14. The thermosphere has two sub-layers:
1. the ionosphere
extends from 80 km to 600 km
2. the exosphere
extends from 600 km into outer space

15. Sub-layer : Ionosphere
The ionosphere is a layer of ionized air in the atmosphere extending from almost 80 km above the Earth's surface altitudes of 600 km and more. In this region of the atmosphere the Sun's energy is so strong that it breaks apart molecules and atoms of air, leaving ions (atoms with missing electrons) and free-floating electrons.
Different regions of the ionosphere make long distance radio communication possible by reflecting the radio waves back to Earth.

16. Auroras are associated with the solar wind, a continuous flow of electrically charged particles from the sun. When these particles reach the earth's magnetic field, some get trapped. Many of these particles travel toward the earth's magnetic poles. When the charged particles strike atoms and molecules in the atmosphere, energy is released. Some of this energy appears in the form of auroras.
Auroras

17. Sub-layer : Exosphere
The exosphere is the highest layer of the atmosphere.
The exosphere extends to 10,000 km above the Earth's surface. This is the upper limit of our atmosphere. The atmosphere here merges into space in the extremely thin air.
Space vehicles and satellites orbit in the exosphere of the atmosphere.