1. the Atmosphere’s Role in Weather

2. What is the Atmosphere?
The atmosphere is a mixture of gases that surround the Earth
The atmosphere is made up of 78% nitrogen, 21%oxygen and 1% argon, CO2, water vapor and other gases
The atmosphere is mostly gas, but contains small amounts of solids and liquids
Solid particles like Dust, ash, dirt, smoke
Liquid water in droplets in clouds

3. Atmospheric Pressure
Air pressure is the measure of the force with which the air molecules push on a surface
Gravity is what holds the Earth’s atmosphere in place
Air pressure changes throughout the atmosphere
As Altitude increases, air pressure decreases
Air pressure is greater near Earth’s surface

4. Layers of the atmosphere
Troposphere – Lowest layer/closest to Earth
Where we live - Densest layer – where weather happens
Stratosphere – 2nd layer
Thin air - cold - contains the ozone layer(absorbs solar energy and UV radiation)
Mesosphere – 3rd Layer
Coldest layer
Thermosphere – Uppermost layer
High temperature caused by fast moving particles that rarely touch one another

5. Heating the Atmosphere - Radiation
The Earth receives energy from the sun by radiation
Radiation is the transfer of energy in electromagnetic waves
The sun’s radiation is absorbed, causes molecules to speed up and increase temperature
This can happen to your skin as well as the surface of the Earth

6. Heating the Atmosphere – Conduction
Conduction is the transfer of thermal energy from one material to another by direct contact
Always moves from warm to cold (ex. Your foot on a hot sidewalk)
When air molecules come in contact with a warm surface thermal energy is transferred to the atmosphere

7. Heating the Atmosphere – Convection
Most Thermal energy in the atmosphere moves by convection
When air is heated it becomes less dense and rises – cool air is more dense and sinks
The continual process of warm air rising and cool air sinking creates a circular movement of air called a convection current

9. The Greenhouse Effect
The process where the gases(such as CO2) in the atmosphere trap thermal energy
Global warming is due to an increased amount of thermal energy being trapped by “greenhouse gases” in the atmosphere
A radiation balance needs to be maintained in order for the Earth to be “livable”
Balance between incoming radiation and outgoing energy